Draft report nz_apples_may_2011

Draft report for the non-regulated analysis
of existing policy for apples from
New Zealand

May 2011

© Commonwealth of Australia 2011
This work is copyright. You may download, display, print and reproduce this material in
unaltered form only (retaining this notice) for your personal, non-commercial use, or use
within your organisation. Apart from any use as permitted under the Copyright Act 1968, all
other rights are reserved. Requests concerning reproduction and re-use should be addressed to
copyright@daff.gov.au or Communication Branch, Department of Agriculture, Fisheries and
Forestry, GPO Box 858, Canberra ACT 2601, Australia.

Cite this report as: Biosecurity Australia (2011) Draft report for the non-regulated analysis
of existing policy for apples from New Zealand. Department of Agriculture, Fisheries and
Forestry, Canberra.

The Australian Government acting through Biosecurity Australia has exercised due care and
skill in preparing and compiling the information in this publication. Notwithstanding,
Biosecurity Australia, its employees and advisers disclaim all liability to the maximum extent
permitted by law, including liability for negligence, for any loss, damage, injury, expense or
cost incurred by any person as a result of accessing, using or relying upon any of the
information in this publication.
Postal address: Biosecurity Australia
GPO Box 858
CANBERRA ACT 2601
AUSTRALIA
Internet: www.biosecurityaustralia.gov.au
Cover image: Royal Gala apple in a Nelson orchard, New Zealand. Biosecurity Australia.

Submissions
This draft report has been issued to give all interested parties an opportunity to comment and
draw attention to any scientific, technical, or other gaps in the data, misinterpretations and
errors. Any comments should be submitted to Biosecurity Australia within the comment
period stated in the related Biosecurity Australia Advice on the Biosecurity Australia website.
The draft report will then be revised as necessary to take account of the comments received
and a final report will be released at a later date.
Comments on the draft report should be submitted to:
Office of the Chief Executive
Biosecurity Australia
GPO Box 858
CANBERRA ACT 2601
AUSTRALIA
Telephone: +61 2 6272 5094
Facsimile: +61 2 6272 3307
Email: plant@biosecurity.gov.au
Internet: www.biosecurityaustralia.gov.au

Draft Report: Review of fresh apple fruit from New Zealand Contents

Contents

List of tables ........................................................................................................... vii

List of figures ......................................................................................................... viii

Acronyms and abbreviations ................................................................................ xii

Abbreviations of units ........................................................................................... xiv

Summary ................................................................................................................. xv

1 Introduction .................................................................................................... 1
1.1 Australia’s biosecurity policy framework ........................................................................ 1
1.2 This pest risk analysis ................................................................................................... 2

2 Method for pest risk analysis........................................................................ 5
2.1 Stage 1: Initiation ........................................................................................................... 5
2.2 Stage 2: Pest risk assessment ...................................................................................... 5
2.3 Stage 3: Pest risk management .................................................................................. 13

3 New Zealand’s commercial production practices for apples ................... 15
3.1 Climate in production areas ......................................................................................... 15
3.2 Pre-harvest .................................................................................................................. 20
3.3 Harvesting and handling procedures ........................................................................... 24
3.4 Post-harvest................................................................................................................. 25
3.5 Production and export statistics................................................................................... 27

4 Pest risk assessments for quarantine pests ............................................. 29
4.1 Fire blight ..................................................................................................................... 30
4.2 Apple leaf curling midge .............................................................................................. 73
4.3 European canker ......................................................................................................... 93
4.4 Pest risk assessment conclusions ............................................................................. 114

5 Pest risk management ............................................................................... 117
5.1 Pest risk management measures and phytosanitary procedures ............................. 119
5.2 Operational systems for maintenance and verification of phytosanitary status ........ 124
5.3 Uncategorised and other pests.................................................................................. 127
5.4 Audit of protocol ......................................................................................................... 127
5.5 Review of policy ......................................................................................................... 127

6 Conclusion ................................................................................................. 129

Appendix A Categorisation for quarantine pests considered in this
review ............................................................................................. 131

v

Draft Report: Review of fresh apple fruit from New Zealand Contents

Appendix B Additional quarantine pest data................................................... 133

Appendix C Biosecurity framework ................................................................. 135

Glossary ................................................................................................................ 140

References ............................................................................................................ 145

vi

Draft Report: Review of fresh apple fruit from New Zealand Tables and figures

List of tables

Table 2.1 Nomenclature for qualitative likelihoods 8
Table 2.2 Matrix of rules for combining qualitative likelihoods 9
Table 2.3 Decision rules for determining the consequence impact score based on the
magnitude of consequences at four geographic scales 11
Table 2.4 Decision rules for determining the overall consequence rating for each pest 12
Table 2.5 Risk estimation matrix 12
Table 3.1 Export volume and percentages of each variety of fruit for exports from New
Zealands three main apple production regions (Pipfruit NZ 2010) 28
Table 4.1 Quarantine pests for apple fruit from New Zealand considered in this risk analysis 29
Table 4.2 Probability of entry, establishment, and spread for Erwinia amylovora 67
Table 4.3 Probability of entry, establishment, and spread for Dasineura mali 88
Table 4.4 Probability of entry, establishment, and spread for Neonectria ditissima 110
Table 4.5 Summary of unrestricted risk estimates for quarantine pests associated with
mature fresh apple fruit from New Zealand 115
Table 5.1 Summary of the assessment of unrestricted risk for quarantine pests 118
Table 5.2 Summary of phytosanitary measures recommended for quarantine pests for
mature fresh apple fruit from New Zealand 119

vii

Draft Report: Review of fresh apple fruit from New Zealand Tables and figures

List of figures

Figure a Map of Australia ix
Figure b Map of major apple producing regions in Australia ix
Figure c A guide to Australia’s bio-climatic zones x
Figure d Diagram of apple fruit xi
Figure 3-1 Map of New Zealand 15
Figure 3-2 Maximum and minimum temperatures and mean monthly rainfall for Hamilton
(Waikato) 1971–2000 17
Figure 3-3 Maximum and minimum temperatures and mean monthly rainfall for Napier
7
(Hawke’s Bay) 1971–2000 17
Figure 3-4 Maximum and minimum temperatures and mean monthly rainfall for Nelson
7
1971–2000 17
Figure 3-5 Maximum and minimum temperatures and mean monthly rainfall for Alexandra
7
(Central Otago) 1971–2000 17
Figure 3-6 Maximum and minimum temperatures and mean monthly rainfall for Stanthorpe,
Qld. 1981–2010 18
Figure 3-7 Maximum and minimum temperatures and mean monthly rainfall for Batlow, NSW
8
1971–2000 18
Figure 3-8 Maximum and minimum temperatures and mean monthly rainfall for Tatura, Vic.
8
(Goulburn Valley) 1981–2010 18
Figure 3-9 Maximum and minimum temperatures and mean monthly rainfall for Geeveson,
8
Tas. (Huon Valley) 1981–2010 18
Figure 3-10 Maximum and minimum temperatures and mean monthly rainfall for Lenswood,
8
SA (Adelaide Hills) 1981–2010 19
Figure 3-11 Maximum and minimum temperatures and mean monthly rainfall for Donnybrook
8
WA 1981–2010 19
Figure 3-12 Representation of divisions within an orchard 20

viii

Draft Report: Review of fresh apple fruit from New Zealand Maps of Australia

Figure a Map of Australia

Figure b Map of major apple producing regions in Australia

ix

Draft Report: Review of fresh apple fruit from New Zealand Maps of Australia

Figure c A guide to Australia’s bio-climatic zones

x

Draft Report: Review of fresh apple fruit from New Zealand Diagram of an apple fruit

Figure d Diagram of an apple fruit

xi

Draft Report: Review of fresh apple fruit from New Zealand Acronyms and abbreviations

Acronyms and abbreviations

Term or abbreviation Definition

ABS Australian Bureau of Statistics

ACERA Australian Centre of Excellence for Risk Analysis

ACT Australian Capital Territory

ALOP Appropriate level of protection

ALPP Areas of low pest prevalence

APAL Apple and Pear Australia Limited

APHIS Animal and Plant Health Inspection Service

APPD Australian Plant Pest Database (Plant Health Australia)

AQIS Australian Quarantine and Inspection Service

BA Biosecurity Australia

BAA Biosecurity Australia Advice

BSG Biosecurity Service Group

CABI CAB International, Wallingford, UK

CMI Commonwealth Mycological Institute

CSIRO Commonwealth Science and Industry Research Organisation

CT Concentration time

DAFF Australian Government Department of Agriculture, Fisheries and Forestry

DAFWA Department of Agriculture and Food, Western Australia (formerly DAWA: Department of
Agriculture, Western Australia)

DPIW Department of Primary Industries and Water, Tasmania

EP Existing policy

EPPO European and Mediterranean Plant Protection Organization

FAO Food and Agriculture Organization of the United Nations

FAS The Foreign Agriculture Service in the United States Department of Agriculture

IDM Integrated Disease Management

IPC International Phytosanitary Certificate

IPM Integrated Pest Management

IPPC International Plant Protection Convention

IRA Import Risk Analysis

IRAAP Import Risk Analysis Appeals Panel

ISPM International Standard for Phytosanitary Measures

MAFNZ Ministry of Agriculture and Forestry New Zealand

MOU Memorandum of Understanding

NASS The National Agricultural Statistics Service in the United States Department of Agriculture

NPPO National Plant Protection Organization

NSW New South Wales

NT Northern Territory

OEPP Organisation européenne et méditerranéenne pour la protection des plantes

PIAPH Product Integrity, Animal and Plant Health Division

PIMC Primary Industries Ministerial Council

xii


PRA Pest Risk Analysis

Qld Queensland

SA South Australia

SPS Sanitary and phytosanitary

Tas. Tasmania

Vic. Victoria

WA Western Australia

WAFGA Western Australia Fruit Growers’ Association

WTO World Trade Organisation

xiii


Abbreviations of units

ºC degree Celsius
g gram
h hour
ha hectare
kg kilogram
km kilometre
L litre
ml millilitre
m metre
3
m cubic metre
mg milligram
mm millimetre
ppm parts per million
µL Microlitre
MPa Mega Pascals

xiv

Draft Report: Review of fresh apple fruit from New Zealand Summary

Summary

This non-regulated analysis of existing policy reassesses the quarantine risks posed by three
pests associated with the importation of apples from New Zealand: fire blight (caused by the
bacterium Erwinia amylovora), European canker (caused by the fungi Neonectria ditissima),
and apple leaf curling midge (Dasineura mali). The analysis is being undertaken to consider
the three pests in order to meet Australia‟s WTO obligations and the requirements of the
Quarantine Act 1908 and relevant sub-ordinate legislation.

The draft report proposes that the current import conditions for apple fruit from New Zealand
be amended and that the importation of apples be permitted, subject to a range of quarantine
conditions.

In November 2006 the Final import risk analysis report for apples from New Zealand (final
IRA report) was published. On 26 March 2007 the Director of Animal and Plant Quarantine
determined the policy to permit import of apples from New Zealand, subject to application of
the quarantine measures specified in the final IRA report. New Zealand challenged the
measures for fire blight, European canker and apple leaf curling midge, through the Dispute
Settlement Body of the World Trade Organization (WTO), claiming that the measures were
inconsistent with Australia‟s international obligations under the Agreement on the Application
of Sanitary and Phytosanitary Measures (SPS Agreement).

A Panel was formed and, on 9 August 2010, ruled that Australia‟s phytosanitary measures for
New Zealand apples were not justified. Australia notified its intention to appeal the Panel‟s
decision and the Appellate Body reported on 29 November 2010, reaffirming the Panel‟s
rulings that Australia‟s phytosanitary measures for New Zealand apples are not justified.
There are no further avenues for appeal. As a member of the WTO, Australia is obliged to
implement the independent reports of the Panel and Appellate Body.

This draft report takes into account the pre-harvest, harvest and post-harvest practices
described as being standard commercial practice for the production of apples for export in
New Zealand. Also considered is new scientific information that was not available when the
2006 final IRA report was completed.

The draft report concludes that when the New Zealand apple industry‟s standard commercial
practices for production of export grade fruit are taken into account, the unrestricted risk for
all three pests assessed achieves Australia‟s appropriate level of protection (ALOP).
Therefore, no additional quarantine measures are recommended, though New Zealand will
need to ensure that the standard commercial practices detailed in this review are met for
export consignments. These practices include:
Application of the integrated fruit production system, or an equivalent, to manage
pests and diseases in orchard
Testing to ensure that only mature fruit is exported to Australia
Maintenance of sanitary conditions in dump tank water
High pressure water washing and brushing of fruit in the packing house
A minimum 600 fruit sample from each lot of fruit packed is inspected and found
free of quarantine pests for Australia.

xv

Draft Report: Review of fresh apple fruit from New Zealand Summary

In addition to the three pests considered in this draft report, the final IRA report in 2006
recommended quarantine measures for a further nine quarantine pests. Of those nine pests,
five leafrollers were assessed as quarantine pests for all of Australia, while two mealybugs,
codling moth, and apple scab (caused by Venturia inaequalis) were assessed as quarantine
pests only for Western Australia. However, apple scab is now considered to be present in
Western Australia and is no longer a quarantine pest requiring measures. The measures
recommended for those remaining pests must also be applied to export consignments and
included:
A 600 fruit sample from each lot of fruit inspected and found free of quarantine pests
for Australia (for leafrollers and mealybugs). New Zealand‟s standard commercial
practice is recognised as meeting this requirement
Establishment of pest free areas, or areas of low pest prevalence for codling moth, or
fumigation with methyl bromide. This measure is only required for lots destined for
Western Australia

This draft report contains details of the risk assessments for the quarantine pests and the
proposed quarantine measures in order to allow interested parties to provide comments and
submissions to Biosecurity Australia within the 60 day consultation period.

xvi

Draft Report: Review of fresh apple fruit from New Zealand Introduction

1 Introduction

1.1 Australia’s biosecurity policy framework
Australia's biosecurity policies aim to protect Australia against the risks that may arise from
exotic pests1 entering, establishing and spreading in Australia, thereby threatening Australia's
unique flora and fauna, as well as those agricultural industries that are relatively free from
serious pests.
The pest risk analysis (PRA) process is an important part of Australia's biosecurity policies. It
enables the Australian Government to formally consider the risks that could be associated
with proposals to import new products into Australia. If the risks are found to exceed
Australia‟s appropriate level of protection (ALOP), risk management measures are proposed
to reduce the risks to an acceptable level. But, if it is not possible to reduce the risks to an
acceptable level, then no trade will be allowed.
Successive Australian Governments have maintained a conservative, but not a zero-risk,
approach to the management of biosecurity risks. This approach is expressed in terms of
Australia's ALOP, which reflects community expectations through government policy and is
currently described as providing a high level of protection aimed at reducing risk to a very
low level, but not to zero.
Australia‟s PRAs are undertaken by Biosecurity Australia using technical and scientific
experts in relevant fields, and involves consultation with stakeholders at various stages during
the process. Biosecurity Australia provides recommendations for animal and plant quarantine
policy to Australia‟s Director of Animal and Plant Quarantine (the Secretary of the Australian
Department of Agriculture, Fisheries and Forestry). The Director, or delegate, is responsible
for determining whether or not an importation can be permitted under the Quarantine Act
1908, and if so, under what conditions. The Australian Quarantine and Inspection Service
(AQIS) is responsible for implementing appropriate risk management measures.
More information about Australia‟s biosecurity framework is provided in Appendix C of this
report and in the Import Risk Analysis Handbook 2011 located on the Biosecurity Australia
website www.biosecurityaustralia.gov.au.

1
A pest is any species, strain or biotype of plant, animal, or pathogenic agent injurious to plants or plant products
(FAO 2009).

1


1.2 This pest risk analysis

1.2.1 Background
Following the release of the Final import risk analysis report for apples from New Zealand in
November 2006, the Director of Animal and Plant Quarantine determined a policy for the
importation of apples from New Zealand. That determination, made on 26 March 2007,
permitted imports of apples subject to the Quarantine Act 1908 and the application of the
quarantine measures as specified in the Final import risk analysis report for apples from New
Zealand (2006 final IRA report).

On 31 August 2007, New Zealand requested consultations with Australia through the World
Trade Organization (WTO), claiming that the quarantine measures relating to Erwinia
amylovora (the cause of fire blight of apples), Neonectria ditissima (the cause of European
canker), and Dasineura mali (apple leaf curling midge) were inconsistent with Australia‟s
obligations under the Sanitary and Phytosanitary Agreement (SPS Agreement). Subsequently,
following a request from New Zealand, the WTO Dispute Settlement Body established a
Panel to examine New Zealand‟s claims. The Panel‟s findings, as modified by the Appellate
Body, were that Australia‟s import risk analysis that recommended quarantine measures for
New Zealand apples was not sufficiently supported by scientific evidence and did not fully
take into account standard commercial practices in New Zealand. The recommended
quarantine measures were therefore inconsistent with Australia‟s obligations under the SPS
Agreement. The Dispute Settlement Body formally adopted the reports of the Appellate Body
and the Panel report as modified by the Appellate Body on 17 December 2010.

In response to that finding the Government announced that a science-based review of the
import risk analysis for New Zealand apples would be conducted by Biosecurity Australia.
The review was to consider the three pests at dispute to meet Australia‟s WTO obligations
and the requirements of the Quarantine Act 1908 and relevant sub-ordinate legislation.

1.2.2 Scope
The scope of the PRA is to re-assess the quarantine risks and measures associated with three
of the pests considered in the 2006 final IRA report; Erwinia amylovora, Neonectria
ditissima, and Dasineura mali. The quarantine measures required for those three pests were
the subject of the WTO dispute.
Other quarantine pests were identified in the 2006 final IRA report, but as the measures
required for those pests were not included in the WTO dispute they are not re-assessed here.
The quarantine requirements recommended in the 2006 final IRA report and determined by
the Director of Animal and Plant Quarantine in March 2007 therefore remain current for those
pests.

1.2.3 Existing policy
International policy
Import policy exists for Fuji apples from Japan (AQIS 1998a). An IRA on apples from New
Zealand has been completed (BA 2006). No apples have been imported into Australia under

2


these policies. Import policy also exists for apples from China (BA 2010) and imports first
arrived in Australia in early 2011.
Import policies also exist for Korean pears from Korea (AQIS 1999), ya pears and Asian
pears from China‟s provinces of Hebei, Shandong and Shaanxi (AQIS 1998b), and fragrant
pears from Xinjiang Uygur Autonomous Region (BA 2005).
The import requirements for these commodities can be accessed at AQIS Import Conditions
database http://www.aqis.gov.au/icon.

Domestic arrangements
The Commonwealth Government is responsible for regulating the movement of plants and
plant products in and out of Australia. However, the state and territory governments are
responsible for plant health controls within Australia. Legislation relating to resource
management or plant health may be used by state or territory government agencies to control
interstate movement of plants or their products.

1.2.4 Contaminating pests
In addition to the pests of apples from New Zealand that are assessed in this PRA, and those
identified in the 2006 final IRA report, there are other organisms that may arrive with the
imported commodity. These organisms could include pests of other crops or predators and
parasitoids of other arthropods. Biosecurity Australia considers these organisms to be
contaminating pests that could pose sanitary and phytosanitary risks. These risks are
addressed by existing operational procedures.

1.2.5 Consultation
On 7 December 2010, Biosecurity Australia Advice (BAA) 2010/38 informed stakeholders of
the formal commencement of a non-regulated analysis of existing policy for the importation
of apples from New Zealand (a review).

1.2.6 Next steps
This draft report gives stakeholders the opportunity to comment and draw attention to any
scientific, technical, or relevant other gaps in the data, misinterpretations and errors.
Biosecurity Australia will consider submissions received on the draft report and may consult
informally with stakeholders. Biosecurity Australia will revise the report as appropriate.
Biosecurity Australia will then prepare a final report, taking into account stakeholder
comments.
The report will be distributed to registered stakeholders and the documents will be placed on
the Biosecurity Australia website.
The Director of Animal and Plant Quarantine will then make a determination. The
determination provides a policy framework for decisions on whether or not to grant an import
permit and any conditions that may be attached to a permit.
A policy determination represents the completion of the process.
The Director of Animal and Plant Quarantine notifies AQIS and Biosecurity Australia of the
policy determination. In turn, Biosecurity Australia notifies the proposer and registered

3


stakeholders, and the Department of Agriculture, Fisheries and Forestry notifies the WTO
Secretariat, of the determination. The determination will also be placed on the Biosecurity
Australia website.

4

Draft Report: Review of fresh apple fruit from New Zealand Method

2 Method for pest risk analysis

This section sets out the method used for the pest risk analysis (PRA) in this report.
Biosecurity Australia has conducted this PRA in accordance with the International Standards
for Phytosanitary Measures (ISPMs), including ISPM 2: Framework for Pest Risk Analysis
(FAO 2007) and ISPM 11: Pest Risk Analysis for Quarantine Pests, including analysis of
environmental risks and living modified organisms (FAO 2004) that have been developed
under the SPS Agreement (WTO 1995).
A PRA is „the process of evaluating biological or other scientific and economic evidence to
determine whether a pest should be regulated and the strength of any phytosanitary measures
to be taken against it‟ (FAO 2009). A pest is „any species, strain or biotype of plant, animal,
or pathogenic agent injurious to plants or plant products‟ (FAO 2009).
Quarantine risk consists of two major components: the probability of a pest entering,
establishing and spreading in Australia from imports; and the consequences should this
happen. These two components are combined to give an overall estimate of the risk.
Unrestricted risk is estimated taking into account the existing commercial production practices
of the exporting country and that, on arrival in Australia, AQIS will verify that the
consignment received is as described on the commercial documents and its integrity has been
maintained.
Restricted risk is estimated with phytosanitary measure(s) applied. A phytosanitary measure is
„any legislation, regulation or official procedure having the purpose to prevent the
introduction and spread of quarantine pests, or to limit the economic impact of regulated non-
quarantine pests‟ (FAO 2009).
A glossary of the terms used is provided at the back of this report.
The PRA was conducted in the following three consecutive stages: initiation, pest risk
assessment and pest risk management.

2.1 Stage 1: Initiation
Initiation identifies the pest(s) and pathway(s) that are of quarantine concern and should be
considered for risk analysis in relation to the identified PRA area.
Part C of the 2006 Final import risk analysis report for apples from New Zealand listed the
pests and diseases with the potential to be associated with exported apples produced using
commercial production and packing procedures. The entries from that table for E. amylovora,
N. ditissima, and D. mali are reproduced in this review in Appendix A.
For this PRA, the „PRA area‟ is defined as Australia. None of the three pests considered are
present in any part of Australia.

2.2 Stage 2: Pest risk assessment
A pest risk assessment (for quarantine pests) is: „the evaluation of the probability of the
introduction and spread of a pest and of the likelihood of associated potential economic
consequences‟ (FAO 2009).
In this PRA, pest risk assessment was divided into the following interrelated processes:

5


2.2.1 Pest categorisation
Pest categorisation identifies which of the pests with the potential to be on the commodity are
quarantine pests for Australia and require pest risk assessment. A „quarantine pest‟ is a pest of
potential economic importance to the area endangered thereby and not yet present there, or
present but not widely distributed and being officially controlled, as defined in ISPM 5:
Glossary of phytosanitary terms (FAO 2009).
The pests identified in Stage 1 were categorised using the following primary elements to
identify the quarantine pests for the commodity being assessed:
identity of the pest
presence or absence in the PRA area
regulatory status
potential for establishment and spread in the PRA area
potential for economic consequences (including environmental consequences) in the
PRA area
The results of pest categorisation for the pests considered in this PRA are set out in columns 4
– 7 in Appendix A and are as they were presented in the2006 Final import risk analysis report
for apples from New Zealand. The steps in the categorisation process are considered
sequentially, with the assessment terminating with a „Yes‟ in column 4 or the first „No‟ in
columns 5 or 6. The quarantine pests identified during pest categorisation were carried
forward for pest risk assessment and are listed in Table 4.1.

2.2.2 Assessment of the probability of entry, establishment and spread
Details of how to assess the „probability of entry‟, „probability of establishment‟ and
„probability of spread‟ of a pest are given in ISPM 11 (FAO 2004). A summary of this process
is given below, followed by a description of the qualitative methodology used in this PRA.

Probability of entry
The probability of entry describes the probability that a quarantine pest will enter Australia as
a result of trade in a given commodity, be distributed in a viable state in the PRA area and
subsequently be transferred to a host. It is based on pathway scenarios depicting necessary
steps in the sourcing of the commodity for export, its processing, transport and storage, its use
in Australia and the generation and disposal of waste. In particular, the ability of the pest to
survive is considered for each of these various stages.
The probability of entry estimates for the quarantine pests for a commodity are based on the
use of the existing commercial production, packaging and shipping practices of the exporting
country. Details of the existing commercial production practices for the commodity are set out
in Section 3. These practices are taken into consideration by Biosecurity Australia when
estimating the probability of entry.
For the purpose of considering the probability of entry, Biosecurity Australia divides this step
of this stage of the PRA into two components:
Probability of importation: the probability that a pest will arrive in Australia when a given
commodity is imported.

6


Probability of distribution: the probability that the pest will be distributed, as a result of the
processing, sale or disposal of the commodity, in the PRA area and subsequently transfer to a
susceptible part of a host.
Factors considered in the probability of importation include:
distribution and incidence of the pest in the source area
occurrence of the pest in a life-stage that would be associated with the commodity
volume and frequency of movement of the commodity along each pathway
seasonal timing of imports
pest management, cultural and commercial procedures applied at the place of origin
speed of transport and conditions of storage compared with the duration of the life
cycle of the pest
vulnerability of the life-stages of the pest during transport or storage
incidence of the pest likely to be associated with a consignment
commercial procedures (e.g. refrigeration) applied to consignments during transport
and storage in the country of origin, and during transport to Australia
Factors considered in the probability of distribution include:
commercial procedures (e.g. refrigeration) applied to consignments during distribution
in Australia
dispersal mechanisms of the pest, including vectors, to allow movement from the
pathway to a host
whether the imported commodity is to be sent to a few or many destination points in
the PRA area
proximity of entry, transit and destination points to hosts
time of year at which import takes place
intended use of the commodity (e.g. for planting, processing or consumption)
risks from by-products and waste

Probability of establishment
Establishment is defined as the „perpetuation for the foreseeable future, of a pest within an
area after entry‟ (FAO 2004). In order to estimate the probability of establishment of a pest,
reliable biological information (lifecycle, host range, epidemiology, survival, etc.) is obtained
from the areas where the pest currently occurs. The situation in the PRA area can then be
compared with that in the areas where it currently occurs and expert judgement used to assess
the probability of establishment.
Factors considered in the probability of establishment in the PRA area include:
availability of hosts, alternative hosts and vectors
suitability of the environment
reproductive strategy and potential for adaptation

7


minimum population needed for establishment
cultural practices and control measures

Probability of spread
Spread is defined as „the expansion of the geographical distribution of a pest within an area‟
(FAO 2004). The probability of spread considers the factors relevant to the movement of the
pest, after establishment on a host plant or plants, to other susceptible host plants of the same
or different species in other areas. In order to estimate the probability of spread of the pest,
reliable biological information is obtained from areas where the pest currently occurs. The
situation in the PRA area is then carefully compared with that in the areas where the pest
currently occurs and expert judgement used to assess the probability of spread.
Factors considered in the probability of spread include:
suitability of the natural and/or managed environment for natural spread of the pest
presence of natural barriers
potential for movement with commodities, conveyances or by vectors
intended use of the commodity
potential vectors of the pest in the PRA area
potential natural enemies of the pest in the PRA area

Assigning qualitative likelihoods for the probability of entry, establishment and spread
In its qualitative PRAs, Biosecurity Australia uses the term „likelihood‟ for the descriptors it
uses for its estimates of probability of entry, establishment and spread. Qualitative likelihoods
are assigned to each step of entry, establishment and spread. Six descriptors are used: high;
moderate; low; very low; extremely low; and negligible (Table 2.1). Descriptive definitions
for these descriptors are given in Table 2.1. The standardised likelihood descriptors provide
guidance to the risk analyst and promote consistency between different risk analyses.
Table 2.1 Nomenclature for qualitative likelihoods

Likelihood Descriptive definition

High The event would be very likely to occur

Moderate The event would occur with an even probability
Low The event would be unlikely to occur
Very low The event would be very unlikely to occur

Extremely low The event would be extremely unlikely to occur

Negligible The event would almost certainly not occur

The likelihood of entry is determined by combining the likelihood that the pest will be
imported into the PRA area and the likelihood that the pest will be distributed within the PRA
area, using a matrix of rules (Table 2.2). This matrix is then used to combine the likelihood of
entry and the likelihood of establishment, and the likelihood of entry and establishment is then
combined with the likelihood of spread to determine the overall likelihood of entry,
establishment and spread.

8


For example, if the probability of importation is assigned a likelihood of „low‟ and the
probability of distribution is assigned a likelihood of „moderate‟, then they are combined to
give a likelihood of „low‟ for the probability of entry. The likelihood for the probability of
entry is then combined with the likelihood assigned to the probability of establishment (e.g.
„high‟) to give a likelihood for the probability of entry and establishment of „low‟. The
likelihood for the probability of entry and establishment is then combined with the likelihood
assigned to the probability of spread (e.g. „very low‟) to give the overall likelihood for the
probability of entry, establishment and spread of „very low‟. A working example is provided
below;

P [importation] x P [distribution] = P [entry] e.g. low x moderate = low

P [entry] x P [establishment] = P [EE] e.g. low x high = low

P [EE] x [spread] = P [EES] e.g. low x very low = very low

Table 2.2 Matrix of rules for combining qualitative likelihoods

High Moderate Low Very low Extremely low Negligible
High High Moderate Low Very low Extremely low Negligible
Moderate Low Low Very low Extremely low Negligible
Low Very low Very low Extremely low Negligible
Very low Extremely low Extremely low Negligible
Extremely low Negligible Negligible
Negligible Negligible

Time and volume of trade
One factor affecting the likelihood of entry is the volume and duration of trade. If all other
conditions remain the same, the overall likelihood of entry will increase as time passes and the
overall volume of trade increases.
Biosecurity Australia normally considers the likelihood of entry on the basis of the estimated
volume of one year‟s trade. This is a convenient value for the analysis that is relatively easy to
estimate and allows for expert consideration of seasonal variations in pest presence, incidence
and behaviour to be taken into account. The consideration of the likelihood of entry,
establishment and spread and subsequent consequences takes into account events that might
happen over a number of years even though only one year‟s volume of trade is being
considered. This difference reflects biological and ecological facts, for example where a pest
or disease may establish in the year of import but spread may take many years.
The use of a one year volume of trade has been taken into account when setting up the matrix
that is used to estimate the risk and therefore any policy based on this analysis does not
simply apply to one year of trade. Policy decisions that are based on Biosecurity Australia‟s
method that uses the estimated volume of one year‟s trade are consistent with Australia‟s
policy on appropriate level of protection and meet the Australian Government‟s requirement
for ongoing quarantine protection.
Based on an analysis presented by the Australian Bureau of Agricultural and Resource
Economics (ABARE 2006), the 2006 final IRA report estimated a volume of trade that could

9


range from 50 million apples to 400 million apples, which correspond to a range of 2.5–20 per
cent of the average Australian apple fruit production and 5–40 per cent of the Australian
domestic fresh apple fruit production. However, in the 2006 analysis, emphasis was given to
the lower end of that range. In the absence of an existing trade it is difficult to estimate the
volume of apples that might be imported in any given year from New Zealand. For this
review, the volume of trade has been estimated as up to 20 per cent of the domestic fresh
apple fruit market.

2.2.3 Assessment of potential consequences
The objective of the consequence assessment is to provide a structured and transparent
analysis of the likely consequences if the pests or disease agents were to enter, establish and
spread in Australia. The assessment considers direct and indirect pest effects and their
economic and environmental consequences. The requirements for assessing potential
consequences are given in Article 5.3 of the SPS Agreement (WTO 1995), ISPM 5 (FAO
2009) and ISPM 11 (FAO 2004).
Direct pest effects are considered in the context of the effects on:
plant life or health
other aspects of the environment
Indirect pest effects are considered in the context of the effects on:
eradication, control, etc
domestic trade
international trade
environment
For each of these six criteria, the consequences were estimated over four geographic levels,
defined as:
Local: an aggregate of households or enterprises (a rural community, a town or a local
government area).
District: a geographically or geopolitically associated collection of aggregates (generally a
recognised section of a state or territory, such as „Far North Queensland‟).
Regional: a geographically or geopolitically associated collection of districts in a geographic
area (generally a state or territory, although there may be exceptions with larger states such as
Western Australia).
National: Australia wide (Australian mainland states and territories and Tasmania).
For each criterion, the magnitude of the potential consequence at each of these levels was
described using four categories, defined as:
Indiscernible: pest impact unlikely to be noticeable.
Minor significance: expected to lead to a minor increase in mortality/morbidity of hosts or a
minor decrease in production but not expected to threaten the economic viability of
production. Expected to decrease the value of non-commercial criteria but not threaten the
criterion‟s intrinsic value. Effects would generally be reversible.

10


Significant: expected to threaten the economic viability of production through a moderate
increase in mortality/morbidity of hosts, or a moderate decrease in production. Expected to
significantly diminish or threaten the intrinsic value of non-commercial criteria. Effects may
not be reversible.
Major significance: expected to threaten the economic viability through a large increase in
mortality/morbidity of hosts, or a large decrease in production. Expected to severely or
irreversibly damage the intrinsic „value‟ of non-commercial criteria.
The estimates of the magnitude of the potential consequences over the four geographic levels
were translated into a qualitative impact score (A–G)2 using Table 2.33. For example, a
consequence with a magnitude of „significant‟ at the „district‟ level will have a consequence
impact score of D.

Table 2.3 Decision rules for determining the consequence impact score based on
the magnitude of consequences at four geographic scales

Geographic scale
Local District Region Nation
Indiscernible A A A A
Magnitude

Minor significance B C D E
Significant C D E F
Major significance D E F G

The overall consequence for each pest is achieved by combining the qualitative impact scores
(A–G) for each direct and indirect consequence using a series of decision rules (Table 2.4).
These rules are mutually exclusive, and are assessed in numerical order until one applies.

2
In earlier qualitative IRAs, the scale for the impact scores went from A to F and did not explicitly allow for the rating
„indiscernible‟ at all four levels. This combination might be applicable for some criteria. In this report, the impact scale of A-
F has changed to become B-G and a new lowest category A („indiscernible‟ at all four levels) was added. The rules for
combining impacts in Table 2.4 were adjusted accordingly.
3
The decision rules for determining the consequence impact score are presented in a simpler form in Table 2.3 from earlier
IRAs, to make the table easier to use. The outcome of the decision rules is the same as the previous table and makes no
difference to the final impact score.

11


Table 2.4 Decision rules for determining the overall consequence rating for each
pest

Rule The impact scores for consequences of direct and indirect criteria Overall consequence rating

1 Any criterion has an impact of ‘G’; or Extreme
more than one criterion has an impact of ‘F’; or
a single criterion has an impact of ‘F’ and each remaining criterion an ‘E’.

2 A single criterion has an impact of ‘F’; or High
all criteria have an impact of ‘E’.

3 One or more criteria have an impact of ‘E’; or Moderate
all criteria have an impact of ‘D’.

4 One or more criteria have an impact of ‘D’; or Low
all criteria have an impact of ‘C’.

5 One or more criteria have an impact of ‘C’; or Very Low
all criteria have an impact of ‘B’.

6 One or more but not all criteria have an impact of ‘B’, and Negligible
all remaining criteria have an impact of ‘A’.

2.2.4 Estimation of the unrestricted risk
Once the above assessments are completed, the unrestricted risk can be determined for each
pest or groups of pests. This is determined by using a risk estimation matrix (Table 2.5) to
combine the estimates of the probability of entry, establishment and spread and the overall
consequences of pest establishment and spread. Therefore, risk is the product of likelihood
and consequence.
When interpreting the risk estimation matrix, note the descriptors for each axis are similar
(e.g. low, moderate, high) but the vertical axis refers to likelihood and the horizontal axis
refers to consequences. Accordingly, a „low‟ likelihood combined with „high‟ consequences,
is not the same as a „high‟ likelihood combined with „low‟ consequences – the matrix is not
symmetrical. For example, the former combination would give an unrestricted risk rating of
„moderate‟, whereas, the latter would be rated as a „low‟ unrestricted risk.
Table 2.5 Risk estimation matrix
Likelihood of pest entry, establishment

High Negligible Very low risk Low risk Moderate risk High risk Extreme risk
risk
Moderate Negligible Very low risk Low risk Moderate risk High risk Extreme risk
risk

Low Negligible Negligible Very low risk Low risk Moderate risk High risk
risk risk

Very low Negligible Negligible Negligible Very low risk Low risk Moderate risk
risk risk risk

Extremely Negligible Negligible Negligible Negligible Very low risk Low risk
and spread

low risk risk risk risk

Negligible Negligible Negligible Negligible Negligible Negligible Very low risk
risk risk risk risk risk

Negligible Very low Low Moderate High Extreme

Consequences of pest entry, establishment and spread

12


2.2.5
The SPS Agreement defines the concept of an „appropriate level of sanitary or phytosanitary
protection (ALOP)‟ as the level of protection deemed appropriate by the WTO Member
establishing a sanitary or phytosanitary measure to protect human, animal or plant life or
health within its territory.
Like many other countries, Australia expresses its ALOP in qualitative terms. Australia‟s
ALOP, which reflects community expectations through government policy, is currently
expressed as providing a high level of sanitary or phytosanitary protection aimed at reducing
risk to a very low level, but not to zero. The band of cells in Table 2.5 marked „very low risk‟
represents Australia‟s ALOP.

2.3 Stage 3: Pest risk management
Pest risk management describes the process of identifying and implementing phytosanitary
measures to manage risks to achieve Australia's ALOP, while ensuring that any negative
effects on trade are minimised.
The conclusions from pest risk assessments are used to decide whether risk management is
required and if so, the appropriate measures to be used. Where the unrestricted risk estimate
exceeds Australia‟s ALOP, risk management measures are required to reduce this risk to a
very low level. The guiding principle for risk management is to manage risk to achieve
Australia‟s ALOP. The effectiveness of any proposed phytosanitary measure (or combination
of measures) is evaluated, using the same approach as used to evaluate the unrestricted risk, to
ensure it reduces the restricted risk for the relevant pest or pests to meet Australia‟s ALOP.
ISPM 11 (FAO 2004) provides details on the identification and selection of appropriate risk
management options and notes that the choice of measures should be based on their
effectiveness in reducing the probability of entry of the pest.
Examples given of measures commonly applied to traded commodities include:
options for consignments – e.g., inspection or testing for freedom from pests,
prohibition of parts of the host, a pre-entry or post-entry quarantine system, specified
conditions on preparation of the consignment, specified treatment of the consignment,
restrictions on end-use, distribution and periods of entry of the commodity
options preventing or reducing infestation in the crop – e.g., treatment of the crop,
restriction on the composition of a consignment so it is composed of plants belonging
to resistant or less susceptible species, harvesting of plants at a certain age or specified
time of the year, production in a certification scheme
options ensuring that the area, place or site of production or crop is free from the pest
– e.g., pest-free area, pest-free place of production or pest-free production site
options for other types of pathways – e.g., consider natural spread, measures for
human travellers and their baggage, cleaning or disinfestation of contaminated
machinery
options within the importing country – e.g., surveillance and eradication programs
prohibition of commodities – if no satisfactory measure can be found

13


Risk management measures are identified for each quarantine pest where the risk exceeds
Australia‟s ALOP. These are presented in the „Pest Risk Management‟ section of this report.

14

Draft Report: Review of fresh apple fruit from New Zealand Commercial production practices

3 New Zealand’s commercial production practices for apples

This chapter provides information on the pre-harvest, harvest and post-harvest practices of the
New Zealand apple industry for the production of fresh apple fruit for export. The practices
described in this section are considered to be standard practice for all export apple production
and Biosecurity Australia has taken them into consideration when estimating the unrestricted
risk of pests that may be associated with the import of this commodity.
While general information on New Zealand apple production is provided, the focus is on
those practices relevant to the three pests that this review considers: fire blight, European
canker, and apple leaf curling midge.

Figure 3-1 Map of New Zealand4

3.1 Climate in production areas5
Apple production in New Zealand occurs on both the north and south islands, with two main
production districts accounting for nearly 90 per cent of the total plantings. The first and most
significant of the production districts is Hawke‟s Bay, which includes the adjacent cities of

4
Map from http://www.newzealand.com/travel/images/maps/bloggers/newzealandmap_large_en.jpg
5
Climate descriptions are taken from http://www.niwa.co.nz/education-and-training/schools/resources/climate/overview

15


Napier and Hastings. Hawke‟s Bay is located on the east coast of the north island at a latitude
of 39.5°S, placing it slightly south of Melbourne, Victoria.
The second major production district is around Nelson located at the northern end of New
Zealand‟s south island at a latitude of 41.3°S. Nelson is at a latitude similar to Devonport,
Tasmania.
The third production district of note is Central Otago, located in the southern central region of
New Zealand‟s south island and includes the cities of Alexandra, Clyde, Cromwell and
Queenstown. At a latitude of around 45°S, the district is slightly further south than the
southernmost parts of Tasmania.
New Zealand has a wide range of climatic conditions, from warm subtropical conditions in
the northernmost areas of the north island, to cool temperate conditions at the southernmost
areas of the south island. Severe alpine conditions also occur in the mountainous areas of the
southern island.
The two largest production areas, Hawke‟s Bay and Nelson are located close to the coast and
therefore do not experience extreme temperatures, the proximity of the Southern Ocean
moderating the climatic conditions. Hawke‟s Bay is sheltered by mountains to the west and
experiences warm, dry summers. Summer daytime temperatures reach 28°C, but rarely exceed
32°C. Winter is mild to cool.
Nelson has similar summer conditions, also being dry, though with temperatures reaching
26°C and only occasionally exceeding 30°C. Winters are colder than in Hawke‟s Bay, but are
still regarded as mild.
In contrast, the Central Otago region, being further inland to the other regions experiences
more severe winter conditions. Winter temperatures are very cold with frequent frosts and
with daytime temperatures rarely exceeding 11°C. The Central Otago region receives only
around one-third the total rainfall experienced in Nelson and Hawke‟s Bay.
The graphs presented below provide an indication of average daily maximum and minimum
temperatures, as well as average rainfall for four sites in New Zealand where apples are
grown. While only a small proportion of export apples are grown there, the Waikato district,
represented by Hamilton, is included because it provides an indication of the climatic
conditions in the north of the island. Substantial research into apple production has also been
undertaken there. The graphs indicate the similar summer temperatures in all of these regions,
though also highlight the comparatively cold winters experienced in the Central Otago region.
The annual rainfall, based on a 30-year average is 360mm for the Central Otago, 803mm for
Hawke‟s Bay, 970mm for Nelson, and 1190mm for the Waikato.
For comparison, the annual rainfall based on a 30-year average in major apple production
regions in Australia is 779mm for Stanthorpe, 967mm for Batlow, 454mm for Goulburn
Valley, 1008mm for the Adelaide hills, 887mm for Huon Valley and 899mm for Donnybrook.
Graphs are also presented for major apple production regions in Australia (Figures 3-2 to 3-
11).

16


Figure 3-2 Maximum and minimum Figure 3-4 Maximum and minimum
temperatures and mean monthly rainfall temperatures and mean monthly rainfall
for Hamilton (Waikato) 1971–20006 for Nelson 1971–20006

Figure 3-5 Maximum and minimum
temperatures and mean monthly rainfall
for Alexandra (Central Otago) 1971–
for Napier (Hawke’s Bay) 1971–20006
20006

6
Climate data from National Institute of Water and
Atmospheric Research. http://www.niwa.co.nz/education-
and-training/schools/resources/climate

17


for Stanthorpe, Qld. 1981–20107 for Tatura, Vic. (Goulburn Valley) 1981–
20107

for Batlow8, NSW 1971–20007 for Geeveson, Tas. (Huon Valley) 1981–
20107

7
Climate data from Bureau of Meteorology
http://www.bom.gov.au/climate/data/index.shtml?bookm
ark=200
8
Batlow data taken from Tumbarumba weather station

18


for Lenswood, SA (Adelaide Hills)
1981–20107

for Donnybrook WA 1981–20107

19


3.2 Pre-harvest

3.2.1 Orchard layout
For registration and trace back purposes, apple orchards can be divided into a number of
smaller units. These include the orchard, the production site and variety/orchard blocks.
An orchard is defined as the total planting in a single location and has its boundary defined by
the registered owner/grower. An orchard is covered by a single Registered Property
Identification Number (RPIN). Depending on size, orchards may be divided into a number of
production sites. Division into production sites are for administrative and pest management
purposes.
Most orchards, if not all, grow a number of different varieties of apples and may have
multiple plantings of a particular variety in different areas within the orchard. Within an
orchard, each continuous planting of a single variety of apple is defined as an orchard block or
variety block. Fruit being packed in a packing house, fruit can be traced back to a specific
orchard block and in some cases specific rows within that orchard block.

Boundary of an
orchard,
covered by a
single RPIN

Boundary of a
production site

Each colour represents a planting
of a single apple variety. There are
6 defined orchard blocks within
this production site.

