Grape Growing guide

THE COLORADO GRAPE
GROWERS' GUIDE
1998 Edition

by

Richard A. Hamman1, Jr., Steven D. Savage, and Harold J. Larsen

Additional copies of this publication available from:
The Other Bookstore: Cooperative Extension Resource Center
115 General Services Building
Colorado State University
Fort Collins, CO 80523
(970) 491-6198

1
Research Viticulturalist, Plant Pathologist (formerly with Colorado State University), and
Research Plant Pathologist and Cooperative Extension Fruit Disease Specialist, respectively.
Colorado State University, Colorado Agricultural Experiment Station - Orchard Mesa
Research Center, 3168 B.5 Road, Grand Junction, CO 81503.

TABLE OF CONTENTS

Introduction Pest Management / Control
Introduction 1 Disease Management 49
Anatomy of the Grapevine 2 Powdery mildew, crown gall,
Grapevine Structures 3 Botrytis bunch rot, sour bunch rot,
& virus diseases.
Establishing a Vineyard Powdery Mildew Fungicide Program 49
Site Selection 4 Insect & Mite Pest Management 57
Common Mistakes in Vineyard Development Nematodes 61
Plant Selection 7 Weed Management 62
Planning a Commercial Vineyard in Colorado 8 Bird Control 63
Nursery Stock and Standards 9
Phylloxera/Rootstocks 10 Wine Grape Varieties
Site Preparation 13 White Varieties -- Vinifera Cultivars 65
Vineyard Development Checklist 14 White Varieties -- Hybrid Cultivars 67
Trellising/Training 15 Red Varieties -- Vinifera Cultivars 68
Planting -- The First Year 18 Red Varieties -- Hybrid Cultivars 69
Grow tubes 21 Relative Cold Hardiness of Grapevines 70
The Training Year (Year 2) 22
The Third Year 26 Table Grape Varieties
Himrod, Interlaken, Lakemont, etc. 71
Maintaining a Vineyard
Water Management 29 Vine Sources
Protection Against Winter Injury 30 Nurseries 74
Frost Protection and Damage Treatment Vineyard Supply Sources 75
Pruning 32
Bleeding 36 Cost Estimates
Re-training Winter Damaged Vines Vineyard Establishment Costs 78
Shoot Tying and Suckering 39 Vineyard Production Costs 79
Shoot Thinning
Leaf Removal 40 Useful Books and Publications
Crop Thinning Books and Publications 80
Hedging 41 Viticulture Trade Magazines 82
Nutrition Analysis and Foliar Sprays Resources on the Internet 82
Zinc, Manganese, & Iron
Crop Estimation 45 (The print version includes Cornell University
Harvest Timing 47 Grape IPM Sheets, not available in this CD-ROM
Sugar content, acidity, pH, & sampling version.)

Introduction
Wine grapes have been grown in several our knowledge of optimal growing practices. The
counties of Colorado since the end of the last viticulture program at Colorado State University
century. A renewed interest in wine grape Orchard Mesa Research Center is currently
cultivation was initiated during the mid-70's and addressing the unique problems facing Colorado
the most dramatic growth of the Colorado Wine growers. The CSU viticulture program provides
Industry is occurring this decade. Since 1990, growers and vintners with technical assistance and
vineyard acreage has increased from 242 to over conducts applied research and field
400 acres. State production levels have also demonstrations in wine grape production.
increased from 107 tons to 755 tons and mature Colorado State University Orchard Mesa Research
vineyards in 1997 averaged 3.4 tons/acre. The Center is located at 3168 B½ Road, Grand
current and future market for Colorado wine Junction, Colorado 81503, 970-434-3264.
grapes appears healthy with 21 licensed wineries This publication is intended to present
that have the capacity to produce approximately what has been learned about the particular needs
215,000 gallons of wine or the equivalent of 1,300 of grapes in a high desert region. The experience
tons. Ninety percent of the Colorado acreage is in of many growers is included as well as that from
Mesa and Delta counties. The issues of cold the test vineyard at the Colorado State University
climate limitations on wine grape culture are of Orchard Mesa Research Center.
extreme importance to Colorado growers. It has Many people contributed to the
been demonstrated that with careful site selection, preparation of this new edition and their help has
varietal selection and use of proper viticultural been truly appreciated. Special recognition is due
management techniques, vineyards can tolerate to the pioneering grape growers of Colorado and
winter conditions to a degree that allows their the visiting scientists who have shared their
survival in selected locations in Colorado. Winter experience and knowledge with us over the last
hardiness is the only limiting factor for grape decade.
culture in the state, since many severe disease and Where trade names are used, no
insect pest problems do not yet play an important discrimination is intended, and no endorsement by
role. Colorado State University is implied.
The unique aspects of grape growing in
Colorado are the indirect effects of high elevation.
Most suitable sites lie between 4,500 and 6,000
feet above sea level – substantially higher than
most growing regions of the world. The high
elevation is accompanied by an extremely dry
climate. Because of these factors the region
experiences intense sunlight and large daily
temperature fluctuations. These features foster
high pigment production and high acid, retention
in most grape varieties just as they do for the
traditional peach and apple crops of the area.
Thus, grapes that survive Colorado winters can
mature and produce fruit with highly desirable
wine making characteristics.
As grape growing is both uncommon and
in a sense new in Colorado, many gaps remain in