Figure 3-12 Representation of divisions within an orchard

3.2.2 Cultivars
In 2010 there was 9 061 hectares of apple and pear production in New Zealand, with 60 per
cent of this in the Hawke‟s Bay district and 28 per cent in the Nelson district (Pipfruit NZ
2010). The Central Otago region is also noted for apple production, but includes only 4 per

20


cent of New Zealand‟s total number of hectares under production. This is a slight increase
over the total planted area of 8 896 hectares in 2009.
While a range of apple varieties are available in New Zealand, the varieties with the greatest
planted area in 2010 were Royal Gala (27 per cent), Braeburn (21 per cent), Jazz™ (11 per
cent), and Fuji (11 per cent). Other varieties include Cox, Cripps Pink (Pink Lady), Granny
Smith, Pacific Beauty™, Pacific Queen™, and Pacific Rose™ (Pipfruit NZ 2010). Pear
orchards make up only a relatively small proportion of the total pipfruit production, with 431
hectares reported in 2010.

3.2.3 Cultivation practices
Commercial apple plantings in New Zealand are typically grown on grafted rootstock. The
use of grafted rootstocks, particularly clonal rootstocks, is preferred as it allows for control
over tree size, ripening of fruit and may also confer resistance to certain pests and diseases.
While a range of rootstocks are available, the New Zealand industry indicated that the M9
variety is most commonly used for new plantings (BSG 2011). M9 rootstock produces a small
tree around 3–4 metres high which bears large fruit, comes into commercial production within
three years from planting and is considered fully grown in five to six years. Plantings of apple
trees on M9 rootstock have a between tree spacing of one metre and a between row spacing of
three metres. M9 rootstock or another dwarfing variety is preferred due to the moderate
growth habit and shorter trees which assist with pest management, spray application and
harvesting.
Canopy management varies between orchards, dependent largely on age, though most trees
are pruned and trained to keep most growth parallel to the row. Branches are trained into a
mostly horizontal position to encourage fruit bearing over vegetative growth. While the
canopies are open, reflective sheets on the orchard floor are used for up to two weeks prior to
harvest to promote full fruit colouring.
Orchard irrigation is most commonly delivered by drip irrigation (BSG 2011). Overhead
sprinklers are not commonly used in New Zealand apple orchards, their use being mostly
limited in use to the Central Otago Region. Use of overhead irrigation in other regions is
avoided due to the potential to result in problems with apple scab (caused by Venturia
inaequalis) early in the season (MAFNZ 2011). Where used, overhead sprinklers can assist in
managing the potential for frost damage.
According to the Pipfruit Industry Statistical Annual the 2009 export production was 302 075
tonnes from 8 484 hectares, or an export yield of around 35 tonnes per hectare across all
varieties of apples. In addition to this there was an export yield of 5 421 tonnes of pears from
412 hectares (Pipfruit NZ 2010). Export yield does not include fruit for the domestic market,
or for processing and juicing facilities. The World Apple and Pear Association reported a total
2009 New Zealand production of 466 000 tonnes (WAPA 2010), or around 54 tonnes per
hectare. However, these figures are inferred values from export volumes and average pack-out
(MAFNZ 2011). Significantly higher yields are reported in a number of the orchards visited in
March 2011, with yields of 75–100 tonnes per hectare expected from recently established
orchards (BSG 2011).

3.2.4 Pest management
In 1996, the Integrated Fruit Production program was first introduced for New Zealand
pipfruit. In subsequent years it was rapidly adopted by the apple and pear industry with 100

21


per cent adoption for export grown fruit reported by 2001 (Wiltshire 2003). The IFP program
has been further developed with the Apple Futures program (Pipfruit NZ 2008a) with an
emphasis on managing chemical residues to the lowest levels possible. In 2010, 87 per cent of
total planted area was managed under IFP (including Apple Futures), 11 per cent as organic;
while only 2 per cent of the total planted area produced solely for the domestic market
(Pipfruit NZ 2010).
While the IFP program is proprietary information that covers all aspects of pipfruit production
in New Zealand, it contains information that is relevant to the management of the pests and
diseases considered in this review. Those key aspects of the IFP program are outlined below.

Fire blight management
In New Zealand, management of fire blight focuses on reducing inoculum levels through
cultural practices in the orchard and use of chemical or biological controls during the most
susceptible infection period, blossom time. The decision to apply chemical or biological
control measures is supported by a computer model based warning system that considers
temperatures, wetness periods and fire blight prevalence in the surrounding area. The model
operated by Pipfruit New Zealand is available to registered growers through the Pipfruit New
Zealand website and is derived from the Maryblyt and Cougarblyt models developed in the
USA and adapted for New Zealand conditions.
The risk period for infection by E. amylovora in New Zealand is during blossom. Unlike some
other regions of the world, New Zealand‟s apple growing areas do not experience severe
frosts later in the season that can cause cracking of branches that provide opportunity for
secondary infections. The risk factors for fire blight infections are:
Open flowers are present with stigmas and petals intact
110 degree hours greater than 18.3°C have accumulated after the first bloom
Dew or at least 0.25mm or rain on the day of infection has occurred; or at least 3mm
rain on the previous day
An average daily temperature of 15.6°C
When considered in light of potential inoculum levels, fire blight symptoms in orchard, in
adjacent orchards, and in the district, growers are provided guidance on whether sprays are
required. The final decision on whether control sprays will be applied is made by orchard
managers.
For chemical control, the antibiotic streptomycin is registered for use. Sprays are applied
during high risk climatic conditions when blossoms are present. Orchard managers aim to
apply the spray 12–24 hours prior to a rain event to allow time for it to dry and also ensure the
application is made late in the day as it is degraded by ultraviolet light. According to orchard
managers streptomycin use is limited due to chemical residue restrictions imposed by markets
such as Europe (BSG 2011).
Alternatively, the biological control Pantoea agglomerans (synonym Erwinia herbicola)
(known as Blossom Bless) is available to orchard managers. Blossom Bless is a commonly
occurring bacterium that can be sprayed onto susceptible tissue where it competes for
infection sites, reducing the opportunity for E. amylovora to infect the tissue. Usage of
Blossom Bless is varied, though multiple applications are common. Depending on the risk
posed by fire blight, Blossom Bless may be applied at 10 per cent, 50 per cent, and 80 per cent
blossom, the effect being cumulative.

22


Finally, bud break promoters are used in some orchards to accelerate the budding process and
reduce the period of time that susceptible host tissue is present on the tree. The mild
conditions in New Zealand can result in blooms being present on trees for a number of weeks.
Budding promoters can reduce this period to around one week.
Frequent inspection of orchards is recommended by the Pipfruit IFP manual, which is
consistent with recommendations made around the world. Inspections are targeted to find
distinctive blight symptoms or “shepherd‟s crooks” on terminal shoots. It is recommended
that symptomatic shoots or branches are pruned out, with the cut to be made 45–60cm below
the symptoms. This should be augmented with removal of any symptomatic tissues during
winter pruning, along with removal or monitoring of alternative host material in the area
surrounding the orchard.
Overhead irrigation is not recommended and is rarely used outside the Central Otago district.
When used, overhead sprinklers are a management tool for frost protection, therefore being
used when conditions are unfavourable for E. amylovora infection.
Data from the 2009–10 season indicates that of all registered apple production blocks in New
Zealand, 3.3 per cent received at least one streptomycin spray and 5.0 per cent received at
least one Blossom Bless spray. Note, however, that these may include blocks that utilised both
control measures and that sprays are applied based on estimates of potential infection not
actual infections.
During a verification visit in March 2011, officials from the Biosecurity Services Group had
the opportunity to discuss the recommendations of the Pipfruit IFP program with orchard
owners, orchard managers, and pest control consultants in both the Hawke‟s Bay and Nelson
districts. The only variation to the measures as described above was the pruning of
symptomatic tissue. Some orchard managers stated their experience that immediate pruning of
„shepherd‟s crooks‟ was not necessary in their orchards where the incidence of symptomatic
tissue was extremely low (BSG 2011). Those orchards were observed to have only the
occasional fire blight strike and were producing high yields of commercial quality fruit.
In considering those orchards where either a low incidence of fire blight symptoms were
observed or which had a history of some fire blight infection, orchard managers described a
“severe” incidence as an average of around one strike per tree. During the verification visit
some trees were observed as having multiple strikes, though the adjacent trees were seen to
have either one strike or no strikes. No bacterial oozes were observed on any of the blighted
limbs.

European canker management
According to the Pipfruit IFP manual, European canker is only considered a problem in high
rainfall areas such as Auckland and Waikato. It may occasionally also pose problems in
Gisborne and Nelson. Spread of European canker is attributed to introduced nursery stock as
well as localised spread from neighbouring infected trees.
Control for European canker focuses on removal of any visible cankers during the winter
pruning period when the symptoms are most easily observed. Removal is through pruning,
ensuring that cuts are at least 10cm below the lowest observed canker to ensure that any
infected wood is removed. Pruning cuts are then recommended to be covered with a sealing
paint that includes an antifungal agent, carbendazim. It is then recommended that any infected
material be removed from the orchard and burned.

23


Antifungal chemicals used for other more economically concerning pathogens are also
considered effective against European canker and contribute to the general control in orchard.
These include sprays to manage black spot (Venturia inaequalis, apple scab) and powdery
mildew (Podosphaera sp.).
During site visits in March 2011, orchard managers in the Nelson region reported that
European canker was known from the region, but uncommon in orchards. For example, only a
single tree on a 40 hectare property had been identified with symptoms during the last 5 years
and the infection was traced back to the introduced nursery stock. At a second orchard in
Nelson, it was reported that symptoms could be found if one were to look hard enough for
long enough.

Apple leaf curling midge management
Under the IFP program, specific monitoring and control programs for apple leaf curling midge
are only recommended for blocks of young trees and trees that have recently been grafted.
Both of these situations can provide the young, vigorous growth that adult apple leaf curling
midge lay eggs onto and on which the developing larvae feed.

For orchards that have recently been planted, or newly grafted, sampling of 40 actively
growing shoots from late November through to early December is recommended, with foliar
application of diazinon if more than 50 per cent of the shoots are infested with eggs.

Monitoring should subsequently occur in January and February, also sampling 40 leaves with
the action threshold again being reached of more than 50 per cent of the sampled leaves are
infested with eggs.

In blocks of mature trees that are producing fruit, the parasitoid Platygaster demades
(Hymenoptera: Platygastridae) and predator Sejanus albisignata (Hemiptera: Miridae) are
considered effective in controlling apple leaf curling midge, provided that broad-spectrum
insecticides have not been applied. Further, while insecticides such as diazinon are
recommended as a foliar spray, application precludes fruit from entering a number of export
markets due to chemical residue requirements. The IFP program does not recommend any
specific monitoring program for apple leaf curling midge in producing blocks with mature
trees. During the March 2011 visit, orchard managers explained that apple leaf curling midge
is not an issue in mature trees as they don‟t produce the required fresh growth for apple leaf
curling midge throughout the season. Some orchards are now monitoring soil moisture to
minimise vegetative growth during the season to maximise fruit production and quality.

3.3 Harvesting and handling procedures
The apple harvest season in New Zealand can commence from early February with varieties
like Pacific Beauty™ and Royal Gala. The season extends until mid-late April with varieties
like Cripps Pink (Pink Lady), Braeburn, and Fuji (Pipfruit NZ 2008c).
Prior to harvest, maturity is monitored by sampling twenty fruit per variety per block from the
orchard and subjecting them to a series of tests: starch pattern index; background and
foreground colour; fruit penetrometer; and soluble sugars (brix). The results of these
laboratory tests indicate that fruit is either ready for harvest, or recommended to be re-tested
after a nominated period of time (BSG 2011). This testing establishes whether the conversion
of fruit starches to sugars has commenced, whether fruit sugars exceed a certain level, and

24


whether fruit colour has developed sufficiently to meet market specifications. Harvesting will
not commence until the maturity levels have reached a minimum level.
Due to the prolonged blossom period for apples in New Zealand, fruit can mature over a
period of time and when harvest commences, it is common for a first pick to target only those
fruit showing higher colour levels and therefore the appropriate level of maturity. Other fruit
will be left to finish ripening and „colouring up‟ for another 4–7 days before a second pick is
undertaken. This process may be repeated as and if necessary and some orchards this season
where onto their fourth pick.
Apples are hand-picked, with some assistance from either portable ladders or motorised
„cherry pickers‟ to reach higher branches. In-field, pickers grade out fruit with obvious signs
of unacceptable damage, including cuts, bruises and tractor damage. Further, evidence of
specific pests can be recorded on field bins to alert packing houses to any pest issues that may
limit access to specific markets.
After harvesting into picker bags, fruit is transferred to field bins that hold approximately
400kg of fruit. Bins are consolidated at the orchard before being transported to the packing
house. Each bin has an attached record that identifies the supplier, grower, orchard, variety,
orchard block and picker that facilitates trace-back.

3.4 Post-harvest

3.4.1 Packing house
Apples will not be accepted by packinghouses unless spray diary clearance has been received
from the Independent Verification Agency (IVA). At the point of receival, apples at all
packing houses are sampled for maturity. As for pre-harvest testing, this includes starch
pattern index, background and foreground colour, fruit penetrometer, and soluble sugars
(brix). At this point, maturity of fruit is further defined into storage grades depending on how
far fruit starch mobilisation has progressed.
The important test for establishing fruit maturity is the starch pattern index test. For the test, a
random sample of apple fruit from bins are taken, sliced in half and the exposed apple flesh
sprayed with an iodine solution. The presence of starch is indicated by a blue–black colour on
the fruit where iodine has reacted with starches. Unripe fruit, where high levels of starch are
present, develop an even dark colour across the entire fruit surface. As fruit reach maturity,
starches are converted into sugars and instead of an even dark colour a distinctive pattern will
develop on the cut surface of the fruit (Reid et al. 1982). As maturity progresses, the amount
of colour reduces.
Fruit may then be processed immediately or sent into cold store for later processing,
depending on fruit volumes and market demands. Having already tested maturity and colour
of fruit, packing houses have a clear indication of market suitability of fruit prior to packing.
The first stage of fruit processing is the water dump where fruit are removed from bins into
water which is circulated to move fruit towards the packing line. The second step is the
movement of fruit into the high pressure washing stage. Here fruit move onto beds of brushed
rollers that continually move fruit while they are subjected to a high pressure spray, the
combined brushing and spraying removing contaminants and leaf material. During the March
2011 verification visit, it was observed that each apple was subject to the high pressure spray
for between 30 and 60 seconds whilst being continually turned due to the counter rotating

25


rollers. This exposed all surfaces of the fruit to the high pressure spray. Any contaminating
material was seen to be blown past the brushed rollers, away from the fruit.
Subsequently, apples are then passed back into a water bath (which is separate from the dump
tank), or directly onto rollers and conveyors that take them into the packing house.
All packing houses observed during the verification visit utilised Nylate® as a post harvest
sanitiser. In water, Nylate® breaks down to two biocidal agents, hypochlorus acid and
hypobromus acid. In some cases, the Nylate® was applied in the dump tank, in other cases
after the high pressure washing. In all cases, application of Nylate® was monitored,
automatically or at specific times, for both concentration and pH.
Grading and sorting of apples was observed to follow a number of different practices. In some
cases, the first stage was hand sorting of apples as they entered the packing house to remove
apples with damage or other symptoms that would make them not suitable for market. Fruit
was then directed to electro-optical grading equipment to determine fruit colour, size and
weight before being directed to specific packing lines.
Alternatively, some packing houses have more advanced grading equipment that allows both
grading and defect detection. In that case, removal of damaged apples still occurred prior to
grading, though less staff were involved as the machinery was responsible for detecting minor
defects that would otherwise have been removed by packing house staff.
After grading, all packing houses were observed to utilise a conveyor system that carried
apples to the appropriate packing line where apples were “dropped” onto the appropriate
packer‟s table.
Apples that do not meet specification were consigned to either processing/juicing or to the
domestic market. Those apples directed to the domestic market were observed to still be free
of damage and rots, but were affected by symptoms of black spot (apple scab), russetting, or
other quality parameters.
The most common form of packaging for apples is the 18kg carton which contains four or five
layers of apples each on top of a moulded cardboard insert. The number of apples and exact
weight depends on the size being packed, with between 95 and 150 apples being common.
Each carton includes a lid. Also observed were single layer cardboard boxes, without lid, each
containing around 40 fruit and weighting 6.5kg. Both of these forms of packaging are
palletised for transport.
Packaging of apples in bulk bins, while not considered a large part of the market, does occur.
Bulk bins are utilised where receiving markets specifically prefer to re-pack on arrival, with
packing into small “clamshells” each with six fruit being an example of such packaging (BSG
2011). For the 2009–10 season, only 0.19 per cent of fruit was exported in bulk bins, and only
to the UK and France (MAFNZ 2011).
During the packing process, phytosanitary and quality control inspections were undertaken by
trained staff and monitored by an Independent Verification Agency. In some cases packing
machinery was configured to randomly drop apples, at a specified rate and including all sizes,
for quality control and phytosanitary inspection on a separate line. In other lines, these
samples were taken as random boxes of packed apples. Any detection of pests or grading
issues were recorded, and any symptoms of possible infestation examined further through
fruit cutting.

26


Any outcomes from the quality control and phytosanitary inspections apply to the entire
processing lot of apples on the packing line at that point in time.

3.4.2 Storage
After packing, palletised boxes of apples were moved to cold stores pending the building of
an export consignment and subsequent export. As described by packing house staff, cold
storage of boxed apples rarely exceed a few weeks.
Primarily, long term cold storage of apples occurs pre-processing and packing, with apples
being stored in the bins they were harvested into. However, in some circumstances and for
some markets storage in packed 18kg cartons may occur for up to a three month period.
Apples stored for extended period of time are reinspected and/or tested for flesh firmness,
sugar levels and any evidence of post-harvest degradation to ensure that the fruit still meets
phytosanitary standards of the importing country and the quality standards expected by the
importer (MAFNZ 2011).
Finally, some extended storage of pre-graded apples occurs for specific markets. In such cases
apples that are of a specific size or colour to suit a particular market will be stored in bulk bins
at the end of a packing line. The bins are then returned to cold storage with the packing house
having knowledge of the exact size and quality. When required for market, such fruit is then
returned to the packing line for packing into boxes. In effect this is a pre-sizing operation,
modified to suit the packing lines in specific export packing facilities.

3.4.3 Export procedures
As export phytosanitary inspections are typically conducted as part of the packing house
processes, apples are ready for export as soon as packed. Computer records determine which
market any consignment is eligible for and are also the basis for phytosanitary certification by
the New Zealand Ministry of Agriculture and Forestry.
In some cases an end point inspection will be conducted on a consignment rather than as an
“in-line” process as part of the packing line process. In those cases the phytosanitary
inspection required by the importing country is conducted by consignment by grower lot.

3.5 Production and export statistics
In the 2009 season, New Zealand is reported to have a total apple production of 466 000
tonnes (WAPA 2010). Of this, the Pipfruit Industry Statistical Annual 2009 reported a 2009
export apple production of 302 705 tonnes, an approximately 16 per cent increase over the
2008 season (Pipfruit NZ 2010). The remainder, or around 35% of the crop, was available for
domestic consumption or processing.
New Zealand apple producers are heavily export focussed. Important markets include the
United Kingdom, the United States of America, the Netherlands, Belgium, Taiwan, and Hong
Kong. Each of those markets imported over 10 000 tonnes of New Zealand apples in 2009
(Pipfruit NZ 2010).
Considered by growing region, approximately 66 per cent of the export fruit came from the
Hawke‟s Bay district, 28 per cent from the Nelson district, and 3 per cent from the Otago
district, these figures corresponding closely to the acreages in these regions.

27


Consistent with the planted acreage per variety, Royal Gala and Braeburn are exported in the
most volume, with Royal Gala having the greatest export production in the Hawke‟s Bay
district and Braeburn in the Nelson district. Fuji and Jazz are the next two varieties exported
in the greatest volume (Table 3.1). Individually, other varieties of apples each make up less
than 5 per cent of the total export volume.

Table 3.1 Export volume and percentages of each variety of fruit for exports from
New Zealands three main apple production regions (Pipfruit NZ 2010)
Hawke’s Bay Nelson Central Otago

Braeburn 29.3% 41.3% 17.0%

Fuji 11.8% 2.8% 7.1%

Jazz 3.8% 14.3% 5.4%

Royal Gala 39.1% 27.2% 26.4%

Total apple exports (tonnes) 202 138 80 485 10 081

3.5.1 Export season
New Zealand‟s primary export markets are in the Northern Hemisphere and include the
United States of America, the Netherlands, Belgium, Germany, Taiwan, Hong Kong,
Thailand, and the United Arab Emirates (Pipfruit NZ 2010). New Zealand fruit is supplied
into these markets to meet counter seasonal demand.
Apple exports begin almost immediately with the first harvest of apples in February and
continue in significant volumes until around July (MAFNZ 2011). Apples can be stored for
long periods and growers and packers have the option to hold apples in cold store
immediately after harvest, or after packing processes until required on the market. The start of
the season is principally defined by the availability of the New Zealand harvest, while the end
of the season is determined by the first availability of apple produced in the northern
hemisphere.
While most exports to the Australian market would likely occur between late February and
late August, it is possible that New Zealand apples could arrive in Australia all year round.
However, it is understood that the majority of large cool store facilities in New Zealand do not
operate all year round, with most produce having been exported prior to the southern
hemisphere‟s spring (BSG 2011). Ultimately, economic factors and market access
opportunities will determine the market window for New Zealand apple exports to Australia.
This review considers the bulk of exports from February until August, with only lower
volumes potentially entering Australia after August.

28

Draft Report: Review of fresh apple fruit from New Zealand Pest risk assessments

4 Pest risk assessments for quarantine pests

Pest risk assessments are presented in this section for the three pests considered by this
review: fire blight, European canker and apple leaf curling midge. Pest risk assessment has
been undertaken to determine whether the risk posed by a pest exceeds Australia‟s ALOP and
thus whether phytosanitary measures are required to manage the risk.
According to the 2006 Final Import Risk Analysis Report for Apples from New Zealand (BA
2006), fire blight, European canker, and apple leaf curling midge are all absent from Australia
and have the potential to establish, spread, and cause economic consequences. These three
pests therefore meet the definition of a quarantine pest. Further, all three of these pests are
present in New Zealand and have the potential to be associated with imported apple fruit. Pest
risk assessment for these three pests is therefore justified. The entries from Part C of the 2006
Final Import Risk Analysis Report for Apples from New Zealand that determined these three
organisms as potential quarantine pests has been included in Appendix A of this review.
All three of these pests are considered to be absent from all of Australia. Therefore, these
assessments are applicable to all of Australia.

Table 4.1 Quarantine pests for apple fruit from New Zealand considered in this risk
analysis

Pest Common name
DOMAIN BACTERIA
Fire blight (Enterobacteriales: Enterobacteriaceae)
Erwinia amylovora (Burrill 1882) Winslow et al. 1920 emend.
Fire blight
Hauben et al. 1998
DOMAIN EUKARYA
Apple leaf curling midge (Diptera: Cecidomyiidae)
Dasineura mali (Kieffer 1904) Apple leaf curling midge
European canker (Hypocreales: Nectriaceae)
Neonectria ditissima (Tul. & C. Tul.) Samuels & Rossman European canker

29

Draft Report: Review of fresh apple fruit from New Zealand Fire blight

4.1 Fire blight
Fire blight, caused by the bacterium Erwinia amylovora has been reported from 46 countries
including New Zealand (van der Zwet 2006). Fire blight-like symptoms were detected on
cotoneaster in the Royal Botanic Gardens Melbourne in April 1997, and diagnostic tests
confirmed that the causal organism was E. amylovora (Rodoni et al. 1999). National surveys
conducted for three years following the detection of E. amylovora have confirmed the absence
of the disease in Australia (Rodoni et al. 1999). The mode of introduction of fire blight into
the Royal Botanic Gardens Melbourne is unknown.
Fire blight is the most serious bacterial disease affecting Malus spp. (apple), Pyrus spp. (pear),
Cydonia spp. (quince), Eriobotrya japonica (loquat), and amenity hosts including Crataegus
spp. (hawthorn), Cotoneaster spp. (cotoneaster) and Pyracantha spp. (firethorn).
The pathogen overwinters almost exclusively in the previous season‟s cankers (Beer and
Norelli 1977) and the primary inoculum is produced mostly as bacterial ooze on the surface of
cankers. The disease cycle begins when cankers on infected hosts ooze bacteria (Brooks
1926), but non-oozing cankers can also harbour bacteria (Miller and Schroth 1972). Primary
and secondary inocula can also originate from wild, amenity, household and garden plants.
The pathogen enters the host through natural openings (for example, stomata or nectaries) or
wounds (such as those caused by pruning or hail). Insects, wind, rain and pruning tools are the
main methods of spreading primary inoculum of E. amylovora. Bees are the primary agents
for secondary spread of inoculum from infested flowers to newly opened ones (Thomson
2000).
Erwinia amylovora infects flowers, young leaves, stems and immature fruits. Flowers are
highly susceptible to infection by E. amylovora (Keil and van der Zwet 1972a), with bacterial
populations occurring almost exclusively on stigmas and reaching 106 to 107 colony forming
units (cfu) per flower (Thomson, 2000). Infection occurs when bacteria, spread by rain or
dew, enters the nectaries. Often the first symptoms, accompanied by ooze, are seen on the
outer surface of the receptacle of fruitlets and the stalks (Beer 1990).
Infection of succulent vegetative tissues often produces a characteristic shepherd‟s-crook
symptom. This is accompanied or followed by a discolouration of the stem and attached
leaves as well as the exudation of ooze. Leaves are rarely infected, but prone to infection after
hail damage (Beer, 1990). Multiplication of E. amylovora could not be demonstrated on leaf
surfaces, and bacteria died within a few hours when exposed to solar radiation or high
humidity levels (Maas Geesteranus and de Vries 1984).
Infected immature fruits differ in appearance depending on when they are infected. Immature
fruit infected with E. amylovora often shrivel and remain attached to trees through winter, but
do not show any signs of oozing. Fruit infected as a result of progressive infection of branches
are less shrivelled and discoloured. Those fruit infected following injury by hail or insects
often develop red, brown or black lesions and may exude ooze (Beer, 1990). Epiphytic
colonisation of the stigmatic surfaces of flowers by E. amylovora may result in bacteria
persisting in low numbers on the dry flower parts subsumed into the calyx-end of the fruit
where they are known to persist for some time (Hale et al. 1987; Sholberg et al. 1988).

4.1.1 Probability of entry
Probability of importation
The likelihood that Erwinia amylovora will arrive in Australia with the trade in fresh apples
for consumption from New Zealand is: MODERATE.

30


Association of the pest with the crop
Erwinia amylovora is known to infect host vegetation including immature fruit (Beer
1990; Norelli et al. 2003).
Fire blight, caused by E. amylovora, is endemic in New Zealand (Cunningham, 1925;
Wilson, 1970; Reid, 1930). The disease is more common in regions on the North Island
(particularly Hawke‟s Bay, where 66 % of export fruit is produced (Pipfruit NZ 2010),
than it is in the cooler areas on the South Island. The lower disease incidence in areas of
the South Island is due mainly to lower temperatures during flowering (Hale and Clark,
1990).
Prior to the implementation of the integrated fruit production program (IFP), the
proportion of designated export areas (DEAs) withdrawn from the export program to
Japan because of the presence of fire blight symptoms caused by E. amylovora, either
within orchards and/or buffer zones (0.5km) after three inspections in the 1994–95
growing season, was 58.8% in Hawke‟s Bay, 63.1% in Nelson, 48.8% in Blenheim and
24.5% in Canterbury. In the 1995–96 season the DEA rejection rate was 56.1% in Nelson
and 16.1% in Blenheim, while during the 1996–97 season, it was 12.2% in Blenheim
(New Zealand Government, 2000). This indicates that fire blight caused by E. amylovora
was widespread in New Zealand during the 1990‟s.
Japan has a significant pome fruit industry (Apple University 2010) and as a result of
negotiations since the Japan-USA apple dispute at the WTO, New Zealand now has access
to the Japan market without specific risk management measures for fire blight (Japan
Apple Regulations 2007).
Since the adoption of the IFP program, symptoms of fire blight have become less common
and growers do not consider it to be an important disease limiting production (BSG 2011).
For example, a key strategy of the IFP program to control fire blight is the application of
sprays to prevent blossom infection based on a predictive model (refer to section 3.2.3 for
more detail on IFP). The number of blocks in New Zealand that applied sprays
(streptomycin or Blossom Bless) to control fire blight infection of blossoms was 9.4%,
10.7%, 11.7% and 8.3% in the seasons of 2006/07, 2007/08, 2008/09 and 2009/10
respectively (BSG 2011). These figures include blocks that sprayed both streptomycin and
Blossom Bless and therefore include some double counting (MAFNZ 2011). In addition,
the application of sprays only indicates that climatic conditions present a high risk for
potential infection events, not actual the actual level of infection.
The predictive model takes account of the presence of fire blight near an orchard.
Therefore, the application of sprays for fire blight provides indirect evidence for the
prevalence of the disease. Even if compliance with the model recommendations is only
50%, any orchard infection rates is likely to be well below the levels recorded in the
1990‟s prior to the implementation of the IFP program.
The incidence of fire blight from year to year mainly depends on spring seasonal
conditions (APPS 2009). Erwinia amylovora requires suitable climatic conditions, warm
temperatures and high humidity, to produce inoculum and cause infection (Brooks 1926;
Beer and Ogenorth 1976; Mills 1955).
The effective management of pests (including fire blight) since the introduction of the IFP
program is likely to have contributed to productivity gains. Since 1997, before the start of
the IFP program, to 2009, productivity (tonnes/ha) of export quality apple varieties has
increased on average by 80% (Wilton 2010). Even for newer varieties, such as Jazz™, that

31


have an extended flowering period and are considered more susceptible to fire blight
(BSG 2011), productivity has more than doubled from 2005 to 2009 (Wilton 2010).
There has been no reported severe outbreak of fire blight since 1998 even though
computer models predict infective events each year in New Zealand as evidenced by the
continued use of sprays to manage fire blight. It is most likely the level of E. amylovora
infection in commercial orchards, as reported from the 1990‟s, is lower as a result of the
full adoption of the IFP program and in particular the targeted management of fire blight
and improved prediction methods.
Association of the pest with the commodity pathway–calyx infestation
Erwinia amylovora is known to infest blossoms and mature fruit (Hale et al. 1987; Norelli
et al. 2003).
The proportion of fruit carrying E. amylovora over a 100-day period from immature
fruitlet stage to harvest, from a severely infected orchard with 75 infections per tree has
been studied using selective media to detect bacteria (Hale et al. 1987). This work, based
on a logistic plot of the data, showed from an initial infestation level of 53% of fruitlets,
by harvest, 3.5% of fruit were infested, a 93% proportional decrease.
Erwinia amylovora predominantly colonise flowers (Thomson, 1986; Thomson, 2000) and
only relatively low bacterial numbers have been recorded on dried remnant flower parts
subsumed into the calyx sinus of mature fruit (Hale et al. 1987; Sholberg et al. 1988;
Temple et al. 2007). All the available literature shows that the highest bacterial population
occurs on the stigma of flowers under suitable environmental conditions. Thereafter the
population of bacteria in remnant flower parts declines as they subsume into the calyx
cavity of fruit. Although it is acknowledged that conditions vary from season to season
and between orchards, the 93% proportional decrease provides a guide to the reduction in
calyx infestation that may be expected as fruit matures.
Hale and Clark (1990) reported calyx infestation in apple fruitlets sampled from a number
of New Zealand orchards with fire blight symptoms, on apple or alternative hosts in the
orchard, averaged 7.4% based on a sample of over 6000 fruitlets. If a 93% decrease in the
level of infestation is applied, the final expected rate of calyx infestation in mature fruit
would be 0.5%. For orchards without fire blight symptoms, no E. amylovora bacteria were
detected from a sample of 4000 fruit (Clark et al. 1993) (Note: Hale and Clark (1990)
report 3200 fruitlets tested, but this was an error). The DNA hybridisation technique used
for these assays was sensitive enough to detect 100 cells of E. amylovora in calyces of
apples (Hale and Clark, 1990).
In a later study, over 60 000 fruitlets were sampled from 10 orchards over four years and
no E. amylovora bacteria could be detected from orchards without fire blight symptoms
(Clark et al. 1993). In one year, fire blight symptoms were detected in three orchards and
0.48% of fruitlets were infested. If the 93% decrease proportional decrease is applied,
0.03% of fruit would likely be infested at harvest.
Previously, it had been reported that 14.7% of fruitlets from a single orchard without fire
blight symptoms at blossom had infested calyces based on information presented in a data
table in Clark et al. (1993). However, the results section of the paper states that the
particular orchard was found to have fire blight symptoms during surveys later in the
season.
In New Zealand E. amylovora has been isolated from calyces of less than 1% of mature
fruit using a direct plating method from a severely infected (75 infections per tree) orchard
(Hale et al. 1987), and 2% of fruit immediately after harvest from orchards with an

32


average level of fire blight symptoms (Hale and Taylor, 1999). This is consistent with the
above data using the 93% proportional decrease.
McManus and Jones (1995) reported the presence of E. amylovora in 75% of calyces of
mature fruit taken from symptomless trees in a severely infected orchard, using a nested
PCR test capable of detecting less than one bacterial cell. These authors also showed that
27% of fruit tested positive using a less-sensitive PCR-dot-blot hybridization test with a
lower detection limit of approximately 20 bacteria. The latter method is less prone to false
positives than nested PCR (McManus and Jones 1995). However, the DNA techniques
used could not distinguish live bacterial cells from dead cells according to the information
provided by McManus (AQIS 1998a). McManus suggested that it is possible that the
DNA of E. amylovora detected was from dead bacteria. Therefore, this data would not
provide an accurate estimation of calyx infestation rates by E. amylovora.
Erwinia amylovora was not isolated by direct plating of washings of the calyx-end or
main portion of fruit (1400) harvested from lightly infected trees (1 to 2 infections per
tree) or fruit (300) harvested from fire blight-free orchards and cool-stored for several
months in New Zealand (Hale et al. 1987).
In other experiments conducted in New Zealand, E. amylovora was not detected at
harvest, either in the calyces or on the surfaces of 173 mature fruit sampled within 5 cm of
inoculum sites approximately four months after artificial inoculation. Although a few
isolates produced slight hybridisation with the DNA probe, none were confirmed as
E. amylovora, based on tests using selective media or PCR (Hale et al. 1996).
Erwinia amylovora was not detected in calyces of 150 mature apple fruit harvested from
orchards without fire blight symptoms in New Zealand. In this study macerated calyx
tissues were assayed using a sensitive PCR technique (Hale and Taylor 1999).
A DNA hybridisation method did not detect E. amylovora in calyces of 750 mature apples
harvested from within 20 cm of inoculated flower clusters, in a season not conducive to
infection or spread of fire blight in New Zealand (Clark et al. 1993).
Based on the data discussed above from the 1980‟s to 1990‟s in New Zealand, which was
prior to the implementation of the IFP program, in the order of 0–3.5%, apples picked
from orchards with fire blight symptoms could be infested with viable bacteria. The
highest values of this range come from apples harvested from severely infested orchards.
In orchards without fire blight symptoms, no bacteria could be detected from large
numbers of fruit sampled from many orchards over several years.
Fruit for export is produced by the industry prescribed IFP program or organic production
methods. Fruit enters export packing houses once compliance with the IFP program spray
recommendations has been confirmed following examination of the growers spray diary
by auditing organisations independent of the industry (MAFNZ 2011).
In West Virginia, USA, E. amylovora was recovered from calyces of 5% of immature fruit
harvested from a healthy orchard, located 30 km from infected orchards but when severe
fire blight symptoms were in the area (van der Zwet et al. 1990). Applying the 93%
proportional reduction to the above 5% figure, 0.4% of mature fruit may contain E.
amylovora in the calyces.
In Ontario, Canada, E. amylovora was not isolated from tissues of the stem-end and calyx-
end of 60 mature fruit harvested from severely infected apple trees (Dueck 1974a).
In British Columbia, Canada, Sholberg et al. (1988) isolated epiphytic E. amylovora
bacteria on naturally contaminated, blemish-free and apparently healthy apple fruit

33


collected at harvest from an orchard severely infected by fire blight from a season
considered exceptional for the disease following hail damage. The apple trees in the
experimental site were either adjacent to or interplanted with pear trees, which were
severely infected by fire blight. The pathogen was isolated using bulked samples of three
fruit, which would have recorded a positive result even if one fruit was contaminated.
Therefore the true infestation rate was between 33–100%. This study did not distinguish
between surface and calyx infested bacteria.
Ceroni et al. (2004) artificially inoculated pear fruit by placing 30µL of a bacterial
suspension (108 cfu mL–1) in the calyx cavity (ca. 3 x 106 cfu) and followed survival in
cold storage. Bacterial numbers in the calyx were detected using PCR (101.8 cfu per calyx
on day 0) decreased exponentially, but small numbers survived up to 101 days. These
numbers were 0.7, 0, 1.5, 0, and 3.7 cfu per calyx respectively, by day 73, 80, 87, 94 and
101.
The bacterial numbers in the calyx of mature fruit under natural conditions would be much
lower than what Ceroni et al. (2004) observed by placing a high dose directly in the calyx
of the harvested fruit. The observation by Ceroni et al. (2004) that longer survival is
possible only in the calyx of pears is in agreement with that of Hale et al. (1987) where, in
the small numbers of apple fruit carrying bacteria at maturity, detections were almost
always in the calyx.
Roberts et al. (1998) reviewed the literature concerning the presence of E. amylovora on
apple fruit in Canada, USA and New Zealand, and provided an average value of 4.9%
infestation for apples from orchards with active fire blight, and an average value of 0.35%
infestation for apples drawn from orchards where there was no consideration of fire blight
status.
A later publication revised this estimate down based on new evidence and clarification or
correction of previously misinterpreted data present in the literature (Roberts and Sawyer
2008). This later work now reports no E. amylovora were detected in apple fruit from
orchards without fire blight symptoms and 1.3% of apple fruit are infested from orchards
with fire blight symptoms. Many apple fruit samples from orchards with symptoms
detected no E. amylovora (Roberts and Sawyer 2008).
More recently, Ordax et al. (2010b) reported no E. amylovora could be detected from 100
apples immediately after harvest from a severely infected fire blight orchard. Sensitive
detection methods were employed that could detect < 1 cfu/ml of calyx extract and would
have detected live or dead bacteria including those in a viable but non-culturable (VBNC)
state.
In the USA, numbers of bacteria on blossoms of apple and pear inoculated with E.
amylovora bacteria decline to very low levels in the calyx of the subsequent mature fruit.
An average of 7 cfu of E. amylovora was recorded from 3.3% of the pear fruit sampled
over two years. In apples, no fire blight could be detected at harvest (Temple et al. 2007).
In a sample of commercial pear orchards, where disease incidence is typically higher than
on apples (Agrios 1997; Paulin 2010a), of the orchards sampled, 27% had fire blight
symptoms and only 1 fruit of 5600 sampled at harvest had E. amylovora with 32 cfu
detected (Temple et al. 2007).
In West Virginia, 5% of immature fruit sampled from a symptomless orchard were
infested and between 1–50 cfu where detected in the calyx (van der Zwet et al. 1990). As
previously shown by many studies, this incidence and level of infestation will decline

34


through time (Hale et al. 1987; Sholberg et al. 1988; Hale and Taylor 1999; van der Zwet
et al. 1990).
In West Virginia USA, van der Zwet et al. (1990) isolated E. amylovora populations
exceeding 1000 cfu per fruit from calyces of mature apples taken from a blight-free
orchard when severe fire blight was present in the area during that year. However, it has
been later confirmed by the senior author of that study that the apples sampled were
immature (WTO 2003).
The highest reported population of E. amylovora on mature apple fruit harvested from an
orchard was recorded in Canada (Sholberg et al. 1988). This work reported the isolation of
an average of 103.3 cfu per mL of viable E. amylovora, from surface and calyx infested
bacteria, from a bulked sample of three harvested mature fruit which were infested
naturally. This infestation equates to approximately 700 cfu per individual infested fruit.
The fruit in this study were sampled from apple trees next to severely infected pear trees
from an exceptional year for fire blight, including hailstorms. This is the highest level of
bacteria recorded from naturally infested mature apple fruit.
Association of the pest with the commodity pathway–infection
McLarty (1924; 1925; 1926) isolated viable E. amylovora from apples that had been
artificially inoculated on the tree when they were immature, allowed to mature and then
held in storage for several months. This demonstrated that E. amylovora could withstand
the physiological changes in fruit as it matured.
Goodman (1954) recovered viable E. amylovora from the tissues directly beneath the skin
of several apples that were retained on the trees until February (late winter). These trees
had been severely affected by fire blight during the previous growing season. The report
also stated that the fruit had moist flesh, indicating that they were not mummified and
therefore supporting the conclusion that they had developed normally.
The recovery of endophytic populations of E. amylovora from developing fruit harvested
(in summer) within 15 cm of blighted shoots but not from 60 cm to 200 cm has been
reported (van der Zwet et al. 1990). These authors also recovered viable E. amylovora
from internal tissues of one maturing apple fruit out of a sample of 160 harvested in July
and August (summer) from apparently symptomless trees of four cultivars.
When mature apples were artificially inoculated with E. amylovora, the bacterium
dispersed into the fruit pulp with a concomitant increase in the bacterial population, at
room temperature, two weeks after inoculation, without producing any fire blight
symptoms. However, the pathogen population did not change during further storage over a
period of five weeks (Jock et al. 2005).
Azegami et al. (2006) experimentally demonstrated systemic movement from the stem
into fruit. These authors examined the invasion and colonization of mature apple fruit by
depositing E. amylovora inoculum concentrations, ranging from 5–10μl drops in most
instances at 104–107 cfu/ml, on cut surfaces of pedicels of fruit, wounds on the shoulder
and the calyx of fruit, fruit bearing twigs with attached fruit and cut fruit flesh (mesocarp).
The authors showed that under these conditions the pathogen can invade mature and
immature apple fruit. It was shown to spread vertically and horizontally and colonise
along vascular bundles, increasing its population. It was reported to spread up to the calyx
end and the flesh just under the exocarp within 3–4 days after inoculation. Irrespective of
fruit maturity the population increased and survived 2–4 weeks or more at 25 ºC. Bacteria
were able to migrate rapidly within twigs and reach the abscission layers between fruit-
bearing twigs and the fruit stem. These experiments were done under high inoculum

35


pressure on freshly cut surfaces and the authors considered that such invasions may not
occur under field conditions.
Tsukamoto et al. (2005) examined the infection frequency of mature apple fruit inoculated
with 10μl drops containing 105 and 104 cfu of E. amylovora on each of the freshly cut
pedicels and enclosed in plastic boxes at 25 ºC. The results showed that E. amylovora
infected mature fruit latently and that it remained viable after 6 months of storage at 5 ºC
in most of the inoculated fruit. The authors suggested that latently infected mature fruit
could transmit the disease over long distances. However, this phenomenon has not been
demonstrated using naturally infected fruit in orchards. Azegami et al. (2006) examined
the invasion of apple fruit after approximately 105 cfu E. amylovora was used to inoculate
fruit bearing twigs in potted plants raised outdoors but placed in a greenhouse before
inoculation. These authors isolated E. amylovora from 3%–5% of symptomless fruit
whose fruit-bearing twigs had been inoculated indicating that the pathogen can move
through the abscission layer and invade the fruit during fruit maturation. The authors
concluded that the possibility cannot be excluded that E. amylovora can invade apple fruit
through fruit-bearing twigs in late summer to yield mature symptomless fruit.
However, the inoculation experiments of Tsukamoto et al. (2005) and Azegami et al.
(2004; 2006) that report fruit infection were criticised because of their highly artificial
nature and they do not support fruit infection under field conditions (Paulin 2010a). There
is not sufficient information to support infection of mature apple fruit (Deckers 2010).
Erwinia amylovora was isolated from internal tissues of fruit harvested from blighted
orchards in Utah, USA (van der Zwet et al. 1990). These authors recovered 1 to 300
colonies of E. amylovora from internal tissues. However, a statement, provided to the
WTO Japan–USA apple dispute by two of the four authors of this report more than 10
years after the work was published, indicated that the internally contaminated fruit
harvested for testing was immature (WTO 2003).
In Canada, mature apples were infected only when high inoculum doses were injected into
the cortex of fruit and bacteria remained viable as long as the fruit was physiologically
active (Dueck 1974a).
Tests conducted to examine the presence of bacteria within ovules and seeds of a range of
plant species identified E. amylovora as one of the bacterial species (Mundt and Hinkle
1976). The authors have not linked the different species of bacteria obtained to the
different plant species tested, but apple and crab-apple were the only Rosaceae species
tested and it is possible that the detection of E. amylovora is from the seeds of these
species. The tested seeds were surface-sterilised, indicating that the bacterium was present
inside the seed. However, this work has been criticised as the methods employed do not
confirm the presence of E. amylovora (Paulin 2010a).
In the USA, E. amylovora was not isolated from any whole or split apple seeds tested (van
der Zwet et al. 1990).
Escherichia coli and E. amylovora belong to the family Enterobacteriaceae and E. coli
could be considered an analogue for E. amylovora. Studies conducted on E. coli report
artificial inoculations using very high inoculum doses on injured fruit (Buchanan et al.
1999; Burnett et al. 2000). These conditions do not reflect the situation that exists
naturally in orchards. Therefore, strict comparison or extrapolation of results relating to
the behaviour of E. amylovora may not be applicable.
Erwinia amylovora can occur in the xylem vessels (Bogs et al. 1998; Vanneste and Eden-
Green 2000), phloem (Lewis and Goodman 1965) and cortical parenchyma (Eden-Green

36


and Billing 1974) of symptomless plants. The persistence of E. amylovora in xylem
vessels seems to be limited, possibly because the salts and water contained within lack
elements required for rapid bacterial multiplication (Gowda and Goodman 1970; Momol
et al. 1998), but still indicates that E. amylovora is able to migrate in symptomless plants
(Momol et al. 1998).
Bacteria tend to aggregate and disrupt the water flow (Sjulin and Beer 1977), which
causes leakage of the vessels and extrusion of bacteria into the parenchyma. Rapid
multiplication of E. amylovora occurs when bacteria escape from the xylem vessels into
intercellular spaces of the cortical parenchyma, resulting in symptom development
(Vanneste and Eden-Green, 2000). Sudden outbreaks of fire blight without any evidence
of inoculum have been attributed to this phenomenon (Thomson 2000).
A recent review of the evidence supports the view that E. amylovora can occur in xylem
vessels (Billing 2011). It is further stated that E. amylovora can multiply in the xylem and
may survive latently for many years, expressing symptoms once the xylem vessel is
damaged and bacteria are released into the parenchyma (Billing 2011).
If bacteria were to occur in the vascular tissue in the tree there is no reason to assume that
they would not find their way into fruits. However, the paucity of evidence of endophytic
infection in mature fruit suggests that if endophytic infection does take place in fruit it
must be a rare event.
Erwinia amylovora was not recovered from aqueous sonicates or core tissues of 1555
mature symptomless apples harvested from blighted trees of seven apple cultivars that
were cold-stored. The sonication–membrane filtration technique was able to detect as few
as 19 cfu and its sensitivity exceeds that for an immunofluorescent assay using
monoclonal antibodies (Roberts et al. 1989).
A Japanese–US study tested 30 900 mature apple fruit from two sites in Washington State,
USA, harvested between 0 to 300 metres from a source of fire blight inoculum. The fruit
was analysed for internal populations of E. amylovora after harvest. Bacteria were not
detected in any of 900 fruit (sourced from fire blight-infected apple trees or directly
adjacent to blighted pear trees) using isolation methods, with this result confirmed by PCR
tests (Roberts 2002). Of the 30,000 fruit placed in cold storage, none developed external
symptoms. Further, no internal symptoms were detected in any of the 1500 fruit that were
sliced open. Of these, 500 were streaked onto plates with selective media, but
E. amylovora was not recovered (Roberts 2002).
Erwinia amylovora could not be isolated from internal tissue of symptomless fruit
harvested from blighted trees, where approximately 20% of the wood on the trees from
which apples were harvested had symptoms of fire blight (Dueck, 1974a).
It has been argued that fruit can be internally infected without showing symptoms, but if
this were to occur many fruit would have developed a rot, and there is no evidence for this
in commercial trade of apples.
It is considered there are no reports of true infection in mature apples under natural
conditions as they are resistant to infection (Paulin 2010a). Even if fruit are artificially
inoculated, they do not develop symptoms of fire blight because the bacteria do not readily
multiply in the mature fruit due to an absence of the required carbohydrate source
(Deckers 2010; Paulin 2010a).

37


In the absence of any new evidence to support fruit infection in mature apple fruit, the
likelihood of fruit infection occurring under natural conditions is considered to be
negligible.
Ability of the pest to survive adverse conditions–viable but non-culturable state
Studies conducted by Biosca et al. (2004) and Ordax et al. (2004; 2006) indicate that
E. amylovora can enter into a viable but non culturable (VBNC) state. Another study,
using an attenuated strain of E. amylovora which had lost its pathogenic ability, confirmed
that E. amylovora can enter into a VBNC state (Sly et al. 2006). This phenomenon may
contribute to an underestimation of the pathogen numbers when culture methods for
detection of E. amylovora bacteria. However, DNA detection techniques, such as PCR,
rely on genetic material in the bacteria and would detect VBNC bacteria as well as dead
and lysed cells and would not result in an under-estimation of E. amylovora.
E. amylovora can be induced to enter into a VBNC state by nutrient starvation (Biosca et
al. 2004) or by the presence of copper (Ordax et al. 2004). E. amylovora is able to survive
and remain infective for six months in sterile irrigation water (Biosca et al. 2004) and the
culturability and pathogenicity of copper-induced VBNC E. amylovora (Ordax et al.
2004) can be restored under sterile conditions.
The studies of Biosca et al. (2004) and Ordax et al. (2004; 2006) were conducted under
artificial conditions (sterile mineral medium and sterile water microcosms) with high
inoculum doses. These conditions differ significantly from those present on apple trees
under natural conditions. Application of copper during apple‟s dormant growth periods
and at flowering to reduce E. amylovora populations in apple orchards could induce this
pathogen to enter into a VBNC state. Ordax et al. (2004) have shown a 106 reduction in
the bacterial population, including bacteria considered to be in the VBNC state, 70 days
after exposure to copper. Given the low numbers of bacteria likely to be present on apples
if copper is applied, these results suggest no culturable bacteria are likely to be present at
fruit maturity.
According to the information presented by several authors (Rahman et al. 1996; Ericsson
et al. 2000; Bogosian and Bourneuf 2001; van Overbeek et al. 2004) the significance of
VBNC in relation to bacterial survival is not yet clearly established. The few studies on
E. amylovora show that only a small proportion of the cells appear to enter a VBNC state.
One study (Sly et al. 2006) was unable to demonstrate recovery of cells to a culturable
state suggesting that the VBNC state may be an irreversible stage towards cell death.
The VBNC hypothesis has frequently generated sharp debate and some proponents argue
that this condition may be a physiological condition prior to cell death (Bogosian and
Bourneuf 2001; McDougald et al. 1998).
No field studies have been undertaken to verify the claim that sudden appearance of fire
blight in apple orchards is due to resuscitation of copper-induced VBNC cells. Ordax et al.
(2006) have suggested that further studies on the interaction of copper with E. amylovora
and the VBNC state are needed to better understand the life cycle of this pathogen and to
optimize the fire blight control strategies.
A recent study has confirmed that E. amylovora can enter a VBNC state in the calyx of
apple fruit in response to copper and then infect receptive host tissue after periods of 7–28
days post calyx inoculation under favourable laboratory conditions (Ordax et al. 2009).
The level of infection recorded in this experiment was low and the culturing of E.
amylovora from infected tissue was several orders of magnitude lower than bacteria that
had not entered the VBNC state.

38


For VBNC to be a risk pathway, bacteria would need to enter the VBNC state in the
orchard and would need to resuscitate before, or during, an infection event in Australia for
infection to occur. Copper is known to induce the VBNC state in the laboratory, but it is
not generally applied at flowering because of plant phytotoxicity (APPS 2009) and there is
still no evidence to confirm resuscitation can occur under natural conditions (Paulin
2010a).
Ability of the pest to survive adverse conditions–Exopolysaccharides and biofilms
Bacteria occur either as independent single cells (planktonic) or as complex multicellular
communities attached to surfaces embedded in exopolysaccharides (EPS) which account
for approximately 90% of the enveloping matrix polymers. Biofilm formation is
widespread among enterobacterial species (Charkowski et al. 2005). These communities
adhere to living or abiotic surfaces, typically at a liquid–solid interface (Hall-Stoodley et
al. 2004).
The matrix in which microbes in a biofilm are embedded can protect them from ultraviolet
(UV) exposure, metal toxicity, acid exposure, dehydration and salinity, phagocytosis,
antibiotics, and antimicrobial agents (Hall-Stoodley et al. 2004; Sapers 2001; Ryu and
Beuchat 2005). In addition, EPS are thought to play a role in protecting the bacterial cell
against desiccation, in adhesion to solid surfaces and also in cellular recognition (Allison
1998). Therefore, EPS can provide a physical barrier to protect cells against
environmental stresses, in addition to being involved in cell adhesion and biofilm
formation (Weiner et al. 1995; Stoodley et al. 2002; Harrison et al. 2005).
Biofilms can also form on the surfaces of containers used for harvesting, transporting, and
displaying foods at retail level (Costerton et al. 1987) and on food surfaces (Carmichael et
al. 1999). Biofilms may exist in uncleaned dump tanks and grading equipment in apple
packing houses. However, it is unlikely that biofilms in dump tanks and on grading
equipment will involve large numbers of E. amylovora, given the conditions that would be
present, including low levels of nutrients, the presence of many other bacterial species and
the poor epiphytic ability of E. amylovora.
Even if bacteria in biofilms are sloughed off surfaces in dump tanks from time to time, the
bacteria are unlikely to attach to fruit because fruit are held in dump tanks for only a very
short time. Bacteria that may be superficially attached to fruit leaving the dump tank
would be washed off by the high-volume high-pressure water wash systems installed in all
New Zealand export packing houses (MAFNZ 2011).
The most important EPS of E. amylovora is amylovoran, which form loose capsules
around the bacterial cells and are an important virulence factor (Bellemann and Geider
1992). E. amylovora also secretes levansucrase for extracellular levan formation in the
presence of sucrose (Geider 2000; 2006). In addition, it produces glucan, which helps in
stabilisation of the cell structure (Smith et al. 1995). Capsulated bacteria protected by an
amylovoran coat survive better under dry conditions as it prevents the loss of residual
water (Geider 2000).
Under laboratory conditions, the EPS of E. amylovora (amylovoran and levan) can be
used as carbon sources by the bacteria during periods of starvation (Ordax et al. 2010a).
The utilisation of EPS may assist in the survival of E. amylovora during periods of
starvation and this factor would be taken into account during the many studies of E.
amylovora survival in the calyx.
It has been reported that copper ions increase the level of the EPS amylovoran (Bereswill
et al. 1998) and that these ions are accumulated on the surface of E. amylovora cells

39


(Zhang et al. 2000). Moreover, it is known that bacterial EPS have a cation-binding
capacity (Gutnick and Bach 2000). E. amylovora in biofilms are over 250 times more
resistant to quaternary ammonium compounds than the same bacteria in suspension
(Marques et al. 2005).
It is thought that EPS contribute to the survival of E. amylovora and therefore allows fire
blight to establish and spread (Bennett and Billing 1978). There is no specific evidence
concerning the role of biofilms and EPS on the survival of low bacterial numbers in
calyces but if EPS did support survival in calyces then this factor would already be
accounted for by the bacterial numbers that have been detected on mature healthy apples.
More recently it has been shown that EPS contributes to the formation of biofilms and
plays an important role in the pathogenesis and disease development of E. amylovora in
plants (Koczan et al. 2009; Lee et al. 2010).
However, biofilms are normally formed in the presence of significant nutrient levels at a
liquid–solid interface. These are quite different conditions to those present in the calyx or
on the surface of apple fruit where the availability of nutrients would be very low and the
occurrence of free water would be quite rare. Under these conditions it is unlikely that
E. amylovora could develop a significant biofilm. This is in contrast to active cankers or
pear slices where nutrient levels are high and water is freely available, resulting in the
copious production of slime that could contribute to biofilm production and bacterial
survival.
Ability of the pest to survive adverse conditions–Quorum sensing
Quorum sensing describes a mechanism of bacterial cell-to-cell communication which
allows bacteria to assess their local population density and/or physical confinement via
secretion and detection of signal molecules (von Bodman et al. 2003). Quorum sensing,
also called autoinduction, is a bacterial defence mechanism known to be associated with
biofilm formation (Harrison et al. 2005).
Quorum sensing is also a mechanism by which bacteria can respond to cell density and
regulate the expression of specialised gene sets which is regulated by the production of a
signal molecule called an autoinducer. Genetic and phenotypic evidence for the existence
of quorum sensing in E. amylovora was described by Venturi et al. (2004) and Molina et
al. (2005, 2006).
Quorum sensing may serve as a defence mechanism against antibiotics (Harrison et al.
2005). It is noted that relevant studies on survival dynamics of E. amylovora reported in
this review already take account of quorum sensing.
Ability of the pest to survive adverse conditions–sigma factor
Sigma factors are regulators of bacterial transcription that can control the expression of
specific proteins. Sigma factors can be activated in response to different environmental
conditions and could play a role that enhances the survival of E. amylovora during periods
of stress.
The sigma factor σS, encoded by the gene rpoS (RNA polymerase, sigma S), regulates
expression of a number of genes that serve to maintain viability of bacteria during periods
of starvation and environmental stress (Kolter et al. 1993). However, Anderson et al.
(1998) demonstrated that expression of rpoS plays no role in the survival of E. amylovora
during overwintering in mature tissue.
The sigma factor plays a role in biofilm formation (Prigent-Combaret 2001), during
periods of nutrient limitation (Zambrano and Kolter 1996) and as a regulator required for

40


virulence (Barak et al. 2005). But the role of sigma factor in E. amylovora is not yet fully
investigated. There is no specific information relevant to survival on apple fruit. However,
if sigma factor enhances the survival of bacteria, then it would also have already been
taken into account when considering the bacterial numbers present in mature apple fruit.
Ability of the pest to survive epiphytically
The role of epiphytic bacteria on the fruit surface may also play a role in the importation
of E. amylovora. However, according to Leben (1965), Miller (1984) and Thomson
(2000), E. amylovora is not strictly a leaf surface epiphyte. Miller and Schroth (1972)
have indicated that while E. amylovora is present on leaves only after blossom infection in
the spring and even in severely diseased trees, it is not detected in hot summer months.
Manceau et al. (1990) concluded that E. amylovora did not have epiphytic fitness in its
biological cycle under the conditions observed in France.
Epiphytic populations of E. amylovora occur almost exclusively on flowers (Thomson
1986; Hale et al. 1996; Hattingh et al. 1986) compared with other aerial surfaces. There is
some evidence that E. amylovora can survive epiphytically on leaves and on the surface
and calyx-end of apple fruit harvested from infected orchards (Sholberg et al. 1988; van
der Zwet et al. 1990) or alternative hosts (Momol and Aldwinckle 2000). Miller and
Schroth (1972) and Miller and van Diepen (1978) argue that E. amylovora is transient on
the leaf surface and usually present after blossom infections have occurred in the orchard.
Leben (1965) does not consider E. amylovora to be a strict epiphyte on the leaf surface.
In the USA, van der Zwet et al. (1990) showed that approximately 4% of apparently non-
infested fruit sourced from a symptomless orchard developed fire blight symptoms when
wounded on the surface. This indicates that bacteria were present on the external surface
of the fruit. However, it was later confirmed by the senior author of that study that the
apples sampled were immature (WTO 2003).
Epiphytic colonies of E. amylovora were not detected on calyces or surfaces of fruit
(number tested was not specified) of six susceptible cultivars from blighted orchards in
West Virginia, USA (van der Zwet et al. 1991).
Maas Geesteranus and de Vries (1984) showed that E. amylovora (washed cells) were
killed by desiccation within 24 hours, within one to two days when stored at 20 ºC, or
within a few hours when exposed to 75% relative humidity or six hours of solar radiation.
Similarly Gottwald et al. (2002) reported that bacteria in the ooze of a similar disease,
citrus canker, die upon exposure to drying and that death is accelerated by exposure to
direct sunlight. Norelli (2004) reported that E. amylovora detected on apple leaves after
rain events in June/July in USA were short-lived.
McManus and Jones (1995) and Sholberg et al. (1988) have shown that leaves are
colonised by E. amylovora. There is also evidence that hail damage can induce
development of fire blight symptoms (Beer 1990).
Vanneste et al. (2004) showed how E. amylovora did not survive on apple leaves in the
field while strains of two of its biological control agents Pantoea agglomerans and
Pseudomonas fluorescens, known to be non-pathogenic epiphytic bacteria, survived
longer.
Dueck and Morand (1975) studied seasonal changes in the epiphytic population of
E. amylovora on apples and pear leaves in Ontario, Canada. The highest epiphytic
prevalence was observed during July and August but in some seasons extending to
September. July is generally regarded as the period of maximum rainfall in Ontario,

41


whereas most apple varieties are harvested during September and October when,
according to their data, epiphytic populations are extremely small.
Ceroni et al. (2004) artificially inoculated pear fruit by immersing the fruit for 15 minutes
in a bacterial suspension with 108 cfu mL–1. After just one day, no bacteria could be
detected on the surface using PCR, indicating that the pear fruit surface is not a favourable
environment for bacterial survival.
Steiner (1998) claims E. amylovora is a competent epiphyte. However, this paper provides
no supporting data for epiphytic survival of the pathogen. The epiphytic fitness of
E. amylovora was discussed at the 9th International Workshop on Fire blight and several
participants were of the view that E. amylovora was a poor epiphyte of the leaf surface
(Norelli and Brandl 2006).
Calzolari et al. (1982) examined 104 samples of dormant buds from plants being imported
into Italy. They detected E. amylovora in only in one sample. While their observation may
have some relevance to spread of fire blight through planting material, it is not a clear
demonstration of the bacterium‟s epiphytic survival. Further, the likelihood of transfer of
bacteria from such a low percentage of infested buds to a clean fruit during picking would
be even lower.
In attempting to study the latent survival of E. amylovora in hibernating shoots, Crepel et
al. (1996) artificially inoculated shoots by cutting the first unrolled leaf and placing 10µL
of a bacterial suspension with 108 cfu/mL on the wound (ca. 1 x 106 cfu), resulting in
bacteria being detected in 30% of the shoots after winter. The bacteria in this study were
most likely not epiphytic and this data cannot be used to demonstrate the presence of
epiphytic bacteria under natural conditions.
Van der Zwet et al. (1988) cited references claiming the detection of low numbers of
epiphytic bacteria, mostly on blossoms and occasionally on leaves during spring.
However, at fruit picking time, the numbers of infested fruit or leaves and the numbers of
bacteria present on them are likely to be very small because of adverse conditions.
Geenen et al. (1981) tested blossoms (when present), as well as young shoots and leaves
of host plants in protected areas of Belgium between May and September, for epiphytic
presence of E. amylovora using two serological methods, agglutination and
immunofluorescence. These authors claimed much higher detection rates using
immunofluorescence. In 1979, the number of positives was four using agglutination
methods and 23 using immunofluorescence. In total they detected 3.8% positives in 1979
and 18.7% in 1980, presumably using immunofluorescence. Detection of epiphytic
populations of E. amylovora are possible only during the blossom period (Geenen et al.
1981). In fact, they have detected infections in nurseries and their surroundings and
although they were testing the protected areas, the authors wrote that; „in some cases the
infection source was detected in the neighbourhood of a place where epiphytic presence of
E. amylovora had been found‟. Further, as they sampled plants from May to September, it
is likely that the positives detected were during blossom time, but no indication is given as
to when or in which parts of the plant (blossoms or leaves) the positives were detected.
As discussed earlier, many authors have reported a rapid decline of epiphytic populations
after the blossom period, and bacterial numbers during fruit picking are likely to be
extremely small. Calzolari et al. (1982) used a range of tests to confirm the identity of the
bacteria. Of 19 samples testing positive for immunofluorescence staining, only one was
considered to be E. amylovora following further tests. That is, 18 out of the 19 samples

42


that were positive to immunofluorescence staining were actually found to be other bacteria
such as Pseudomonas syringae.
Roberts (1980) highlighted some problems with immunofluorescent diagnosis of fire
blight because of cross-reactions between E. amylovora and other bacteria, even those of
different genera. Calzolari et al. (1982) says immunofluorescence staining also permits
detection of dead cells. The identifications of Geenen et al. (1981) above are therefore not
definitive as they could have been detecting bacteria other than E. amylovora.
Persson (1999) tested leaves of five different fire blight host plants (in areas where fire
blight outbreaks had occurred two years earlier) using fatty acid analysis, identification
being considered accurate when similarity indexes exceeded 0.6. Leaves were sampled
three times (early June, mid July and late August) during two seasons and each sample
consisted of 75 leaves bulked together. E. amylovora was detected at one sampling
occasion each year. Given the approach by others using a range of methods to confirm the
identity of the bacterium (Calzolari et al. 1982; Roberts et al. 1989), it is not clear whether
fatty acid analysis with a similarity index of 0.6 alone is sufficient to confirm the identity
of E. amylovora.
Thomson and Gouk (1999) concluded that only transient populations of E. amylovora are
present on leaves following rain storms with the number of leaves infested declining very
quickly after rain storms. Therefore there would only be a limited opportunity for leaves to
act as a source of contamination for fruit being harvested.
Other studies support the ability of E. amylovora to survive nutrient-poor conditions (Wei
et al. 1992; Wei and Beer 1995; Wei et al. 2000). These studies propose that certain
conditions in the plant apoplast, including low nutrient status, may act as environmental
signals triggering the transcription of hrp genes that produce the secretion machinery and
virulence proteins, which in turn interact with plant cells to give hypersensitive and/or
pathogenic reactions. Contact between bacteria and plant cells is critical for the
development of this reaction (Kim and Beer 2000). The above studies do not provide any
supporting evidence for the ability of E. amylovora to survive as an epiphyte or infestation
outside the cuticle (the outer limit of the apoplast) and without contact with plant cells.
In fact, these studies provide indirect evidence for the opposite characteristics observed,
namely the poor ability of E. amylovora to survive as an epiphyte. Further, even with
regard to hrp gene expression of E. amylovora, whether the apoplast can be considered a
low nutrient environment is questionable at it is where E. amylovora will normally
rapidily multiply. Movement of sugars in the apoplast before phloem loading and after
phloem unloading is well established (Taiz and Zeiger 2002), and the ideal conditions
present for the bacterium in the apoplast containing sugars may explain why it spreads
mostly in the apoplast.
Burnett et al. (2000) and Kenney et al. (2001) used confocal scanning laser microscopy to
study epiphytic survival of E. coli on apple fruit after fruits were rinsed for 15 to
30 minutes in suspensions containing high doses of the bacterium. These authors observed
the bacterium attaching to the cuticle, wax plates, clefts, lenticels, etc. However, in spite
of strong indications that most pathogenic bacteria do not survive desiccation and
exposure to sunlight, the above authors did not examine the presence of bacteria on the
artificially inoculated fruit after exposure to such natural environmental conditions.
Further, conditions equivalent to rinsing in suspensions with high concentrations of
bacteria for 30 minutes will not occur with apples in the field. In addition, the ecological
niches of the two bacteria are very different and therefore it is questionable as to whether
E. coli studies can be directly extended to E. amylovora.

43


Work conducted by Thomson and Gouk (1999) using the sensitive leaf imprinting
technique showed populations of E. amylovora were detected on less than 25% of the
leaves near infections, but the pathogen was detected on 90% of the leaves during or soon
after a rainstorm. These populations declined rapidly with the onset of dry conditions and
only 7% of leaves tested positive after two days.
Experiments conducted by Ockey and Thomson (2006), using a sensitive imprinting
technique showed that the mean leaf area covered by E. amylovora colonies within 0.3 m
of an inoculum source in the orchard increased from nearly zero before rain to 3–24%
immediately after rain and declined to almost zero again a day after rain. A similar trend
was observed in the laboratory study where the mean leaf area colonised by E. amylovora
following inoculation declined from 53–75% on the day of the inoculation to 2.5–3% on
the day following inoculation.
Norelli and Brandl (2006) reported that when plants were inoculated with cold bacteria
(4 ºC) and incubated at high temperature (35 ºC), E. amylovora became established within
young leaves via hydathodes and glandular trichomes and rapidly declined on the surface
of older leaves. These authors showed that under controlled conditions E. amylovora
populations rapidly decreased on apple leaves from 104 per leaf at constant 24 ºC and high
relative humidity (80–95%) within 48 hrs. Low E. amylovora populations (10 cfu per leaf)
were detected 6 and 14 days after inoculation. Based on confocal microscopy of the leaf
surface, these authors reported that there was no evidence that E. amylovora multiplied on
the leaf surface either at 24 ºC or 35 ºC. Norelli and Brandl (2006) also observed that
E. amylovora detected on leaves sampled from orchards after rain were short-lived. These
observations indicate that mature leaves may have a low population of bacteria which
could increase immediately after rain but decline to a very low level soon after the rain
event.
In an experiment using cells from cultured E. amylovora and cells in air-dried ooze taken
from diseased fruits, apple fruit were inoculated by spraying the suspension of bacteria to
runoff with 105 to 107 cfu per mL (Temple et al. 2004; abstract only). Fruit were then
sampled periodically for up to 35 days to detect E. amylovora (Temple et al. 2004).
Populations of 103 to 105 cfu of E. amylovora per fruit were recovered from 64% of fruit
(n = 420) immediately after spraying. The rate of recovery and population size declined
with time, regardless of the method of inoculum production. The recovery of E.
amylovora declined to 6% and 1% of sampled fruit respectively at 7 and 14 days after
inoculation. At 35 days, only 8 cfu of E. amylovora were recovered from two of 330 fruit.
Fire blight symptoms were not observed on inoculated trees or fruit.
Later, the work by Temple and colleagues were published as a full text article that
comprehensively described the experimental methods. Under field conditions, immature
pear or apple fruit on the tree were artificially covered by an inoculum suspension with
107 cfu per ml, or calyces infested with inoculum from ooze (108–109 cfu) (Temple et al.
2007). Populations of E. amylovora declined by an order of magnitude every three to four
days in the first two weeks after inoculation. From a starting population of 1.6 x 107 cfu,
by day 56, only one pear fruit of 450 tested positive and had only four cfu (Temple et al.
2007). This study confirmed the poor survival and rapid decline of E. amylovora bacteria,
even from very high levels, on the surface of fruit.
There is no evidence that E. amylovora bacteria would survive on the surface of apple
fruit better than on leaves. Erwinia amylovora bacteria are susceptible to a range of factors
(UV light, heat, desiccation, lack of nutrients, competition) that will quickly result in
death. Any contamination by epiphytic bacteria, from vegetative or other source material

44


would be exposed to the same conditions. It is considered epiphytic bacteria outside the
calyx are very unlikely to contribute to the importation of E. amylovora into Australia
(Paulin 2010a; Deckers 2010).
Overall, the likelihood that viable epiphytic bacteria occur on the leaves and mature fruit
surface (except the calyx) at the time of apple picking is very low and the likelihood of
transfer of bacteria to clean fruit during picking and transport would be even lower. Any
epiphytic bacteria that do contaminate the fruit surface will only survive for a very short
period.
Ability of the pest to survive existing pest management
All export orchards are registered with Pipfruit NZ Inc and utilise either the Integrated
Fruit Production program or a certified organic program. These programs provide
guidance for targeted management of fire blight. Measures include the preventative
application of sprays during flowering (Blossom Bless only for organic fruit) and the
targeted pruning of infected shoots and cankers that limit the prevalence of fire blight in
trees. Infected immature fruit do not develop to maturity, show obvious symptoms, and
would not be harvested.
Ability of the pest to survive packing, transport and storage conditions

The pulp temperature of fruit at harvest is relatively high. To lower this pulp temperature,
fruit may be subjected to at least a short pre-cooling treatment before it is put through
packing house procedures. A survey has shown that 71% of the respondents, responsible
for exporting over 90% of the crop, use pre-cooling treatment routinely in the packing
house (MAFNZ, 2005a).
Pre-cooling may affect the survival of E. amylorvora as it has been shown that cold
conditions increase the mortality of bacteria (see discussion below on cold storage).
However, the short period of time fruit are exposed to pre cooling, including higher
relative humidity, is unlikely to significantly affect E. amylovora present in the calyx.
Bacteria protected in the calyx are unlikely to be removed in the dump tank, at least in
closed calyx varieties.
Packing houses utilise disinfectants such as chlorine or Tsunami® and, increasingly,
Nylate® during water washing procedures and in dump tanks. In 2005, only 53% of pack
houses used disinfectants. In 2011, 99% of export fruit produced under the IFP program
are disinfected (MAFNZ 2011). The concentration of chlorine used varies between 5 and
50 ppm and peroxyacetic acid (Tsunami®), and bromo-chloro-dimethylhydantoin
(Nylate®), as alternatives to chlorine, as per label instructions. Monitoring of disinfectants
is done manually at specific times on each day or automatically (MAFNZ 2005a). For fruit
produced under organic methods, contributing approximately 8% of exports (Pipfruit NZ
2010), fruit wash tank water is regularly replaced to remove contaminating material
(MAFNZ 2011).
Although, wash water for organic fruit does not contain a sanitiser, exopolysaccharides
(EPS) of E. amylovora are water soluble (Maas Geesteranus and de vries 1984; Ordax et
al. 2010a). The main EPS of E. amylovora (amylovoran) is an acidic polysaccharide with
strong water-binding activity with strong water-binding activity, i.e., it is a typical
hydrophilic EPS of the kind found among many Gram-negative bacteria; EPS with these
properties form loose slime layers which readily disperse in water (Ayres et al. 1979;
Politis and Goodman 1980; Belleman et al. 1994; Nimtz et al. 1996; Pers comm.; Dr Chris
Hayward April 2011). For example, 95% of the EPS of E. amylovora is removed by a
single high speed washing (Ayers et al. 1979). EPS protect E. amylovora and are known

45


to promote survival (see section–Ability of the pest to survive adverse conditions–
Exopolysaccharides and biofilms). Any epiphytic E. amylovora bacteria will not survive
for long (see section– Ability of the pest to survive epiphytically) and with reduced levels
of EPS, survival is likely to be even shorter.
In 2005, 93% of packing houses used high pressures washing (MAFNZ 2005a). High
pressure washing is now standard practice and is used at 100% of export packing houses
(MAFNZ 2011).
The increased use of high pressure sprays is likely to increase the penetration of
disinfectants, when used on non organic fruit, into the protected region of the calyx.
Although it is recognised disinfectants will not kill 100% of any remaining bacteria, they
would reduce their numbers (Deckers 2010; Paulin 2010a). For organic fruit, it has been
reported that high pressure washing can be as effective in removing micro-organisms as
200 ppm chlorine (Bechat 1999). Even low pressure washing can remove approximately
90% of E. amylovora on apple fruit (Roberts and Reymond 1989).
Brushing would not remove bacteria present in the calyx-ends of fruit, as these areas are
inaccessible. Even if waxing were to occur, bacteria will survive low-temperature waxing,
as the thermal death point of E. amylovora ranges from 45 to 50 ºC (van der Zwet and
Keil 1979).
Bacteria infesting the calyx-end of fruit would not be detected during visual inspection.
Packaging, which aims to minimise moisture loss and maximise heat dissipation, will not
reduce the bacterial population in the calyx.
The ability of E. amylovora to survive on mature pear and apple for several weeks after
cold storage and in some instances develop symptoms while in storage was reported
(Anderson 1952; Dueck 1974a; Nachtigall et al. 1985). However, these papers report the
use of high inoculum doses injected into the cortex of fruit, which does not reflect natural
conditions.
When mature fruit are inoculated by swabbing calyces of apples with high levels of E.
amylovora (an average of 107 cfu per mL), a level of infestation that is many orders of
magnitude higher than naturally infested calyces, the initial population steadily decreased
to an undetectable level over a six month period in cold storage (Sholberg et al. 1988).
Hale and Taylor (1999) inoculated mature fruit at the calyx-end with different
concentrations of E. amylovora ranging from 10 to 107 cfu per fruit, and kept them in cool
storage (2 ºC ± 0.5 ºC) for 25 days or cool-stored them for 25 days before incubating at
room temperature (about 20 ºC) for a further 14 days in the laboratory. The results indicate
that after cool storage alone, E. amylovora was detected by PCR in 90% and 20% of fruit
inoculated with 107 cfu and 104 cfu respectively, and in less than 8% of fruit inoculated
with 10, 102 or 103 cfu at the end of this 25-day period. It was also reported that after cool
storage, E. amylovora was isolated only from 75% of fruit inoculated with 107 cfu and in
10% of fruit inoculated with 104 and 105 cfu. However, after cool storage and incubation
at room temperature, E. amylovora was detected in 35% of fruit inoculated with 107 cfu
and in 3% of fruit inoculated with 105 cfu, but not in fruit inoculated with 10, 102,103 or
104 cfu.
In another experiment, mature fruit inoculated with the various concentrations of
E. amylovora were subjected to cool storage alone or alternatively, cool storage and
incubation under commercial conditions (see Table 2 of Hale and Taylor (1999)). This
data show that after cool storage, E. amylovora was detected (by PCR) in 3%, 10%, 28%

46


and 66% of fruit inoculated with 10, 103, 105 and 107 cfu respectively. E. amylovora was
isolated from only 7% of fruit inoculated with 107 cfu and not from any other fruit (data
not shown in table). After cold storage (25 days) and incubation (14 days) E. amylovora
was detected in 36% of fruit inoculated with 107 cfu, 6% of fruit inoculated with 105 cfu,
but not from any other fruit. E. amylovora was isolated from fruit inoculated with 105 or
107 cfu, but not from any other fruit. These results show that bacterial populations (104 cfu
or below) on cool-stored fruit incubated at room temperature (about 20 ºC) for 14 days
decrease to levels undetectable by the sensitive PCR technique.
Hale and Taylor (1999) also reported that before cool storage E. amylovora was detected
by PCR in 2% of fruit sourced from orchards with fire blight symptoms, but not in any
fruit after either from cool storage or cool storage and return to ambient temperatures.
E. amylovora was not isolated from any stored fruit tested. These authors also reported
that E. amylovora was neither detected nor isolated from fruit harvested from
symptomless orchards before or after cool storage.
Taylor and Hale (2003) inoculated the calyces of the closed-calyx variety Braeburn. These
authors showed that bacterial populations in the calyx decreased from 106 cfu to 102 cfu
over a 20-day period and from 104 to non-culturable levels after 14 days. These authors
also showed that populations of E. amylovora in calyces infested with 102 cfu decreased to
non-culturable levels after 8 days in storage. PCR tests, which would detect the DNA of
both live and dead bacteria, detected E. amylovora in calyces infested with 106 cfu and
104 cfu, but not in those with 102 cfu after the 20-day cool-storage period.
Roberts (2002) reported that out of 30,000 apples sampled from trees adjacent to infected
trees, then cold-stored for two to three months, and no external symptoms were found. A
total of 1500 fruit were also examined for internal symptoms but none were infected.
However, E. amylovora was not isolated from any of the fruit (900) in the sub-sample
examined before storage. Therefore, the absence of bacteria after this period cannot
necessarily be attributed to the effects of cold storage. However, this data is useful in
regard to studies of the potential for apples to carry E. amylovora.
Mature fruit inoculated with a suspension of 107 cfu, less than 100 cfu per fruit could be
detected after 4 weeks, and no bacteria could be detected after eight weeks in cold storage
using a sensitive detection method that could detect as little as 2 cfu (Temple et al. 2007).
Recent work in Spain has shown that no E. amylovora could be detected from 300 mature
apples after 10 months in cold store. Sensitive detection methods were employed that
could detect < 1 cfu/ml of calyx extract and would have detected live or dead bacteria
including those in a viable but non-culturable (VBNC) state (Ordax et al. 2010b).
The studies above show that any E. amylovora in the calyx present at harvest will decrease
through time while in storage and eventually all apples will be free of viable bacteria. The
time required for this to occur is variable, depending on the conditions and starting
population, but covers a period from about a week to a maximum of six months.
Experiments using apples infested at levels that represent naturally occurring levels of E.
amylovora in the calyx typically have undetectable levels after a relatively short period of
time.
The longer fruit are held in cold storage in New Zealand, the number of infested fruit and
number of E. amylovora bacteria per fruit will decline.
For harvested fruit in long-term storage in New Zealand (either cold storage or controlled
atmosphere storage), the continued decline in bacterial numbers will result in the majority,
or all, of this fruit being free of viable bacteria.

47


Conclusion on probability of importation

The information presented indicates that Erwinia amylovora is wide spread in New Zealand,
and importantly is recorded in the two major apple growing areas of Hawke‟s Bay and Nelson
that jointly produce 93 per cent of the export crop. However, while the pathogen is present in
apple growing areas, the majority of orchards are likely to be free of symptoms. There has
been no detection of E. amylovora bacteria in the calyx of apples sourced from orchards free
of fire blight symptoms. In orchards, E. amylovora is actively managed through the removal
of inoculum sources. In spring, blossom infection is managed through the application of
sprays as recommended by a predictive model of infection events.
For E. amylovora to be imported into Australia, either fruit would need to harbour an
infection by the bacterium, or fruit parts would need to be infested by bacteria. If fruit
infection occurs, infected fruit does not mature and will not be harvested. There is no evidence
that supports mature fruit infection can occur under natural conditions. With regard to
epiphytic (surface) contamination, there is considerable evidence the E. amylovora bacteria
will not survive. Fruit infection and epiphytic pathways are therefore considered to be of no
significance. However, calyx infestation of mature fruit has been well documented. For calyx
infestations to occur, seasonal climatic conditions need to be conducive for the production of
E. amylovora inoculum which can then infest the floral parts that are subsumed into the calyx
of the developing fruit. Such calyx infestations are documented to only involve small
populations of bacteria. It is well documented that the calyx is an adverse environment for E.
amylovora because of the lack of nutrients and moisture. The number of infested fruit, and the
number of bacteria in those infested fruit, will therefore decline with time.
While any population of E. amylovora bacteria would be declining in number, bacterial
populations have been reported to survive for a sufficient length of time that would allow
importation of some infested apples when considering a significant volume of trade.
In summary, considering a significant volume of trade, the evidence shows that E. amylovora
has the potential to be associated with fruit from major export areas in New Zealand, but that
the proportion of infested fruit will be small and the bacterial populations in low numbers per
fruit. Both the infestation rate and bacterial populations will be affected by climate from year
to year and by orchard management practices. The evidence supports a rating of „moderate‟
for the importation of E. amylovora.
Probability of distribution
The likelihood that E. amylovora will be distributed in a viable state within Australia with
imported fruit and transferred to a suitable host is: EXTREMELY LOW.
Distribution of the imported commodity in the PRA area
Minimal on arrival inspection procedures, that includes checks that the consignment is as
described on the phytosanitary certificate would not detect calyx infested fruit.
Imported fruit will be distributed throughout Australia as wholesalers and retailers are
located at multiple locations and would facilitate the distribution of apples potentially
infested with E. amylovora.
Erwinia amylovora would need to survive transportation and storage within the PRA area.
Fruit is typically stored and transported in refrigerated containers maintained at cool
temperatures and receival temperatures in the range of 1–10 ºC are required by a major
retailer (Woolworths 2010). The storage and transport conditions are likely to continue the
decline in bacterial numbers in the calyx (see discussion in importation).

48


Once fruit is displayed for retail sale and sold it will be exposed to ambient temperatures.
As previously discussed, the decline in bacterial numbers will continue once the fruit is
returned to ambient temperatures. For example, bacteria in naturally infested apple calyces
that are exposed to cold storage for 25 days and then ambient temperatures decline to
undetectable levels in 14 days at 20 ºC using the sensitive PCR detection technique (Hale
and Taylor 1999).
Imported fruit may be packed by orchard wholesalers that would be in close proximity to
commercial fruit crops. Orchard wholesaler waste may be dumped at a site within the
premises or in landfills close to orchards. Before waste is finally disposed of, it could
remain exposed to the elements (for example, in a skip) near the packing house.
Occasionally workers and visitors could discard apple cores in the orchard itself. The
packing of New Zealand fruit from bulk bins and/or the repacking of boxes of New
Zealand fruit would bring packing house workers and host trees (apples and pears) into
close proximity to both New Zealand apples and apple waste. However, the bacteria in the
calyx would then need to move to the new host (see discussion in– Ability of the pest to
move from the pathway to a suitable host and Ability of the pest to move from the pathway to a
suitable host)
However, the export data from New Zealand shows that the majority of fruit exported
(99.8% in 2009–10) is in retail-ready boxes or trays that will not require repacking in
Australia (MAFNZ 2011). It is likely the majority of fruit will be distributed to retailers,
potentially through wholesale markets, without the need for re-packing. Only a small
volume would be likely to be re-packed within Australia.
Availability of hosts
Apples purchased via retail outlets can enter the environment after being purchased by
consumers. The majority of the population (and therefore the majority of apple
consumption) is in the capital cities significant distances from most commercial apple and
pear orchards. However, hosts of E. amylovora are present in many home gardens, parks
and roadsides in large cities.
Common hosts of this pathogen include species in the genera where fire blight is the most
serious bacterial disease including Malus spp. (apple), Pyrus spp. (pear), Cydonia spp.
(quince), Eriobotrya japonica (loquat), and amenity hosts including Crataegus spp.
(hawthorn), Cotoneaster spp. (cotoneaster) and Pyracantha spp. (firethorn). These hosts
all belong to the sub-family Maloideae of the family Rosaceae (CABI, 2005).
Other host species in the family Rosaceae that are susceptible to infection by E. amylovora
are Rosa rugosa (sub-family Rosoideae) (Vanneste et al. 2002) and Prunus salicina (sub-
family Amygdaloideae) (Mohan and Thomson, 1996). The pathogen also infects raspberry
and blackberry (Rubus spp.) plants, which belong to the Rosoideae sub-family. Strains
isolated from Rubus spp. were host-specific and did not infect apple or pear (Starr et al.
1951; Ries and Otterbacher 1977; Heimann and Worf 1985).
The potential for flowers of non-host plants to support epiphytic growth of E. amylovora
has also been reported (Johnson 2004; Johnson et al. 2006). The overlapping of flowering
times between apple trees and non-host plants could enhance the chances of pollinators
distributing the inoculum during foraging.
Many suitable hosts are commonly grown in Australia and are present in areas where
apples would be sold and consumed. However, host susceptibility of all hosts is variable
throughout the year and only some of these host species are highly susceptible to E.
amylovora and would play a role in the distribution of the pathogen (Paulin 2010a).

49


Fruit trees in commercial orchards are planted in high-density monocultures of suitable
hosts. Fruit trees and ornamental plants that are hosts of E. amylovora may be found in
household gardens, although their density would be low. The use of irrigation may create
climatic conditions more conducive for infection to household and garden plants.
Risks from by-products and waste
Although the intended use of fresh fruit is human consumption, waste material would be
generated (e.g. overripe and damaged fruit, uneaten portions). Whole or parts of the fruit
may be disposed of at multiple locations throughout Australia in compost bins or amongst
general household or retail waste.
Orchard wholesaler waste is disposed of into isolated areas within the orchard itself or in
landfills close to the orchard. These disposal sites are surrounded mostly by pome fruit
grown as a monoculture and wild and amenity plants are less abundant. Consumers may
also occasionally discard fruit waste along roadsides and recreation areas.
A relatively high proportion of household and retail waste would be managed through
regulated refuse collection and disposal services. Managed waste will remove any E.
amylovora bacteria from the household and environment, reducing the likelihood that
susceptible plants will be exposed to this pathogen.
E. amylovora does not produce resting cells or spores (Roberts et al. 1998) and it is
vulnerable to desiccation (Maas Geesteranus and de Vries 1984) and dry conditions (Jock
et al. 2005). It is known that exopolysaccharides of E. amylovora capsules prevent cells
from losing water, which can help bacteria to survive dry environmental conditions
(Geider 2000; Jock et al. 2002). However, the recorded survival of E. amylovora in
calyces would take into account the role of EPS.
Viability of E. amylovora is adversely affected by high temperature and low relative
humidity (Maas Geesteranus and de Vries 1984). Erwinia amylovora cells can survive in
the dark for considerable periods, but are killed rapidly when exposed to ultraviolet
light/full sunlight (Maas Geesteranus and de Vries 1984).
The infested calyces of fruit discarded near susceptible hosts could be considered a source
of inoculum for infections in new areas.
However, by the time of disposal to the environment, the majority of the bacteria would
no longer be viable, particularly for apples kept in long term cold storage, and those
remaining would be in an attenuated state due to adverse conditions of the calyx (lack of
nutrients, desiccation, heat etc). The remaining bacteria in the calyx of waste would
continue to be exposed to adverse environmental conditions that decrease the number of
viable bacteria.
Waste material should either have an adequate inoculum dose in a viable state or bacteria
must multiply to a concentration that could initiate an infection. When cores are discarded
into the environment, nutrients released from damaged cells in apple cores could
encourage any remaining viable bacteria in the calyx to multiply. The multiplication of E.
amylovora on apple waste is considered possible (Paulin 2010a) but this has never been
observed and there is no evidence to support this can occur. If this were to occur, bacteria
that have been subjected to adverse conditions require a long lag phase before growth
resumes under favourable conditions (Madigan and Martinko 2006). Even for freshly
cultured E. amylovora inoculated into host flower nectaries, a lag phase of 6–36 hours is
required before rapid growth can occur (Wilson et al. 1990).