1

Figure 1. Anatomy of the grapevine.

2

Figure 2. Grapevine structures.

3

Establishing a Vineyard
Site Selection
There are limits to the absolute cold Cold air is heavier than warm and sinks to the
temperatures that grapevines can survive, and the ground; the gradient formed (cold air below to
suitability of a location greatly depends on the warm air above) is called an inversion. Cold air
frequency of large temperature changes. In also acts like a liquid and flows to the lowest
general, arid continental weather is subject to point. Slopes of two to three percent are
dramatic changes and thus grape survival is sufficient to allow much of the cold air to move
feasible only in restricted areas that are somehow away, drawing down warmer air from higher
buffered from these changes. Large bodies of layers. This process is extremely important in
water, lacking in Colorado, moderate temperature determining how cold a specific site will become
changes. In the high desert region, the mildest, on a calm, clear night. Temperature differences of
most buffered climates occur in certain major as much as 10oF can occur in sites that are in close
river valleys such as the Grand Valley of the proximity, but have different cold air drainage
Colorado, the North Fork Valley of the Gunnison characteristics. Often the coldest winter
and the Arkansas River Valley near Canon City. temperatures and the most damaging spring frosts
The protection afforded by these geologic features occur during calm nights following the general
is beyond the scope of this publication, but the cooling by a storm or cold front. Sites that escape
historic success of other fruit crops often is the spring frosts also will often be warmer during
best indicator of a location's suitability for grape midwinter episodes. Such differences can be
production. critical for vine damage. Because grapes start
Within these major areas, localized growth fairly late in Colorado (usually early
microclimates play an important role in the May), there is only a short period during which
feasibility of planting grapes on a specific site. frost damage may occur. Frost is actually a threat
The most important feature is cold air drainage over a longer period in California and other major
(See Figure 1). Under calm conditions, the earth grape growing regions. As a rule of thumb, avoid
radiates energy to the sky and receives heat from planting wine grapes where there are 150 frost-
the air closet to it. free days or less.

Common Mistakes That Can Cause Poor Vineyard Development

Site: planting in the wrong site (poor drainage)
Vine purchase: poor quality
Timing of planting: planting too late in the season
Irrigation system: inadequate or not installed, poor use

4

Figure 3. Vineyard site selection factors.

The exposure of a slope relative to the sun undesirable soil types need to be discussed.
is a more complicated factor. During the day, a Deep soils - at least 3 to 5 feet - are needed
south or west facing slope will be some-what to discourage shallow rooting. Many cultivated
warmer throughout the year; however, this feature soils are sufficiently deep, but have formed clay
is not necessary to ripen grapes in Colorado even hardpans. This can prevent grapes from rooting
though it is important in other locations such as deeply, which is their natural growth
northern Germany. In fact, warming of soil on a characteristic. Checking for hardpans and taking
south slope during the winter in Colorado can steps to eliminate them (i.e., deep ripping) are
reduce winter survival. critical steps in vineyard establishment; hardpans
Soils can play an important role in grape or other obstructions to deep water percolation
survival and potential wine quality. Ideal soils are need to be avoided or changed. The grape grower
deep, well-drained and not overly fertile. Such must be able to control the water status of the soil
soils are difficult to find in many parts of to manage vine hardiness. Extremely gravelly
Colorado with a climate sufficient for grape soils can prove difficult to water adequately in the
growth. For this reason, the limits due to semi-arid climate of Colorado; however,

5

extremely heavy clay soils that cannot be drained However, true drip systems can accumulate salts
should be avoided. if insufficient volume is applied.
Grapevines have lower requirements for A vineyard must have good quality water
mineral nutrient levels than many other crops. available throughout the growing season; water
Therefore, few soils require substantial from drain ditches should not be used because of
fertilization to support grapes. High nitrogen possible high salt content or unknown pesticide
avail-ability can inhibit the transition of grapes residue. Water is required during April to May
from vegetative to fruiting to dormant states and for planting. Irrigation systems must be
thus should be used with caution. operational before planting occurs. Finally,
High salt is a more common soil problem midwinter desiccation can kill many vines in
than over/underfertility in western Colorado. The Colorado and must be prevented with a late fall
parent materials for many soils in the area are very irrigation to recharge the soil reservoir
high in calcium sulfates (gypsum) and carbonates. intentionally dried out after harvest. This is best
Grapes are not tolerant of high salts, and thus applied after a frost to prevent any possibility of
unleached soils or spots that accumulate salts the vine's returning to a vegetative state.
through seepage and evaporation will not support Other factors to consider in site selection
vine growth. Analyze soil samples for a planting are wind, hail, deer and birds. Extremely windy
site. These tests include a check of soil sites could be troublesome due to mechanical vine
conductivity which is an indication of salt content. damage and desiccation. Certain locations may
Conductivities of less than 4 mmhos/cm are tend to have a higher probability of hail damage.
considered safe. Those above 6 mmhos/cm are Check with neighbors for historical weather
considered to be very damaging to grapes. Check patterns. Bird feeding is a common problem in
the salt content at various depths at the planting small vineyards with trees or other refuges for
site; a low salt content near the surface does not birds nearby. Deer and elk can cause major
guarantee a low salt content at a depth of 2 to 3 damage to both mature and immature vines.
feet. In soils with previous cropping history, one Fencing is the most effective means of control.
generally encounters salt problems in discreet In summary, critical aspects to avoid in
areas fed by seepage from irrigation canal vineyard site selection are frost pockets, shallow
systems. Areas with high water tables also are or poorly drained soils, high salt accumulations,
unsuitable for grapes due to high salts and poorly irrigated and overfertilized locations.
excessive moisture. Desirable factors include unobstructed slopes, and
Areas with sufficiently low salt levels are relatively deep and well drained salt free soils
common, and it is possible to maintain low salt without serious nutrient imbalances.
levels with low volume irrigation systems.

6

Figure 4. Wine grape varieties by acreage in Colorado. Source: 1997 CSU grower survey.

Plant Selection
Once a suitable site is chosen, many like (See Figure 4). Additionally, many
critical decisions and steps must be taken before varieties have not been tested in Colorado.
the grapes arrive. Perhaps the most critical Even so, there are many varieties where not
decision is which grape varieties to utilize. (Note: enough is known to either strongly
It is often necessary to place orders nine months to recommend or tentatively discourage their
a year ahead of planting). Relatively few of the planting. Wine grape varieties are presented
thousands of grape varieties known are of any in Section V and table grape varieties are
present or potential commercial value. The grape discussed in Section VI.
grower must consider the relative winter
hardiness, marketability, and potential quality of
the variety when grown in Colorado. Visit 4 or 5
wineries and determine what varieties are
currently in demand and what the future market
looks