50


The availability of water in fruit waste, as measured by water potential, is an important
factor that will affect bacterial growth. Water potential is described by a scale from zero,
for pure water, to increasingly negative numbers for water containing dissolved substances
(sugars, salts etc). For example, sea water has a water potential of about –3.0 Mega
Pascals (MPa) (Salisbury and Ross 1992). Water potential is a measure of the tendency of
water to move from one area to another due to osmosis, gravity, mechanical pressure, and
matrix effects including surface tension (Salibury and Ross 1992).
The water potential in fruit waste will affect the ability of E. amylovora to utilise nutrients
in the waste for growth. It has been shown in live host plants, fire blight disease resistance
increases as moisture content and water potential decreases (Shaw 1934; van der Zwet and
Keil 1979). Disease infection and severity is linked to bacterial growth (van der Zwet and
Keil 1979; Agrios 1997).
In more recent work, fire blight disease incidence and severity in susceptible tissue of crab
apple approached zero at water potentials of –3.0 MPa and was zero at −4.0 MPa (Pusey
2000). Maximum disease incidence and severity occurred at water potentials above –2.0
MPa, and disease severity continued to increase above –1.0 MPa (Pusey 2000).
In an additional experiment, fire blight incidence and severity in susceptible apple tissue
was zero at –2.77 MPa (Pusey 2000).
Apple leaves have a water potential of –0.5 MPa at full turgor before sunrise and this can
decrease to –1.5 MPa during the day or –2.0 MPa in water stressed plants (Mpelasoka
2001). „Braeburn‟ apples, sampled at commercial harvest in New Zealand, have a water
potential of about –1.4 MPa and an osmotic potential of –2.0 MPa (Mpelasoka 2001).
Osmotic potential will equal water potential when the pressure of the solution is zero.
Apples stored at 0 C can lose about 3% of their weight over 12–17 weeks and the majority
of this is due to water loss through the apple skin (Mpelasoka 2000; Zegbe et al. 2008;
Maguire et al. 2001). At ambient temperatures of 20 C, the rate of weight loss increased
to about 5% in 18 days (Zegbe et al. 2008). Small increases in solute concentration, such
as from water loss, result in large decreases in water potential (see figure 3-6 p54,
Salisbury and Ross 1992).
In addition to water loss, commercial fruit are harvested when fruit starch has started to
mobilise. The conversion of starch to sugars in the fruit will continue post harvest (Mills
et al. 1996) that is likely to increase solute concentration, further decreasing water
potential in the fruit. A study has shown that the water potential of several varieties of
apple fruit decreased by 10–20% over an eight day period when kept at conditions that
approximate retail sale conditions (20 C) (Dobrzañski et al. 2000).
In dry conditions, it is likely discarded apple waste will continue to lose moisture rapidly,
promoted by the loss of fruit skin integrity, to levels well below that recorded in living
tissue and significantly decreasing the water potential and therefore the availability of
water for bacterial growth. The decrease in water potential affecting bacteria in the calyx
would also be relevant for any bacteria that may occur in the flesh of the fruit if fruit
infection was a pathway of concern.
In wet conditions, nutrients may wash from the apple waste and enter the calyx under
higher water potentials. However, if water can enter the calyx then water may also wash
E. amylovora bacteria from the waste into the soil. Soil is likely to be an adverse
environment for E. amylovora (see below).

51


In addition, under wet conditions saprophytic micro-organisms will colonise the waste and
metabolise available nutrients. Erwinia amylovora is not considered a good competitor
against other epiphytic bacteria that are naturally found on surface of apple or pear fruit
fruit (Roberts et al. 1989; Temple et al. 2007; Paulin 2010a). The epiphytic bacterium
Pantoea agglomerans has been shown to survive at significantly higher numbers than E.
amylovora during fruit maturation to harvest (Temple et al. 2007). Detection frequency of
epiphytic bacteria on apple fruit is not affected by cold storage over a period of 80–114
days (Roberts et al. 1989).
Pantoea agglomerans is likely to be associated with New Zealand apple fruit as it is the
biological control agent in the widely used commercial product Blossom Bless (MAFNZ
2011). Blossom Bless is used to manage E. amylovora blossom infections and is applied
when a computer model predicts climatic conditions are suitable (MAFNZ 2011).
Therefore, the apples most likely to have a calyx infestation of E. amylovora are the ones
most likely to contain P. agglomerans.
Bacteria differ markedly in growth rate under optimum conditions. For example,
representative members of the Enterobacteriaceae have a generation time of 20 minutes or
less, and many other common saprophytic bacteria have a doubling time of less than 45
minutes, whereas plant pathogenic bacteria have a markedly slower growth rate (Mason
1935). Erwinia amylovora has a doubling time of 66–94 minutes at optimal temperature
(Hildebrand 1938; Billing 1974b; Shrestha et al. 2005). In contrast, under optimal
conditions P. agglomerans has an estimated doubling time of approximately 30–35
minutes (Para and Baratti 1984; ca. from Figure 7 in Jung et al. 2002).
In addition to the direct competition from saprophytes many strains of P. agglomerans are
antagonistic to E. amylovora though the production of antibiotics (Wilson and Lindow
1993; Vanneste 1996; Wilson et al. 1992). Pantoea agglomerans is also known to reduce
the pH of its environment (Pusey et al. 2008) to levels that are known to reduce, or even
stop, E. amylovora growth (Shreatha et al. 2005). Antagonistic strains of P. agglomerans
associated with imported apples will further reduce the capacity of E. amylovora to grow
on apple waste.
The availability of nutrients, including complex structural polysaccharides that E.
amylovora is not known to metabolise (Billing et al. 1961), would also favour the growth
of saprophytic micro-organisms. Erwinia amylovora is known to be nutritionally
fastidious (Schroth et al. 1974), uses a much smaller range of carbon sources than
saprophytes (Cabrefiga et al. 2007), and therefore specific nutrients or carbon sources may
not be available for growth to occur in waste material. The slow growth rate of E.
amylovora and specific nutritional requirements will limit its capacity to compete with
saprophytes on apple waste.
Apple waste disposed of in compost may be subjected to high temperatures (60 C), which
would kill E. amylovora – many pathogens, including Enterobacteriaceae, are killed
within a few days during composting (Anonymous, 2004b; Noble and Roberts 2004). The
thermal death point of E. amylovora ranges from 45 to 50 ºC (van der Zwet and Keil
1979) and 10 minutes is required at 50 ºC in laboratory cultures (Billing et al. 1961). For
example, E. amylovora is known to be reduced to undetectable levels during composting
of host material for seven days at temperatures of greater than 40 ºC (Bruns et al. 1993).
At higher compost temperatures of 55 ºC, less than two and half days is required to
remove E. amylovora (Noble and Roberts 2004). Apple waste disposed of in landfills or
compost heaps would be rapidly contaminated and colonised by saprophytic micro-

52


organisms, hastening the decay process and minimising the likelihood of E. amylovora
survival.
Similarly, mammals or birds could consume apple waste and remove E. amylovora from
the environment.
When cores are discarded into the general soil environment, E. amylovora can survive for
a limited period provided there are high levels of inoculum; 106 cfu per gm of soil (Ark
1932; Hildebrand et al. 2001; Thomson 1969).
Bacteriophages that destroy E. amylovora have been readily isolated from soil beneath
apple and pear trees (Baldwin and Goodman 1963; Erskine 1973; Hendry et al. 1967;
Schnabel et al. 1998). Erwinia amylovora is often overgrown with other bacteria when
isolations are done from organic material, suggesting that the pathogen may not survive
long in that environment (AQIS 1998a). Survival in soil is not considered to be
epidemiologically significant (Roberts et al. 1998).
Survival of E. amylovora under unfavourable conditions such as on nitrocellulose filters,
in non-host plants as well as in inoculated mature apples and in infested apple stem
sections was studied by Jock et al. (2005). These authors found that in a sterile dry
environment an E. amylovora EPS mutant, and to a lesser extent its parental wild-type
strain decreased within 3 weeks to a low titre. However, under moist conditions the
decrease of viable cells occurred only partially for both strains. In tissues of mature
apples, E. amylovora cells slowly dispersed and could still be recovered after several
weeks of storage at room temperature at a low titre.
Ability of the pest to move from the pathway to a suitable host
Bacteria that have survived fruit maturation, packing house procedures, storage and
transport, ambient temperatures and a range of adverse environmental effects, and micro-
organism competition, and remain in a viable state in the calyx of an imported apple
would then need to be transferred to a host.
Fire blight bacteria do not have a specific dispersal mechanism. To transfer E. amylovora
to a susceptible host, a vector must pick up the bacteria in sufficient numbers to initiate a
new infection. Many genera of arthropods and insects have been associated with the
transmission of E. amylovora (van der Zwet and Keil 1979). However, this situation
relates to insects attracted to active cankers on a host with bacterial ooze, that is known to
be attractive to, and readily sticks to, insects (Paulin 2010a; Paulin 2010b).
It has been speculated that birds, particularly starlings could be involved in fire blight
transmission (Billing and Berrie 2002). Although they are known to inhabit landfill sites
and are capable of pecking fruit, no evidence is found in the literature to confirm their
involvement (Paulin 2010a).
The most likely mechanism of transfer of bacteria from discarded apples to a receptive site
in a susceptible host is by browsing insects (AQIS 1998a; Deckers 2010; Paulin 2010a).
Discarded apples are attractive to a wide range of insects and this attraction may be
increased by rotting. Bees are known to be involved in the secondary spread of fire blight
disease from infected blossoms (Thomson 2000).
Browsing insects would most likely be attracted to the exposed flesh of a partially eaten
apple because of easy access to nutrients. To access E. amylovora bacteria, insects
attracted to waste would need to enter the apple calyx, which is the remains of dried
flower parts and is likely to be free of nutrients. In closed calyx varieties the likelihood a

53


vector would come into contact with E. amylovora would even be lower unless some
mechanical damage or fruit rotting allowed access for vectors.
Once a vector came into contact with viable bacteria in the calyx the bacteria would need
to adhere to the vector. Bacteria in the calyx are unlikely to be in a metabolic state to
produce extra cellular polysaccharides (EPS) that are fresh, and therefore „sticky‟ and also
attractive to potential insect vectors (Paulin 2010a; Paulin 2010b). The lack of fresh EPS
on bacteria in the calyx is likely to limit the number of bacteria adhering to a vector.
Contaminated vectors that travel directly to a site receptive to infection have the highest
likelihood of transferring bacteria to an infection site. However, browsing insects will not
necessarily visit a receptive site directly after being contaminated with bacteria. Bacteria
are more likely to be deposited on non receptive material as receptive sites are limited and
are not always available throughout the year (see discussion below in Ability of the pest to
initiate infection of a suitable host). In addition, the majority of fruit will be imported
during autumn and winter, well before host flowering (MAFNZ 2011), when hosts are
most receptive to infection.
Once bacteria have adhered to a browsing insect, they will be removed from the relatively
protected calyx and will then be exposed to lower humidity and UV light (during daylight)
that will further increase bacterial mortality.
The vector transmission of E. amylovora from apple waste is considered a particularly
unlikely occurrence (Paulin 2010a), there is no evidence to support this can happen and
therefore the likelihood of this occurring is rather small (Deckers 2010).
A recent laboratory experiment has shown that Mediterranean fruit fly can act as a vector
of E. amylovora from infested apple fruit (Ordax et al. 2010b). In this experiment, apples
where infested with high concentrations of fresh bacterial suspension at 11 cuts on the
fruit surface (ca. 16.5 x 106 cfu per fruit: in comparison, the highest number of bacteria
recorded from freshly harvested fruit, from the calyx and fruit surface is ca. 700 cfu per
fruit (Sholberg et al. 1988)).
Flies were then introduced to two apples soon after inoculation, caged on the fruit for 48
hours, and were seen actively feeding on the bacterial suspension under optimal conditions
for the pathogen and the vector survival. The exposed flies were then transferred to
receptive hosts. Under these artificial conditions, with fresh bacteria in suspension on the
fruit surface, the flies become contaminated and transferred bacteria to a suitable host that
had been wounded and caused infection.
This study showed transmission could occur under favourable artificial conditions, which
do not replicate conditions that would occur with imported apple fruit. In the pathway
considered in this review of policy, bacteria are within the adverse environment of the
calyx, in low numbers and in an attenuated state. The experiment of Ordax et al. (2010b)
is more closely aligned to the vector transfer of E. amylovora from oozing cankers on
plant material, a method of dispersal that is already well known in the epidemiology of the
fire blight (van der Zwet and Keil 1979).
It has been previously considered that rotting of the apple could involve multiplication of
fire blight bacteria resulting in the production of bacterial ooze, known to be attractive to
insects, and this would assist in vector transfer of bacteria.
However, mature fruit do not have a suitable carbohydrate source (amylum) necessary for
rapid bacterial growth and there is no evidence to support the bacterial growth of E.
amylovora in apple waste (Deckers 2010; Paulin 2010a). Even when the fruit cortex is

54


artificially inoculated with high levels of fresh inoculum symptoms failed to develop
(Anderson 1952; Dueck, 1974a; Nachtigall et al. 1985).
A recent study has reaffirmed that the flesh of fresh apple fruit does not lead to the
multiplication of E. amylovora to produce symptoms or bacterial ooze (Ordax et al.
2010b).
In the absence of supporting evidence, the development of bacterial ooze on discarded
apple waste is considered negligible.
Taylor et al. (2003a) artificially inoculated 600 apple calyces with 106 cfu of a genetically
marked strain of E. amylovora for two seasons (a total of 1200 inoculated fruit) during
flowering. The infested apples were hung in apple orchards near open receptive flowers
for a 20-day period over two consecutive seasons. The study did not use damaged apples,
that may be more attractive to insects, but it did provide a large source of fresh inoculum
in the calyx, in very close proximity to apple blossoms, during a period that contained
highly suitable conditions for fire blight infection. E. amylovora was not detected by either
culture or PCR tests on apple flowers, leaves, rain water, or trapped insects.
Hale et al. (1996) also reported that there was no detectable spread of E. amylovora from
heavily infested calyces. Bacteria are disseminated by water, but are vulnerable to
desiccation if the water film dries out before they reach the infection site (Maas
Geesteranus and de Vries 1984). However, it is difficult to imagine a likely scenario of
movement of E. amylovora from the calyx of an apple to a suitable infection point
involving water as a vector.
Mechanical transmission of fire blight bacteria has also been considered possible. For
example, packing of New Zealand fruit in packing houses closely associated with apple
orchards could result in the exposure of workers and equipment to E. amylovora bacteria.
However, given the location of the bacteria in the calyx and the likely mode of
importation there does not seem to be a suitable pathway. Mechanical transfer from apple
fruit is not considered relevant for the distribution of fire blight (Deckers 2010; Paulin
2010a). In the absence of supporting new evidence the mechanical transfer of E.
amylovora is likely to be negligible.
Ability of the pest to initiate infection of a suitable host
Once a vector has been contaminated with bacteria it will need to transfer the bacteria to a
receptive host, in suitable numbers, while conditions are suitable for epiphytic growth on
the stigma and subsequent movement to the hypanthium for infection to occur.
In addition to blossoms, infection can also be initiated under suitable conditions in the
absence of flowers through numerous natural openings including stomata and hydathodes
(Rosen 1935; Hildebrand 1937) or wounds (Beer 1990) caused by insect damage, hail
damage or by any mechanical damage.
There is no accepted threshold number of bacteria required to initiate an infection, and this
may vary with environmental and host factors. One cell of E. amylovora can potentially
infect pomaceous flowers through the hypanthium. However, the minimum infective dose
generally depends on environmental conditions, pathogen aggressiveness, and host
susceptibility. The likelihood of infection increases with inoculum load and high levels of
fresh inoculum (>104 cfu) are required for high rates of infection (Cabrefiga and
Montesinos 2005; Pusey and Smith 2008).
Hildebrand (1939) reported that a single bacterium, from an active culture, was sufficient
to cause infection in detached flowers when placed directly in the hypanthium and

55


incubated under optimal conditions in the greenhouse, and that this success rate increased
with higher doses of inoculum. However, this experiment occurred under conditions to
maximise infection with bacteria in optimal condition and directly inoculating the
hypanthium; a process that would not occur during the importation of apples (Deckers
2010; Paulin 2010a). It has also been reported that experiments that manipulate bacteria to
very low numbers are extremely difficult to perform and results from these manipulations
should be considered with caution (Paulin 2010a).
Van der Zwet et al. (1994) showed under optimal conditions that five bacteria, placed
directly onto the nectaries, were sufficient to cause fire blight symptoms in apple flowers
in one season, but in another season a minimum of 5000 bacteria per blossom were
required for infection to occur. However, the experimental technique inoculated the
hypanthium in unopened flowers (something which cannot occur in the field), where
humidity would be higher than in open flowers and the bacteria would have some
protection from UV light. This type of inoculation experiment removed the need for
bacterial multiplication on the stigma that is required under natural conditions for
infection to occur.
Low populations of viable or actively dividing E. amylovora artificially inoculated on to
healthy pear stigmas under optimal conditions can multiply rapidly to high populations
and infection rate increases as inoculum levels increase (Thomson 1986; Thomson et al.
1999).
Artificial inoculations of pear flowers with 100 cfu resulted in infections that were
positively correlated with incubation temperature (Beer and Norelli 1975).
Experiments were conducted in New Zealand (Hale et al. 1996) to determine the number
of E. amylovora cells required to infect apple and cotoneaster flowers. These authors
reported that when flowers were inoculated with 1 to 104 cfu per flower under ideal
conditions, disease symptoms did not develop and E. amylovora were detected. Fire blight
symptoms were only observed when the inoculum dose of E. amylovora exceeded 106 cfu
(Taylor et al. 2003b).
In host plants, the most susceptible site is the stigma in flowers, and the population of
E. amylovora on stigmas is 1 to 6 log units higher than in other flower parts (Thomson
2000). Flowers are abundant in spring in pome and other susceptible fruit trees, and from
late winter to early summer on some susceptible amenity plants. The flowering stage is the
only stage when injury to tissue is not required for insects or wind-driven rain to cause
infection by E. amylovora.
Non-host plants that allow survival and limited multiplication of E. amylovora (Johnson
2004; Johnson et al. 2006) may slightly extend the potential “infection” period. However,
this is unlikely to significantly increase the likelihood of establishment as infection of a
host plant via this route would then require two rather than one transfer events. That is
transfer of bacteria from an imported apple to a non-host plant then transfer from the non-
host plant to a host plant.
For E. amylovora to establish initially, factors such as availability, numbers and
distribution of susceptible hosts are important considerations. In Australia, abundant
susceptible apple plants are grown as monocultures in orchards. A large number of
alternative hosts are also present in apple growing areas in hedgerows and along
roadsides. The host must be at a stage of development susceptible to infection.
The most receptive plant organs to infection are the flowers present during spring. The age
of the flowers has an influence on the growth and establishment of E. amylovora (Gouk

56


and Thomson 1999). These authors showed that under New Zealand conditions, 1- to 3-
day-old flowers supported bacterial populations but bacterial numbers did not increase in
flowers older than three days. Thomson (1986) and Thomson et al. (1999) showed that
flowers were colonised over a period of 2 to 6 days, but the incidence of blossom infection
increased from 0 to 100% in only two warm days in an orchard with numerous oozing
cankers.
In contrast, stigmas of crab-apple trees supported bacterial growth in 4- to 10-day-old
flowers, depending on temperature and pollination. However, disease incidence was
relatively high only when hypanthia were inoculated at ages between 0 to 4 days (Pusey
2004). Later it was shown infection rates steadily decreased over a 10 day period from
flower opening (Pusey and Smith 2008).
There are also several species of amenity trees that are sparsely distributed but able to
produce flowers almost throughout the year (Merriman 1996). However, trade data
indicates the majority of imported fruit will arrive in Australia before spring (MAFNZ
2011), separating the importation of inoculum temporally from the most likely point of
infection.
In addition to the host and pathogen, the third factor required for successful disease
establishment involves the environmental conditions. E. amylovora is capable of growing
between 6 ºC and 37 ºC, with optimum temperature conditions spanning 25 ºC to 27 ºC in
laboratory conditions (Billing et al. 1961). Under field conditions, immediately after a
wetting event caused by rain or heavy dew, colonised flowers would be infected when the
average daily temperature is equal to or greater than 16 ºC and petals are intact (Steiner et
al. 2000).
Rain or dew facilitates the movement of E. amylovora from the stigmas to the hypanthium
where infection may occur (Thomson, 1986; Thomson and Gouk, 1992). Steiner (1990)
and Lightner and Steiner (1993) demonstrated that rain, hail, wind and dew could act as
initiators of epidemics of fire blight.
The climatic requirements of fire blight would limit the number of suitable infection
periods during a year. For example, in winter when temperatures are too low for bacterial
growth and in summer when moisture can be limiting factor (Van Der Zwet and Keil
1979; Steiner 1990; Deckers 2010; Paulin 2010a).
Successful infection could take place if viable bacteria were present to infect susceptible
host tissues under favourable environmental conditions, provided that each step listed
above is completed. If there is a very low likelihood of the entire chain of events being
completed, then there is a very low risk of establishment of fire blight. However, a break
in any step of this chain of events would prevent the establishment of the disease.
There is currently no evidence that supports the hypothesis that E. amylovora located in a
calyx of an imported apple can initiate an infection in a suitable host under natural or
experimental conditions. It is considered the likelihood of this occurring would be
exceptional (Deckers 2010) or extremely low (Paulin 2010a). In contrast, it has been well
established that the calyx of mature apple fruit is an unfavourable environment for E.
amylovora, where the bacteria are attenuated, cannot multiply, and over time will die.
There is indirect evidence from epidemiological work that supports the proposition that
fire blight is not moved by the trade in apples. Pulsed-field gel electrophoresis (PFGE)
patterns of E. amylovora strains in Europe and the Mediterranean region were studied by
Jock et al. (2002). These authors observed a well ordered pattern of distribution of PFGE
types without any evidence of mixing in spite of unrestricted trade in fruit in most

57


European countries. The authors concluded that the patterns of distribution of strains
suggest a sequential spread of fire blight from England and Egypt into neighbouring
countries. If fruit trade between countries resulted in numerous introductions of fire blight
bacteria, it would be expected that PFGE patterns would be similar in different areas.
New Zealand has been exporting apples to Taiwan and China for several years without
specific risk management measures for fire blight (MAFNZ 2011). China is the largest
producer of apples in the world (Branson et al. 2004). There have been no reports of fire
blight in either of these export destinations. Exports of apples from the southern to
northern hemisphere would land fruit during spring when host plants are flowering and at
the most susceptible stage for infection.
Conclusion on probability of distribution
For Erwinia amylovora to be distributed to a suitable site on a susceptible host within
Australia, any bacteria imported would need to remain in a viable state and be transferred in
sufficient numbers to either the blossom or a wound on a host plant.
As discussed in assessing the probability of importation, Erwinia amylovora is likely to be
present in a viable state in the calyx in low numbers, and in only a small proportion of
imported apples. The calyx is an adverse environment for E. amylovora and during retail
storage and display, then purchase by consumers, the decline in bacterial numbers will
continue. The decline in bacterial numbers will be accelerated by removal of fruit from any
cold storage and subsequent exposure to ambient temperatures. Apple waste that enters
regulated waste disposal or composting would remove any E. amylovora from the
environment. Under wet conditions, competition from other micro-organisms would further
decrease bacterial survival on any remaining apples. In particular, imported apples with
highest chance of E. amylovora infestation are likely to be associated with anatagonistic
bacteria that are known to survive and grow significantly better under adverse conditions than
E. amylovora. For infested fruit that do enter the environment under dry conditions, water loss
is likely to prevent any E. amylovora bacteria utilising nutrients in the apple waste, limiting
their ability to recover from an attenuated state and then multiply.
If any attenuated bacteria survived these adverse conditions, then transfer to a host would
need to occur. Vectors would need to come into contact with any viable bacteria that are
restricted to the calyx. Physical access for vectors can be restricted in closed calyx apple
varieties and vectors are unlikely to be attracted to the calyx as it is free from nutrients.
Bacteria would subsequently need to adhere to a browsing insect which is unlikely in the
absence of extracellular polysaccharides that assist in vector attraction and adherence to the
vector. Any E. amylovora adhering to insects would then need to be transferred to a restricted
number of receptive sites on a host, and under suitable climatic conditions to initiate an
infection.
The most susceptible stage for infection in hosts is the blossom. If E. amylovora bacteria were
to infect a blossom in Australia, it would first need to survive the many months from the
autumn apple harvest in New Zealand until the Australian spring when hosts are typically in
flower. There is no evidence that naturally occurring E. amylovora bacteria in apple calyces
can survive this length of time. Further, there is no direct evidence that vector transmission
can occur under natural conditions from apple waste, even though it has been hypothesised. A
rating of „extremely low‟ for the probability of distribution of E. amylovora via the calyx of
some imported apples is supported.

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Overall probability of entry
The overall probability of entry is determined by combining the probability of importation
(moderate) with the probability of distribution (extremely low) using the matrix of rules
shown in Table 2.2 on page 9.
The likelihood that Erwinia amylovora will enter Australia as a result of trade in the
commodity and be distributed in a viable state to a suitable host: EXTREMELY LOW.

4.1.2 Probability of establishment
The likelihood that E. amylovora will establish within Australia based on a comparison of
factors in the source and destination areas that affect pest survival and reproduction is HIGH.
In the estimating the probability of distribution, the PRA has already considered the
sequence of events necessary to allow sufficient infective inoculum to reach a suitable
infection site under suitable climatic conditions to initiate infection. The probability of
establishment will consider whether this initial infection will lead to the longer term
infection that will result in the completion of the pathogen lifecycle on host plants through
an entire year to account for seasonal differences that may affect establishment.
Availability of suitable hosts, alternative hosts in the PRA area
In Australia the sub-family Maloideae has at least 16 host genera susceptible to fire blight,
each containing several species (given within parentheses). They are: serviceberry,
Amelanchier spp. (6); chokeberry, Aronia spp. (3); Japanese quince, Chaenomeles spp.
(5); cotoneaster, Cotoneaster spp. (30); hawthorn, Crataegus spp. (19); quince, Cydonia
spp. (3); loquat, Eriobotrya sp. (1); Heteromeles sp. (1); apple, Malus spp. (17); medlar,
Mespilus sp. (1); Photinia spp. (4); firethorn, Pyracantha spp. (8); pear, Pyrus spp. (9);
Indian hawthorn, Rhaphiolepis spp. (2); and mountain ash, Sorbus spp. (23) (AQIS
1998a).
Occasionally, natural infections of E. amylovora occur on species not belonging to the
sub-family Maloideae; for example, on Japanese plums (Prunus salicina) when there is an
active source of inoculum of E. amylovora nearby (Mohan and Thomson, 1996). In
Germany, E. amylovora infection was detected on young fruits of plums (P. domestica)
(Berger et al. 2000).
The potential for E. amylovora to grow epiphytically on flowers of non-host species of fire
blight such as Acer (maple), Amelanchier (serviceberry), Cytisus (Scotch broom), Populus
(cottonwood), Prunus (stone fruit), Rubus (blackberry, raspberry), Salix (willows) and
Symphoricarpos (snowberry) has been reported in USA (Johnson 2004; Johnson 2006).
Most of these hosts are present in Australia.
Rubus spp. could serve as potential sources for establishment of fire blight. Strains of
E. amylovora pathogenic to Rubus spp. were originally described as E. amylovora f. sp.
rubi (Starr et al. 1951). A subgroup within this group seemed to be capable of cross-
pathogenicity with Maloideae (Momol et al. 1997).
Australia has a similar mix of apple varieties to New Zealand. The majority of Australian
apple and pear cultivars planted are highly susceptible to E. amylovora (Vanneste et al.
2002). Many of the new high-density plantings of apple are on fire blight susceptible
rootstocks of M.9 and M.26. Commercial apples are grown in orchards in temperate
Australia. Apples are also grown in many suburban backyards.

59


Some highly susceptible alternative hosts (cotoneaster and hawthorn) are commonly
grown as hedgerows in home gardens, along roadsides and in parks. In Tasmania,
hawthorn and cotoneaster are planted along the roads for hundreds of kilometres.
Alternative hosts are also present as feral plants, but their populations are generally
scattered. Derelict and abandoned apple orchards were found in a survey conducted in the
Adelaide Hills in South Australia and such orchards may be present in other areas
(Creeper and Nicholson 2005).
Of the recorded hosts, fire blight is a serious bacterial disease affecting apple, pear,
quince, loquat, hawthorn, cotoneaster and firethorn. It is considered these primary hosts
will provide the highest chance of fire blight establishing in Australia (Paulin 2010a).
Detailed information on exact flowering times for pome fruit production areas is not
available. Flowering patterns vary with latitude and altitude. However, it has been shown
for the Goulburn Valley that the flowering period for apple and pear coincides with
suitable infection periods for E. amylovora (Gouk 2008).
The estimated flowering time of host plants susceptible to E. amylovora in the Adelaide
Botanic Gardens is given by Merriman (2002). He showed that host plants (for example,
Malus spp., Pyrus spp., Cotoneaster spp., Crataegus spp., Sorbus spp., Amelanchier spp.,
Cydonia spp., Mespilus spp., Prunus spp., Rubus spp., Rhaphiolepis spp.) mostly flower in
spring, with some commencing flowering at the end of winter. Cotoneaster spp. And
Photinia spp. Flower in spring and summer. Production of secondary blossoms (rat-tails)
in late spring and early summer is likely to prolong the potential period of disease
establishment.
Susceptibility of native plants to E. amylovora is unknown. However, none of the few
native plants in the Rosaceae are closely related to any known hosts of fire blight.
Suitability of the environment
Erwinia amylovora is native to North America and was initially recorded from England in
1958 (van der Zwet and Kiel 1979). Since then is has established across continental
Europe and to Mediterranean countries in Europe, Middle East and North Africa (CABI
2002; Bonn and van der Zwet 2000). Many of these countries, particularly the
Mediterranean countries, have climates broadly similar to temperate regions of Australia
(Peel et al. 2007).
An incursion of E. amylovora was detected in Melbourne in May 1997 and subsequently
eradicated (Rodoni et al. 1999). It is not known how long the disease was present but the
period of time was sufficient for bacterial growth to allow the expression of symptoms.
In most years, environmental conditions in many Australian apple and pear growing areas
(notably the Goulburn Valley) are favourable for infection (Penrose et al. 1988;
Wimalajeewa and Atley 1990; Fahy et al. 1991). Apple production in Australia is
confined to high rainfall areas. In these areas, the temperature during the blossoming
period is higher than the threshold required for fire blight development (Roberts 1991).
Incidence of blossom blight increased at relative humidity above 60%, with 100%
infection at relative humidity above 85% (Norelli and Beer 1984). These climatic
conditions occur in the spring in most locations where pome fruit is grown and less
frequently in summer.
During winter, low temperatures are likely to limit suitable infection periods (Steiner
1990).

60


Hailstorms are common in pome fruit growing areas in Australia (QFVG 2000). These
cause injuries on plant tissues, predisposing them to infection (Brooks 1926; Keil et al.
1966).
Several potential infection days and multiple infection periods for fire blight occur at
blossoming in apple production areas of Queensland, New South Wales and Victoria
(Atley 1990; Fahy et al. 1991; QFVG 1996; Wimalajeewa and Atley 1990).
A recent study has confirmed that the Goulburn Valley in Victoria, the main pome fruit
region of Australia, has suitable climatic conditions for inoculum production and infection
in spring that coincide with the main blossom period and results in many potential high
risk infection events (Gouk 2008). This study used the two most important predictive
models for blossom infection that have been used effectively in North America and New
Zealand to predict infective events and manage blossom infection (Steiner 1990; van der
Zwet et al. 1994; Biggs et al. 2008; Manktelov and Tate 2001).
Reproductive strategy and the potential for adaption
Stable differences in virulence of some strains have been found on different genotypes of
varieties of apple (Norelli et al. 1984).
In artificial favourable conditions at 25–30 C the doubling time of multiple isolates of E.
amylovora ranged from 66–90 minutes (Hildebrand et al. 1398; Billing 1974b; Shreatha et
al. 2005). Similar growth rates were recorded for E. amylovora in host tissue (Billing
1974b). Only one day of optimum temperature would be sufficient for low populations of
E. amylovora to multiply to 105 to 106 cfu per blossom (Thomson et al. 1999) provided
there is no competition from other micro-organisms and that nutrient, temperature and
humidity are optimal.
The stigmas of blossoms are the most receptive sites for initiation of new infections,
where bacteria can multiply rapidly. Bacterial populations often reach 106 to 107 cfu per
healthy flower (Thomson 1986; Johnson et al. 2009). However, blossom infection occurs
only when bacteria reach the hypanthium (floral cup) under favourable conditions
(Thomson 2000).
One bacterium placed directly in the hypanthium was sufficient to cause blossom infection
under controlled inoculations in the laboratory (Hildebrand, 1937). In some seasons five
bacteria, and in another 5000 were sufficient to cause blossom infection (van der Zwet et
al. 1994). However, as previously discussed the experimental methods employed in these
studies do not occur under field conditions. For inoculum sourced from a canker,
inoculum levels are unlikely to be limiting as bacterial ooze can contain 108 to 1010 cfu/ml
(Beer 1979).
Hale et al. (1996) found that when blossoms were inoculated with between 1 to 104 cfu,
there were no disease symptoms and E. amylovora could not be detected in the blossoms.
Taylor et al. (2003b) demonstrated that successful infection of flowers occurred only
when the populations of E. amylovora exceeded 106 cfu on flowers that are less than four
days old.
Exopolysaccharides in E. amylovora capsules prevent cells from losing water, which can
be an important means of survival under dry environmental conditions (Geider 2000).
Polysaccharide material is readily rehydrated, enhancing the viability of bacterial cells
(Keil and van der Zwet 1972a). Bacteria can also form dry strands of polysaccharide
material. These are present mainly during blooming and are considered important in
dissemination (Ivanoff and Keitt 1937).

61


Erwinia amylovora can survive in the previous year‟s cankers (Beer and Norelli 1977) and
as latent infections in internal stem tissues (Brooks 1926; Miller 1929).
Erwinia amylovora can remain viable on fruit spurs following blossom infection until bud
burst the following spring (Dye 1949).
Erwinia amylovora could survive 11 weeks in nectar and 8 weeks in honey at 4 C.
Survival was much shorter at higher temperatures. Debris, wax and propolis (glue used by
bees to cement combs to hives and close up cells) were poor media for survival. In pollen,
E. amylovora survived 40 weeks at 15 C and more than 50 weeks at 4 C (Wael et al.
1990).
Under low relative humidity, the bacteria can survive in the dry exudate from cankers for
up to 1 or 2 years (Rosen, 1938; Hildebrand, 1939) but under humid conditions survival
time was much shorter (Hildebrand, 1939).
Erwinia amylovora can survive in the dark for considerable periods, but is killed rapidly
on exposure to ultraviolet light/full sunlight (Southey and Harper 1971).
The importance of VBNC state, biofilm/aggregates and sigma factor on the survival of
E. amylovora has been discussed previously. Preliminary evidence suggests that the above
factors may have a role to play in the survival of E. amylovora, and although they are not
completely understood under field conditions, they would be taken into account in the
survival studies of E. amylovora bacteria in the calyx.
Repeated use of streptomycin can result in the development of resistant strains of
E. amylovora (Thomson et al. 1993; Jones and Schnabel 2000). Streptomycin resistance in
bacteria can occur as a result of chromosomal mutation of the gene rpsL or gene
acquisition by plasmids or transposons (Jones and Schnabel 2000). Resistance determined
by a chromosomal gene in the bacterium is not readily transferred during cell division but
genes in acquired (plasmid) resistance strains are readily transmissible from one bacterium
to another, even if these two bacteria belong to different species or genera (Vanneste and
Voyle 1999).
Streptomycin-resistant strains have been found in Hawke‟s Bay in New Zealand since
1991 (Thomson et al. 1993; Vanneste and Yu 1993). Continued monitoring up to year
2000 failed to find streptomycin resistance outside Hawke‟s Bay.9 Since finding
streptomycin resistance the use of this chemical has become much more targeted and is
now based on a predictive system. For example, in 2004 only 10% of apple blocks used
streptomycin (MAFNZ 2005a). The reduction in the quantity and frequency of use of
streptomycin will reduce the chance of resistant strains developing. More recent
information, over a period from 2006/07 to 2009/10, has reported on average, only 6.3%
of blocks applied streptomycin (BSG 2011).
Bacteria can become resistant to streptomycin either by enzymatic modification of
streptomycin or from the modification of the target molecule. Based on the type of
resistance, streptomycin resistant bacteria can be categorised into two groups. Group A
bacteria are resistant to extremely high levels of streptomycin, but the resistance cannot be
transferred to other bacteria. Bacteria belonging to group B are resistant to lower levels of
streptomycin but this resistance is transferable to other bacteria including bacteria from
other species or other genera. All strains of E. amylovora isolated from Hawke‟s Bay

9
http://www.hortnet.co.nz/publications/nzpps/resist/streptom.htm. Accessed on 6 June 2005.

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belong to group A (Vanneste 2004). The development of streptomycin resistance in
E. amylovora was because of the mutation of genes and not plasmid-borne (Thomson et
al. 1993). On the basis of available information, the transfer of streptomycin resistance
genes from one organism to another would not occur.
Cultural practices and control measures
Streptomycin is the most effective chemical to control fire blight, particularly at
blossoming (van der Zwet and Keil 1979), but it is not a registered chemical in Australia.
New chemicals (for example, oxytetracycline, fosetyl-aluminium, oxolinic acid) have
been tested in the USA and found to be effective as replacements for copper compounds
and streptomycin (Psallidas and Tsiantos 2000). These chemicals are currently not
registered for use in Australia for control of fire blight.
Naturally occurring bacterial antagonists (for example, Pantoea agglomerans [synonym:
Erwinia herbicola] and Pseudomonas fluorescens) have proven to be effective against
blossom infection (Johnson and Stockwell 2000; Cabrefiga et al. 2007) although results
can be variable in some locations (Sundan et al. 2009). Application of Pseudomonas
fluorescens strain A506 (Blightban A506®) applied to emerging flowers controlled fire
blight by pre-emptive competitive exclusion of E. amylovora (Lindow et al. 2004).
Mixtures of P. fluorescens and P. agglomerans were more effective in suppressing flower
infection by E. amylovora (Johnson et al. 2004).
Commercial formulations of strains of Pseudomonas fluorescens and Pantoea
agglomerans (synonym: Erwinia herbicola), that produce antibiotics and compete for
space and nutrients, have been used as biocontrol agents (Wilson and Lindow 1993;
Vanneste 1996). Pantoea agglomerans is recorded from rosaceous hosts in Australia
(APPD 2003) as Erwinia herbicola. P. fluorescens has not been reported on rosaceous
hosts in Australia.
New antagonists for the control of E. amylovora, such as non-virulent strains of
E. amylovora, yeasts, Gram-positive bacteria and mixtures of bacteriophages specific to
E. amylovora have shown promise in cultural tests or greenhouse assays, but have not
been widely tested under field conditions (Ritchie and Klos 1977; Palmer et al. 1997).
Use of prohexadione-calcium, a plant growth regulator, which reduces vegetative shoot
growth in apple led to lowered incidence of fire blight (Deckers and Schoofs 2004; Norelli
and Miller 2004).
Commercial orchards in Australia do not employ any specific management methods that
would limit the establishment of E. amylovora. However, general pruning practices may
incidentally remove cankered wood. However, symptoms of fire blight can resemble other
diseases (Rodoni et al. 1999) and may initially be considered unimportant.
Less use of disease control and heavy pruning practices in garden and household situations
may favour establishment of the disease.
Conclusion on probability of establishment
If E. amylovora has infected a suitable host, the disease can develop quickly and survive
within a perennial host for multiple years. Erwinia amylovora is known to have established in
a number of countries with very similar climatic conditions to Australia. Erwinia amylovora
has previously infected hosts in Australia under natural conditions. Computer models that
have been shown to accurately predict infection events indicate that many parts of Australia
are climatically suitable for E. amylovora, including the major pome fruit growing regions. In
addition, there are several suitable ornamental hosts that are widely scattered across Australia.

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In countries where E. amylovora occurs, the application of antibiotics and antagonistic
bacteria are the most effective strategies to manage infection periods during blossom.
However, the products used overseas are not registered for use against E. amylovora in
Australia and there is no need for them to be applied prophylactically for a bacterium that is
not known to occur in Australia. In addition, fire blight symptoms can be confused with other
diseases and may go unnoticed or assumed to be of no significance. As there are currently no
targeted management practices that would be effective against E. amylovora in commercial
production sites, there would be nothing to prevent E. amylovora establishing a persistent
population. Further, control measures of any sort are unlikely to be applied on amenity or
feral hosts and this would increase the likelihood of the pathogen establishing. The evidence
supports an assessment rating of „high‟ for the establishment of E. amylovora.

4.1.3 Probability of spread
The likelihood that fire blight will spread based on a comparison of factors in the area of
origin and in Australia that affect the expansion of the geographic distribution of the pest is:
HIGH.
Suitability of the natural/or managed environment
Apples and pears in commercial orchards would be conducive to localised disease spread.
Suitable host plants in nurseries distributed across states could rapidly spread the disease
to new districts. The scattered distribution of host plants in household/garden situations
and wild amenity plants would confine disease spread to localised areas.
Given the geographical location of Western Australia and Tasmania there are natural
barriers that would limit the natural spread of the pathogen across those borders.
Fire blight is native to North America and was initially recorded from England in 1958
(van der Zwet and Kiel 1979). Since then is has spread across continental Europe and to
Mediterranean countries in Europe, Middle East and North Africa (CABI 2002; Bonn and
van der Zwet 2000). Many of these countries, particularly the Mediterranean countries,
have climates broadly similar to temperate regions of Australia (Peel et al. 2007).
More recently, fire blight has continued to spread in the Mediterranean region and has
now been recorded from Syria and Morocco (Ammouneh et al. 2007; Fatmi and Bougsiba
2008).
Most years, environmental conditions in many Australian apple and pear growing areas
(notably the Goulburn Valley) are favourable for infection and spread of E. amylovora
(Penrose et al. 1988; Wimalajeewa and Atley 1990; Fahy et al. 1991; Gouk 2008). Large
areas of land are planted with cultivars of apple and pear susceptible to fire blight as a
monoculture (for example, the Goulburn Valley, Granite Belt, Batlow).
Flowering periods extend over three months, for example, from the second week of
September to the third week of November in Orange, New South Wales (Penrose et al.
1988).
Alternative hosts in the vicinity of orchards are available either as intentionally planted
trees or volunteer plants established from seeds dispersed in the environment (Billing
1980).
Hail, strong winds or thunderstorms cause injuries to plant tissues, predisposing them to
infection (Brooks 1926; Keil et al. 1966). Rain (wind-blown or splashed) is probably the
major factor in spreading primary inoculum from oozing overwintering cankers (Miller
1929), and is also a means of secondary spread of E. amylovora inoculum (Thomson

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1986). The presence of ooze, accompanied by warm temperatures and rain, provides ideal
conditions for spread and infection (Hildebrand 1939). During rain, dried ooze is
rehydrated and then spread by splash dispersal (Eden-Green 1972).
Rain also indirectly aids survival and spread of the bacterium by diluting nectar in the
hypanthium, thus providing more favourable conditions for multiplication (Ivanoff and
Keitt 1941).
Streptomycin is the most effective chemical to control fire blight, particularly at
blossoming (van der Zwet and Keil 1979), but it is not currently a registered chemical in
Australia.
Recent research has identified the effectiveness of kasugamycin as a product that controls
blossom infestation and subsequent shoot infection in apple and pears (McGhee and
Sundin 2011: Adaskaveg et al. 2011). However, this product is not currently a registered
chemical in Australia.
Presence of natural barriers
The major apple production areas are confined to six states of Australia and, to a small
extent, the Australian Capital Territory. More than one growing region occurs in some
states. These areas have differing climatic conditions and are separated by long distances,
including desert areas between some states. There is potential for rapid spread within
growing areas but spread between major production areas would be slower depending on
movement of infected plants.
Potential for movement with commodities, conveyances or vectors
There is circumstantial evidence that E. amylovora can be spread long distances over land
or sea by birds (Meijneke 1974; Billing 1974a) or aerosols transported by high altitude air
currents (Meijneke 1974).
The studies on PFGE patterns of E. amylovora strains in Europe and the Mediterranean
region indicate a sequential spread from England and Egypt into neighbouring countries
(Jock et al. 2002). These authors concluded that the pattern types were well grouped
without any observed mixing. If E. amylovora was introduced via trade in apples the
PFGE patterns would have been several rather than single pattern in different parts of
Europe, North Africa and the Middle East.
The pathogen can spread from infected to healthy trees via pruning tools, hands, boots and
machinery (Psallidas and Tsiantos 2000). It also can spread through trash (leaves, stems,
twigs and soil).
Erwinia amylovora can survive on artificially contaminated wood for limited periods, but
transfer from there has not been demonstrated on uninjured fruit (Ceroni et al. 2004).
The pathogen has spread over long distances through movement of planting material
(Bonn 1979; van der Zwet and Walter 1996; Calzolari et al. 1982). The detection of E.
amylovora in vegetative material can be difficult (Rodoni et al. 1999). A recent review has
stated E. amylovora can survive for many years in the xylem tissue and symptoms do not
express until the xylem is damaged and the bacteria invade the parenchyma tissue (Billing
2011). These are factors that could assist in the spread of E. amylovora in planting
material.
Seventy-seven genera of arthropods have been implicated in the secondary spread of
E. amylovora from oozing cankers and infested blossoms. These include honeybees,
aphids, pear psylla (Psylla pyricola), tarnished plant bug (Lygus pratensis), leafhoppers
and numerous flies (van der Zwet and Keil 1979).