7

Planning a Commercial Vineyard in Colorado

Considerable planning and investigative growing season. Grapevines typically use
work is needed before planting a vineyard on a between 20-25 inches of moisture per season
new site. This preliminary work can minimize or depending on conditions (soil, climate, etc.).
prevent future problems and often can determine Have the water analyzed if you suspect high salt
ultimate success or failure. Some questions that content or if you are pumping from a well.
must be addressed are as follows. It is critical that an irrigation system that
Economic Considerations: Will this can supply adequate water for young vines is
project be economically viable? Gather all functional before planting begins. The most
information possible and look carefully at start-up important aspect of the irrigation system is that it
costs and annual expenses; then evaluate your be reliable. Much of the acreage being newly
projected returns. Market potential must be planted is using micro-irrigation rather than
explored before planting grapes. Ask several surface irrigation. Both systems will grow grapes
local wineries what varieties they are currently however, the micro-irrigation system has
buying and what they anticipate buying in 3 years. advantages such as; maintaining soil moisture at
Ask them the current price per ton paid for these an optimum level, increased irrigation efficiency,
varieties. Supply and demand often directly affect improved chemical application, reduced weed
winegrape prices. growth, automation, and adaptability to difficult
Climate: Is it suitable or not? soil and terrain conditions.
Winegrapes have been successfully grown in over Previous crop history? Observe other
60 countries with a variety of climates. Between crops that are growing on or adjacent to the
160-200 frost free days are needed to mature fruit proposed vineyard site. These crops can give
of many varieties grown in Colorado. Mid-winter valuable clues to problem areas. Poor growth and
low temperatures of -10oF and lower can injure or low production may indicate problem areas and
kill buds and canes. Weather data gathered on the the need for further investigation. Subsurface
vineyard site are invaluable, however, be cautious water created by over-watering neighbors can be a
when interpreting weather data obtained from a problem. Careful observation of irrigation
station located some distance from the actual practices of land uphill and adjacent to your
vineyard site. Temperature differences of 10oF or proposed vineyard site can help identify the need
more between the station and vineyard may occur. for a drainage system or an alternate site.
Site: What is a good site? Site selection Any wildlife problems? Some vineyard
cannot be over emphasized. Planting the vineyard sites are excellent homes for rabbits, prairie dogs,
in the wrong site can be very discouraging and deer and elk. These animals can cause
costly. Continual retraining and low production considerable damage to new or established
are frustrating and labor intensive. The ideal vineyards if preventative measures are not taken.
vineyard site will be sloped (hill sides are best) If you suspect these animals are near by
and have very well drained soil with no hard pans. but see no evidence or signs, check with neighbors
Avoid low lying valleys or areas where water and who may have historical knowledge of wildlife
cold air naturally settle. patterns in the area.
Water: Is irrigation water available Fencing may be required before planting
when you need it? Most fruit growing areas in your vineyard.
western Colorado are irrigated by open ditches
from either rivers or reservoirs. Check
availability of the irrigation water throughout the

8

Nursery Stock and Standards
The majority of grapevines are sold as number 1 dormant rooted cutting and a 1 year
dormant rooted cuttings. The dormant rooted number 2 cutting. The 2 year number 1 is a more
cuttings are either grafted or self rooted. These vigorous cutting and will transplant with better
rooted cuttings are graded by nursery industry success and become productive quicker than the
standards. number 2 cutting. The rooted cutting should be
Becoming familiar with these standards produced in a Phylloxera free nursery and
can make the difference between success and certified as virus free. Although certified virus-
failure. Figure 5 demonstrates the relative size free vines are initially more expensive, they avoid
differences between a 2 year number 1 dormant the higher costs of lower production and poor
rooted cutting and a 1 year number cutting and plant health that virus-infected vines experience
will transplant with better success and become later. These cuttings should be ordered as far in
advance as possible - usually one year prior to
planting.

Figure 5. Typical nursery grading differences. The 2 YR #1 cutting is most desirable followed by the 1 YR #1 and then
#2 cutting.

9

Rootstocks and Phylloxera
The primary reason for planting rootstock- growing region with only 380 acres planted,
grafted vines is the presence of phylloxera, a tiny however, the size of the industry or the climate
aphid-like root louse that spends most of its life does not make Colorado immune from phylloxera.
cycle in the soil feeding on grape vine roots. Phylloxera has not been detected on the western
Susceptible vines eventually die. slope of Colorado and has only been observed in
The most effective technique in managing Baca County (1993-Kondratieff) on a native
phylloxera has been the use of tolerant or resistant american grape species. Currently, the Colorado
rootstocks. Grafting 2 different varieties or wine industry is 98% self-rooted. In 1995
species to form a plant with desired characteristics approximately 6 acres of rootstock grafted vines
is a technique that has been used for centuries in were planted in Colorado. Rootstocks should be
fruit tree production and viticulture. This cultural considered in new plantings as an insurance
practice was first used to change variety, increase against possible infestation.
vigor or increase limestone tolerance with A new strain of phylloxera called biotype
grapevines. B has recently become a major problem for
It wasn't until after the great European California growers using AXR #1 rootstocks. The
phylloxera epidemic during the decade of 1860, AXR #1 rootstock is susceptible to biotype B
that the use of rootstocks increased dramatically. phylloxera. California growers are spending
In France, the phylloxera epidemic had spread at a millions of dollars replanting AXR #1 rootstock
rate of 12.5 miles a year and by the end of the vineyards to resistant rootstock-grafted vines.
19th century, grape phylloxera had killed more Due to the problem California has encountered
than two-thirds of the vineyards on the continent. with AXR #1 being susceptible to phylloxera
At that time, all of the vineyards on the European biotype B, Colorado growers should avoid
continent were planted to self-rooted Vitis planting on rootstocks that have Vitis vinifera
vinifera. The interest to control this pest was parentage (see table 1). In 1992, four phylloxera
extremely important. Grafting the susceptible resistant rootstocks (3309C, 420 A, 101-14 and
wine varieties to the resistant American species 5C) were planted for study at the Orchard Mesa
worked well and became an adopted practice that Research Center. These rootstocks were selected
led to a chaotic period (1880-1930). Nurseries for their phylloxera resistance and low-to-
offered an assortment of rootstocks which caused moderate vigor. The results of this study are not
new problems that were not previously known. complete and their recommendations would be
Rootstocks were extensively studied in Europe premature. Consequently, rootstock
and the New World for more than a century. recommendations for Colorado is
Research after 1950 revealed that several aspects limited to experience from other cool climate
of scion behavior such as tolerance to soil borne grape growing regions (e.g. New York,
pests and diseases, vigor, productivity, Washington, Oregon). Based on experience from
adaptations to growing conditions, resistance to these areas vigorous rootstocks that tend to
chlorosis, etc. were dependent on features of the produce undesirable rank growth (eg. 5BB, 5C,
rootstock. (See tables 1-4). 504, 99 Richter, Kober 125 AA) should be
In the 1850's, phylloxera was brought to avoided. Rank excessive growth is winter tender
California from the eastern US. In 1988, growth and rootstocks with this characteristic
phylloxera was discovered in commercial should only be used in very low vigor sites
vineyards in Washington state and in 1990 it was (sandy, rocky well drained soils with low
discovered in vineyards in Oregon. Both fertility). Rootstocks with low to moderate vigor
Washington and Oregon are relatively new grape (eg. 3309, 101-14, 420-A) are more desirable for
growing regions. Colorado is also a new grape most Colorado sites. Rootstocks require

10

protection during the cold winter months. to regenerate in the event of very cold trunk
Routine hilling of soil 6-10 inches above the graft killing temperatures.
union in the fall will protect enough scion tissue

Table 1. Common rootstocks listed by parentage (Morton and Jackson, 1988)

Parentage Rootstock

Riparia Riparia gloire de Montpellier (Portalis)
Riparia, Berlandieri SO4, 5 A, 5 BB, 5 C, 8 B, 34 E.M., 125 AA, 225 Ru, 420 A,
157-11 C, 161-49 C, RSB 1, Cosmo 2 & Craciunel 2 & 71
Riparia, Labrusca Vialla
Riparia, Rupestris 3306 C, 3309 C, 101-14 Mgt, Schwarzmann
Riparia, Vinifera 143 A, 143 B
Rupestris Rupestris du Lot (St. George)
Rupestris, Berlandieri 57 R, 99 R, Prosperi Super 99 R, 110 R, 140 RU, 775 P,
779 P, 1103 P, 1447 P
Rupestris, Vinifera AXR 1 (ARG 1), 93-5 C ("XX"), 1202 C
Berlandieri, Vinifera 41 B, 333 E.M., Fercal
Complex (2 species) 44-53 M, 1613 C, 1616 C, 1045 P, 196-17 Ca, 216-3 CA,
4010 Ca, Dog Ridge, Golia, Grezot 1, Harmony,
Salt Creek (Ramsey), Tampa

11

Table 2. Phylloxera resistance rating; based on potted vines and Italian phylloxera. 10 is absolute
resistance, 5 is tolerable resistance and 0 is completely susceptible. (from Pastena, B. 1976 Trattato di
Viticoltura Italiana)

Rating Rootstock

10 rotundifolia
9 riparia, berlandieri, and cordifolia
8 rupestris, 779P, 420A, 41B(?)
7 St George, 1103P, 140Ru, 11OR, 775P, 41B (in Palermo), 1447P
6 3306C, 3309C, 225Ru, SO4, 5BB, 161-49, 157-11, 1045P, 44-53
5 Solonis, Jacquez
4 AXR#1, several hybrid direct producers
2-3 several vinifera cultivars: Tannat, Nocera, Olivetta, Carignane,
Sangiovese, Barbera, Trebbiano dorato, Sauvignon, Grecanico
1 hybrid direct producers (many S.V. numbers, some Seibel)
0 Vinifera and more hybrid direct producers.