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Australia has at least 27 of these species or closely related species (AQIS, 1998b). Several
crawling, browsing, flying insects or other animals have the potential to spread bacterial
ooze from overwintering cankers to blossoms (Schroth et al. 1974). Pollinating insects,
primarily bees, are agents of secondary spread of the pathogen.
Managed hives of honeybees are used in contract pollination of apple orchards. Feral
honey bees can also act as pollinators. Bees generally fly up to two to four kilometres to
forage, and are major vectors in the rapid spread of E. amylovora (Hoopingarner and
Waller, 1992).
In Germany, Hildebrand et al. (2000) detected E. amylovora in 4.3% of insects examined,
but of the insects caught from apple trees with localised symptoms, only 2.1% were
contaminated with E. amylovora. This pathogen could be detected in or on green lacewing
(Chrysoperla carnea) for at least five days after coming in contact with the bacterium, and
in or on aphids (Aphis pomi) for 12 days following contact (Hildebrand et al. 2000).
People (for example, consumers, gardeners, nursery workers) handling infected immature
apples could unknowingly transfer the inoculum to susceptible host plants.
Potential natural enemies
It has been reported that one reason why Australian orchards have remained free of fire
blight is in part due to natural antagonists (Sosnowski et al. 2009). There is evidence for a
unique microflora consisting of closely related related saprophytic Erwinia species in
Australian orchards, which requires further investigation (Sosnowski et al. 2009)
Conclusion on probability of spread

Erwinia amylovora has a proven ability to spread across a continent and within a number of
countries that have similar climatic conditions to Australia. Computer models indicate the
suitability of Australian climatic conditions for blossom infection and there is a wide
distribution of multiple hosts within Australia. Once cankers form on hosts, numerous insect
vectors are able to quickly spread the pathogen over distances of kilometres. Longer distance
spread would be facilitated by movement of asymptomatic planting material via the nursery
industry.
Targeted and general management practices likely to be effective against E. amylovora are not
currently employed in Australia and the lack of disease management would initially favour
rapid increases in inoculum levels that would facilitate E. amylovora being spread by vectors.
The evidence supports a rating of „high‟ for the spread of E. amylovora.

4.1.4 Overall probability of entry, establishment and spread
The probability of entry, establishment and spread is determined by combining the probability
of entry, of establishment and of spread using the matrix of rules shown in Table 2.2 on page
9.
The likelihood that Erwinia amylovora will enter Australia by the pathways discussed in this
PRA, be distributed in a viable state to susceptible hosts, establish in that area and
subsequently spread within Australia is: EXTREMELY LOW as set out below.

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Table 4.2 Probability of entry, establishment, and spread for Erwinia amylovora

Importation Distribution Entry Establishment Spread PEES*
Moderate Extremely Extremely High High Extremely
low low low
*Probability of entry, establishment and spread.

4.1.5 Consequences
The consequences of the entry, establishment and spread of Erwinia amylovora in Australia
have been estimated according to the methods described in Table 2.3 on page 11.
Based on the decision rules described in Table 2.4 on page 12, that is, where the consequences
of a pest with respect to a single criteria is „F‟, the overall consequences are estimated to be
HIGH.
Reasons for the ratings are provided below:
Criterion Estimate and rationale
Direct
Plant life or health F – Significant at the national level:
Fire blight, caused by E. amylovora is a serious disease of pome fruit trees worldwide (Schroth et al. 1974)
and is the most destructive disease of pears (Agrios 1997).
Fire blight epidemics can develop rapidly in orchards with no history of the disease, killing many large limbs
or even whole trees. In some instances, fire blight causes no significant economic damage, even in orchards
with severe blight in the previous season. Within these extremes, the incidence and severity of the disease
can vary between orchards and seasons (Steiner 2000a).
In addition to pome fruit, E. amylovora can infect several host species belonging to the sub-family
Maloideae of the family Rosaceae (CABI 2005). Introduced plants belonging to the sub-family Maloideae
are widespread in Australia. Susceptibility of native plants to E. amylovora is unknown. However, none of
the few native plants in the Rosaceae are closely related to any known hosts of fire blight.
In New Zealand, losses for the Hawke‟s Bay region were estimated to be at least NZ$10 million during 1998
(Vanneste 2000).
In 1976–77, the annual damage in the USA from fire blight was estimated at US$2–5 million, despite regular
control of the disease (Kennedy 1980). A fire blight outbreak on apple trees in south-west Michigan in May
2000 caused losses estimated at US$42 million, including US$10 million in crop losses for the season and
US$9 million in tree losses. Tree losses are reported to include 220 000 young trees and 80 000 prime
bearing age trees (MDA 2001) and another source reported a total of 377 000 trees were lost because of fire
blight (Longstroth 2001).
Importantly, when the impact of fire blight in one year results in the large scale death of fruit bearing trees,
production losses will continue until new plantings become established. It has been reported that in
Michigan there would be an additional US$23 million in crop losses expected (Longstroth 2001; Longstroth
2002).
On the west coast of the USA, fire blight was first recorded in California in the 1880‟s (van der Zwet and
Keil 1979. Young orchards were frequently wiped out and bearing orchards recorded severe production
losses of 20–50% (Bonn and van der Zwet 2000).
In Europe, fire blight has caused variable damage between countries and depending on the host and variety
(Bonn and van der Zwet 2000). In England, after initial outbreaks in pears in the 1960‟s, fire blight is now
considered to be of minor importance. In contrast, in one nursery alone, fire blight resulted in $6 million
damage to orchard and nursery trees in 1982 (Bonn and van der Zwet 2000). In some Mediterranean
countries fire blight has also been prevalent and has caused damage in Cyprus and Israel. For example, in
Cyprus fire blight resulted in some cultivars ('Beurre Superfine' pear and 'Pera Pedi' apple) being totally
destroyed (Bonn and van der Zwet 2000).
The Australian pome fruit industry is highly valuable. For example, the gross value of industry by State for
the 2006/2007 financial year is (ABS 2008);
o Victoria, $330 million
o South Australia, $80 million
o NSW, $77.5 million
o Queensland, $33.9 million
o Western Australia, $41 million
o Tasmania, $38.5 million
The loss of production in a worst-case scenario, for all production areas in Australia, has been estimated at

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50% and 20% for pear and apple respectively (Roberts 1991).
Bhati and Rees (1996) estimated that the annual potential loss in pome fruit production would be
$125 million if E. amylovora were to establish in all regions of Australia. This represents 37.5% of the gross
annual value of pome fruit production in Australia.
If fire blight were to establish, and assuming disease severity was high from year to year, the value of lost
production between 1997 and 2002 would have been $424 million in Victoria, $141 million in New South
Wales, $97 million in Tasmania, $66 million in Western Australia, $50 million in South Australia and
$49.4 million in Queensland, equivalent to a total of $827 million over this five-year period assuming
disease severity were similar from year to year (Oliver et al. 1997). It is estimated that, if fire blight were to
establish, up to 30% of total Australian production would be lost over five years (TAPGA 2002).
However, as mentioned previously disease severity is unlikely to be high from year year (van der Zwet and
Kiel 1979; Paulin 2010a) as its prevalence is limited by suitable climatic conditions.
For South Australia, a 10% loss of yield has been estimated to cost growers about $3.5 million or at least
$11.1 million of gross South Australian food revenue (AAPGA 2000).
Street (1996) estimated the loss of annual income as a result of a fire blight outbreak in Stanthorpe to be
$20.9 million, of which growers in the Shire of Stanthorpe would lose $7 million. Queensland Fruit and
Vegetable Growers (QFVG) predicted an annual production loss of $20.9 million, if fire blight occurred in
the Granite Belt region (QFVG 2000).
Hinchy and Low (1990) estimated an annual loss of $77 million, if fire blight became established in the
Goulburn Valley. If fire blight infection was 5% in the Goulburn Valley, the estimated cost for pears would
be $2.9 million each year (Bhati and Rees 1996). Oliver et al. (1997) estimated that the total revenue loss for
the Goulburn Valley as a result of fire blight would have been $410 million between 1997 and 2002
assuming disease severity were similar from year to year.
More recently a study has estimated the consequences of E. amylovora in Australia could in the range of $33
to $95 million per year depending on the model used to estimate consequences and confidence assigned to
those estimates (Cooke et al. 2009).
If E. amylovora were to occur in the Goulburn Valley, prevention and control measures would be
implemented. Dead trees would be replaced, tolerant varieties would be replanted or other crops might even
replace pome fruit. Pome fruit production in this region could permanently decline by 55% to 60%
(Kilminster, 1989).
One tonne of pears used for canning returns $270 to the grower, and is converted to approximately $1890
worth of canned pears at the wholesale level. One tonne of fresh apples returns about $400 to the grower,
worth about $1375 at the wholesale market. It is estimated that fruit valued at $80 million at the farm gate is
valued at $400 million at wholesale, and double that at retail level (NVFA 2000). Ardmona and SPC (now
amalgamated) canning factories in Shepparton, Victoria, generate sales of $415 million a year, of which
approximately $120 million is in exports (Commonwealth of Australia 2001). Ardmona bought about
$30 million worth of fruit per year, and canned fruit generated added value amounting to $160 million. A
reduction in the throughput of pome fruit products would result in capital-intensive processing plants,
designed for continuous operation in the Goulburn Valley, being underused (Kilminster 1989).
Wittwer (2004) concluded that if fire blight established in the Goulburn Valley region the value of lost
aggregate household consumption would be $870 million or a 1.4% long-term decline in the Goulburn
Valley‟s income.
The conclusion of these predictive studies is the fact that potential consequences could be high if fire blight
reached outbreak conditions as reported overseas. These predictions estimate direct impacts of a scale that
are not seen overseas where fire blight is present as they assume a consistently high impact from year to
year. International experience shows disease impact is certainly not consistent from year to year where the
disease is known to occur as outbreaks sporadically. However, the impact of a single severe outbreak year in
Michigan resulted in lasting consequences through the removal of diseased trees and a long term loss of
productivity until replanted trees reached commercial maturity.
It has been reported that the disease incidence is higher when fire blight first establishes in a new country
and then its prevalence declines and it appears more sporadically (Atkinson 1971; Bonn and van der Zwet
2000). Australia has not selected for resistant varieties of apple and pear, nor currently applies targeted
disease management measures that may limit the impact of fire blight. Further, the major pome fruit
producing region in Australia is reported to have a very suitable climate based on fire blight predictive
models (Gouk 2008). These factors could allow for more severe and regular damage in Australia compared
to countries where the disease has been established for many decades and were targeted management
practices have been developed and widely adopted by industry.
The consequence of fire blight establishing in Australia has been considered and the direct impact of fire
blight is unlikely to be highly significant at the regional level (Paulin 2010a). However, alternative opinions
support the contention that the consequences of fire blight to plant health are high (Deckers 2010; Schrader
2010) and this is equivalent to the rating considered for consequences expected in other regions (Sgrillo
2010). Further, it is recognised that it is very difficult to quantify the disease development in terms of
economic loss (Paulin 2010b). In taking the uncertainty around the likely consequences into account,
including recent expert opinion and the concentration of the pome fruit industry in one State, a rating of „F‟
is considered appropriate.

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Other aspects of A – Indiscernible at the local level:
the environment There are no known direct impacts of fire blight on any other aspects of the environment.
There are 17 Australian native plant species that belong to the main family Rosaceae, viz Aphanes
australiana, Geum urbanum, Prunus turneriana, five species of Acaena and nine species of Rubus. Prunus
turneriana belong to the sub family Amygdaloideae and all other sixteen species to the sub family
Rosoideae. Hence, there are no Australian native plants belonging to the sub family Maloideae to which
most fire blight susceptible hosts belong.
Occasionally some Rosaceae species which are not within Maloideae have been shown to be susceptible to
fire blight. Among Prunus species (Amygdaloideae) only P. salicina (Japanese plum) and P. domestica
(European plum) are susceptible under natural conditions (see data sheet in Part C). Susceptibility of P.
turneriana has not been tested but like most other Prunus species is unlikely to be susceptible under natural
conditions.
The strain of E. amylovora affecting Rubus species (E. amylovora f.sp. rubi) appears to be different from
that infecting Malus and Pyrus (see data sheet in Part C). Therefore the strain infecting apple in New
Zealand is unlikely to infect Rubus species native to Australia. Further, there are no reports of fire blight
detection on Rubus species in New Zealand.
Indirect
Eradication, E – Significant at the regional level:
control etc. In the USA, management of fire blight adds about 30% to chemical costs and an additional US$100 per acre
for pruning costs annually. These figures translate to $700 and $1000 per hectare for pears and apples
respectively, and $275 per hectare for pruning (Oliver et al. 1997).
In the event of a fire blight outbreak, industry and the Australian Commonwealth and State Governments
would incur substantial costs, associated with losses of production and trade restrictions, regulatory
enforcement and implementation of the contingency plan (control/eradication and surveillance/monitoring).
The loss in revenue to the Australian pome fruit and nursery industries as a result of the detection of
E. amylovora in the Royal Botanic Garden Melbourne in 1997 was estimated at $20 million (Rodoni et al.
2006). These authors estimated the cost of surveys, eradication programs, diagnostics and publicity at
$2.2 million. Eradication of E. amylovora has also been tried in other countries without success and
highlight the difficulty and expense involved (Sosnoski et al. 2009). However, in Norway eradication events
continue as the program has severely reduced the prevalence of the disease in combination with
unfavourable seasonal conditions (Sosnoski et al. 2009).
Two scenarios for the economic impact of a fire blight outbreak in the Goulburn Valley were examined. In
the first scenario, a loss of $260 million was predicted for an outbreak that caused a 30% yield loss and
where the disease was eradicated in five years. In the second scenario, predicted losses were $870 million
when the disease outbreak was not controlled and yield reduction for apple and pear was estimated at 20%
and 50% respectively (Rodoni et al. 2006).
The E. amylovora eradication program carried out in and around Melbourne cost the Australian Government
and the Victorian Government about $2.8 million (ANAO 2000).
Adamson (2006) estimated that if fire blight were to establish in Australia, the apple industry which now
returns $33,000–40,000 per ha would result in a net loss of $11 000–18,000 per ha. This author also
estimated that there are one million trees over the age of six years valued at $99.4 million in 2001–02.
Therefore, payment of compensation for growers affected by fire blight could involve large sums of money.
The suggested that the costs of replanting a hectare of apples in the Batlow region of NSW would be around
$10,000 (Commonwealth of Australia, 2001) and could be as high as $40,000 (APAL 2005).
The use of streptomycin is no longer allowed in many countries due to development of resistant strains and
residue problems. However, as an emergency measure streptomycin may be allowed in Australia as is done
in Germany, under strict regulations (Moltmann et al. 2006). However, given the concern about antibiotic
use, streptomycin may not be approved for routine fire blight control.
Several novel chemical and biological materials are now registered for commercial use to control fire blight
as alternatives to streptomycin. The use of growth-regulating acylcyclohexanediones such as prohexadione-
Ca („Apogee‟) (Bazzi et al. 2003; Norelli et al. 2003) and biological control agent Pseudomonas fluorescens
strain A506 („BlightBan A506‟) are good examples. Other promising and environmentally friendly
approaches, especially the use of systemic acquired resistance inducers and other biological agents, are
showing promising results for potential use in the future.
Additional costs would be incurred for modification of orchard management programs, including the use of
chemicals, disinfestation of machinery, and regulatory enforcement of quarantine conditions.
If eradication was attempted organic growers may be compelled to use streptomycin (in the absence of an
effective alternative). This would result in these growers immediately losing their certification for growing
organic apples and the premium prices associated with the sale of such products (Commonwealth of
Australia 2001).
The eradication action taken in Melbourne was successful, when the disease was restricted to a limited
number of hosts in a Botanic Garden. Successful eradication is less likely to occur when early detection does
not occur.
Domestic trade E – Significant at the regional level:
The indirect impact on domestic trade or industry would be minor at the national level, significant at a

69


regional level and highly significant at the district level. A rating of „E‟ was therefore assigned to this
criterion.
Restrictions in interstate movement and trade of fruit and susceptible host plants are likely to occur, as they
did after the detection of E. amylovora in the Royal Botanic Gardens Melbourne. The costs incurred by the
Victorian pome fruit and nursery industries were around $7 million in lost sales and depressed prices, as a
result of restrictions on the movement of host plants and related produce (Rodoni et al. 2006).
The viability of several other sectors associated with pome fruit production, such as packing houses,
transport operators, packaging suppliers, repairers of agricultural equipment, agricultural suppliers, the
banking and finance sector and retail industries in general within all growing regions, would certainly be
affected.
Kilminster (1989) concluded that a fire blight outbreak in Australia would result in at least a 50% reduction
in fresh apple fruit in both the export and domestic markets. Supplies to the juicing sector could decline by
30–40% if the apple supply fell by 50%.
The transport sector is estimated to generate a turnover of $471 million in the Goulburn Valley, Victoria.
This represents 1050 jobs, or around 4.6% of local employment. The freight industry‟s value is estimated at
$218 million, representing around 500 jobs. Transport operators in the Goulburn Valley spend around
$33.4 million annually, of which 76% is spent locally. Each year, trucks to the value of $52 million are
purchased locally.
The value of interactions with the banking and finance sector in the Goulburn Valley is around $3.4 million,
and around $21 million from this region‟s business services sector, annually.
Fertilisers and chemicals constitute 10% of total grower costs for pome fruit production in the Goulburn
Valley. It is estimated that growers purchase $7– 8 million worth of sprayers. Based upon an assumed 40%
reduction in pome fruit production, this region would be expected to lose between $2 to 3 million annually
(Street 1996).
Australia is currently the world‟s fourth largest exporter of honey. In Victoria alone, 38 300 beehives are
used for pollination in pome fruit orchards (Commonwealth of Australia 2001). An outbreak of fire blight
could lead to a reduction in bee foraging, resulting in lowered production of honey and fewer hives being
available for contract pollination of orchards.
International trade A – Unlikely to be discernible at the local level
The estimated loss of export revenue for 1997 would have been $25 million, with a total loss of $183 million
between 1997 and 2002 (Oliver et al. 1997).
Apples and pears are exported to premium markets in the UK and European countries, and to the bulk
markets of south-east Asia. At present, none of these countries impose restrictions on apple imports from
countries where E. amylovora occurs.
Access to other markets in countries free from E. amylovora could be affected. Several importing countries
will either: not import fruit from Australia, suspend imports pending scrutiny of data concerning the disease
or impose phytosanitary measures, which could result in Australia losing competitive advantage over other
producers. South American countries, for example, require fruit to be chlorine dipped, and Japan delayed
approving the importation of apples from Tasmania for two years pending the outcome of disease surveys,
after detection of E. amylovora in the Royal Botanic Gardens Melbourne. As a result, lost sales revenue for
the Tasmanian industry was estimated at $10 million (Rodoni et al. 2006). Further as a consequence of the
detection of E. amylovora in Melbourne the Philippines temporarily suspended the trade in apples, China
required three annual surveys for fire blight in Tasmania – a condition that China still requires for apples
exported from Tasmania to China despite eradication of the disease.
However, it is now extremely unlikely trade in apples would be affected as countries free of fire blight,
including China and Japan, have recently removed targeted import requirements for this pathogen.
Streptomycin, the most effective chemical for fire blight control, is not registered for use in the horticultural
industry. It may be permitted for emergency use in the event of a fire blight outbreak in Australia. Absence
of any maximum residue limits for streptomycin may also affect trade at least in the short term.
Environmental and A – Unlikely to be discernible at the local level
non-commercial Any indirect impacts of fire blight on the environment are unlikely to be discernible at the local level. A
rating of „A‟ was assigned to this criterion.
One issue that was considered was the potential effect on the environment of chemicals that may be used to
control fire blight should it establish. The assessment on this point concentrates on the indirect impacts (not
direct impacts such as cost as suggested by one stakeholder) of the use of chemicals such as copper and
antibiotic sprays (mainly streptomycin).
Copper sprays are already in use in Australia to control a range of pests of plants including apples. It is
unlikely that the use of copper sprays for fire blight control would lead to any discernable increased impact
on the environment compared to the current use of copper sprays.
Streptomycin or any other antibiotic sprays are not currently registered for the control of plant pests in
Australia but possibly could be permitted for emergency use under strict controls in an eradication program.
Registration for more widespread use would require the evaluation of the environmental impact of the use of
antibiotics. Significant issues that would need to be considered include the potential that resistance to the
antibiotic may develop (streptomycin resistance has been found overseas (Thomson et al. 1993)) and the
potential for residues in other products such as honey.

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4.1.6 Unrestricted risk estimate
Unrestricted risk is the result of combining the probability of entry, establishment and spread
with the estimate of consequences. Probabilities and consequences are combined using the
risk estimation matrix shown in Table 2.5 on page 12.
Unrestricted risk estimate for Erwinia amylovora

Overall probability of entry, establishment and spread Extremely low

Consequences High

Unrestricted risk Very Low

As indicated, the unrestricted risk for Erwinia amylovora has been assessed as „very low‟,
which achieves Australia‟s ALOP. Therefore, additional risk management measures are not
recommended for this pest.

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Draft Report: Review of fresh apple fruit from New Zealand Apple leaf curling midge

4.2 Apple leaf curling midge

Dasineura mali
Dasineura mali is a fly with four life stages: egg, larva (or maggot), pupa and adult. Malus
species (apple and crab-apple trees) are the only hosts of D. mali. This species is native to
northern Europe, and has been introduced to both North America and New Zealand (Gagné
2007).
The adult is a small fly, 1.5–2.5 mm long, with dusky wings covered by fine dark hairs. Adult
females have a characteristic red abdomen. Eggs are transparent pink to orange-red in colour
and laid on the edge or upper surface of unfolding leaves. Sometimes eggs are laid singly, but
most often are laid in groups, with 30–40 eggs being considered typical. Larvae are tiny
legless maggots that are pink in colour when they first emerge from eggs, then turn pale-
yellow, becoming reddish-orange as they develop into the final larval stage (instar)
(Hortresearch 1999b) . When fully grown, larvae are 1.5–2.5 mm long (LaGasa 2007).
Pupation takes place in a white silken cocoon 2–2.5 mm in length (LaGasa 2007). Mature
pupae are brown in colour, distinct from the orange colour of the late instar larvae that forms
the cocoon (Tomkins 1998).
The adult female deposits eggs in the leaf folds or along the margins of immature apple leaves
(LaGasa 2007). After hatching the tiny larvae begin feeding, causing the margins of the apple
leaves to become tightly curled (galled) (Tomkins 1998). Infested leaves eventually roll into
distorted tubes and may discolour becoming red to brown and then brittle, before they finally
drop from the tree (Antonelli and Glass 2005). Terminal shoots are stunted as a result of this
leaf damage. Some of the larvae pupate in the damaged or rolled leaves, while most drop to
the ground to pupate and overwinter, emerging as adults the following spring. The midge can
complete multiple generations per year, depending on latitude (Tomkins 1998).
In New Zealand, apple leaf curling midge is known to occur from Clyde in the Central Otago
district, to Auckland on the north island. At its southernmost distribution apple leaf curling
midge is thought to have only two generations per year, while up to seven generations are
reported in Hamilton on the north island (Tomkins 1998), although that latter figure is debated
and four to five generations are considered more likely (Cross 2010). In New Zealand, D. mali
survives the winter as cocooned pre-pupae or pupae (Tomkins 1998).
The risk posed by D. mali is that mature larvae or pupae may be present on apple fruit. While
the larvae preferentially pupate in the ground, there are reports from New Zealand of pupation
occurring on apple fruit (Lowe in Smith and Chapman 1995; HortResearch 1999b). In these
cases, the pupal cocoon is firmly attached to the outside of the fruit at either the stalk end or
calyx end. If viable cocooned apple leaf curling midges were to survive packing house
processes, storage and transport, midges could enter the Australian environment and have the
potential to establish a population.


The likelihood that Dasineura mali will arrive in Australia with the importation of fresh
apples for consumption from New Zealand is: MODERATE.
Supporting information for this assessment is provided below:

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Dasineura mali is considered widespread in New Zealand. Tomkins (1998) reports that it
„is probably found wherever apple trees are grown in New Zealand‟.
While infestation levels reportedly vary between apple cultivars, no cultivar is considered
to be immune from infestation (Tomkins 1998). The key factor for infestation of leaves,
as determined during host susceptibility trials, was the availability of fresh terminal
growth when adult midges have emerged from pupation and commenced flying (Todd
1959). A similar conclusion was reached by Smith and Chapman (1995).
Present in New Zealand since the 1950‟s (Morrison 1953), D. mali was considered a
secondary pest that was effectively controlled by insecticides applied for other insect
pests. However, in the early 1990‟s pest pressures had reportedly increased, particularly
in the Auckland district, Hawke‟s Bay, and Nelson (Wilton 1994). These reports were
confirmed in the Waikato district near Auckland (Tomkins et al. 1994).
Rogers et al.. (2006) state that D. mali activity and significance as a pest declined
following the introduction of Integrated Fruit Production (IFP) program to the apple
sector through the mid to late 1990‟s.
The seasonal abundance of D. mali is significantly affected by climatic factors. In
particular, the dry summers in Hawke‟s Bay and Otago districts are reported to reduce
population size and delay the emergence of subsequent generations (Tomkins et al..
2006). Importantly, rain events result in the softening of leaf rolls, which assists mature
larvae escape leaf rolls in order to pupate (Tomkins 1998).
Insecticides are not recommended for control of D.mali in producing blocks of mature
trees as biological control is considered more effective (Pipfruit NZ 2008b). Further, the
low abundance of vigorous growing material late in the season also limits the impact of
D. mali. In recently planted orchards, or for recently grafted trees, foliar applications of
diazinon is recommended if more than 50 per cent of new shoots are infested with eggs.
Control of D. mali in New Zealand involves a range of biological control agents such as
the egg parasitoid Platygaster demades (Hymenoptera: Platygasteridae) and predatory
mites such as Anystis spp. (Acarina: Anystidae) (Shaw and Wallis 2008). The mirid bug
Sejanus albisignata (Hemiptera: Anthocoridae) is also noted as a predator of D. mali eggs
(Shaw and Wallis 2008).
Platygaster demades lays its eggs in the eggs of D. mali, with larvae developing inside
the growing midge. Platygaster demades adults emerge a few days after D. mali spins its
cocoon, killing the midge in the process (HortResearch 1999b).
High levels of parasitism by P. demades has been reported in New Zealand, but is related
to how closely the emergence of the parasitoid and D. mali are synchronised (Shaw et al.
2005). In the Nelson district, parasitism rates of up to 83 per cent of the first D. mali
generation were found, though second generations of D. mali were parasitised at rates as
low as 3 per cent. However in third and fourth generations, which occurred from late
January until early March, parasitism rates of 53 per cent and 58 per cent were recorded.
In a fifth generation in April, a parasitism rate of 80 per cent occurred. These late
generations are those that would be present as well developed larvae and pupae during
harvest of apples in New Zealand.

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Similar parasitism results were found in the North Palmerston district, which is between
Wellington and Hawke‟s Bay. In that study, the parasitism rates were 55, 41, 68 and 73
per cent of the first, second, third and fourth (overwintering) generations respectively (He
and Wang 2007).
Association of the pest with the commodity pathway
Dasineura mali primarily pupates in the ground, but occasionally mature larvae may spin
cocoons and pupate on fruit (Tomkins 1998; Hortresearch 1999b). In those cases,
cocoons are firmly attached to the skin of the fruit at either the stalk or calyx end
(HortResearch 1999b). Contamination of fruit by pupae is considered incidental,
occurring when mature larvae exiting leaf rolls get caught around the stem or calyx of
fruit when attempting to drop to the ground.
However, presence of cocoons on fruit is not a reliable indicator that live insects are
present. Dasinuera mali pupae may have already completed development and emerged,
resulting in empty cocoons, or pupae may have been killed due to parasitism or other
factors.
In the Waikato region (near Auckland), Tomkins et al. (1994) found fruit infestation
levels up to 11.5 per cent, with 98 per cent of those fruit contaminated by only a single
cocoon. However, up to three cocoons were found on some fruit. The highest levels of
contamination and damage to shoots and leaves were found in unsprayed blocks and
blocks treated only with the insecticide dimethoate. Tomkins et al. (1994) noted that the
incidence of D. mali was rapidly increasing at that time, with up to 93 per cent of shoots
having been damaged.
Similarly, Tomkins (1998) noted that most fruit was contaminated by only a single pupal
cocoon, but that up to 40 cocoons per fruit had been observed in fruit from unsprayed
orchards, though this is considered exceptional.
During trials of the IFP program that involved a total of 88 orchards across all major
production areas, D. mali contamination of apple fruit, as assessed in the field, was found
to range from 0.05 per cent to 1.40 per cent, with an average of 0.60 per cent, sampled
across all growing regions (Walker et al. 1997).
Data collected from fruit submitted to packinghouses from 1999 to 2003 indicates that the
mean level of D. mali fruit infestation, sorted by year and by variety, was in all cases
below 0.2 per cent for Nelson and below 0.03 per cent for Hawke‟s Bay (MAFNZ
2005b). The maximum midge infestation for any one processing line (described in the
data as typically 15–50 field bins in Nelson and 15–70 field bins in Hawke‟s Bay) of
apples reached 5.36 per cent in Nelson (compared with the average infestation of 0.19 per
cent in the same year and for the same apple variety) and 5.45 per cent in Hawke‟s Bay
(compared to the average of 0.03 per cent). These figures were taken from field
incidence.
Rogers et al. (2006) found that between 37 and 42 per cent of D. mali cocoons found on
fruit were unoccupied, compared with 63 per cent of cocoons found to be unoccupied by
Tomkins et al.. (1994). Of all cocoons present, 59 per cent were determined to contain
only dead pupae, based on a visual assessment and prodding of pupae (Rogers et al.
2006). If a pupa did not move when prodded it was considered to be dead. Expressed as a
proportion of occupied cocoons, 75 per cent contained dead pupae (Rogers 2008)
Based on the data available, an average of around 50 per cent of D. mali cocoons found
on fruit might be occupied by a pupa, either dead or alive, with as few as 25 per cent of

75


those pupa being viable. This would suggest that of all cocoons found on fruit, as few as
13 per cent might contain a viable pupa. However, there is clearly a substantial difference
between in the cocoon occupancy rates found by Tomkins et al. (1994) and Rogers et al.
(2006) and that highlights either seasonal variations or production site variations, or both.
Recognising that the available data reflects only limited studies at two specific points in
time and that there is likely to be variation from season to season and from orchard to
orchard, an upper limit to the number of cocoons containing viable pupae in the range of
30 to 50 per cent is adopted.
If infested leaves were to contaminate field bins, there would be some opportunity for
midge larvae to move from leaves to fruit. If larvae were to move onto fruit, it is
uncertain whether they would be of a suitable development stage to immediately spin a
pupal cocoon or otherwise become attached to the apple skin so as to remain on the apple
after washing and brushing processes. The relative absence of fresh leaf material on
producing apple trees during the harvest period also suggests that any such contamination
would be unlikely.
Standard post-harvest processing includes washing and brushing of apples. As pupal
cocoons are firmly attached in the calyx or stem end of apples, it is not clear whether
brushing would reliably reach and dislodge cocoons. Similarly, washer pressure may not
be adequate to remove all cocoons.
Walker and Bradley (2006) found that while high pressure water washing did reduce the
contamination of fruit from 0.38 per cent to 0.33 per cent, the results were not statistically
significant. Utilising newer high pressure washing also yielded results that were not
statistically significant. These washing processes were developed primarily for other pests
of potential quarantine concern, including mealybugs and leafrollers.
Dasineura mali is a quarantine pest for the state of California. Dasineura mali has been
detected during pre-clearance inspection of New Zealand applies destined for the US
market (MAFNZ 2005b).
Data from 2001–2004 from endpoint inspections for the US market indicated average
fruit contamination levels ranging from 0.10 per cent to 0.38 per cent, with an average
across all years of 0.16 per cent (Pipfruit NZ 2005). This indicates that low level
infestations can remain associated with fruit after the post-harvest processing of apples in
New Zealand and can subsequently be detected during quarantine inspections.
Dasineura mali has also been detected in several USA ports on New Zealand apples
exported to the USA (USDA-APHIS 2003), further indicating that D. mali is, at least
occasionally, associated with export consignments and can be detected during quarantine
inspections.
If apple leaf curling midges were to survive and remain associated with apples through
post-harvest grading and packaging, they would then be subjected to cold storage with the
consignment.
Commercially, apples are cold stored to maintain freshness and reduce loss in quality. For
example, a storage temperature range between 1°C and 10°C is recommended by one
retailer (Woolworths 2010), though it is expected that any extended period of storage
would occur at the lower end of this temperature range.
For apples destined for Australia, the period of any cold storage could range from a few
days to many months. However, no data is available that indicates the effect of

76


commercial cold storage temperatures on the viability of apple leaf curling midge pupae.
As D. mali overwinters as late larvae or pupae, it is likely that it could survive for
extended periods of cold storage. Indeed, if only moderately low temperatures were
utilised, the effect on D. mali is likely to be negligible.
In summary, Dasineura mali is likely to be present in most or all orchards producing export
fruit both during the growing season and during harvest. Further, infestation of fruit is a
recorded phenomenon, with cocoons able to remain associated with apple fruit throughout
post-harvest processing. This is supported by the evidence that D. mali cocoons have been
detected during end-line quarantine inspections in New Zealand.
However, evidence indicates that while D. mali is present in orchards, the populations are at
low levels during the harvest period, are subject to biological control in orchards, and are only
incidentally associated with apple fruit if larvae happen to get caught in either the stem or
calyx end of an apple when falling to the orchard floor to pupate. Further, the data from New
Zealand indicates that a large proportion of cocoons associated with apple fruit are either not
occupied by pupae, contain pupae that have been parasitised, or contain pupae that have died
due to other reasons. Allowing for variations between seasons, between 30 and 50 per cent of
any cocoons found on fruit are likely to contain a potentially viable pupa. Based on historic
inspection data from New Zealand, less than 3 per cent of consignments are found to hold
D. mali pupae, with infestations rates averaging around 0.16 per cent.
The information presented indicates that there is potential for some consignments of apples
from New Zealand to contain apple leaf curling midge pupae that are viable and remain
undetected during the minimal on-arrival quarantine processes at the Australian border.
Recognising that there is potential for this event to occur, though not with certainty in all
consignments or in all years, indicates that the probability that viable D. mali would be
imported into Australia should be assigned a risk rating of „moderate‟.

The likelihood that Dasineura mali will be distributed within Australia in a viable state, as a
result of the processing, sale or disposal of the commodity is: VERY LOW.

Distribution of the imported commodities in the PRA area
Minimal on-arrival inspection procedures include only a check that the consignment is as
described on the commercial documentation and that its integrity has been maintained.
Therefore, as this process does not include any inspection of fruit, any infestation would
not be detected. Any infested fruit would therefore be released from quarantine to
importers.
located at multiple locations and this would facilitate the distribution of any infested fruit.
Any viable apple leaf curling midge pupae would need to survive transportation and
storage within the PRA area. Fruit is typically stored and transported in refrigerated
containers maintained at cool temperatures and receival temperatures in the range of 1–
10 ºC are required by a major retailer (Woolworths 2010).
While there have been no studies to determine the cold tolerance of D. mali, this pest is
known to overwinter as a cocooned larva or pupa (Tomkins 1998), and studies into

77


emergence of adults utilised a 7 day period at 4°C to simulate an overwintering scenario
(Tomkins et al. 2000). In the absence of contradictory information it is assumed that short
duration cold storage of fruit would have little or no effect on survival of any D. mali
associated with apple fruit. The ability for a range of ages of larval or pupal D. mali to
overwinter would, in part, be one explanation for the extended period of emergence of
first generation midges found by Tomkins et al. (2006).
However, export data from New Zealand shows that the majority of fruit exported is in
retail-ready boxes or trays that do not require repacking (MAFNZ 2011). It is very likely
the majority of fruit will be distributed to retailers, potentially through wholesale markets,
without the need for re-packing. Only a small volume relative to the total imports would
be expected to be re-packed in Australia.
The only hosts for D. mali are Malus species (which includes apple and crab-apple trees).
Apples are grown commercially in most states of Australia and are also grown as
backyard fruit trees at some households. Both apples and crab-apples may be found as
ornamental, amenity, or feral trees in Australia.
Empty cocoons can be found on apple fruit and this has been attributed to midges that
have completed pupation (Tomkins et al. 1994). While it is not considered that a site other
than the calyx or stem end of an apple would need to be located by midges in order to
complete pupation, disposal of fruit within the vicinity of a host tree would be required
otherwise there would be no opportunity for eggs to be laid on suitable host material
within Australia.
Suitable host material in the form of young leaves and flowers are mostly present during
spring, though some flushes of growth may occur throughout the growing season and until
late summer. While some of this suitable leaf material may be present on trees when the
first fruit are imported from New Zealand each year (around March), any adult midges
emerging after this time, but before suitable material were present in spring would not
survive long enough to potentially initiate an infestation. Therefore, any imported midges
would need to overwinter in Australia until suitable host material became available.
On heavily infested trees, D. mali is reported to lay „a few‟ eggs on older leaves that are
already infested with larvae (HortResearch 1999b). However, it is not clear whether well-
developed leaves present during or after harvest would be attractive to female midges or
whether the larvae emerging from eggs on mature leaves would be able to complete
development.
Completion of development
The life stage of any D. mali imported into Australia on apple fruit would be cocooned
larvae or pupae and would need to complete development within Australia.
To complete pupation, any midges entering Australia would not need to find a new
pupation site. Empty cocoons can be found on apple fruit and this has been attributed to
midges that have completed development (Tomkins et al. 1994). The disposal of any
waste material to compost facilities, or the decay of any waste material disposed of in the

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environment may affect the survival of any cocooned midges that enter Australia. The
effect of this has not been quantified.
Environmental conditions would need to be suitable for pupation to be completed. In
laboratory studies, pupation lasted 30 days at a constant temperature of 23°C (MAFNZ
2006a). A lower developmental threshold has not been specifically determined for D.
mali, but recent evidence suggested that midges would complete pupation after 295
degree-days were accumulated above 6.44°C (Cross 2010), based on the data presented by
Shaw et al. (2005).
Following any cold storage, late stage larvae and pupae would need to complete
development. Given the potential range of ages in any midges on imported apples, it
would be expected that the emergence of adult midges would occur over a period of time.
An emergence period spanning six to eight six weeks has been recorded for field
populations of midges pupating in the soil (Tomkins et al. 2006). If any imported midges
were to enter diapause due to cold storage conditions, suitable conditions to break
diapause would need to occur. If suitable conditions did not occur, pupae may remain in
diapause until the following year (Cross 2010).
If any midge pupae entering Australia were not to be exposed to suitable environmental
conditions for a sufficient length of time, it is likely that they would not be able to
complete their development. The length of time necessary would be dependent on how far
developed the pupae are, but if they were developed, it has been suggested that adult
emergence could occur almost as soon as environmental conditions were suitable (Cross
2010).
Of any pupae present on imported apples, a proportion are likely to be parasitized by
Platygaster demades which lays its eggs onto D. mali eggs. The parasitoid develops inside
the growing D. mali larva and emerges from the pupa. Parasitism rates reported by Shaw
et al. (2005) in the Nelson district ranged from 53 per cent to 80 per cent for the third,
fourth and fifth generations of D. mali, which are the generations most likely to be
associated with mature, harvest ready, fruit.
Similar parasitism results were found in the North Palmerston district, which is between
Wellington and Hawke‟s Bay. In that study, the parasitism rates were 55, 41, 68 and 73
per cent of the first, second, third and fourth (overwintering) generations respectively (He
and Wang 2007).
generated (e.g. overripe and damaged fruit, uneaten portions and apple cores). Whole
apples or parts of the fruit may be disposed of at multiple locations throughout Australia in
compost bins or amongst general household or retail waste.
For apples imported in a retail ready state, no additional sorting or grading would be
expected to occur. Boxes would be sold at wholesale markets or imported directly by retail
operations, possibly for further re-distribution.
It is unlikely that any significant volume of waste material would be produced from the
handling, sale and movement of „retail ready‟ apples. Waste material would however be
produced at the retail level, where any produce damaged in transit or affected by post-
harvest degradation is removed during retail display of apples. Such waste would be
principally whole apples and may be placed in bins to end up in either composting
facilities, landfills, or with general waste.

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For apples imported in bulk bins for repacking, any grading or repacking operation has the
potential to generate a quantity of waste material. Such material would be due to
downgrading or “culling” fruit showing damage, degradation, or otherwise considered not
suitable for market.
Orchard wholesaler waste may be disposed of into isolated areas within the orchard itself
or in landfills close to the orchard. These disposal sites are surrounded mostly by pome
fruit grown as a monoculture and wild and amenity plants are less abundant.
Apples purchased via retail outlets could enter the environment after being purchased by
consumption) is in the capital cities that are significant distances from most commercial
apple orchards. However, hosts of D. mali are present in home gardens, parks and
roadsides in large cities.
regulated refuse collection and disposal services. Managed waste will remove fruit from
the household and environment, reducing the likelihood that susceptible plants will be
exposed to this pest.
Consumers may occasionally discard fruit waste along roadsides and recreation areas.
Dasineura mali is capable of independent flight. After emerging from cocoons, any
midges within the vicinity of apple or crab-apple trees would be able to move to them
without requiring the aid of wind or a vector.
Adult male D. mali have been recorded to fly distances of at least 50 metres (Cross and
Hall 2009), though longer distance flight may also be possible (Cross 2010). While
specific studies on the flight potential of females have not been conducted, similar flight
distances would be expected.
Suckling et al. (2007) further reported that the maximum colonisation distance for females
was 30m.
Ability of the pest to initiate infestation of a suitable host
As neither the male or female adult midges feed on apple foliage infestation is only
considered here to have the potential to occur if a mating pair of midges were present in
the same location.
Adult female midges held at 4°C with moisture available survive 4–5 days, and rarely 6
days. Further, most male and female midges held at 18–20°C in a low airflow
environment survived less than one day (Cross 2010). A shorter life span of 1–2 days has
also been reported (Suckling et al. 2007).
Based on field studies, Todd (1959) determined that maximum emergence of adult midges
extended over five days, but that three days later only a limited number of midges could
be observed. While definitive studies are not available, the available data indicates that
adult midges are short lived, surviving up to four days under field conditions and less if
conditions are not favourable.
In New Zealand, emergence of D. mali adults after winter can span a six to eight week
period (Tomkins et al. 2006). This might be explained by either a range of developmental
ages of midges being present in the overwintering generation, or be due to the individual
midge‟s response to environmental and other cues to complete pupation. In either case, a

80


“window of emergence” would be expected for random populations of midges that were to
enter Australia.
For mating to occur, at least one male and one female midge would need to be within
flight range of each other during a limited period of time.
With no post-harvest processing, fruit contamination levels up to 5.45 per cent in a single
“line” has been recorded in exceptional years (MAFNZ 2005b). In typical years, the
average level of contamination across all “lines” is substantially below 0.2 per cent.
However, export endpoint inspections are considered to be more representative of the
commercial trade in apples. As indicated under the probability of importation, an average
fruit contamination level of cocoons ranges from 0.10 per cent to 0.38 per cent with some
variation between seasons (Pipfruit NZ 2005).
Further, as reported by Tomkins et al. (1994), 63 per cent of cocoons on fruit did not
contain pupae. Rogers et al. (2006) reported a more conservative figure between 37 and
42 per cent.
The parasitism levels of 53 to 58 per cent reported by Shaw et al. (2005) for third and
fourth generation D. mali and 68 to 73 per cent parasitism reported by He and Wang
(2007), suggests that at least half of all pupae in cocoons would most likely already be
dead, or fail to emerge.
As described in Section 3, a standard packinghouse practice in New Zealand for apples
includes a minimum sample of 600 fruits being inspected for evidence of pests. The
detection of a quarantine pest, including D. mali, would rule that processing line ineligible
for the Australian market. Based on a 600 fuit sample where no pests are found the
maximum level of fruit infestation would not exceed 0.5 per cent. With approximately half
of those infestations being cocoons that are empty or contain non-viable pupae, a
maximum infestation level of 0.25 per cent of fruit with viable insects would occur.
However, based on historic inspection for the US market, infestation levels after packing
house processes are 0.16 per cent (Pipfruit NZ 2005). Allowing for empty cocoons and
parasitised midges, the proportion of fruit with potentially viable midges is 0.08 per cent.
Vail et al. (1993) presented formulae to calculate the number of fruit required for a
chance of a mating pair occurring if an infestation level is specified. Using those methods,
if imported fruit with a 0.08 per cent infestation rate of viable pupa were to enter the
Australian environment, 263 fruit would need to be disposed of in one place to result in a
1 per cent chance of a potential mating pair existing. This uses the observed average
infestation rate of 0.16 per cent from New Zealand exports to the US (Pipfruit NZ 2005)
and assumes only 50 per cent of cocoons contain a viable pupa. Higher rates of parasitism,
or pupal mortality, as seen in many of the research results, greatly increase the number of
fruit that would be required.
The limited life span of adult D. mali also needs to be taken into account. As reported by
Tomkins et al. (2006), the emergence period for D. mali in New Zealand spans six to eight
weeks. Given the limited life span of adult midges in the environment, any individual
would only be present for a small portion of the predicted emergence period, thereby
reducing the chance that a mating event could occur.
The scenario of a large number of apples being disposed of in one place and within the
flight range of D. mali of a host is very unlikely to occur in a domestic or retail
environment. However, it might occur in commercial repacking facilities.