Table 3. Resistance to nematodes (Meloidogyne spp.) (from Pouget and Delas, 1989)

Rootstock Variety Resistance

3309C low
Gravesac low
110R low
161-49 low
41B low
Riparia Gloire moderate
420A moderate
Fercal moderate
101-14 high
140Ru high
1103P high
SO4 high

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Table 4. Resistance to lime-induced chlorosis; value of the Chlorosing Power Index (IPC) above which
symptoms appear.(from Pouget and Delas, 1989)

Rootstock Variety IPC

Riparia Gloire 5 Low
101-14 10
3309C 10
Gravesac 20
110R 30
1103P 30
SO4 30
420A 40
161-49C 50
41B 60
140Ru 90
Fercal 120 High

Site Preparation
Preparing the site for a vineyard is very this time, surveying the vineyard for row
important and should be planned out in advance. orientation and vine spacing will facilitate the
One of the first steps in preparation is to remove planting process. Planting holes are most often
all trees, stumps, rocks, wire, and even old augered, although in clay soils this can produce a
unusable irrigation pipe. Reluctance to remove "flower pot" effect. Holes can be made in the fall
that wonderful shade tree is often regretted later before planting and will weather sufficiently to
when the vines planted near the shade of the tree prevent this. Holes augered in the spring should
don't grow like the vines planted in the open, have their sides cut away (caved in) at planting in
unshaded field. Special soil preparation decisions order to break any glazing of the hole wall. Vines
like deep ripping or weed control are best attended can also be planted in a V-ditch with the aid of a
to before vines are planted, especially if the use of tractor mounted V-ditcher. A very reliable but
big machinery is required. Perennial weeds such often disliked method of planting is simple hand
as bindweed (Convulvus sp.) or even alfalfa are digging. Individual vine stakes should be placed
very persistant and are best removed if treated before or during planting since delays in their
with herbicides (i.e. glyphosate) the season before placement during the training year can be costly in
planting, typically at the end of August. If a terms of proper vine formation.
subsurface hardpan (created by equipment use or a
natural impervious layer) is suspected, the
vineyard should be deep ripped below that depth
before planting when the soil is dry, typically the
first of September. Powerful heavy machinery
(D-8 cat or larger) is required for effective ripping
of 45 inches or more. The ripped field will
benefit from freeze/thaw action if left uncultivated
during the winter months. As soon as the winter
moisture subsides, disk, plow, disk, and float
(level) your vineyard site for final preparation. At

13

Vineyard Development Checklist
(One year in advance)

Determine Market outlook and winery demand, and select appropriate

varieties.

Determine physical and chemical suitability of soil (back hoe, soil test).

Check irrigation water availability and quality.

Check for diseases and nutritional imbalances of existing crops.

Control perennial weeds: bindweed.

Clear site and level the land if needed.

Rip the soil when it is dry (August-September).

Disc, plow, smooth soil in preparation for planting.

Survey the vineyard site.

Make scale drawing of the proposed new vineyard.

Order #1 certified virus free dormant rooted cuttings from nursery.

Install irrigation system.

Install elk/deer fence (if necessary).

Lay out and plant vineyard in the spring after frost hazard is past and soil

has warmed.