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Any apples disposed of would need to remain in a suitable condition for pupation to
complete. If disposed of in the environment, any rotting of apples, or unfavourable
climatic conditions, may reduce the number of emerging adults.
In summary, for Dasineura mali to successfully distribute within Australia and result in the
potential for eggs to be laid on a suitable host plant in Australia, any pupae entering Australia
would need to both survive until emergence and be in sufficient proximity to both a host plant
and an individual of the opposite sex within a limited window of opportunity.
Considering the infestation rates observed for commercially washed and brushed apple fruit in
New Zealand, a significant number of apples would need to be disposed of at the same place
for a chance of a mating pair to occur. When the proportion of empty cocoons found
contaminating fruit, the impact of parasitism, and the delayed emergence of adults from
cocoons is taken into account, a very large quantities of apples would need to be disposed of
into a single environmental location, and within the flight range of D. mali of a suitable host
plant. It is considered that this specific sequence of events would be very unlikely to occur
and therefore the likelihood that D. mali will be distributed within Australia in a viable state is
assessed as „very low‟.

(moderate) with the probability of distribution (very low) using the matrix of rules shown in
Table 2.2 on page 9.
The likelihood that Dasineura mali will enter Australia as a result of trade in the commodity
and be distributed in a viable state to a suitable host is: VERY LOW.

The likelihood that Dasineura mali will establish based on a comparison of factors in the
source and destination areas that affect pest survival and reproduction: MODERATE.
In estimating the probability of distribution, the PRA has already considered the sequence of
events necessary to result in a viable mating pair of D. mali midges to be present at the same
time and within the vicinity of a host plant. The probability of establishment will consider
whether the presence of a mating pair could lead to eggs being laid on suitable host tissue and
result in both an initial and subsequent generations of D. mali in Australia. For establishment
to complete successfully, the introduction of D. mali would need to result in a population that
is able to survive throughout an entire year.
Availability of suitable hosts and alternative hosts in the PRA area
The only hosts for D. mali are apple trees (including crab-apple). Apples are grown
commercially in most states of Australia and are also grown as backyard fruit trees at
some households. Both apples and crab-apples may be found as ornamental, amenity, or
feral trees in Australia.
However, while hosts are available in both urban and rural environments, only young
leaves and the bracts of flowers are considered suitable host material for D. mali to
develop on (Tomkins 1998). Therefore, any D. mali emerging in Australia would only

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have the potential to lay eggs and establish a founding population in a specific seasonal
window.
Young leaves and flowers are mostly present during spring, though some flushes of
growth may occur throughout the growing season and until late summer. While some
suitable leaf material might be present on trees when the first fruits are imported from
New Zealand each year (around March), any adult midges emerging after this time, but
before suitable material was present in spring would not survive long enough to be able to
lay eggs at a suitable site for larvae to subsequently feed.
On heavily infested trees, D. mali is reported to lay a small number of eggs on older leaves
that are already infested by larvae (HortResearch 1999b). However, it is not clear whether
well-developed leaves present during or after harvest would be attractive to female midges
or suitable for egg laying in the absence of preferred unfolding leaves.
The likely sites for initial establishment of D. mali in Australia would be anywhere that
imported material is disposed of. This could be in any urban, periurban or rural area.
However, as discussed under the probability of distribution, the greatest likelihood of a
large volume of apples being disposed of in one place would be at or near a re-packing
facility.
However, even if a mating pair of midges were present in the vicinity of a host plant, the
environmental conditions where this occurred may not be suitable for D. mali to survive.
In Europe, D. mali is reported as present in Finland, Norway and Sweden in the north and
Bulgaria, Italy, and Macedonia in the south (CABI CPC 2008). This distribution spans the
latitudes from around 38°N to 65°N. Dasineura mali has not been reported in Greece,
Turkey, or Spain, for example, even though apples are grown in these countries. This
suggests that environmental conditions can be unfavourable for D. mali, even where
apples are grown.
The northernmost parts of New Zealand are at a latitude of 35°S, with Auckland being at
around 37°S. This is approximately the same latitude as Albany in Western Australia,
Adelaide in South Australia and Wollongong in New South Wales.
Extended cold conditions may be required to break any diapause in midges entering the
Australian environment (Cross 2010). Diapause is known for other species of Dasineura
(Axelsen et al. 1997), though definitive studies have not been completed for D. mali
(Cross 2010). Cold storage during transport of apples may be sufficient to break diapause.
Laboratory studies have indicated that adult D. mali are sensitive to dry conditions (Hall
and Cross 2006). Hot dry conditions experienced in some inland horticultural growing
regions may be unsuitable for D. mali to establish a population.
Dasineura mali is established in Washington State, USA, (CABI CPC 2008), but only in
coastal areas west of the Rocky Mountain (Cross 2010). The absence of sufficient summer
rainfall has been proposed as the reason why D. mali has not established in inland
Washington State (Cross 2010).
It is possible that the relatively dry environmental conditions in many regions of Australia
where apple and crab-apple trees are grown would be unsuitable for D. mali to survive
long enough to establish a persistent population. This, along with potential absence of
suitable conditions to enter or break diapauses, would appear to be the case in countries
such as Greece, Turkey and Spain that produce apples, but have no records of D. mali
(CABI CPC 2008).

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Dry conditions are also reported to both reduce and delay subsequent generations of D.
mali (Tomkins et al. 2006). Importantly, rain events result in the softening of leaf rolls
which assists mature larvae escape to pupate (Tomkins 1998). Dry conditions are likely to
reduce the number of successful generations and this may increase the likelihood of local
extinction.
When the climatic data presented in Figures 3.2–3.11 is compared, it can be seen that
areas such as Stanthorpe in Queensland have a similar temperature range to the Waikato
district and Hawke‟s Bay. Stanthorpe also has substantially more summer rainfall, a factor
for potential survival of D. mali. While it substantially north of the Waikato district in
New Zealand, the high altitude results in moderated climatic conditions that appear to be
suitable for D. mali to establish. Broadly similar conditions also exist in Batlow, New
South Wales.
Reproductive strategy and the potential for adaptation
Dasineura mali needs to mate in order to produce viable eggs.
Adult female midges release a pheromone to attract male midges for mating (Harris et al.
1996). The pheromone has been isolated (Hall and Cross 2006).
Females are reported to commence “calling” for mates two hours after emerging from
pupation (Suckling et al. 2007).
The pheromone has subsequently been utilised to develop a trap for male D. mali (Cross
and Hall 2009). The greatest catch of male midges occurred in traps at ground level. In
tests involving a geographically isolated apple orchard it was also found that the greatest
catch of male midges occurred within 10 meters of the edge of the orchard. However,
midges were trapped at distances up to 50 meters. Greater distances were not tested.
If a male midge were present within flight range of a female midge, it is considered likely
that pheromones would attract the male midge and that mating could then occur.
Subsequent to mating, female midges are reportedly attracted by volatiles released by
apple foliage, with a marked preference for immature foliage (Galanihe and Harris 1997).
It is likely that females would be able to find suitable host material for egg laying, if it
were present.
In New Zealand, the parasitoid wasp P. demades provides control of D. mali (Tomkins et
al. 2000). However, P. demades is not present in Australia.
Generalist predators such as Anystis sp. and Sejanus albisignata also provide some control
of D. mali in New Zealand (Shaw and Wallis 2008). While Sejanus species are not
recorded from Australia, there are two species of Anystis in Australia, A. wallacei and A.
baccarum (AICN 2005). These species, or other generalist predators, may result in some
mortality in any D. mali populations. However, it is not considered that they would
prevent D. mali from establishing a founding population.
European earwig (Forficula auricularia) has also been established as a predator of D. mali
larvae and will bite through leaves to access its prey (He et al. 2008). European earwig is
widespread in Australia (AICN 2005), but while it may reduce population sizes of D. mali,
it is unlikely to prevent a persistent population establishing.
The habit of midge larvae feeding in leaf rolls is likely to reduce the impact of any
insecticides sprayed in the vicinity of an establishing population of D. mali. Further, any
such chemical sprays are unlikely to be applied to wild, amenity, or backyard apple trees.

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In summary, if a male Dasineura mali were to be present within close proximity to a female at
the same time, the male midge would be assisted in locating the female by pheromones
making it likely that mating would occur. However, there is only a limited seasonal window
during which any resulting mated female would have suitable plant material on which to lay
eggs. Further, the potential areas within Australia where D. mali could establish a persistent
population appear to be restricted to areas with favourable climatic conditions.
While there may be some impact from predation of any D. mali eggs by generalist predators
already present in Australia, there is no evidence that environmental conditions would not be
suitable in at least some parts of Australia for eggs to hatch and larvae to commence
development. Higher temperatures and drier conditions in many areas in Australia may be
unfavourable for midges, but the effect may only be to delay pupation and subsequent
generations of D. mali, not necessarily to prevent development and subsequent pupation
completely.
The formation of leaf rolls or galls as a result of midge larvae feeding would create a
protected environment which would limit any impact that predators and pesticides may have
on developing midges. However, whatever protective advantage leaf rolls provide D. mali,
they are not sufficient to allow D. mali to establish in areas where the climate is not suitable.
However, if larvae were to survive until this time and climatic conditions sutiable, it is likely
that they would be able to develop through to pupal stages and for a second generation to
occur.
Therefore, both environmental and biological factors are expected to result in some mortality
of any initial generations of D. mali, and likely prevent establishment in many regions of
Australia. However, there would remain potential for establishment in the southern latitudes,
and at higher altitudes, if a mating pair was to occur. As a signiciant part of the Australian
population is located in Melbourne, Canberra and Hobart, a significant proportion of imported
fruit could be expected to be distributed to these, more suitable areas for D. mali. The
probability of D. mali establishing a population in Australia, if a mating pair were to occur,
would then be limited only by a seasonal window of suitable host material. It is possible,
though not certain, that a population could establish and persist into the foreseeable future and
this supports a risk rating of „moderate‟.

The likelihood that Dasineura mali will spread based on a comparison of those factors in the
area of origin and in Australia that affect the expansion of the geographic distribution of the
pest is: MODERATE.

The northernmost parts of New Zealand are at a latitude of 35° south, with Auckland
being at around 37° south. This is approximately the same latitudes as Albany in Western
Australia, Adelaide in South Australia, Shepparton in Victoria and Wollongong in New
South Wales.
From Europe, D. mali is reported as present in Finland, Norway and Sweden in the north
and Bulgaria, Italy, and Macedonia in the South (CABI CPC 2008). Dasineura mali has
not been reported in Greece, Turkey or Spain, for example, even though apples are grown
in these countries and there are no quarantine measures in place against D. mali. The

85


distribution of D. mali appears to have reached an equilibrium with the pest spanning the
northern latitudes from 38°N to 65°N (CABI CPC 2008; Cross 2010). This indicates that
environmental conditions are unfavourable for D. mali, even in places where apples are
grown.
Diapause is known for other species of Dasineura (Axelsen et al. 1997). As host material
for D. mali is not present all year long, larvae or pupae would need to enter diapauses to
survive the winter months. While definitive studies have not been conducted to establish
the conditions required to break diapause in D. mali, an extended period of exposure to
cold temperatures is believed to be necessary (Cross 2010). Researchers have used
extended storage at cold temperatures to simulate conditions that may be required to
break diapauses (Tomkins et al. 2000).
While extended cold conditions occur in some regions of Australia, especially at southern
latitudes, it is likely that appropriate triggers for D. mali to enter and exit diapauses would
not occur in all locations. Therefore, it is unlikely that D. mali could spread to all areas of
Australia and establish persistent populations.
Laboratory studies have indicated that adult D. mali are sensitive to dry conditions (Hall
and Cross 2006).
It is possible that the relatively dry environmental conditions in many regions of Australia
where apple and crab-apple trees are grown would be unsuitable for D. mali to spread.
These areas are likely to be at more northern latitudes where temperatures are higher, and
also drier inland areas.
Based on the evidence from the northern hemisphere, it could be inferred that D. mali
could spread as far north as 38°S, or to include the southernmost parts of South Australia,
Victoria, and all of Tasmania. Alternately, as the northernmost parts of New Zealand are
at a latitude of 35°S, with Auckland and the Waikato district being at around 37°S, it
could be inferred that D. mali has potential to spread to areas such as Albany in Western
Australia, Adelaide in South Australia and Wollongong in New South Wales.
However, inferring distribution only from latitude information is likely to be unreliable.
The climatic data presented in Figures 3.2–3.11 shows that commercial apple growing
areas such as Stanthorpe in Queensland have a similar temperature range to the Waikato
district and Hawke‟s Bay and substantially more summer rainfall. While it is substantially
north of the Waikato district in New Zealand, the high altitude results in moderated
climatic conditions that appear to be suitable for D. mali to establish. Broadly similar
conditions also exist in Batlow, New South Wales.
Therefore, it is presumed that there are likely to be areas within Australia with climatic
conditions suitable for D. mali to spread to, even if they do not occur across the whole of
the continent.
While some pest control programs, including the use of insecticides, would be in place in
commercial apple orchards in Australia, these are not targeted for D. mali and therefore
would be unlikely to prevent D. mali spreading to commercial orchards.
Pest control programs are unlikely to be applied in most urban environments. Therefore,
it is not likely that D. mali would be prevented from spreading to, or within, urban
environments.

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The main Australian commercial apple orchards are in six states of Australia with natural
barriers existing between these areas including arid areas, climatic differentials and long
geographic distances.
Adult D. mali is capable of independent flight. Adult males have been trapped with
pheromone lures at distances up to 50m (Cross and Hall 2009) though longer distances
were not tested. At most, the adult flight range is probably limited to a few hundred
meters. This limited capacity for dispersal would limit unaided spread to only nearby
areas where hosts are present.
Unfavourable climatic conditions such as deserts and arid areas separate many of
Australia‟s urban areas and many commercial growing areas. The unfavourable
conditions and absence of host material in these areas would limit unaided spread to
defined areas.
Dasineura mali eggs and larvae are associated primarily with leaves of apple and crab-
apple trees. Cocoons containing either mature larvae or pupae are primarily found in the
soil underneath trees, though may occasionally be found in leaf rolls, on fruit, or
underneath bark and around pruning cuts (HortResearch 1999b).
The importation of apple stocks from Holland was attributed to the means of the
introduction of D. mali to New Zealand (Morrison 1953). This suggests that long distance
spread of D. mali would be aided by movement of nursery stock.
Trees grown in planter bags and described as “heavily infested” were used by Tomkins et
al. (2000) as a source of D. mali pupae from soil for emergence experiments across five
sites in New Zealand. That study reported a total of 1 884 midge and P. demades adults
being trapped in one instance. This indicates that D. mali could be moved long distances
in the soil associated with nursery stock and potted trees.
As discussed under the probabilities of importation and distribution, fruit produced under
commercial systems that include in-field pest control, and have been washed and brushed
are unlikely to move sufficient numbers of D. mali to result in long distance spread.
However, fruit that has not passed through standard washing, brushing and grading
processes may contribute to some long distance spread of D. mali.
While some interstate movement restrictions apply to both nursery stock and apple fruit,
such restrictions would not prevent intra-state spread of D. mali. Interstate restrictions,
which are targeted at other pests, may also be insufficient to prevent spread.
In summary, having established a persistent population in a single location, the independent
flight capability of adult Dasineura mali has the potential to allow localised spread, either
within an orchard or between adjacent orchards. If D. mali were to establish in an urban area,
short distance flight could also spread between properties and within a township or city
generally. Long distance spread would rely on the movement of infested commodities.
Historically, movement of infested nursery stock has been attributed to the spread of D. mali
between countries and could result in the spread of this pest between major areas of Australia.
Ultimately, environmental conditions in some regions of Australia would be expected to limit
the areas which D. mali could spread to, with its range expected to be restricted to southern
latitudes and higher altitudes, although definitive studies would be required to better define
with accuracy where this pest could spread to. These southern areas and higher altitude areas

87


such as Stanthorpe do, however, contain either a large proportion of Australia‟s residential
areas or commercial apple production sites.
Based on this information, the likelihood that D. mali will spread within Australia is
moderated by the range of environmental conditions that are expected to be suitable for the
pest‟s survival, and also by the limited capacity for independent movement. This information
supports a risk rating for spread of „moderate‟.

9.
The likelihood that Dasineura mali will enter Australia by the pathways discussed in this
subsequently spread within Australia is: VERY LOW as set out below.

Table 4.3 Probability of entry, establishment, and spread for Dasineura mali

Moderate Very low Very low Moderate Moderate Very low

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4.2.5 Consequences
The consequences of the entry, establishment and spread of Dasineura mali in Australia have
been estimated according to the methods described in Table 2.3 on page 11.
Based on the decision rules described in Table 2.4 on page 12, that is, where the consequences
of a pest with respect to one or more criteria is „D‟, the overall consequences are estimated to
be LOW.
The reasoning for these rating is provided below:

Direct
Plant life or health D – Significant at the district level:
The only known hosts for apple leaf curling midge are Malus species (CABI CPC 2008); this includes apple
and crab-apple trees. Developing midge larvae feed on leaves, causing affected leaves to curl tightly,
discolour, and potentially drop of the tree (Berry and Walker 1989).
Feeding damage can be severe in young, developing trees where damage to the terminal growth can cause
permanent stunting of the tree (Collyer and van Geldermalsen 1975; Kolbe 1982). However, mature trees are
reported to be able to withstand considerable damage (Penman 1984).
Feeding damage can affect a significant proportion of new growth, with 9–40% of leaves on new shoots
being damaged according to research by Smith and Chapman (1995). Severe defoliation may also occur if
fresh terminal growth is available late in the season and if midge populations are high (Todd 1959).
However, despite the potential for damage to foliage, fruit production in mature trees is not reported to be
affected, even when midge damage is severe (Todd 1959; Antonelli and Glass 2005).
Fruit damage has been reported to occur if populations are high (HortResearch 1999b), particularly during
flowering (Tomkins 1998), though such reports appear to be rare (Cross 2010).
MacPhee and Finnamore (1978) report that in the native range of apple leaf curling midge it has occasionally
been an economic pest (England). However, they also reported the in the 1930‟s it was a significant concern
in USA soon after its introduction in the east coast.
Surveys of Apple leaf curling midge have shown it has potential to be a significant pest, or at least cause
concern to growers in most apple growing regions of New Zealand (Smith and Chapman, 1995; Tomkins et
al., 1994). However, these reports were prior to the introduction of the integrated fruit production system.
If apple leaf curling midge were to be introduced to Australia, and in the absence of control measures or
effective biological control agents, midge populations could rapidly increase in those areas where the climate
is suitable. As discussed under the probability of establishment and the probability of spread, this could
include areas where a large proportion of the Australian population reside, and numerous areas where
commercial apple production occurs.
Damage is likely to affect developing fruit trees, nursery stock and also cause some cosmetic damage to
amenity and wild trees, though these are not common in urban areas.
Other aspects of A – Indiscernible at the local level:
the environment There are no known direct impacts of apple leaf curling midge on any other aspects of the environment.
There have been no reports of reduction of keystone species, reduction of plant species that are major
components of ecosystems and endangered native plant species, or significant reduction, displacement or
elimination of other plant species.
Indirect

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Eradication, D – Significant at the district level:
control etc. Eradication may be attempted if any incursion were limited to a specific, well defined area. Costs for an
eradication campaign are likely to be high, with potential removal of large numbers of host trees and
extensive application of chemical sprays being required.
If eradication were not attempted, growers and fruit tree nurseries would likely need to employ some level of
control for apple leaf curling midge to limit damage.
While biological controls effective against apple leaf curling midge are established in New Zealand, similar
control programs are not developed in Australia for this pest.
Control programs, in the absence of effective natural enemies have relied upon chemical spray programs,
particularly early in the season, although these are not considered as effective as biological control (Shaw et
al. 2003; Pipfruit NZ 2008).
Establishment, or changes to, an integrated pest management program to include apple leaf curling midge in
Australian orchards is likely to take a number of years while seasonal timings for chemical sprays are
determined and natural enemies are either introduced or augmented in orchards. While this occurs, it is
expected that there would be a substantial increase in the use of insecticides for control of apple leaf curling
midge because of difficulties involved in estimating optimum times for insecticide application.
Domestic trade D – Significant at the district level:
If apple leaf curling midge were present in Australia, restrictions on domestic trade may be imposed on the
movement of fruit, either intra- or inter-state.
Any domestic movement restrictions are likely to result in either reduced movement of fruit, impacting on
growers, or additional costs in meeting any quarantine requirements.
Damage to fruit has been reported, including the skin being distorted by bumps (Tomkins 1998) caused by
high populations of apple leaf curling midge affecting developing fruitlets. While such damage is apparently
rare (Cross 2010), a reduction in the aesthetic quality could result in of fruit not meeting consumer
expectations and result in reduced acceptance of fruit that is slightly affected right through to outright
rejection of imperfect fruit.
International trade D – Significant at the district level:
For the period January–October 2010, Australia exported 3 949 tonnes of apples with a value of
AUD$6.99 million.
In the case of New Zealand, apple leaf curling midge larvae and pupae found on harvested fruit can lead to
the rejection of fruit for pre-clearance export to countries such as Japan (Lowe, 1993) or treatment upon
arrival in California (Anonymous, 2002).
If apple leaf curling midge became established in Australia, trading partners may reject consignments of
apples infested with apple leaf curling midge.
Environmental and B – Minor significance at the local level:
non-commercial Control measures can be broadly classified into two categories: chemical control or biological control.
Increased insecticide use could cause undesired effects on the environment. The introduction of new
biological control agents could affect existing biological control programs.
The only hosts of apple leaf curling midge are apples. These are mainly grown under intensive cultivation in
orchards or as a backyard fruit tree. There would be little effect on environmentally sensitive or protected
areas because few apple trees grow in such areas.
There could be some unintended side-effects on the environment due to changes in pest control programs in
apple orchards and in nurseries, though this are only likely to occur, at most, on a small scale.

Unrestricted risk estimate for Dasineura mali

Overall probability of entry, establishment and spread Very low

Consequences Low

Unrestricted risk Negligible

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As indicated, the unrestricted risk for Dasineura mali has been assessed as „negligible‟, which
achieves Australia‟s ALOP. Therefore, additional risk management measures are not

91

Draft Report: Review of fresh apple fruit from New Zealand European canker

4.3 European canker

Neonectria ditissima
European canker, caused by the fungus Neonectria ditissima, is an important disease affecting
apples, pears and many species of hardwood forest trees (Swinburne 1975; Castlebury et al.
2006). The disease mostly affects branches and trunks of trees, causing cankers. Infection is
initiated through leaf and bud scars, bark disruptions such as pruning cuts and wounds, or
woolly aphid galls (Swinburne 1975). In apples and pears, the fruit can also be infected and
develop rots. Foliage is not affected (Butler 1949).
Typically, infection of fruit occurs at the blossom end, through either open calyx, lenticels,
scab lesions or wounds caused by insects (Swinburne 1964, 1975; McCartney 1967).
Sometimes the rot can develop at the stem-end (Bondoux and Bulit 1959; Swinburne 1964) or
rarely on the surface of the fruit when the skin is damaged (Bondoux and Bulit 1959). Apple
varieties vary greatly in their susceptibility to the disease, but no variety is immune (McKay
1947).
The disease was detected in 1954 in six blocks within four orchards in Spreyton, Tasmania,
but it was eradicated by 1991 (Ransom 1997). The disease is not known to occur in Australia
(APPD 2005).
The fungus produces two types of spores: conidia in spring and summer, and ascospores in
autumn and winter. Spores are dispersed by rain splash and wind. Spores germinate over a
temperature range of 2–30°C, the optimum being 18–24°C in laboratory experiments
(Munson 1939). Under field conditions, temperatures of 11–16°C with a measure of leaf
wetness provide the best predictors of disease prevalence (Beresford and Kim 2011).
The risk pathway of particular relevance to N. ditissima is primarily any latent infection in
fruit that would not have been detected during harvesting or during sorting and packing
processes.

The likelihood that N. ditissima will arrive in Australia with the trade in fresh apples for
consumption from New Zealand is: VERY LOW.

The disease mostly affects branches and trunks of trees of a range of species, including
apples, causing cankers. Infection is initiated through leaf and bud scars, bark disruptions
such as pruning cuts and wounds, or woolly aphid galls (Brook and Bailey 1965;
Swinburne 1975).
Apple varieties vary greatly in their susceptibility to the disease, but no variety is immune
(McKay 1947).

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In New Zealand, N. ditissima has been reported in Auckland, the Waikato, Coromandel,
Northland, Taranaki, Westland, Gisborne, Bay of Plenty, Hawke‟s Bay and Nelson.10
European canker has been established in Auckland, the Waikato, Bay of Plenty and
Taranaki for many years and now occurs in some orchards in the wetter parts of the
Nelson district, with isolated instances of infection in the Gisborne area (Wilton 2002a).
The incidence and severity of the disease in these districts varies between seasons,
depending on environmental conditions and orchard practices.
European canker is not regarded as a major disease in New Zealand outside the Auckland
region where the disease has been endemic since the 1930‟s (Atkinson 1971).
The restricted distribution and prevalence of European canker in New Zealand is likely to
be linked to moisture. European canker is a disease present in damp climates (Butler 1949)
and climatic conditions are critical to its development, both through inoculum production
and infection by N. ditissima (Munson 1939; Dubin and English 1974). The sporulation,
dispersal and infection by N. ditissima require mild conditions with prolonged periods of
wetness (McCraken et al. 2003b).
Temperature and duration of wetness have been shown to be the critical factors
contributing to infection (Swinburne 1975; Latorre et al. 2002). Neonectria ditissima
readily survives at temperatures between 2 C and 30 C, in ideal artificial growth
conditions, with the optimum temperature for disease development being 18 C –24 C
(Munson 1939; Butler 1949). Under controlled environmental conditions using high
fungal inoculum levels (106 conidia per millilitre) and performing inoculations less than 1
hour after leaf abscission, conidia germinate in a temperature range of 6°–32°C with no
infection occurring at 5°C regardless of the wetness duration (Latorre et al. 2002). A
minimum of 2–6 hours of wetness was required at the optimum temperature, with a longer
wetting period required at lower temperatures (Latorre et al. 2002; Grove 1990a).
In Europe, European canker is an important disease in regions with annual rainfall of 653
mm to 791 mm, and average summer temperatures between 8 C (minimum) and 21 C
(maximum) (McCraken et al. 2003b).
However, annual rainfall alone is considered a poor predictor of disease prevalence
(Latorre 2010; Swinburne 2010a) and duration of leaf wetness in combination with
suitable temperature provide a more reliable predictor of European canker (Swinburne
2010a). Recent work predicts disease prevalence under field conditions is best predicted
by temperatures of 11 C–16 C and a measure of leaf wetness (number of rainfall days per
month) (Beresford and Kim 2011).
Under field conditions, infection incidence varies significantly depending on the season.
Latorre et al. (2002) report that variations of 0.01% to 48.3% incidence have been
obtained on one-year-old twigs taken from the same unmanaged orchard in both dry and
wet seasons. Field data obtained in California indicated that several days of free moisture
were required to obtain high levels of infection (Dubin and English 1974).
In New Zealand, European canker is established in the wetter districts of the Waikato
region (average annual rainfall 1190 mm) and Auckland (1240 mm), and has restricted
distribution in the Nelson (970 mm) and Gisborne (1051 mm) regions (Atkinson 1971;
MAFNZ 2004). The disease has been recorded in Hawke‟s Bay (803 mm) but MAFNZ

10
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(2004) states that there was no evidence of subsequent infection. European canker has not
been recorded in the drier districts of Otago (360 mm) or Marlborough (655 mm)11. Later
work predicts the current distribution of European canker in New Zealand based on
temperature and leaf wetness (Beresford and Kim 2011).
A survey of apple sites throughout New Zealand in 1990 found 2% of sites were infected
with N. ditissima occurring predominantly in Northland, Auckland, Waikato, Coromandel,
Bay of Plenty and Nelson (Braithwaite 1996).
European canker is endemic in the Waikato and Auckland districts that contribute ≤3% of
total apple export trade from New Zealand (MAFNZ 2000a; Pipfruit NZ 2010).
A survey detected only one tree with European canker in Nelson and that tree was
subsequently removed (MAFNZ 2000c). However, by 2002 the disease appeared to have
spread to some orchards in the Motueka and Moutere area and pockets of Waimea
orchards of Nelson (Murdoch 2002).
The establishment and spread of the disease in these areas was attributed to extraordinarily
wet springs and autumns during 1998, 2000 and 2001 and coincided with large-scale
introductions of planting material from Waikato (MAFNZ 2004). There are no restrictions
on the movement of planting material between districts in New Zealand and this could
present a pathway for introducing new inoculum. Murdoch (2002) and Wilton (2002a)
confirm that the spread of European canker out of the Auckland and Waikato areas has
been through the movement of infected nursery plants or graft wood.
European canker has been reported three times in Hawke‟s Bay on samples collected
between 1967 and 197512. Since this time there have been no further reports of European
canker symptoms in the Hawke‟s Bay area (MAFNZ 2004). The disease is considered
absent from Hawke‟s Bay, Wairarapa, Marlborough, Canterbury and Otago (Wilton
2002b; Wilton 2004).
In Nelson, where the disease occurs sporadically in wet seasons, 28% of the total export
trade is produced (Pipfruit NZ 2010). The rest of the apple export trade is supplied from
the Hawke‟s Bay and Otago (about 69%) where the disease has not been recorded since
1975 or has never been recorded.
Association of the pest with the commodity pathway
In apple species, fruit can also be infected and may develop rots. Foliage is not affected
(Butler 1949). Typically, infection of fruit occurs at the blossom end, through the open
calyx, lenticels, scab lesions or wounds caused by insects. This is called „eye rot‟
(McCartney 1967; Swinburne 1964; Swinburne 1975). Sometimes the rot can develop at
the stem-end (Bondoux and Bulit 1959; Swinburne 1964) or rarely on the fruit‟s surface
when the skin is damaged (Bondoux and Bulit 1959).
In France, the rot has been recorded from fruit, and has been observed to spread to the
seed cavity, and the fungus has been isolated from the mycelium surrounding the seeds
(Bondoux and Bulit 1959), but this has not been observed in California (McCartney 1967).
In dessert varieties of fruit, infection can lead to the development of rot before harvest
(Swinburne 1964; Swinburne 1971a; Swinburne 1975), but infection usually remains
latent and generally develops into a rot during storage (Bondoux and Bulit 1959;

11
http://www.niwa.cri.nz/edu/resources/climate/summary/summary.xls. Checked on 15 November 2005.
12

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Swinburne 2010a). In cooking varieties, rots rarely become apparent until after fruit has
been stored for 3–7 months (Swinburne 1975).
Latency of infection is reported to be associated with accumulation of benzoic acid, a
substance toxic to fungi in the acid condition in young and immature fruit (Swinburne
1975). An infection occurring in young, immature fruit will not grow because of high
benzoic acid toxicity. However, as acidity decreases and sugar levels increase with
ripening, the toxicity of benzoic acid decreases and the fungus resumes growth. The
typical rainfall and temperature patterns of major New Zealand apple export areas would
suggest latent infection is very unlikely to occur as conditions during fruiting are not
favourable for conidia production and subsequent fruit infection (Beresford and Kim
2011).
For fruit to become infected with N. ditissima, prolonged periods of wetness in the
summer months is required for (a) the production of spores (conidia) on active stem
cankers, (b) the dissemination of those spores in run-off from cankers onto the developing
fruit and (c) a sufficient period of leaf-wetness to allow the deposited spores to germinate
and colonise limited areas within the calyx or lenticels. All three events need to occur for
fruit to become infected (Swinburne 2010a).
In Europe, where rainfall in summer coincides with spore release and flower/fruit
production, fruit rot can be a major problem (Swinburne 1975). For example, in south east
England, a survey of fruit rots showed N. ditissima resulted in only 0.1–0.2% of fruit
losses on average over three years from 100 orchards (Berrie 1989). However, in 1987/88,
after a very wet July and August, a survey of 16 commercial stores recorded mean losses
to N. ditissima rots had increased to 4.3% and one store recorded 50% losses (Berrie
1989).
In France, even when European canker is on the tree (Bondoux and Bulit 1959) and
conditions of temperature and free moisture are suitable (Latorre et al. 2002), under
favourable wet summer conditions fruit infection only occurs exceptionally and reached a
maximum of 2% in one fruit lot (Bondoux and Bulit 1959).
In the south east of England, under artificial conditions with high inoculum and humidity,
fruit infection has been recorded to occur most readily up to four weeks after flowering
and infection can continue to occur on fruit one week before harvest under suitable
conditions (Xu and Robinson 2010).
By contrast, in California, United States, rainfall and infection of plant material generally
occur in winter. Fruit infection is rare, only occurring when there is unusually high
summer rainfall (Nichols and Wilson 1956; McCartney 1967).
The USA situation is similar to that in the two main apple growing regions of New
Zealand, Hawke‟s Bay and Nelson, both areas being in the rain shadows of mountain
ranges with a high percentage of cloudless days, long growing seasons and high light
intensity. Because of the low summer rainfall, irrigation is usually necessary. Overhead
irrigation that could assist in disseminating spores and cause fruit infection is only used
for frost management and is only common in the Otago district where European canker
has never been recorded (MAFNZ 2011). In addition, low temperatures that would justify
frost management are not conducive to European canker (Beresford and Kim 2011) if N.
ditissima was recorded from the region in the future.
Fruit rot caused by N. ditissima has been reported in New Zealand (Brook and Bailey
1965; Braithwaite 1996). A study showed that of 3300 rotted fruit sent for examination to

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HortResearch between 1999 and 2005, seven (0.21%) collected from the Waikato region
were found to be infected with N. ditissima (MAFNZ 2005a).
A search on New Zealand‟s Hortnet13 found no literature on fruit rot caused by
N. ditissima, whereas there was extensive information available on other apple fruit rots in
New Zealand including apple scab (V. inaequalis), bitter rot (Glomerella cingulata), black
rot (Botryosphaeria obtusa), ripe rot (Pezicula spp.) and various core rots, suggesting that
European canker rots are not an important issue in New Zealand apples.
Fruit infection will only occur if cankers are present in the orchards (Bondoux and Bulit
1959) and exposed to prolonged periods of wetness to induce spore production and
dispersal. Given that climatic conditions typically reported for major export areas
(Hawke‟s Bay, Nelson and Otago which produce 97% of export fruit) during the harvest
periods are normally dry and not conducive to spore release and winters are not too wet
(NIWA 2004), fruit infection is extremely unlikely to occur.
In the higher rainfall areas of Auckland and the Waikato region, where European canker is
present and climatic conditions are more conducive to cankers on trees mainly due to
wetter winters (NIWA 2004), fruit could become infected during the harvest period. Fruit
infected late in the season, and showing no obvious rot symptoms, could be picked from
these orchards.
Recent research has supported the suitability of the Auckland region for European canker
disease based on a worldwide comparison of climate suitability (Beresford and Kim
2011). However, the study highlights that the Auckland region has on average poor
climate conditions for fruit infection and this information is supported by the very low
level of fruit infections recorded from New Zealand (Brook and Bailey 1965; Braithwaite
1996; MAFNZ 2005a).
All export orchards are registered with Pipfruit NZ Inc and utilise either the Integrated
Fruit Production program or a certified organic program that includes various disease
management programs. These programs provide guidance for targeted management of a
range of pathogens including European canker and other fungi such as those that cause
mildew and apple scab that would limit the prevalence of European canker in trees
(Latorre 2010; Swinburne 2010a).
Fruit can only enter export packing houses once compliance with the IFP program spray
recommendations have been confirmed by spray diary clearance by auditing organisations
independent of the industry (MAFNZ 2011).
In addition, various disease management measures to control summer fruit rots in New
Zealand orchards, including cultural practices (removal of diseased wood and rotting fruit
from trees and orchard floors) and the use of fungicides from late November/early
December until withholding periods (MAFNZ 2005a) would greatly reduce the likelihood
of N. ditissima infections being present.
European canker rots were last reported in New Zealand from a survey conducted from
1999 to 2005 (MAFNZ 2005a). During this time, the IFP program has been adopted by
New Zealand growers (Wiltshire 2003) and further refined by Pipfruit NZ Inc (MAFNZ
2011). This includes a high level of awareness by orchard managers and best practice

13
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management recommendations including removal of cankered wood and the application
of fungicides. It is likely the broad adoption of the IFP program has contributed to the
lack of detections of European canker rots.
A recent study on fruit rots in New Zealand sampled over 12,000 apples from the Hawke‟s
Bay area, that included treatments to promote rot development (wounding, cold storage),
and found no European canker rots (Scheper et al. 2007).
In mature dessert apple varieties, fruit infected with European canker can rot in the field
before harvest (Swinburne 1975), with affected fruit either falling before maturity or being
eliminated during picking (Bondoux and Bulit 1959), thereby reducing the likelihood of
latent infections in export fruit. In cooking varieties and immature fruit, fruit infections
can remain latent and express themselves after 3–7 months of storage (Swinburne 1975;
Snowdon 1990a) especially if contamination occurs towards the end of the season
(Bondoux and Bulit 1959). New Zealand does not export immature apples or significant
volumes of cooking varieties.
Fungicidal dips before storage of fruit are not used in New Zealand (MAFNZ 2003a)
indicating that storage rots are not a significant issue in New Zealand.
Packing houses utilise disinfectants such as chlorine or Tsunami® and, increasingly,
Nylate® during water washing procedures and in dump tanks. In 2005, only 53% of pack
houses used disinfectants. In 2011, 99% of export fruit produced under the IFP program
are disinfected (MAFNZ 2011). The concentration of chlorine used varies between 5 and
50 ppm and peroxyacetic acid (Tsunami®), and bromo-chloro-dimethylhydantoin
(Nylate®), as alternatives to chlorine, as per label instructions. Monitoring of disinfectants
is done manually at specific times on each day or automatically (MAFNZ 2005a). For fruit
produced under organic methods, contributing approximately 8% of exports (Pipfruit NZ
2010), fruit wash tank water is regularly replaced to remove contaminating material
(MAFNZ 2011).
In 2005, 93% of packing houses used high pressures washing (MAFNZ 2005a). High
pressure washing is now standard practice and is used at 100% of export packing houses
(MAFNZ 2011). The increased use of high pressure sprays is likely to increase the
penetration of disinfectants, when used on non organic fruit, into the protected region of
the calyx. It is likely the use of disinfectants, when used on non organic fruit, will kill the
majority of conidia (Swinburne 2010a). For organic fruit, it has been reported that high
pressure washing can be as effective in removing micro-organisms as 200 ppm chlorine
(Beuchat 1999).
Neonectria ditissima conidia from various inoculum sources that could contaminate fruit
or survive disinfectants and washing are unlikely to be a source for infection as they are
sensitive to desiccation even at high relative humidity (Latorre 2010; Swinburne 2010a).
Dubin and English (1975) reported that viability of spores dropped by 67% after 3 h
exposure at 11 C even at 88% relative humidity. Munson (1939) reported that germination
falls off steadily to zero after desiccation in the atmosphere of a laboratory for 5 to 6 days.
Standard packing house procedures will remove fruit that does not meet export quality
requirements, including fruit rots (MAFNZ 2011). Only latent infections in fruit are likely
to pass undetected during packing and sorting procedures.
Once latently infected fruit has entered the packing house, external treatments (washing
and brushing) are unlikely to adversely affect survival of internal infections.

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Once latently infected fruit has entered the supply chain, cold storage conditions are
unlikely to adversely affect survival. European canker is known to survive temperatures as
low as 2°C (Munson 1939; Butler 1949) and mycelia are known to grow at temperatures
approaching 0°C (Lortie and Kuntz 1963).
For fruit that is stored for a significant time, re-inspection occurs to ensure fruit meets
market requirements (MAFNZ 2011). It is likely that latently infected fruits that can
develop rots during this time (Berrie et al. 2007) will be removed during this inspection.
In summary, while N. ditissima has been recorded in New Zealand, and within some apple
producing areas, climatic conditions both limit the distribution of this pathogen and its
incidence in those regions where it is recorded. The limited distribution and prevalence
greatly reduces the potential for a source of inoculum to be present in orchards that might
produce apples for export. Further, specific environmental conditions are required over an
extended period of time to produce spores that could potentially infect fruit. As discussed,
these conditions are unlikely to occur in any export region. The very low level of fruit
infections recorded in New Zealand supports this limited potential for fruit infection.
Further, export fruit is produced in orchards using targeted and general management measures
to control N. ditissima. These management measures limit the inoculum levels within an
orchard and therefore reduce the opportunity for fruit infection, even when climatic conditions
are favourable. In the packing house, fruit are then treated with disinfectants/high pressure
sprays that will limit surface contamination of short lived spores. Grading procedures will also
remove apples with visible fruit rots to meet commercial and phytosanitary requirements. The
evidence supports a rating of „very low‟ for the importation of N. ditissima.

The likelihood that N. ditissima will be distributed in a viable state within Australia with
imported fruit and transferred to a suitable host is: VERY LOW.
Distribution of the imported commodity in the PRA area
Minimal on-arrival inspection procedures, that may include a visual inspection of the fruit
surface, are unlikely to detect latently infected fruit.
located at multiple locations and would facilitate the distribution of latently infected fruit.
Neonectria ditissima would need to survive transportation and storage within the PRA
area. Fruit is typically stored and transported in refrigerated containers maintained at cool
temperatures and receival temperatures in the range of 1–10 ºC are required by a major
retailer (Woolworths 2010). Neonectria ditissima is known to survive temperatures from
2°C to 30°C (Munson 1939; Butler 1949) and mycelia are known to grow at temperatures
approaching 0°C (Lortie and Kuntz 1963). Thus, transport and storage conditions are
unlikely to have any impact on the survival of latent N. ditissima infections in imported
apples distributed for sale.

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Occasionally workers and visitors could discard apple cores in the orchard itself. The
packing of New Zealand fruit from bulk bins and/or the repacking of boxes of New
Zealand fruit would bring packing house workers and host trees (apples and pears) into
close proximity to both New Zealand apples and apple waste.
However, data from New Zealand shows that the majority of fruit exported is in retail-
ready boxes or trays that will not require repacking in Australia (MAFNZ 2011). It is very
likely the majority of fruit will be distributed to retailers, potentially through wholesale
markets, without the need for re-packing. Only a small volume would likely to be re-
packed in Australia.
A large number of suitable hosts for European canker infection are widely distributed
throughout Australia, with apples (Malus spp.) and pears (Pyrus spp.) grown
commercially in most states. Most commercial apple fruit cultivars are susceptible to
N. ditisima (Anonymous 1988; CABI 2003).
Common hosts of this fungus include tree species in the genera Acer (maple), Aesculus
(horse chestnut), Alnus (alder), Betula (birch), Carya (hickory), Cornus (dogwood),
Corylus (hazel), Fagus (beech), Fraxinus (ash), Juglans (walnut and butternut),
Liriodendron tulipifera (tulip tree), Malus (apple), Populus (aspen), Prunus (cherry),
Pyrus (pear), Quercus (oak), Salix (willow), Sorbus (rowan tree), Tilia (American
basewood) and Ulmus (elm) (CABI 2005; Flack and Swinburne 1977).
Apples purchased via retail outlets could enter the environment after being purchased by
consumption) is in the capital cities that are significant distances from most commercial
apple and pear orchards. However, hosts of European canker are present in many home
gardens, parks and roadsides in large cities.
Many suitable hosts are commonly grown in Australia and are present in areas where
apples would be sold and consumed. However, host susceptibility is variable between
species and only some of these host species are highly susceptible to N. ditissima (Flack
and Swinburne 1977) and they will be subject to the same climatic requirements necessary
for infection as apple trees.
generated (e.g. overripe and damaged fruit, uneaten portions and apple cores). Whole or
parts of the fruit may be disposed of at multiple locations throughout Australia in compost
bins or amongst general household or retail waste.
Fruit discarded near susceptible hosts could be a source of inoculum for initial infections
in new areas. Such fruit discarded into the environment could rot and potentially develop
viable fungal inoculum that could initiate new infections. Fruit trees in commercial
orchards are planted in high-density monocultures of suitable hosts. Fruit trees and
ornamental plants that are hosts of N. ditissima may be found in household gardens,
although their density would be low. The use of irrigation may create climatic conditions
more conducive for infection to household and garden plants.
Orchard wholesaler waste is disposed of into isolated areas within the orchard itself or in
landfills close to the orchard. These disposal sites are surrounded mostly by pome fruit
grown as a monoculture and wild and amenity plants are less abundant. Consumers may
also occasionally discard fruit waste along roadsides and recreation areas.

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regulated refuse collection and disposal services. Managed waste will remove N. ditissima
from the household and environment, reducing the likelihood that susceptible plants will
be exposed to this pathogen.
Apple waste disposed of in compost may be subjected to high temperatures (60 C), which
can be expected to kill the fungus – many fungi are killed within a few days during
composting (Anonymous 2004b). European canker mycelia growth is retarded at 30°C
and it is killed at 37°C under laboratory conditions (Munson 1939). Apple waste disposed
of in landfills or compost heaps would be rapidly contaminated and colonised by
saprophytic microorganisms, hastening the decay process and minimising the likelihood of
conidia development. Similarly insects, mammals or birds could consume apple waste.
European canker can produce two types of spores, conidia and ascospores (Swinburne
1975). Conidia are known to be dispersed by rain splash and ascospores by wind
(Swinburne 1975).
When European canker was present in Tasmania, only conidia were reported as an
inoculum source on host plants (Ransom 1997). Ascospores are more likely to form on
cankers on woody parts of plants (Swinburne 1975) and have only rarely been recorded on
fruits under specific favourable conditions (Dillon-Weston 1927; Swinburne 2010a).
Even under damp English conditions, perithecia rarely develop on infected fruit in waste
dumps (Swinburne 1964). Perithecia are the structures on which ascospores form, and
without their development to maturity, no ascospores can be produced (Swinburne 1975).
There is only one study that reported perithecia and ascospores on fruits collected from
trees (Dillon-Weston 1927). Here only three apples collected from a total of 700
mummified fruit from an English orchard infected with N. ditissima cankers developed
perithecia (0.4%) although the number increased to 49 (7%) when the fruit were incubated
in the laboratory under more favourable conditions than would exist in the field (Dillon-
Weston 1927). The production of ascospores on fruit does not feature in any subsequent
epidemiological study (Swinburne 2010a).
There is no evidence that perithecia would fully develop and produce ascospores on fruit
under the typically drier conditions experienced in Australia (Latorre 2010; Swinburne
2010a). It is extremely unlikely that airborne ascospores would play a role in the
distribution of European canker from latently infected apples to a suitable host in
Australia.
Although wind disperses some conidia in the absence of rain (Swinburne 1971b) they are
mainly splash-dispersed (Munson 1939) and this is considered the only realistic mode of
dispersal for conidia from infected apples (Latorre 2010; Swinburne 2010a).
Before dispersal can occur, conidia will need to be produced by the fruit that entered
Australia with a latent infection and that has not been disposed, composted, eaten or
colonised by saprophytic micro-organisms. That small proportion of remaining fruit will
require extended periods of suitable temperature and moisture for this to occur (Swinburne
1971b) and prolonged periods of 100% humidity are considered necessary for conidia
production (Swinburne 2010a).
Fruit rotting in retail packs or in a domestic environment at less than 100% relative
humidity is unlikely to produce conidia (Swinburne 2010a). When conidia are formed
from rots they do so in relatively small numbers (Swinburne 2010b).

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Even in regions such as Northern Ireland (Loughgall) with rain in all seasons and
moderate temperatures, more than five hours of leaf wetness was required for spore
discharge to resume from mature cankers following a few dry days throughout the year
(Swinburne 1971b). Conidia production from cankers is lowest during autumn (Swinburne
1975) and in one study no conidia were produced for several months of the year
(Swinburne 1971b).
The situations in regions with pronounced dry periods, such as California, conidia are not
produced during summer when rainfall is low (Wilson 1966). Spore formation from
mature cankers on trees does not begin until several days after the first significant rainfall
event of the rainy period (Wilson 1966).
Neonectria ditissima does not produce resting cells and spores are killed by prolonged
desiccation from high temperature and low relative humidity (Dubin and English 1975).
Liquid phase water is required for germination of conidia and their viability is sharply
reduced when exposed to relative humidity between 85 to 100% for 3 to 12 hours at 11 C
and 19 C (Dubin and English 1975). Once conidia are produced from rots they will only
survive for short periods of time without moisture (Latorre 2010; Swinburne 2010a).
The most probable maximum distance for dispersal by rain splash of conidia from cankers
on trees is 10 m (Marsh 1940). One report suggests this might actually be as much as
125 m under stormy conditions (Swinburne 1975) but this is not supported by data. These
studies relate to conidia produced from cankers on trees; the distances are likely to be far
less for conidia originating from the upper surface of infected fruit on the ground. Conidia
produced on the sides and base of discarded fruit will have minimal opportunity to
disperse.
It has been reported that in East Malling, England, approximately 50kg of discarded
canker wood were pulverized and placed under potted trees of a highly susceptible apple
variety, Spartan (Swinburne 2010b). No cankers were observed on the trees subsequently;
suggesting it is very unlikely conidia produced near the ground will transfer to a host and
cause infection.
Vectors
Transfer of N. ditissima by birds or insects has not been demonstrated and N. ditissima
does not have any specific insect vectors or mechanisms to allow transmission from apples
to a suitable host. Birds inhabit branches of trees and also feed on discarded fruit.
Although it is theoretically possible that birds could get spores on their feet or beaks while
feeding on a discarded fruit and then transfer them to a branch of a susceptible plant, there
is no evidence to support this can or has occurred.
The possible role of woolly aphid as a vector has been mentioned (Brook and Bailey 1965;
Marsh 1940; Munson 1939) although infection through this route has not been
demonstrated and its involvement is doubted by some (McKay 1947). Wiltshire (1914)
found that while woolly aphids carried conidia of the canker fungus, inoculation of the
fungus through this means was unsuccessful. Woolly aphid is a common apple pest in
Australia; however, it is unlikely that aphids would colonise a discarded fruit and transfer
N. ditissima to a healthy tree.
The role of vectors transferring conidia from fruit has been considered recently and there
is no supporting evidence this can occur (Latorre 2010; Swinburne 2010a). In the absence
of supporting evidence, vector transmission of conidia is considered to be extremely
unlikely.

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Ability of the pest to initiate infection of a suitable host
After conidia has been successfully produced and transferred to a susceptible host,
temperature and duration of wetness are critical factors contributing to successful infection
(Swinburne 1975; Latorre et al. 2002). Neonectria ditissima readily survives at
temperatures from 2 ºC to 30 C (Munson 1939; Butler 1949) with the optimum
temperature for disease development being between 18 ºC to 24 ºC under laboratory
conditions. These conditions are quite common in temperate and subtropical parts of
Australia. However, under field conditions, temperatures in the range of 11 ºC –16 ºC are
a better predictor of disease prevalence (Swinburne 2010a; Beresford and Kim 2011).
A minimum of 2 to 6 hours wetness duration is required at the optimum temperature
(20°C) in the laboratory with a longer wetting period required at lower temperatures for
infection to occur (Latorre et al. 2002; Grove 1990a). Swinburne (1975) reported that a
minimum of 6 hours wetness duration was required for significant infection to take place.
Under artificial conditions, Latorre et al. (2002) demonstrated that 2 hours wetness
duration was sufficient for disease development at 20°C when inoculations were
performed within 1 h of leaf abscission when leaf scars were highly susceptible. No
infection occurred at 5°C, regardless of the duration of the wetness period (Latorre et al.
2002).
Dubin and English (1974) found that under field conditions in California, N. ditissima
infections only occur where rainfall is abundant for long periods of time. Field data
indicated that several days of free moisture were required to obtain high levels of
infection.
Some regions in Australia with a high number of rainfall days during some months from
autumn to spring have been shown to be marginally suitable for infection. In summer, low
rainfall and high temperatures are unfavourable for disease development (Beresford and
Kim 2008; Beresford and Kim 2011).
Environmental conditions in nurseries, including use of overhead irrigation, may create
favourable microclimates and be conducive to disease infection.
The number of conidia required to initiate an infection varies depending on environmental
and host factors. In artificial inoculations under optimal laboratory conditions as few as 10
or 12 conidia have produced infections (McCraken et al. 2003b; Cooke 2003). In field
experiments where leaf scars where artificially inoculated, then covered with a plastic bag
to maintain humidity, five conidia were insufficient to initiate infection, while 50 to 500
did so readily (Dubin and English 1974).
Entry points for infection by N. ditissima are available throughout most of the year
(Swinburne 1975) with wound sites caused by leaf fall in autumn and leaf cracks from
onset of spring bud burst presenting natural infection sites (Wiltshire 1921; Wilson 1966).
Winter pruning cuts (Marsh 1939) and lesions caused by other pathogens such as
V. inaequalis present other entry points for infection (Swinburne 1975; Brook and Bailey
1965).
The age of leaf scars and wound sites, and then rainfall, are critical for infection
(Swinburne 1975). Under experimental conditions infection via the leaf scar could occur
up to four weeks after leaf fall (Wilson 1966). However, field tests in California indicated
that only 5% of leaf scars can remain susceptible to infection for 10 days when inoculated
with 300 conidia and covered in a plastic bag to maintain humidity (Dubin and English
1974). Leaf scars are highly susceptible to infection within the first hour after leaf fall and
become much less susceptible over the next hour (Crowdy 1952).

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The susceptibility of pruning cuts to infection decreases considerably after a seven-day
period (Seaby and Swinburne 1976).
Therefore, although entry points could be available all year, their susceptibility to
infection decreases quickly and infection can only occur when they coincide with suitable
climatic conditions.
When European canker was present in Tasmania, there were no restrictions on the
movement of apple fruit from the Spreyton area (Tasmanian Government Proclamation
1955) and there are no records of it initiating infection by fruit from this source.
In summary, very low numbers of latently infected fruit that have been imported in some
years are likely to survive transport and storage conditions. Most imported fruit will be
disposed in a variety of ways that will result in the eventual death of N. ditissima through
managed waste disposal, composting, being out-competed by other micro-organisms and
desiccation. The remaining latently infected fruit that survives these processes will then need
to be exposed to favourable climatic conditions including high levels of moisture with suitable
temperatures to allow N. ditissima to produce conidia. As discussed, Australia has marginal
climatic conditions for N. ditissima that will limit production of conidia on fruit. The conidia
that are produced from rots occur in low numbers and they can only be dispersed short
distances by rain splash. Therefore, only infected fruit that have been disposed of in very close
proximity to a suitable host could result in successful dispersal.
Infection will then occur only if a suitable number of spores reach a host that is receptive to
infection under favourable climatic conditions. Australia has marginal climatic conditions that
will limit infection. Conidia require a wound on a host plant for infection to occur and these
are not available throughout the year. Once a receptive infection site is made, the receptivity
of the site decreases quickly further limiting the availability of infection sites through the year.
It is very unlikely that these specific criteria for successful dispersal of N. ditissima would
occur and therefore the evidence supports a rating of „very low‟ for the distribution of N.
ditissima.

(very low) with the probability of distribution (very low) using the matrix of rules shown in
Table 2.2 on page 9.
The likelihood that Neonectria ditissima will enter Australia as a result of trade in the
commodity and be distributed in a viable state to a suitable host is: EXTREMELY LOW.

The likelihood that European canker will establish within Australia based on a comparison of
factors in the source and destination areas that affect pest survival and reproduction is
MODERATE.
In estimating the probability of distribution, the PRA has already considered the sequence
of events necessary to allow infective inoculum to reach a suitable infection site under
suitable climatic conditions to initiate infection. The probability of establishment will

104


consider whether this initial infection will lead to the longer term infection that will result
in the completion of the pathogen lifecycle on host plants through an entire year to
account for seasonal differences that may affect establishment.
Availability of suitable hosts, alternative hosts in the PRA area
In Australia, apples and pears are grown in most states as commercial crops with most
apple cultivars being susceptible, although susceptibility is greater in some than in others.
All apple cultivars are apparently susceptible to canker to some degree (Anonymous 1988;
Swinburne 1975). Breeding programs seeking to develop resistant cultivars are still in
progress (CABI 2003).
During the outbreak of N. ditissima in Tasmania, varietal susceptibility was recorded with
Granny Smith and Delicious cultivars showing severe symptoms often with systemic
infection (Ransom 1997). Granny Smith is still a major variety of apple grown in
Australia. For example, Victoria produces 39% of Australia‟s apples and 22% of these are
Granny Smith (APAL 2008).
Nurseries with high numbers of susceptible host plants are widely dispersed throughout
Australia.
Apples and pears are grown as backyard household and garden plants along with many
other alternative wild and amenity plants, although they are generally scattered and
present in low density.
Braun (1997) reports that European canker was present in hedgerows of maple and poplar
trees around orchard blocks in Nova Scotia, but suggested the random distribution of the
canker within the orchard indicated the inoculum originated from within the orchard rather
than from the surrounding hedgerows. Flack and Swinburne (1977) reported that
European canker in apple trees was more numerous in rows adjacent to hedges infected
with European canker.
European canker has previously established in Tasmania and was considered to have
persisted there for many decades until it was officially eradicated in the 1990‟s (Ransom
1997). Of the blocks infected, two were severely affected by N. ditissima and 200 trees
were removed (Ransom 1997). This information shows that once hosts are infected,
damage can reach high levels, and European canker can persist, despite eradication efforts
(removing diseased wood), for many decades under Australia climatic conditions in one
location.
Infection is initiated through leaf and bud scars, bark disruptions such as pruning cuts and
wounds, or woolly aphid galls (Swinburne 1975). Entry sites for infection by N. ditissima
on new hosts near the initially infected plant are available during most of the year.
However, successful infection depends on the existence of receptive infection sites
synchronized with adequate moisture and suitable temperature (Latorre 2010; Swinburne
2010a).
Recent climate models have confirmed Tasmania as marginal for European canker
(Beresford and Kim 2011). This work predicts with some accuracy the suitability of the
climate for European canker around the world. Although this work does not cover other
areas of Australia, an earlier version of this work presented information that predicts other
apple growing regions of Australia would also be marginally suitable for European canker
(Beresford and Kim 2008).

105


Another climate model predicted a greater range of locations that would be suitable for
European canker in Australia (Baker and Mewett 2009). However, this study noted that
conditions in Australia are typically less conducive (warmer and drier) than regions of the
world where European canker is highly prevalent. The model also predicts regions of New
Zealand are very suitable for European canker where the disease is rarely present or
absent. This work may be considered a more conservative model in predicting European
canker establishment.
Nursery plantings as well as household and garden plants are not solely dependent on
natural rainfall and are regularly irrigated throughout the growing period. This means that
wetness and humidity around these plants could be favourable for establishment of the
disease.
Reproductive strategy and the potential for adaption
Currently there is no information on strains of the fungus exhibiting fungicide tolerance or
the ability to overcome some resistance observed in certain apple cultivars.
Under suitable environmental conditions, production of conidia and ascospores on plants
can occur throughout the year and their tolerance of low temperatures are considered
special adaptations that N. ditissima has developed (Marsh 1940). In vitro, the germination
rate was 2.6 times faster for ascospores than conidia, suggesting that European canker may
be more aggressive in areas where abundant ascospores are produced during leaf fall
(Latorre et al. 2002).
However, although perithecia were observed on host plants in Tasmania during the
European canker outbreak, these did not mature to form ascospores (Ransom 1997).
Ascospores have only been recorded from the most suitable climatic regions in New
Zealand (Brook and Bailey 1965) that are considered more suitable for European canker
than regions in Australia (Beresford and Kim 2011).
In Sonoma County, California, where the climate is more typical of much of temperate
Australia, ascospores were only produced in two of an eight year period (Wilson 1966). It
is not certain that ascospores would be produced under Australian conditions, but if they
were, it is likely to be an irregular event linked to seasons and years with suitable climatic
conditions.
The number of conidia required to initiate an infection varies depending on environmental
and host factors. In artificial inoculations under optimal laboratory conditions as few as 10
to 12 conidia have produced infections (McCraken et al. 2003b).
In field experiments where leaf scars where artificially inoculated, then covered with a
plastic bag to maintain humidity, five conidia were insufficient to initiate infection, while
50 to 500 did so readily (Dubin and English 1974). It has been reported that approximately
1000 conidia are required for leaf scar infection (CABI 2003).
The primary method of survival of the pest is in cankers on infected trunks and branches
of affected host plants. The fungus grows slowly into the wood, while the host produces
callus around the canker year after year. The fungus can survive on infected twigs and
branches left on the orchard floor.
Neonectria ditissima can survive as a latent and symptomless infection in susceptible
apple trees for up to 3 to 4 years (Berrie et al. 2000; Lovelidge 2003; McCracken et al.
2003a; McCraken et al. 2003b), resuming growth during more conducive climatic
conditions. The latent infection of trees may be the reason for the length of time required
to achieve eradication in Tasmania (Swinburne 2010a).

106


Spores do not appear to help in long-term survival as they are killed by prolonged
desiccation (Dubin and English 1975).
Integrated pest management programs (IPM) used in Australia, including fungicide
applications to control apple scab and other fungal pests (e.g. powdery mildew), will assist
in reducing opportunities for the establishment of the pest. However, it is acknowledged
that IPM is only a management tool and may not always reduce the opportunities for
establishment of pests, for in some seasons no matter what IPM program was in place, if
environmental conditions were conducive, pests could occur.
Less use of disease control and heavy pruning practices in garden and household situations
may favour establishment of the disease.
In summary, if N. ditissima were to have infected a host in Australia, it would be able to
survive and multiply within such a host, many of which occur within Australia. Neonectria
ditissima previously survived at one location in Tasmania for several decades, with some
blocks severely affected, but without completing its entire life cycle. However, in New
Zealand it has not established in all areas of that country with establishment being limited by
climatic factors.
The climatic suitability for N. ditissima will vary in Australia with apple growing areas
considered climatically marginal for the pathogen. In many areas and years the climate is
unlikely to support the establishment of N. ditissima. In commercial orchards, standard
management practices to control other fungal diseases and remove disease wood will further
limit establishment. While it is not certain that N. ditissima would establish following
successful distribution, it is an event that could occur in some years and locations. Therefore
the evidence supports a rating of „moderate‟ for the establishment of N. ditissima.

The likelihood that N. ditissima will spread based on a comparison of factors in the area of
origin and in Australia that affect the expansion of the geographic distribution of the pest is:
MODERATE.

Apart from apples, the spread of the disease to other host species in the natural
environment has been reported in both the USA and Europe. In New Zealand, N. ditissima
is recorded on three alternative hosts, namely, loquat (Eriobotrya japonica), kowhai
(Sophora microphylla) and coprosma (Coprosoma areolate) trees.14
Braun (1997) reports European canker was present in hedgerows and on maple and poplar
trees around orchard blocks in Nova Scotia but suggested the random distribution of the
canker within the orchard indicated the inoculum originated from within the orchard rather
than from the surrounding hedgerows. Flack and Swinburne (1977), however, reported
that European canker in apple trees was more numerous in rows adjacent to hedges
infected with European canker.

14

107


The fact the disease spread to a few closely located orchards in Spreyton in Tasmania,
probably after a single entry point, or a cluster of closely related events, indicates that the
managed environment of Australia can support local spread, although the extent of
dispersal was quite limited despite being present for many years.
The lack of spread may have been because of the absence of airborne ascospores which
are better suited to long-distance dispersal than conidia (Ransom 1997), combined with
marginal climatic conditions (Beresford and Kim 2011). The use of chemicals to control
apple scab may also have limited disease spread (Latorre 2010; Swinburne 2010a).
There were no reports of the disease spreading to wild and amenity plants, including forest
plants or household and garden plants during the 40-year eradication program in Tasmania
(Ransom 1997). However, in addition to the lack of ascospore detection in Spreyton
(Ransom 1997), the limited spread can also be attributed to the eradication program which
began within two years of confirmation of the disease (Ransom 1997).
The eradication program involved the use of chemicals to prevent the development of
sporodochia, removal and burning of severely infected trees, prohibition of movement of
propagation material out of the quarantined zone, etc. Without the eradication effort, the
spread of European canker could have occurred as was reported by P.J. Samson (cited in
Ransom 1997) who said that „it could easily have become established in the region if left
unchecked‟.
However, European canker symptoms were reported to be present for about 20 years prior
to commencement of the European canker eradication program and the pathogen failed to
spread beyond a limited number of closely located orchards (Ransom 1997).
Apples and pears in commercial orchards could be conducive to localised disease spread.
Suitable host plants in nurseries distributed across states could rapidly spread the disease
to new districts. The scattered distribution of host plants in household/garden situations
and wild amenity plants would confine disease spread to localised areas.
Given the geographical location of Western Australia and Tasmania there are natural
barriers that would limit the natural spread of the pathogen across those borders.
Fruit (including pods), bark and stems (above-ground shoots, trunks and branches) as host
plant parts that can carry spores and hyphae (vegetative tissue) of the pathogen both
internally and externally (CABI 2003). Therefore, the nursery, hardwood timber and
mulch industries can also be involved in spread of the pest. Foliage is not affected (Butler
1949) and leaf trash is unlikely to present a pathway unless twigs with active canker are
present.
When European canker was present in Tasmania, there were no restrictions on the
movement of apple fruit from the Spreyton area (Tasmanian Government Proclamation
1955) and there are no records of it spreading by fruit from this source.
Long-distance movement of European canker is primarily the result of movement of
infected nursery stock. A study in the UK, called the „Millennium trial‟ concluded that
approximately 6% of the infection in new orchards could be associated with nurseries but
this figure could sometimes be larger (McCraken et al. 2003b). Disease establishment in
new regions through nursery stock can be significant in low rainfall areas where the plants
can remain symptomless for three to four years. There are no cost effective methods for
detecting the pathogen in symptomless wood, making it difficult to estimate the size of the

108


problem. In situations of high disease pressure, which only occur during periods of highly
favourable leaf wetness and temperature, movement of inoculum from neighbouring
sources is of more concern than nursery infection (McCraken et al. 2003b).
In New Zealand, European canker has been introduced to new areas through the
introduction of planting material (Murdoch 2002; Wilton 2002a) despite the routine
application of fungicides to cuttings (MAFNZ 2003a). Symptomless planting material is
likely to be the main method of the long distance spread of European canker to new areas
in Australia.
Apples would be used mostly for consumption by humans and would be widely consumed
around the states and territories. However, there is no evidence in the literature that
indicates that long-distance spread of disease is due to movement of fruit. Conidia can
develop in rotted fruit but whether this contributes to local spread has never been
demonstrated (Latorre 2010; Swinburne 2010a).
Involvement of insects and birds as vectors is speculated (Butler 1949; Agrios 1997). In
particular, the possible role of woolly aphid as a vector has been mentioned (Brook and
Bailey 1965; Marsh 1940; Munson 1939) although infection through this route has not
been demonstrated and its involvement is doubted by some (McKay 1947). In the absence
of supporting evidence, vector transmission of conidia is considered to be extremely
unlikely.
In summary, the restricted spread of N. ditissima in Tasmania, even before eradication efforts
commenced, show the spread of this pathogen under Australian conditions in this instance
was restricted. This is supported by recent information that in general Australia has a marginal
climate for N. ditissima including major production areas. The marginal climate will limit the
production of airborne spores that could assist in the rapid local spread of the disease.
When N. ditissima was present in Tasmania, there is no information that planting material was
moved from the infested area, and after pathogen detection, this was prohibited by regulation.
Latent infection (asymptomatic) of planting material is known as an important method of
allowing the spread of N. ditissima, particularly in regions of low rainfall. Latent infection by
N. ditissima in hosts that would be used for planting material, that cannot be adequately
detected, would then be transported over longer distances through the nursery industry. The
presence of multiple host species, which are scattered in distribution in the PRA area, would
assist in the spread of the pathogen when climatic conditions are favourable. The evidence
therefore supports a rating of „moderate‟ for the spread of N. ditissima.

9.
The likelihood that Neonectria ditissima will enter Australia by the pathways discussed in this
subsequently spread within Australia is: EXTREMELY LOW as set out below.

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Table 4.4 Probability of entry, establishment, and spread for Neonectria ditissima

Very Low Very low Extremely Moderate Moderate Extremely
low low

4.3.5 Consequences
The consequences of the entry, establishment and spread of N. ditissima in Australia have
been estimated according to the methods described in Table 2.3 on page 11.
Based on the decision rules in Table 2.4 on page 12, that is, where the consequences of a pest
with respect to one or more criteria are „D‟, the overall consequences are estimated to be
LOW.
The reasoning for these ratings is provided below:

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Direct
Plant life or health D – Significant at the district level:
Establishment of European canker in districts with suitable climatic conditions could be significant with
reduced yields and additional orchard practices required (see below).
European canker is one of the most economically damaging diseases of apple in Europe, North America and
South America (Grove 1990a; Latorre et al. 2002; Anonymous 2005b). In Spreyton (Tasmania), Ransom
(1997) cites a personal communication from P.J. Samson which said, „the diseased wood collapsed rapidly
after infection, suggesting that disease posed a very real threat to apple production‟. Atkinson (1971) states
the disease also causes considerable damage to trees in private gardens in New Zealand. The main economic
impact of the disease results from destruction and removal of individual trees or whole orchards because of
girdling of branches, which can significantly reduce crop production yields (Anonymous 1991). Presence of
the disease substantially increases costs of winter pruning, fungicide treatments and the removal of stem
lesions and infected branches (including fruit wood) contributes significantly to reductions in both fruit
yields and profitability. However, this damage occurs in regions with a suitable climate for inoculum
production, dispersal and infection.
In some apple cultivars under favourable environmental conditions, e.g. Northern Ireland, fruit rot can also
be a significant problem. Fruit rot generally develops in the field or before harvest, although storage losses
of 10–60% of the stored fruit crop have been reported in various parts of the world (Swinburne 1964;
Swinburne 1975). The climatic conditions that allow for significant fruit rots in Northern Ireland include
summer rainfall that promotes fruit infection (Swinburne 2010a). This is unlikely to occur in the typically
drier and hotter climate of Australia compared to Northern Ireland.
Nurseries producing or selling pome fruit and other host plants can be affected significantly if the disease
establishes, as tree structure can be compromised by removing cankers. The appearance of canker lesions on
the main stems of young trees in newly planted orchards can at times require tree replacement, ranging from
10% (Lovelidge 1995) to the whole plantation (Grove 1990a). During the eradication effort in Tasmania: (a)
more than 200 trees out of approximately 1600 had to be removed and burnt (b) Delicious and Granny Smith
showed severe symptoms, often with systemic infection, necessitating removal of whole trees of these
cultivars (c) at least 30% of the trees with infected limbs removed subsequently developed further infection
with entire trees requiring removal (Ransom 1997). This behaviour of the disease under Australian
conditions supports the conclusion that the impact on plant life and health, particularly of apple and pear
where the disease is most damaging (CABI 2005), would be significant at a district level and of major
significance at the local level.
Neonectria ditissima is responsible for damage to many host species used for timber through reductions in
both quality and quantity of marketable logs, although there are no estimates of the magnitude of loss (Flack
and Swinburne 1977). Such hosts are not grown as commercial forest trees in Australia. Although Prunus
serotina (black cherry) and Juglans nigra (black walnut) are listed as hosts, there are no reports indicating
significant economic consequences to these industries. The damage to species used as garden, amenity and
household plants could be significant, affecting isolated populations of poplar, beech and other ornamental
host plants. Although Malus, Pyrus and some Prunus species are hosts to N. ditissima. Lohman and Watson
(1943) studying Nectria species associated with diseases of hardwoods concluded that N. ditissima cannot
be considered strictly a canker-Nectria of Rosaceous hosts.
In Australia, recent climate models have confirmed Tasmania as marginal for European canker (Beresford
and Kim 2011). This work predicts with some accuracy the suitability of the climate for European canker
around the world. Although this work does not cover other areas of Australia, an earlier version of this work
presented information that predicts that most other apple growing regions of Australia would be marginally
suitable for European canker (Beresford and Kim 2008). These apple growing areas include the major
production area of the Goulburn Valley in Victoria. The marginal climatic suitability of Australia will limit
any potential impact N. ditissima may have on host plants.

111


Other aspects of C – Significant at the local level:
the environment The Australian community places a high value on its forest and garden environments and several hosts of
N. ditissima constitute a component of these environments. Such hosts are sparsely distributed however, and
any impact would be restricted to the district level. There was no evidence of infection in alternative host
plants in Tasmania (Ransom 1997); however, this may have been because of marginal climatic conditions
(Beresford and Kim 2011) and the absence of airborne ascospores that are better suited to long-distance
dispersal than conidia (Ransom 1997).
Many host plants of N. ditissima are forest, garden and amenity plants and these are generally scattered or
found in localised patches. There was no evidence of infection or damage to such plants in Tasmania during
the eradication program (Ransom 1997). However, the disease is known to be common on such
environmental hosts in North America and Europe (CABI 2003) particularly in cool and wet climates. In the
event of establishment and spread of the disease in Melbourne‟s elm tree population, there could be highly
significant effects when seasonal conditions are highly suitable. The City of Melbourne has calculated the
6500 elm trees in the City of Melbourne are each worth approximately $10,000 (Shears 2005) and an
outbreak of European canker could be significant at the local level. N. ditissima has not been reported to
infect Eucalyptus spp. (Keane et al. 2000).
Neonectria canker is considered to be most severe on stressed trees15, a situation highly applicable to trees in
the dry, low nutrient soils of the Australian environment. Further, any damage to branches or twigs exposing
the cambium can provide infection courts (Lortie 1964). Opportunities for damage are likely to be greater in
a stressed environment. Further, N. ditissma has been collected from quite a few non-host species in New
Zealand16 indicating that the spores are widespread when conidia and ascospores are produced. With such
spread of spores, trees in stressed environments are likely to be easily infected. However, the typically drier
conditions of Australia are unsuitable for disease development.
Indirect
Eradication, D – Significant at the district level:
control etc. Once established, European canker is both difficult and expensive to eradicate. Except for Tasmania
(Australia) and the Republic of Korea, other countries with the disease have not been able to eradicate it.
Even in Tasmania where the outbreak was restricted to only four orchards, the eradication process required
nearly 40 years (Ransom 1997).
General control methods for European canker include fungicide sprays, paints applied to pruning cuts,
cultural control, improving host plant resistance and the prevention of fruit rot (Swinburne 1975; CABI
2003). Implementing these measures would require a multifaceted approach that would increase the costs to
growers depending on the severity of the disease from year to year.
Cultural practices and chemical measures used to control apple scab (V. inaequalis) in Australian apple
growing regions would assist in controlling European canker. Fungicides commonly used for apple scab
control in Australia including Bordeaux mixture, copper oxychloride, captan, carbendazim, dodine,
dithianon and other chemicals (Williams et al. 2000) are reported to also control European canker (Atkinson
1971; Brook and Bailey 1965). The above fungicides can reduce cankers by 65 to 90%, although spray
treatments alone cannot eradicate existing infections and must be supplemented by removing cankers and
treating wounds with an effective paint (Cooke 1999). New generation chemicals such as strobuliruns
provide effective control of European canker (Lolas and Latorre 1997; Creemers and Vanmechelen 1998).
If the disease establishes in wild or amenity plant species (for example, crab-apple, elm and willow) control
would be more difficult, as they are not subject to any integrated pest management programs and application
in an urban situation would be difficult.
Domestic trade D – Significant at the district level:
Currently pome fruit can move freely across all states and territories borders except for Western Australia,
but the detection of the disease in one state could result in the application of quarantine restrictions by other
states on planting material. Restrictions were placed on the movement of nursery stock from disease affected
areas in Tasmania (Ransom 1997). This could have a highly significant impact locally and significant
consequences across a district, particularly for nurseries involved in propagation of planting stock. For
example, the incursion and eradication of E. amylovora in Victoria was estimated to cost the Victorian
nursery industry around $3 million as a result of trade restrictions placed on movement of nursery stock
(Rodoni et al. 2004).

15
http://www.extension.umn.edu/yardandgarden/ygbriefs/p431nectria.html Checked on 15 March 2011.

112


International trade A –Indiscernible at the local level:
Major export markets for Australian apples include Malaysia, Singapore and the United Kingdom, with Sri
Lanka, Indonesia, Philippines, China (Hong Kong), Taiwan, Fiji and Papua New Guinea constituting other
significant markets. Current exports to Japan are for Fuji apples from Tasmania only. All varieties of apples
from any part of Australia are permitted for export to the other countries. Of these importing countries,
European canker is not recorded in the tropical countries Malaysia, Singapore, Sri Lanka, Philippines, China
(Hong Kong), Taiwan, Fiji and Papua New Guinea, mainly because of the lack of host plants and favourable
climatic conditions. The disease is already present in all apple growing countries other than Australia. The
impact of an outbreak of European canker in Australia would not have a discernible impact on the current
apple export trade.
An outbreak in forest species will not impact on Australian timber exports because timber from species that
are hosts to European canker is not exported from Australia.
New Zealand is able to export apples to most markets around the world, regardless of the presence of
European canker in the export production areas, including countries that do not have the disease. Similarly
there are no phytosanitary restrictions on the movement of apple fruit exported from Japan to countries free
of N. ditissima (Fukuda 2005). Therefore, if the disease did become established in Australia it would not
affect the international export of fruit.
Environmental and B – Minor Significance at the local level:
non-commercial Establishment of European canker could necessitate increased chemical usage in some situations and this
may have undesirable effects on the local environment as well as being of minor significance on the future
placement of plant species (for example, elm trees) at the local level.
Sustainability of communities in the nine or so major apple growing areas across Australia is significant to
the local economy. Tourism in these areas, especially during harvesting periods, can be significant and
depends on the health of the fruit crop.
There could be minor social impacts at a local level if several orchards were affected by European canker,
owing to reduced crop yields.

Unrestricted risk estimate for Neonectria ditissima

Overall probability of entry, establishment and spread Extremely Low

Consequences Low

Unrestricted risk Negligible

As indicated, the unrestricted risk estimate for N. ditissima has been assessed as „negligible‟,
which achieves Australia‟s ALOP. Therefore, additional risk management measures are not

113

Draft Report: Review of fresh apple fruit from New Zealand Pest risk assessment conclusions

4.4 Pest risk assessment conclusions

Key to Table 4.2 (starting next page)
Genus species EP pests for which policy already exists. The outcomes of previous assessments and/or reassessments in this IRA are presented in table 4.2
Genus species state/territory state/territory in which regional quarantine pests have been identified

Likelihoods for entry, establishment and spread
N negligible
EL extremely low
VL very low
L low
M moderate
H high
P[EES] overall probability of entry, establishment and spread

Assessment of consequences from pest entry, establishment and spread
PLH plant life or health
OE other aspects of the environment
EC eradication control etc
DT domestic trade
IT international trade
ENC environmental and non-commercial
A-G consequence impact scores are detailed in section 2.2.3
A Indiscernible at the local level
B Minor significance at the local level
C Significant at the local level
D Significant at the district level
E Significant at the regional level
F Significant at the national level
G Major significance at the national level
URE unrestricted risk estimate. This is expressed on an ascending scale from negligible to extreme.

114

Draft Report: Review of fresh apple fruit from New Zealand Pest risk assessment conclusions

Table 4.5 Summary of unrestricted risk estimates for quarantine pests associated with mature fresh apple fruit from New Zealand

Likelihood of Consequences URE
Pest name Entry Establishment Spread P[EES]
importation distribution Overall direct indirect Overall
PLH OE EC DT IT ENC

DOMAIN BACTERIA

Fire blight (Enterobacteriales: Enterobacteriaceae)
Erwinia amylovora M EL EL H H EL F A E E A A H VL

DOMAIN EUKARYA

Apple leafcurling midge (Diptera: Cecidomyiidae)
Dasineura mali M VL VL L M VL D A D D D B L N

European canker (Hypocreales: Nectriaceae)
Neonectria ditissima VL VL EL M M EL D C D D A B L N

115

Draft Report: Review of fresh apple fruit from New Zealand Pest risk management

5 Pest risk management

This chapter provides information on the management of identified quarantine pests. This
non-regulated analysis reviews only three of the pests of quarantine concern: fire blight
(caused by Erwinia amylovora), European canker (caused by Neonectria ditissima), and apple
leaf curling midge (Dasineura mali). The conclusions presented in this draft report are that
when the New Zealand apple industry‟s standard commercial practices for production of
export grade fruit are taken into account, the unrestricted risk for all three pests assessed
achieves Australia‟s appropriate level of protection (ALOP). Therefore, no additional
quarantine measures are recommended, though New Zealand will need to ensure that the
standard commercial practices detailed in this review are met for export consignments. These
practices include:
Application of the integrated fruit production system, or an equivalent, to manage
pests and diseases in orchard
Testing to ensure that only mature fruit is exported to Australia
Maintenance of sanitary conditions in dump tank water
High pressure water washing and brushing of fruit in the packing house
A minimum 600 fruit sample from each lot of fruit packed is inspected and found
free of quarantine pests for Australia.
In addition, the 2006 final IRA report considered a further 13 pests, nine of which were
determined to pose a risk that exceeded Australia‟s ALOP and for which measures were
recommended. For clarity the conclusions of the 2006 final IRA report for those additional 13
pests are presented below.

117


Table 5.1 Summary of the assessment of unrestricted risk for quarantine pests

Pest Unrestricted risk Additional Measures
Required?

2011 Non-regulated analysis

Fire blight (Erwinia amylovora) Very Low N

European canker (Neonectria ditissima) Negligible N

Apple leaf curling midge (Dasineura mali) Negligible N

2006 Final IRA report

Garden featherfoot (Stathmopoda horticola) Negligible N

Grey-brown cutworm (Graphania mutans) Very low N

Leafrollers: Low Y
Brownheaded leafroller (Ctenopseustis herana)
Brownheaded leafroller (Ctenopseustis obliquana)
Greenheaded leafroller (Planotortrix excessana)
Greenheaded leafroller (Planotortrix octo)
Native leafroller (Pyrogotis plagiatana)

Apple scab (Venturia inaequalis) (WA only) Moderate N17

Codling moth (Cydia pomonella) (WA only) Low Y

Mealybugs: Low Y
Citrophilus mealybug (Pseudococcus calceolariae) (WA only)
Mealybug (Planococcus mali) (WA only)

Oriental fruit moth (Grapholita molesta) (WA only) Very low N

Oystershell scale (Diaspidiotus ostreaformis) (WA only) Negligible N

In referring to the recommendations of the 2006 final IRA report it is noted that New
Zealand‟s standard practice of sampling 600 fruit per lot during packing operations was not
specifically taken into account. Thus, for leafrollers and mealybugs, the recommendation in
the 2006 final IRA report was for phytosanitary inspection of 600 fruit per lot, with any lots
found to contain leafrollers to be withdrawn from export, and for any lots found to contain
mealybugs to be withdrawn from export to Western Australia. For leafrollers, additional
actions were recommended to determine the level of internal fruit infestation.
As the 600 unit inspection is already undertaken as standard practice during packing house
operations, no further inspection is required. Any lot found to be infested with leafrollers or
mealybugs is to withdraw from export to Australia or Western Australia, depending on the
pest(s) detected. Alternately, lots may be subjected to a suitable remedial action, such as an
approved fumigation treatment to ensure there are no viable quarantine pests.

17
Subsequent to the release of the release of the Final Import Risk Analysis Report for Apples from New Zealand in
November 2006, Venturia inaequalis has been detected in Western Australia and is no longer considered a regional
quarantine pest. Quarantine measures are therefore not required.

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5.1 Pest risk management measures and phytosanitary
procedures
The pest risk management measures are based on the requirement for New Zealand growers
and packing houses to adhere to existing commercial practices described in this report (refer
to Section 3) and as summarised in the introduction to this chapter. These standard practices
are subject to verification and audit by the Biosecurity Services Group prior to the
commencement of trade, and as required. These practices include;
The application of the integrated fruit production system, or an equivalent, to manage
pests and diseases in the orchard.
Testing of fruit from a new variety and block combimation on-arrival at the packing
house. Fruit maturity will be tested using the starch pattern index. The testing will
ensure that only mature fruit is exported to Australia.
The maintenance of sanitary conditions in the dump tank and the high pressure spray
water through use of sanitisers at label rates that are monitored daily for concentration
and pH. Alternatively, dump tank and the high pressure spray water sanitation is
mantained through regular replacement of water.
The use of high pressure water washing and brushing of fruit in the packing house.
A minimum 600 fruit sample from each lot of fruit packed is inspected and found free
of quarantine pests for Australia. A lot of fruit is “a number of units of a single
commodity, identifiable by its homogeneity of composition, origin etc., forming part of
a consignment” (FAO 2009). In New Zealand, this includes the volume of fruit of a
single variety packed at one time and which has been picked from one orchard on one
day. New Zealand packing houses often refer to this as a „line‟ of fruit.
In this section, discussion of the management options is divided into two parts. Risk
management measures are evaluated for quarantine pests for the whole of Australia (including
Western Australia) where the unrestricted risks exceed Australia‟s ALOP. Following this, risk
management options are discussed for the quarantine pests for Western Australia only,
because these pests occur in other parts of Australia but are absent from Western Australia.

Table 5.2 Summary of phytosanitary measures recommended for quarantine pests
for mature fresh apple fruit from New Zealand

Pest Measures

Arthropods

Leafrollers: Option 1: Withdrawl of export lots found during packing house
inspections to be infested with leafrollers (minimum
Brownheaded leafroller (Ctenopseustis herana) 600 unit inspection per lot)
Brownheaded leafroller (Ctenopseustis obliquana) Option 2: Methyl bromide fumigation at an approved rate for
Greenheaded leafroller (Planotortrix excessana) export lots found during packing house inspections
to be infested with leafrollers (minimum 600 unit
Greenheaded leafroller (Planotortrix octo) inspection per lot)
Native leafroller (Pyrogotis plagiatana)

Codling moth (Cydia pomonella) (WA only) Option 1: Pest free areas of pest free places of production or
production sites (ISPM4, 10)
Option 2: Areas of low pest prevalence
Option 3: Methyl bromide fumigation

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Pest Measures

Mealybugs: (WA only) Option 1: Withdrawl of export lots found during packing house
inspections to be infested with mealybugs
Citrophilus mealybug (Pseudococcus calceolariae) (minimum 600 unit inspection per lot)
Mealybug (Planococcus mali) Option 2: Methyl bromide fumigation at an approved rate for
export lots found during packing house inspections
to be infested with mealybugs (minimum 600 unit
inspection per lot)

5.1.1 Pest risk management for quarantine pests for the whole of Australia
The 2006 final IRA report identified five species of leafrollers as quarantine pests for the
whole of Australia and having an unrestricted risk above Australia‟s ALOP.

Management for leafrollers

Option 1: Withdrawl of export lots found to be infested with leafrollers
The 2006 final IRA report recommended that each lot be inspected on the basis of a 600-unit
sample selected at random across the whole lot. A unit is one piece of fruit. That inspection is
undertaken as standard practice in New Zealand apple packing houses. If leafrollers of
quarantine concern to Australia are detected during that inspection, the lot should be removed
from export to Australia. The removal of any lots found to be infested with leafrollers would
reduce the likelihood of importation for leafrollers to at least „very low‟. The restricted risk
would then be reduced to at least „very low‟, which would achieve Australia‟s ALOP.
Also identified in the 2006 final IRA report was some uncertainty over the level of internal
infestation by brownheaded leafrollers (Ctenopseustis spp.) and greenheaded leafrollers
(Planotortrix spp.). For that reason, New Zealand is requested to provide additional
information to address the issue of internal infestation. One way to verify the level of internal
infestation would be the examination of a 600 cut fruit sample for the presence of internal
larvae of brownheaded and greenheaded leafrollers from export lots. The 600 cut fruit sample
could be taken from reject fruit. Based on the results, the need for fruit cutting will be
reviewed.

Option 2: Methyl bromide fumigation of lots found to be infested with leafrollers
Instead of withdrawing from export lots found to be infested with leafrollers, a methyl
bromide fumigation treatment of could be undertaken.
Where fumigation with methyl bromide is utilised as the remedial action for leafrollers, it
must be carried out for 2 hours according to the specifications below:
32 g/m3 at a pulp temperature of 21 °C or greater – minimum concentration time (CT)
product of 47 g.h/m3; or
40 g/m3 at a pulp temperature of 16 °C or greater – minimum CT product of 58 g.h/m3; or
48 g/m3 at a pulp temperature of 10 °C or greater – minimum CT product of 70 g.h/m3.
It is recommended that fruit should not be fumigated if the pulp temperature is below 10 °C
and that fumigations should be carried out in accordance with AQIS fumigation standards or
an equivalent.
All pre-shipment (off-shore) fumigation certificates would need to contain the following
fumigation details:

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the name of the fumigation facility
the date of fumigation
rate of methyl bromide used, that is initial dosage (g/m³)
the fumigation duration (hours)
ambient air temperature during fumigation (°C)
minimum fruit pulp temperature during fumigation (°C).
The objective of this measure is to reduce the likelihood of importation for leafrollers to at
least „very low‟. The restricted risk would then be reduced to at least „very low‟, which would
achieve Australia‟s ALOP.

5.1.2 Pest risk management for pests for Western Australia only
Under the risk management and operational framework section, the 2006 final IRA report
proposed that fruit not be permitted access to Western Australia as no suitable risk
management measures had been identified for apple scab (caused by Venturia inaequalis).
The report further noted that if measures were to be developed that the measures
recommended for mealybugs and codling moth, as listed in the pest specific risk assessments,
would need to be applied.
Since the 2006 final IRA report, there have been detections of Venturia inaequalis in Western
Australia and containment and eradication efforts have not been put in place. As a result, this
pathogen is no longer considered a regional quarantine pest for Western Australia. It is
therefore proposed that importation of apples into the states of Western Australia be
permitted, subject to measures listed in section 5.1.1 and supplemented by the measures in
this section that are specific to produce destined for Western Australia.

Management for mealybugs

Option 1: Withdrawl of export lots found to be infested with mealybugs
The 2006 final IRA report recommended that each lot be inspected on the basis of a 600-unit
sample selected at random across the whole lot. A unit is one piece of fruit. That inspection is
undertaken as standard practice in New Zealand apple packing houses. If mealybugs of
quarantine concern to Western Australia are detected during that inspection, the lot should be
removed from export to Western Australia. The removal of any lots found to be infested with
mealybugs would reduce the likelihood of importation for mealybugs to at least „very low‟.
The restricted risk would then be reduced to at least „very low‟, which would achieve
Australia‟s ALOP.

Option 2: Methyl bromide fumigation of export lots found to be infested with
mealybugs
Instead of withdrawing from export lots found to be infested with leafrollers, a methyl
bromide fumigation treatment of could be undertaken.
Where fumigation with methyl bromide is utilised as the remedial action for mealybugs, it
must be carried out for 2 hours according to the specifications below:

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an equivalent.
fumigation details:
The objective of this measure is to reduce the likelihood of importation for mealybugs to at
least „low‟. The restricted risk would then be reduced to at least „very low‟, which would
achieve Australia‟s ALOP.

Management for codling moth
The 2006 final IRA report recommended three alternate measures for codling moth: sourcing
fruit from pest free areas, pest free places of production or pest free production sites; sourcing
fruit from areas of low pest prevalence; or methyl bromide fumigation. Visual inspection was
not assessed as an effective measure due to the potential for infestations to be undetectable by
visual means.

Option 1: Area freedom
Area freedom is a measure that might be applied to manage the risk posed by codling moth. If
MAFNZ wishes to consider pest free areas or pest free places of production or pest free
production sites as a potential management measure for codling moth, the Biosecurity
Services Groups would assess any proposal from New Zealand.
The requirements for establishing pest free areas are set out in ISPM 4: Establishment of pest
free areas (FAO 1996) and ISPM 10: Requirements for the establishment of pest free places
of production and pest free production sites (FAO 1999).
MAFNZ would be responsible for the establishment of pest free area status through official
surveys and monitoring. Survey results must be submitted to the Biosecurity Services Group
before access can be considered.

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Option 2: Areas of low pest prevalence
Low pest prevalence is a measure that might be applied to manage the risk posed by codling
moth to Western Australia. The requirements for establishing areas of low pest prevalence are
set out in ISPM 22: Requirements for the establishment of areas of low pest prevalence (FAO
2005). As noted in the 2006 final IRA report, MAFNZ administers an export phytosanitary
certification program for the export of apples to Taiwan to manage the risk of codling moth. A
similar program for production and export of apples to Western Australia might be applied to
manage the risk posed by codling moth. Components of such a program could include:
registration of grower designated production sites
monitoring and trapping for codling moth
specific codling moth control requirements
specific requirements for submission of fruit to packing houses
grower compliance agreement.
MAFNZ would be responsible for the establishment of areas of low pest prevalence by
official surveys and monitoring. These survey results must be submitted to the Biosecurity
Services Group before access could be considered.
Option 3: Methyl bromide fumigation
It is recommended that the methyl bromide fumigation treatment could be performed for
consignments where fruit cannot be sourced under Option 1, or Option 2, and when codling
moth is detected at either pre-clearance in New Zealand or on-arrival inspection in Australia.
Where fumigation with methyl bromide is utilised as the measure for codling moth, it must be
carried out for 2 hours according to the specifications below:
an equivalent.
fumigation details:
The objective of these measures is to reduce the likelihood of importation for codling moth to
at least „very low‟. The restricted risk would then be reduced to at least „very low‟, which
would achieve Australia‟s ALOP.

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5.1.3 Consideration of alternative measures
Consistent with the principle of equivalence detailed in ISPM 11: Pest risk analysis for
quarantine pests including analysis of environmental risks and living modified organisms
(FAO 2004), Biosecurity Australia will consider any alternative measure proposed by
MAFNZ, providing that it achieves Australia‟s ALOP. Evaluation of such measures or
treatments will require a technical submission from MAFNZ that details the proposed
treatment and includes data from suitable treatment trials.

5.2 Operational systems for maintenance and verification of
phytosanitary status
A system of operational procedures is necessary to maintain and verify the phytosanitary
status of fresh apple fruit from New Zealand. This is to ensure that the recommended risk
management measures have been met and are maintained.
It is recommended that MAFNZ or other relevant agency nominated by MAFNZ, prepare a
documented work plan for approval by the Biosecurity Services Group that describes the
phytosanitary procedures for the pests of quarantine concern for Australia and the various
responsibilities of all parties involved in meeting this requirement.
Details of the operational system, or equivalent, will be determined by agreement between the
Biosecurity Services Group and MAFNZ.

5.2.1 Audit and verification
The objectives of the recommended requirement for audit and verification are to ensure that:
an effective approved documented system is in operation for the orchard, the packing
house and during transport.
The phytosanitary system for apple export production, certification of export orchards, pre-
export inspection and certification is subject to audit by the Biosecurity Services Group. An
initial audit will be conducted by the Biosecurity Services Group before commencement of
exports. Audits may be then conducted at the discretion of the Biosecurity Services Group
during the entire production cycle and as a component of any pre-clearance arrangement, if
such an arrangement is entered into.
Biosecurity Services Group orchard audits will measure compliance with orchard registration
and identification, pest/disease management including maintenance of a spray
diary/monitoring, record management, the administration and verification of area freedom
status for any pests as relevant and if accepted by Australia.
Biosecurity Services Group packing house audits of participants in the export program will
include the verification of compliance with packing house responsibilities, traceability,
labelling, segregation and product security, and the MAFNZ certification processes.

5.2.2 Registration of export orchards
The objectives of this recommended procedure are to ensure that:
apple fruit is sourced from registered export orchards producing export quality fruit, as
the pest risk assessments are based on existing commercial production practices

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export orchards from which apple fruit is sourced can be identified so investigation and
corrective action can be targeted rather than applying it to all contributing export orchards
in the event that live pests are intercepted.

5.2.3 Registration of packing houses and treatment facilities and auditing of
procedures
apple fruit is sourced only from registered packing houses, processing export quality fruit,
as the pest risk assessments are based on existing commercial packing activities
reference to the packing house and the orchard source (by name or a number code) are
clearly stated on cartons destined for export of fresh apple fruit to Australia for trace back
and auditing purposes.
It is recommended that packing houses be registered before commencement of harvest each
season. A list of registered packing houses should be kept by MAFNZ and maintained as
current in order to facilitate trace-back of any consignment.
Registration of packing houses and treatment facilities in the initial export season would
include an audit program conducted by the Biosecurity Services Group before exports
commence. After the initial approval, MAFNZ would be required to audit facilities at the
beginning of each season to ensure that packing houses and treatment facilities are suitably
equipped to carry out the specified phytosanitary tasks and treatments. Records of MAFNZ
audits would be made available to the Biosecurity Services Group on request.
Packing houses will be required to identify individual orchards with a unique identifying
system and identify fruit from individual orchards by marking cartons or pallets (i.e. one
orchard per pallet) with a unique orchard number or identification.
Where apple fruit is fumigated prior to export, this process could only be undertaken in
facilities that have been registered with and audited by MAFNZ for that purpose. MAFNZ
would be required to register all export fumigators, as well as fumigation facilities before
export activity commences. Registered fumigators would need to comply with the current
MAFNZ standards for export facilities, and also comply with Australian Fumigation
Accreditation Scheme (AFAS) standards. Copies of registration and fumigation chamber test
records would need to be made available to AQIS if requested.

5.2.4 Packaging and labelling
apple fruit recommended for export to Australia is not contaminated by quarantine pests
or regulated articles (e.g. trash, soil and weed seeds)
unprocessed packing material (which may vector pests not identified as being on the
pathway) is not imported with fresh apple fruit
all wood material used in packaging of the commodity complies with AQIS conditions
(see AQIS publication Cargo Containers: Quarantine aspects and procedures)
secure packaging is used if consignments are not transported in sealed containers directly
to Australia

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the packaged apple fruit is labelled with the orchard registration number for the purposes
of trace back to registered orchards
the pre-cleared status of apple fruit is clearly identified.

5.2.5 Specific conditions for storage and movement
product for export to Australia is secure by segregation from non-precleared product and
to prevent mixing or cross-contamination with produce destined elsewhere
the quarantine integrity of the commodity during storage and movement is maintained.

5.2.6 Freedom from trash
All apples for export must be free from trash, foreign matter and pests of quarantine concern
to Australia. Freedom from trash will be confirmed by the inspection procedures. Export lots
or consignments found to be contain trash, foreign matter, or pests of quarantine concern to
Australia should be withdrawn from export unless and approved remedial action is available
and applied to the export lot or consignment.

5.2.7 Pre-export phytosanitary inspection and certification by New Zealand
authorities
all consignments have been inspected in accordance with official procedures for all
visually detectable quarantine pests and other regulated articles (including soil, animal
and plant debris) at a standard 600 unit sampling rate per lot whereby one unit is one
apple fruit
an international phytosanitary certificate (IPC) is issued for each consignment upon
completion of pre-export inspection and treatment to verify that the relevant measures
have been undertaken offshore
each IPC includes:
- a description of the consignment (including orchard number and packing house
details)
and
- an additional declaration that „The fruit in this consignment has been produced in New
Zealand in accordance with the conditions governing entry of fresh apple fruit to
Australia and inspected and found free of quarantine pests’.

5.2.8 On-arrival quarantine inspection
consignments undergo appropriate quarantine inspection on arrival in Australia.
On arrival, AQIS will undertake a documentation compliance examination for consignment
verification purposes, followed by quarantine inspection before release from quarantine on
arrival in Australia. The inspection will verify that the consignment is as described on the

126


phytosanitary certificate and that required phytosanitary actions have been undertaken. To
verify the phytosanitary status of the consignment, AQIS will randomly sample 600 fruit from
each consignment.

5.2.9 Remedial action(s) for non-compliance
The objectives of the recommended requirements for remedial action(s) for non-compliance
are to ensure that:
any quarantine risk is addressed by remedial action, as appropriate
non-compliance with import requirements is addressed, as appropriate.

5.3 Uncategorised and other pests
If an organism, including contaminating pests, is detected on apple fruit, either in New
Zealand or on-arrival in Australia, that has not been categorised, it will require assessment by
the Biosecurity Services Group to determine its quarantine status and whether phytosanitary
action is required. Assessment is also required if the detected species was categorised as not
likely to be on the import pathway. If the detected species was categorised as on the pathway
but assessed as having an unrestricted risk that achieves Australia‟s ALOP due to the rating
for likelihood of importation, then it would require reassessment. The detection of any pests
of quarantine concern not already identified in the analysis may result in remedial action
and/or temporary suspension of trade while a review is conducted to ensure that existing
measures continue to provide the appropriate level of protection for Australia.

5.4 Audit of protocol
Prior to the first season of trade, a representative from the Biosecurity Services Group will
visit areas in New Zealand that produce apples for export to Australia. They will audit the
implementation of agreed import conditions and measures including registration, operational
procedures and any treatment facilities.

5.5 Review of policy
The Biosecurity Services Group reserves the right to review the import policy after the first
year of trade or when there is reason to believe that the pest and phytosanitary status in New
Zealand has changed.
MAFNZ must inform the Biosecurity Services Group immediately on detection in New
Zealand of any new pests of apples that are of potential quarantine concern to Australia or a
significant change in the application of existing commercial practices considered in this draft
report.

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Draft Report: Review of fresh apple fruit from New Zealand Conclusion

6 Conclusion

The findings of this draft report for the non-regulated analysis of existing policy for apples
from New Zealand report are based on a comprehensive analysis of relevant scientific
literature. Biosecurity Australia considers that the risk management measures proposed in this
draft report will provide an appropriate level of protection against the pests identified as
associated with the trade in apple fruit from New Zealand. Biosecurity Australia will consider
any other measures suggested by stakeholders that would achieve Australia‟s ALOP.

129

Draft Report: Review of fresh apple fruit from New Zealand Appendix A

Appendix A Categorisation for quarantine pests considered in this review

As detailed in section 2.2.1, pest categorisation is the process that identifies which of the pests with the potential to be on the commodity are
quarantine pests for Australia and require pest risk assessment. A „quarantine pest‟ is a pest of potential economic importance to the area
endangered thereby and not yet present there, or present but not widely distributed and being officially controlled, as defined in ISPM 5:
Glossary of phytosanitary terms (FAO 2009).
A comprehensive pest categorisation for apples from New Zealand was presented as Part C of the Final import risk analysis report for apples
from New Zealand which was published in November 2006. For clarity, the entries from the categorisation table presented in that final IRA
report for the three pests considered in this review are reproduced below.
Scientific name Common Reference for Presence in Australia Potential for being on mature Potential for Potential for Consider
name/s presence in apple fruit establishment or consequences species
New Zealand Reference spread further?
Comments if applicable Comments if
applicable

Bacteria

Erwinia amylovora (Burrill 1882) Fire blight MAFNZ (2000b); No Likely Feasible Significant Yes
Winslow et al. (1920) emend. Hauben et MAFNZ (2002b)
al. 1998 E. amylovora was Fire blight is endemic in New (Bonn, 1999);
detected in the Melbourne Zealand. Fruit sourced from infected (Vanneste,
(Syn. = Micrococcus amylovorus (Burrill Royal Botanic Garden in orchards have the potential to carry 2000)
1882); Bacillus amylovorus (Burrill 1882) 1996 and its eradication epiphytic bacteria (Hale et al., 1987)
Trevisan 1889; Bacterium amylovorus was confirmed by a survey
(sic) (Burrill 1882) Chester (1897)) in 1997 (Jock et al., 2000)
[Enterobacteriaceae: Enterobacteriales]

Fungi

Neonectria galligena (Bres.) Rossman & European MAFNZ (2000b); No (APPD, 2005) Likely Feasible Significant Yes
Samuels (1999) canker; eye MAFNZ (2002b) (Swinburne,
rot; Has been eradicated from It causes a primary fruit spot. Latent 1970)
(Syn. = Nectria galligena Bres. (1901); cylindrocarp Tasmania (Ransom, 1997) fruit infections may occur
Fusarium heteronemum Berk. & Broome on fruit rot (Swinburne, 1971a)
(1865); Cylindrocarpon heteronema
(Berk. & Broome) Wollenw. [as
’heteronemum’] (1926); Cylindrocarpon
mali (Allesch.) Wollenw. (1928))
[Hypocreales: Nectriaceae]

131

Draft Report: Review of fresh apple fruit from New Zealand Appendix A

Scientific name Common Reference for Presence in Australia Potential for being on mature Potential for Potential for Consider
name/s presence in apple fruit establishment or consequences species
New Zealand Reference spread further?
Comments if applicable Comments if
applicable

Insects - Diptera

Dasineura mali Keiffer Apple MAFNZ (2000b) No Likely Feasible Significant Yes
leafcurling
[Diptera: Cecidomyiidae] midge (McLaren and Fraser, Larvae are primary pest on foliage; Apple tree
1994) larvae can pupate on fruit (MAFNZ, shoots damaged
2000b) and tree growth
retarded
resulting in
decreased fruit
yield in Europe
and New
Zealand
(Tomkins et al.,
1994); (Smith
and Chapman,
1995); (CABI,
2000)

132

Draft Report: Review of fresh apple fruit from New Zealand Appendix B

Appendix B Additional quarantine pest data

DOMAIN BACTERIA

Quarantine pest Erwinia amylovora (Burrill 1882) Winslow et al. 1920, emend. Hauben et al. 1998

Synonyms Micrococcus amylovorus Burrill 1882
Bacillus amylovorus (Burrill 1882) Trevisan 1889
Bacterium amylovorum (Burrill 1882) Chester 1901

Common name(s) fire blight

Main hosts Besides the species in the genera Malus and Pyrus, there are 129 species of plants belonging to 37
genera of the family Rosaceae that have been reported to be susceptible to E. amylovora (van der
Zwet and Keil, 1979). These authors showed that most of the hosts are susceptible only when
inoculated artificially. The natural host range of E. amylovora is now generally considered to be
restricted to genera of the subfamily Maloideae (formerly: Pomoideae) of the family Rosaceae
(CABI 2007). Plants belonging to the subfamilies Rosoideae and Amygdaloideae can also be
affected (Momol and Aldwinckle 2000).
Primary hosts of economic and epidemiological significance: Cotoneaster spp. (cotoneaster),
Crataegus spp. (hawthorns), Cydonia oblonga (quince), Eriobotrya spp. (bolanchin, loquat, etc.),
Malus spp. (apple), Prunus salicina (Japanese plum), Pyracantha spp. (firethorn) and Pyrus spp.
(pears) (Douglas 2006; CABI 2007)
Secondary hosts: Amelanchier spp. (serviceberry), Chaenomeles spp. (flowering quince), Mespilus
spp. (medlar), Rubus spp. (blackberry, raspberry) and Sorbus spp. (mountain ash, rowan) (Douglas
2006; CABI 2007)
Within each genus given as hosts of fire blight, there are species or cultivars that may show high
level of resistance under natural conditions or artificial inoculations (van der Zwet and Keil 1979;
CABI 2007).

Distribution Presence in Australia: Erwinia amylovora was detected on Cotoneaster in the Melbourne Royal
Botanic Garden in 1997, and its eradication was confirmed by national survey (Rodoni et al. 1999;
Jock et al. 2000).
Presence in the US: Every region of the US (Bonn and van der Zwet 2000), AL, CA, CO, CT, GA,
IL, LA, MD, ME, MI, NC, NY, OH, OR, PA, TX, UT, VA, WA, WV, WI (CABI 2007)
Presence elsewhere: Albania, Armenia, Austria, Belgium, Bermuda, Bosnia and Herzegovina,
Bulgaria, Canada, Croatia, Cyprus, Czech Republic, Denmark, Egypt, France, Germany, Greece,
Guatemala, Hungary, Iran, Ireland, Israel, Italy, Jordan, Lebanon, Luxembourg, Macedonia, Mexico,
Moldova, Montenegro, Netherlands, New Zealand, Norway, Poland, Romania, Serbia, Slovakia,
Slovenia, Spain, Sweden, Switzerland, Turkey, United Kingdom (CABI 2007)
DOMAIN EUKARYA

Quarantine pest Dasineura mali (Kieffer, 1904)

Synonyms Perrisia mali Kieffer, 1904
Common name(s) apple leafcurling midge, apple leaf midge
Main hosts Malus spp. are the only hosts of D. mali (Tomkins 1998)

Distribution Presence in Australia: No record found
Presence in the US: MA, NY, WA (CABI 2007; CABI/EPPO 2008)
Presence elsewhere: Argentina, Austria, Belgium, Bosnia-Herzegovina, Bulgaria, Canada, Finland,
France, Germany, Hungary, Italy, Macedonia, Netherlands, New Zealand, Norway, Poland,
Romania, Russia, Serbia, Slovenia, Sweden, Switzerland, United Kingdom (CABI 2007; CABI CPC
2008)
DOMAIN FUNGI

Quarantine pest Neonectria ditissima (Tul. & C. Tul.) Samuels & Rossman

Synonyms Cylindrocarpon heteronema (Berk. & Broome) Wollenw. (Anamorph)
Cylindrocarpon mali (Allesch.) Wollenw.
Cylindrocarpon willkommii (Lindau) Wollenw.
Fusarium heteronemum Berk. & Broome
Fusarium mali Allesch.
Fusarium willkommii J. Lindau
Nectria galligena Bres.
Nectria magnoliae M.L. Lohman & Hepting

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Draft Report: Review of fresh apple fruit from New Zealand Appendix B

Neonectria galligena (Bres.) Rossman & Samuels

Common name(s) European canker
Main hosts Acer spp. (maples), Aesculus sp. (horse-chestnut), Alnus incana (grey alder), Betula spp. (birches),
Carpinus betulus (common hornbeam), Carya spp. (hickories), Cornus nuttallii (Pacific dogwood),
Corylus avellana (hazel), Fagus spp. (beeches), Frangula alnus (alder buckthorn), Fraxinus spp.
(ashes), Juglans spp. (walnuts), Liriodendron tulipifera (yellow poplar), Malus pumila (apple), Nyssa
sylvatica (blackgum), Populus spp. (poplars), Prunus serotina (black cherry tree), Pyrus spp.
(pears), Quercus spp. (oaks), Rosa spp. (rose), Rhus typhina (staghorn sumac), Salix spp.
(willows), Sorbus aucuparia (rowan), Tilia americana (American basswood), Ulmus spp. (elms)
(CABI 2007)

Distribution Presence in Australia: The disease has been eradicated from Tasmania (Ransom 1997). No record
found from any other states.
Presence in the US: CA, CT, FL, IL, IN, MA, MD, ME, MI, MN, MS, NC, ND, NH, NJ, NY, OR, PA,
RI, SD, TN, VA, VT, WA, WV (CABI 2007, Farr and Rossman 2009)
Presence elsewhere: Afghanistan, Argentina, Austria, Belgium, Bulgaria, Canada, Chile, China,
Czech Republic, Denmark, Estonia, Faeroe Islands, France, Germany, Greece, Hungary, Iceland,
India, Indonesia, Iran, Iraq, Ireland, Italy, Japan, South Korea, Lithuania, Lebanon, Macedonia,
Madagascar, Malaysia, Mexico, Netherlands, New Zealand, Norway, Poland, Portugal, Romania,
Russia, Saudi Arabia, Slovakia, South Africa, Spain, Sweden, Switzerland, Syria, Taiwan, Ukraine,
United Kingdom, Uruguay (CABI 2007, Farr and Rossman 2009)

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Draft Report: Review of fresh apple fruit from New Zealand Appendix C

Appendix C Biosecurity framework

Australia’s biosecurity policies
The objective of Australia‟s biosecurity policies and risk management measures is the
prevention or control of the entry, establishment or spread of pests and diseases that could
cause significant harm to people, animals, plants and other aspects of the environment.
Australia has diverse native flora and fauna and a large agricultural sector, and is relatively
free from the more significant pests and diseases present in other countries. Therefore,
successive Australian Governments have maintained a conservative, but not a zero-risk,
approach to the management of biosecurity risks. This approach is consistent with the World
Trade Organization‟s (WTO‟s) Agreement on the Application of Sanitary and Phytosanitary
Measures (SPS Agreement).
The SPS Agreement defines the concept of an „appropriate level of protection‟ (ALOP) as the
level of protection deemed appropriate by a WTO Member establishing a sanitary or
phytosanitary measure to protect human, animal or plant life or health within its territory.
Among a number of obligations, a WTO Member should take into account the objective of
minimising negative trade effects in setting its ALOP.
Like many other countries, Australia expresses its ALOP in qualitative terms. Australia‟s
ALOP, which reflects community expectations through Australian Government policy, is
currently expressed as providing a high level of sanitary and phytosanitary protection, aimed
at reducing risk to a very low level, but not to zero.
Consistent with the SPS Agreement, in conducting risk analyses Australia takes into account
as relevant economic factors:
the potential damage in terms of loss of production or sales in the event of the entry,
establishment or spread of a pest or disease in the territory of Australia
the costs of control or eradication of a pest or disease
and the relative cost-effectiveness of alternative approaches to limiting risks.

Roles and responsibilities within Australia’s quarantine system
Australia protects its human18, animal and plant life or health through a comprehensive
quarantine system that covers the quarantine continuum, from pre-border to border and post-
border activities.
Pre-border, Australia participates in international standard-setting bodies, undertakes risk
analyses, develops offshore quarantine arrangements where appropriate, and engages with our
neighbours to counter the spread of exotic pests and diseases.
At the border, Australia screens vessels (including aircraft), people and goods entering the
country to detect potential threats to Australian human, animal and plant health.

18
The Australian Government Department of Health and Ageing is responsible for human health aspects of
quarantine.

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The Australian Government also undertakes targeted measures at the immediate post-border
level within Australia. This includes national co-ordination of emergency responses to pest
and disease incursions. The movement of goods of quarantine concern within Australia‟s
border is the responsibility of relevant state and territory authorities, which undertake inter-
and intra-state quarantine operations that reflect regional differences in pest and disease status,
as a part of their wider plant and animal health responsibilities.

Roles and responsibilities within the Department
The Australian Government Department of Agriculture, Fisheries and Forestry is responsible
for the Australian Government‟s animal and plant biosecurity policy development and the
establishment of risk management measures. The Secretary of the Department is appointed as
the Director of Animal and Plant Quarantine under the Quarantine Act 1908 (the Act).
The Biosecurity Services Group (BSG) within the Department takes the lead in biosecurity
and quarantine policy development and the establishment and implementation of risk
management measures across the biosecurity continuum, and:
though Biosecurity Australia, conducts risk analyses, including IRAs, and develops
recommendations for biosecurity policy as well as providing quarantine policy advice
to the Director of Animal and Plant Quarantine
through the Australian Quarantine and Inspection Service, develops operational
procedures, makes a range of quarantine decisions under the Act (including import
permit decisions under delegation from the Director of Animal and Plant Quarantine)
and delivers quarantine services
coordinates pest and disease preparedness, emergency responses and liaison on inter-
and intra-state quarantine arrangements for the Australian Government, in conjunction
with Australia‟s state and territory governments.

Roles and responsibilities of other government agencies
State and territory governments play a vital role in the quarantine continuum. The BSG work
in partnership with state and territory governments to address regional differences in pest and
disease status and risk within Australia, and develops appropriate sanitary and phytosanitary
measures to account for those differences. Australia‟s partnership approach to quarantine is
supported by a formal Memorandum of Understanding that provides for consultation between
the Australian Government and the state and territory governments.
Depending on the nature of the good being imported or proposed for importation, Biosecurity
Australia may consult other Australian Government authorities or agencies in developing its
recommendations and providing advice.
As well as a Director of Animal and Plant Quarantine, the Act provides for a Director of
Human Quarantine. The Australian Government Department of Health and Ageing is
responsible for human health aspects of quarantine and Australia‟s Chief Medical Officer
within that Department holds the position of Director of Human Quarantine. Biosecurity
Australia may, where appropriate, consult with that Department on relevant matters that may
have implications for human health.
The Act also requires the Director of Animal and Plant Quarantine, before making certain
decisions, to request advice from the Environment Minister and to take the advice into

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account when making those decisions. The Australian Government Department of
Sustainability, Environment, Water, Population and Communities (DSEWPC) is responsible
under the Environment Protection and Biodiversity Conservation Act 1999 for assessing the
environmental impact associated with proposals to import live species. Anyone proposing to
import such material should contact DSEWPC directly for further information.
When undertaking risk analyses, Biosecurity Australia consults with DSEWPC about
environmental issues and may use or refer to DSEWPC‟s assessment.

Australian quarantine legislation
The Australian quarantine system is supported by Commonwealth, state and territory
quarantine laws. Under the Australian Constitution, the Commonwealth Government does
not have exclusive power to make laws in relation to quarantine, and as a result,
Commonwealth and state quarantine laws can co-exist.
Commonwealth quarantine laws are contained in the Quarantine Act 1908 and subordinate
legislation including the Quarantine Regulations 2000, the Quarantine Proclamation 1998, the
Quarantine (Cocos Islands) Proclamation 2004 and the Quarantine (Christmas Island)
Proclamation 2004.
The quarantine proclamations identify goods, which cannot be imported, into Australia, the
Cocos Islands and or Christmas Island unless the Director of Animal and Plant Quarantine or
delegate grants an import permit or unless they comply with other conditions specified in the
proclamations. Section 70 of the Quarantine Proclamation 1998, section 34 of the Quarantine
(Cocos Islands) Proclamation 2004 and section 34 of the Quarantine (Christmas Island)
Proclamation 2004 specify the things a Director of Animal and Plant Quarantine must take
into account when deciding whether to grant a permit.
In particular, a Director of Animal and Plant Quarantine (or delegate):
must consider the level of quarantine risk if the permit were granted, and
must consider whether, if the permit were granted, the imposition of conditions would
be necessary to limit the level of quarantine risk to one that is acceptably low, and
for a permit to import a seed of a plant that was produced by genetic manipulation –
must take into account any risk assessment prepared, and any decision made, in
relation to the seed under the Gene Technology Act, and
may take into account anything else that he or she knows is relevant.
The level of quarantine risk is defined in section 5D of the Quarantine Act 1908. The
definition is as follows:
reference in this Act to a level of quarantine risk is a reference to:
(a) the probability of:

(i) a disease or pest being introduced, established or spread in Australia, the
Cocos Islands or Christmas Island; and

(ii) the disease or pest causing harm to human beings, animals, plants, other
aspects of the environment, or economic activities; and

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(b) the probable extent of the harm.

The Quarantine Regulations 2000 were amended in 2007 to regulate keys steps of the import
risk analysis process. The Regulations:
define both a standard and an expanded IRA,
identify certain steps, which must be included in each type of IRA,
specify time limits for certain steps and overall timeframes for the completion of IRAs
(up to 24 months for a standard IRA and up to 30 months for an expanded IRA),
specify publication requirements,
make provision for termination of an IRA, and
allow for a partially completed risk analysis to be completed as an IRA under the
Regulations.
The Regulations are available at www.comlaw.gov.au.

International agreements and standards
The process set out in the Import Risk Analysis Handbook 2011 is consistent with Australia‟s
international obligations under the SPS Agreement. It also takes into account relevant
international standards on risk assessment developed under the International Plant Protection
Convention (IPPC) and by the World Organisation for Animal Health (OIE).
Australia bases its national risk management measures on international standards where they
exist and when they achieve Australia‟s ALOP. Otherwise, Australia exercises its right under
the SPS Agreement to apply science-based sanitary and phytosanitary measures that are not
more trade restrictive than required to achieve Australia‟s ALOP.

Notification obligations
Under the transparency provisions of the SPS Agreement, WTO Members are required,
among other things, to notify other members of proposed sanitary or phytosanitary
regulations, or changes to existing regulations, that are not substantially the same as the
content of an international standard and that may have a significant effect on trade of other
WTO Members.

Risk analysis
Within Australia‟s quarantine framework, the Australian Government uses risk analyses to
assist it in considering the level of quarantine risk that may be associated with the importation
or proposed importation of animals, plants or other goods.
In conducting a risk analysis, Biosecurity Australia:
identifies the pests and diseases of quarantine concern that may be carried by the good
assesses the likelihood that an identified pest or disease or pest would enter, establish
or spread

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assesses the probable extent of the harm that would result.
If the assessed level of quarantine risk exceeds Australia‟s ALOP, Biosecurity Australia will
consider whether there are any risk management measures that will reduce quarantine risk to
achieve the ALOP. If there are no risk management measures that reduce the risk to that level,
trade will not be allowed.
Risk analyses may be carried out by Biosecurity Australia‟s specialists, but may also involve
relevant experts from state and territory agencies, the Commonwealth Scientific and Industrial
Research Organisation (CSIRO), universities and industry to access the technical expertise
needed for a particular analysis.
Risk analyses are conducted across a spectrum of scientific complexity and available
scientific information. An IRA is a type of risk analysis with key steps regulated under the
Quarantine Regulations 2000. Biosecurity Australia‟s assessment of risk may also take the
form of a non-regulated analysis of existing policy or technical advice to AQIS. Further
information on the types of risk analysis is provided in the Import Risk Analysis Handbook
2011.

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Draft Report: Review of fresh apple fruit from New Zealand Glossary

Glossary


Abiotic Relating to non-living objects, substances and processes (e.g. geological, geographical and
climatic factors)

Abscission The normal shedding from a plant of an organ that is mature or aged, e.g. a ripe fruit, an old leaf

Additional declaration A statement that is required by an importing country to be entered on a phytosanitary certificate
and which provides specific additional information on a consignment in relation to regulated
pests (FAO 2009).
Aestivate Also ‘estivate’ – to pass the summer in a dormant or torpid state
Apoplast The contents of a plant cell, excluding the cell cytoplasm (i.e. the cell walls and spaces between
cells)

Appropriate level of The level of protection deemed appropriate by the Member establishing a sanitary or
protection (ALOP) phytosanitary measure to protect human, animal or plant life or health within its territory (WTO
1995).

Area An officially defined country, part of a country or all or parts of several countries (FAO 2009).

Area of low pest An area, whether all of a country, part of a country, or all parts of several countries, as identified
prevalence (ALPP) by the competent authorities, in which a specific pest occurs at low levels and which is subject to
effective surveillance, control or eradication measures (FAO 2009).

Arthropod The largest phylum of animals, including the insects, arachnids and crustaceans

Ascospore A sexual spore produced in a perithecia
Attenuated To weaken or grow less
Bacteriophage A virus that infects a bacterium

Biological control Also ‘biocontrol’ – a method of controlling pests and diseases in agricultural production that
relies on the use of natural predators rather than chemical agents
Biosecurity Australia The unit, within the Biosecurity Service Group, responsible for recommendations for the
development of Australia’s biosecurity policy.
Biosecurity Service The group responsible for the delivery of biosecurity policy and quarantine services within the
Group (BSG) Department of Agriculture, Fisheries and Forestry.

Biotic Relating to living organisms, substances and processes

Calyx A collective term referring to all of the sepals in a flower
Cambium Hard woody tissue (bark) found in the stems of perennial dicotyledons

Canker General term for a large number of different plant diseases characterised by the appearance of
small areas of dead tissue

Certificate An official document which attests to the phytosanitary status of any consignment affected by
phytosanitary regulations (FAO 2009).

Cfu Colony forming unit, CFU is used to determine the number of viable bacterial cells in a sample
Conidiophore A simple or branched, fertile hypha bearing conidiogenous cells from which conidia are
produced

Conidium A non-motile, usually deciduous, asexual spore
Consignment A quantity of plants, plant products and/or other articles being moved from one country to
another and covered, when required, by a single phytosanitary certificate (a consignment may
be composed of one or more commodities or lots) (FAO 2009).
Control (of a pest) Suppression, containment or eradication of a pest population (FAO 2009).

Crawler Intermediate mobile nymph stage of certain Arthropods
Crotch Area where tree trunk splits into two or more limbs

Cultivar A cultivated plant selection that can be propagated reliably in a prescribed manner
Cytoplasm A jelly-like material composed mostly of water that fills the cell, maintaining its shape and
consistency whilst also providing suspension to the organelles

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Diapause Period of suspended development/growth occurring in some insects, in which metabolism is
decreased

Endangered area An area where ecological factors favour the establishment of a pest whose presence in the area
will result in economically important loss (FAO 2009).

Endemic Belonging to, native to, or prevalent in a particular geography, area or environment

Endophytic (of a pest) Describes the endophytic (internal) colonisation (infection) of the core of an apple or the plant
itself, and is generally associated with the development of disease symptoms

Entry (of a pest) Movement of a pest into an area where it is not yet present, or present but not widely distributed
and being officially controlled (FAO 2009).

Epidemiology The study of factors influencing the initiation, development and spread of infectious disease; the
study of disease in populations of plants

Epiphytic (of a pest) Describes the epiphytic colonisation (infestation) of the surface, calyx and stem-end of apple
fruit, although the fruit and plant is unlikely to display disease symptoms

Establishment Perpetuation, for the foreseeable future, of a pest within an area after entry (FAO 2009).

Exopolysaccharide A high molecular-weight polymer composed of saccharide (sugar) subunits produced by cells,
often to prevent them from losing moisture under dry environmental conditions

Exudation Active secretion of fluid from cells as a result of disease or injury

Fecundity The fertility of an organism

Fresh Living; not dried, deep-frozen or otherwise conserved (FAO 2009).

Fruitlet A very small fruit soon after formation
Fumigation A method of pest control that completely fills an area with gaseous pesticides to suffocate or
poison the pests within

Genotype The specific genetic makeup (or genome) of an individual organism
Genus A taxonomic category ranking below a family and above a species and generally consisting of a
group of species exhibiting similar characteristics. In taxonomic nomenclature the genus name is
used, either alone or followed by a Latin adjective or epithet, to form the name of a species
Gram negative bacteria Bacteria that are not stained dark blue or violet by Gram staining, in contrast to Gram positive
bacteria. The difference lies in the cell wall of the two types; in contrast to most Gram positive
bacteria, Gram negative bacteria have only a few layers of peptidoglycan and a secondary cell
membrane made primarily of lipopolysaccharide.
Gram positive bacteria Bacteria that are stained dark blue or violet by Gram staining, in contrast to Gram negative
bacteria, which are not affected by the stain. The stain is caused by a high amount of
peptidoglycan in the cell wall, which typically, but not always lacks the secondary membrane and
lipopolysaccharide layer found in Gram negative bacteria.
Host An organism that harbours a parasite, mutual partner, or commensal partner, typically providing
nourishment and shelter.

Host range Species capable, under natural conditions, of sustaining a specific pest or other organism (FAO
2009).
Host range The collection of hosts that an organism can utilise as a partner or parasite.
Hypanthium A bowl-shaped part of a flower consisting of the bottoms of the sepals, petals and stamens stuck
together. It is present in all members of the Rosaceae (rose) family

Hypha A long branching filament that along with other hyphae (plural), forms the feeding structure of a
fungus called the mycelium.

Import permit Official document authorising importation of a commodity in accordance with specified
phytosanitary import requirements (FAO 2009).

Import risk analysis An administrative process through which quarantine policy is developed or reviewed,
incorporating risk assessment, risk management and risk communication.
Infection The internal ‘endophytic’ colonisation of a plant, or plant organ, and is generally associated with
the development of disease symptoms as the integrity of cells and/or biological processes are
disrupted

Infestation The ‘epiphytic’ colonisation of the surface of a plant, or plant organ, and is characterised by the
absence of disease symptoms

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Infestation (of a Official document authorising importation of a commodity in accordance with specified
commodity) phytosanitary import requirements (FAO 2009).

Inoculum Pathogen or its parts, capable of causing infection when transferred to a favourable location

Inspection Official visual examination of plants, plant products or other regulated articles to determine if
pests are present and/or to determine compliance with phytosanitary regulations (FAO 2009).

Instar A stage of insect larval development which is between two moults

Intended use Declared purpose for which plants, plant products, or other regulated articles are imported,
produced, or used (FAO 2009).

Interception (of a pest) The detection of a pest during inspection or testing of an imported consignment (FAO 2009).

International Standard for An international standard adopted by the Conference of the Food and Agriculture Organization,
Phytosanitary Measures the Interim Commission on phytosanitary measures or the Commission on phytosanitary
(ISPM) measures, established under the IPCC (FAO 2009).

Introduction The entry of a pest resulting in its establishment (FAO 2009).

Keystone species Any species that exerts great influence on an ecosystem, relative to its abundance

Larva A juvenile form of animal with indirect development, undergoing metamorphosis (for example,
insects or amphibians)
Lenticel A small oval/rounded spot on the stem or branch of a plant, from which the underlying tissues
may protrude or roots may issue, either in the air, or more commonly when the stem or branch is
covering with water or earth.
Lot A number of units of a single commodity, identifiable by its homogeneity of composition, origin
etc., forming part of a consignment (FAO 2009).

Lysed Dissolution or destruction of cells

Mature fruit Commercial maturity is the start of the ripening process. The ripening process will then continue
and provide a product that is consumer–acceptable. Maturity assessments include colour, starch
index, soluble solids content, flesh firmness, acidity, and ethylene production rate

Midge A small two-winged insect belonging to the Order Diptera

Mortality The total number of organisms killed by a particular disease

Mycelium The vegetative body of a fungus, consisting of hyphae

National Plant Protection Official service established by a government to discharge the functions specified by the IPPC
Organization (NPPO) (FAO 2009).
Nectary The gland that secretes nectar, usually located at the base of the flower

Nymph The immature form of some insect species that undergoes incomplete metamorphosis. It is not
to be confused with a larva, as its overall form is already that of the adult

Official control The active enforcement of mandatory phytosanitary regulations and the application of mandatory
phytosanitary procedures with the objective of eradication or containment of quarantine pests or
for the management of regulated non-quarantine pests (FAO 2009).

Orchard A contiguous area of apple trees operated as a single entity

Ovule A structure found in seed plants that develops into a seed after fertilisation
Parasitoid An insect parasitic only in its immature stages, killing its host in the process of its development,
and free living as an adult (ISPM 5)

Pathogen A biological agent that can cause disease to its host

Pathway Any means that allows the entry or spread of a pest (FAO 2009).

PCR Polymerase chain reaction; is a technique in molecular genetics that permits the
analysis/detection of any short sequence of DNA (or RNA) even in samples containing only
minute quantities of DNA or RNA.

Pedicel The stalk of a flower

Peduncle A flower stalk, or stem

Perithecium A flask or jug-shaped fungal fruiting body that is slightly open at one end
Pest Any species, strain or biotype of plant, animal, or pathogenic agent injurious to plants or plant
products (FAO 2009).

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Pest categorisation The process for determining whether a pest has or has not the characteristics of a quarantine
pest or those of a regulated non-quarantine pest (FAO 2009).

Pest free area (PFA) An area in which a specific pest does not occur as demonstrated by scientific evidence and in
which, where appropriate, this condition is being officially maintained (FAO 2009).

Pest free place of Place of production in which a specific pest does not occur as demonstrated by scientific
production evidence and in which, where appropriate, this condition is being officially maintained for a
defined period (FAO 2009).

Pest free production site A defined portion of a place of production in which a specific pest does not occur as
demonstrated by scientific evidence and in which, where appropriate, this conditions is being
officially maintained for a defined period and that is managed as a separate unit in the same way
as a pest free place of production (FAO 2009).
Pest risk analysis (PRA) The process of evaluating biological or other scientific and economic evidence to determine
whether an organism is a pest, whether it should be regulated, and the strength of any
phytosanitary measures to be taken against it (FAO 2009).

Pest risk assessment (for Evaluation of the probability of the introduction and spread of a pest and of the associated
quarantine pests) potential economic consequences (FAO 2009).

Pest risk management Evaluation and selection of options to reduce the risk of introduction and spread of a pest (FAO
(for quarantine pests) 2009).
Petiole The stalk of a leaf, attaching the blade to the stem
Phenotype An individual organism’s total physical appearance and constitution, or a specific manifestation
of a trait, such as size or eye colour, that varies between individuals

Pheromone Any chemical produced by a living organism that transmits a message to other members of the
same species

Phloem In vascular plants, the tissue that carries organic nutrients to all parts of the plant where needed

Phytosanitary certificate Certificate patterned after the model certificates of the IPPC (FAO 2009).
Phytosanitary measure Any legislation, regulation or official procedure having the purpose to prevent the introduction
and/or spread of quarantine pests, or to limit the economic impact of regulated non-quarantine
pests (FAO 2009).
Phytosanitary regulation Official rule to prevent the introduction and/or spread of quarantine pests, or to limit the
economic impact of regulated non-quarantine pests, including establishment of procedures for
phytosanitary certification (FAO 2009).

Polyphagous Feeding on a relatively large number of hosts from different genera.
Polyphagous Feeding on a relatively large number of host plants from different plant families
Polysaccharide A relatively rich carbohydrate composed of simple sugars linked together
Pome fruit A type of fruit produced by flowering plants in the subfamily Maloideae of the Family Rosaceae

PRA area Area in relation to which a pest risk analysis is conducted (FAO 2009).

Propagule A reproductive structure, e.g. a seed, a spore, part of the vegetative body capable of
independent growth if detached from the parent
Pupa An inactive life stage that only occurs in insects that undergo complete metamorphosis, for
example butterflies and moths (Lepidoptera), beetles (Coleoptera) and bees, wasps and ants
(Hymenoptera)

Quarantine pest A pest of potential economic importance to the area endangered thereby and not yet present
there, or present but not widely distributed and being officially controlled (FAO 2009).
Quarantine pest A pest of potential economic importance to the area endangered thereby and not yet present
there, or present but not widely distributed and being officially controlled (ISPM 5)
Quiescent Inactive, latent, or dormant, referring to a disease or pathological process

Quorum sensing The ability of bacteria to communicate and coordinate behaviour via signalling molecules
Regulated article Any plant, plant product, storage place, packing, conveyance, container, soil and any other
organism, object or material capable of harbouring or spreading pests, deemed to require
phytosanitary measures, particularly where international transportation is involved (FAO 2009).

Restricted risk Risk estimate with phytosanitary measure(s) applied.

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Rootstock A stump with an established healthy root system, onto which a tree part (scion) with fruiting
properties desired by the propagator, during the process of plant propagation by mechanical
grafting

rpoS The rpoS (RNA polymerase, sigma S) gene encodes the sigma factor σS and regulates
expression of a number of genes that serve to maintain viability of bacteria during periods of
starvation and environmental stress
Saprophyte An organism deriving its nourishment from dead organic matter

Scion A tree part with fruiting properties desired by the propagator that is grafted onto a rootstock.

Sepal A segment of the calyx of a flower. In a ‘typical’ flower, sepals are green and lie under the more
conspicuous petals

Sporodochia A cluster of condidiophores that arise from a stroma or a mass of hyphae

Spread Expansion of the geographical distribution of a pest within an area (FAO 2009).

Spread (of a pest) Expansion of the geographical distribution of a pest within an area (ISPM 5)

Spread potential (of a Likelihood of the spread of a pest
pest)

SPS Agreement WTO Agreement on the Application of Sanitary and Phytosanitary Measures (WTO 1995).
Stakeholders Government agencies, individuals, community or industry groups or organizations, whether in
Australia or overseas, including the proponent/applicant for a specific proposal, who have an
interest in the policy issues.
Stigma A part of the female organ of a flower, essentially the terminal part of a pistil

Stoma (Also ‘stomate’) A tiny opening or pore, found mostly on the undersurface of a plant leaf, and
used for gaseous exchange

Streptomycin An antibiotic used in the control of fire blight
Symptomless Without any visible indication of disease by reaction of the host, e.g. canker, wilt
Systems approach(es) The integration of different risk management measures, at least two of which act independently,
and which cumulatively achieve the appropriate level of protection against regulated pests (FAO
2009).

Thorax The division of an animal’s body located between the head and abdomen. In insects, the thorax
is one of the three main segments of the body
Trash Soil, splinters, twigs, leaves and other plant material, other than fruit stalks.
Unrestricted risk Unrestricted risk estimates apply in the absence of risk mitigation measures.

Vector An organism that does not cause disease itself, but which causes infection by conveying
pathogens from one host to another

Viable Alive, able to germinate or capable of growth
Virulence The relative ability of an infectious agent to do damage to a host organism
Xylem In vascular plants, the tissue that carries water up the root and stem

144

Draft Report: Review of fresh apple fruit from New Zealand References

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