14

Trellising/Training:
There are several dozen different trellis trellis system. Vineyard potential, variety vigor,
systems in use today. We do not attempt to and canopy spacing are the most important and to
discuss them all in this grape guide. Each trellis a lesser degree economic factors. Vineyard
system is unique and has a function specific to potential would include environmental factors (i.e.
each situation. The handbook for canopy temperature, topography, soil, rainfall and wind)
management Sunlight into Wine by Smart and and cultural management decisions (shoot
Robinson is an excellent reference for those who thinning, fertilization, irrigation etc.). Variety
need more information on various trellis/training vigor can often determine the choice of trellis
systems. The scope of this section is to provide system. For example, choosing a single wire
some major factors to consider when selecting trellis as compared to an improved multiwired
your trellis and to provide some basic information trellis system with moveable foliage wires may be
on constructing a commonly used vertical shoot sufficient for varieties with low vigor. Vines with
positioned trellis system. excess vigor (long shoots, lateral growth, and
Trellising and training go hand in hand. shading) may need a more extensive trellis system
Training is the strategic development of grapevine such as a Geneva Double curtain, U-trellis or Lyre
structure and the trellis supports that vine system. The high vigor trellis systems usually
structure. The basic goal of trellising and training divide the canopy to support a higher number of
is to maximize production, facilitate cultural buds and thus increasing canopy surface area.
operations (i.e. spraying, tillage, pruning, Canopy spacing is a combination of row
harvesting), improve canopy microclimate and to spacing and vine spacing. In Colorado, the
support the mechanical load of the vine. distance between rows varies from 6 to 12 feet.
The initial choice of a trellis system is Equipment availability, tractor widths and
critical because vineyards are long term and compaction has most growers planting 9 to 10 feet
usually trellised only once. Vineyard retrofitting between rows. Specialized narrow vineyard
or converting a vineyard to an improved trellising equipment is not readily available in Colorado and
system is possible during the dormant season but thus 30-50 HP standard farm tractors are common.
can be very costly. Closer row spacings (6 to 7 feet) increases soil
In the last 20 years trellising of grapevines compaction with standard tractors. As a general
has seen considerable advances. The advances rule of thumb, row-spacings should not be planted
have been initiated by the desire to improve fruit closer than the height of the trellis (shading can
quality, produce higher yields and increase occur).
vineyard mechanization (trimming, leaf removal, Vine spacing, the distance between vines
harvesting and winter pruning). These new within the vine row is a combination of vine
improved trellis systems have had the most genetic vigor, soil capability and climatic factors.
significant impact on vineyard canopy Vineyards in Colorado commonly have vine
management. Some common features of spacings between 4 and 8 feet. Vineyard sites that
improved trellis systems are; increased canopy are fertile and productive need larger distances
surface area, decreased canopy density, increased between vines. Soils in many vineyards of
capability for mechanization, improved yield and western Colorado substantially vary within the
quality, better spray penetration, less disease vineyard and may require vine spacing
(Botrytis and Powdery Mildew) and increased adjustments within a 200 foot vine row. Soil
winter hardiness (more sun canes and less analysis and visual inspections before planting can
shade canes). assist in these decisions. Genetic vigor variation
The following factors are the most among varieties also plays an important role with
important considerations when selecting your vine spacing. Site specific vigor i.e. how well a

15

particular variety grows in that specific and are driven 4 feet.
site/situation would be ideal, but unfortunately Posts: Lodgepole pine and native juniper
only general information exists at this time. posts are frequently used in Colorado vineyards.
Genetically vigorous varieties typically require Pine posts are the most common and are typically
more distance between vines than less vigorous pressure treated with a mixture of copper,
varieties. Vineyards in cooler sites generally have chromium and arsenic salts (CCA). Once bound
less growth (vigor) than warmer sites and in the wood, CCA treatment becomes insoluble
therefore narrower spacings are more suitable. and non-toxic to vines. Juniper posts contain
Growers in Colorado who have ignored soil or natural preservatives and are not treated. An
genetic vigor differences have had trouble training advantage of pine posts is the ability to be able to
their vines to maximum production levels because drive them into the soil with a hydraulic power
of overcrowding, too dense of canopy, poor spray driver. Driving the posts with the narrow end
penetration and training/pruning confusion. down compresses the soil and increases post
stability. Driving the posts is also more
The Vertical Shoot Positioned Trellis economical than boring a hole and hand tamping.
(VSP) The importance of a stake per vine cannot be over
The VSP trellis is a good canopy stressed. When vineyard construction begins do
management system for low to moderately not neglect a stake per vine. Individual vine
vigorous vines. The VSP works well in Colorado stakes vary in size, material (metal, wood, plastic,
and the one described here is currently used at the bamboo) and strength. Select a stake that will last
OMRC. The VSP trellis contains either fixed or for a good 15-20 years. These stakes will aid the
moveable pairs of foliage wires that enable the retraining efforts and help stabilize and protect the
grower to form a narrow vertical canopy (see vine if mechanical weed control is used.
figure 6). The VSP trellis system can be used Wire: Trellis wire usually ranges between
with either cane-pruned vines or spur-pruned 10 and 13 gauge. Twelve and a half gauge high
vines on unilateral or bilateral cordons. Shoots tensile wire is common and normally wound on
are kept between the foliage wires by lifting the 100 pound spools that contain 4,000 linear feet. A
moveable foliage wires and attaching them at spinning jenny, a device used to unwind the
successive heights on either side of the line posts wire painlessly in the field is a must for any trellis
and hand tucking. This procedure is usually construction. The wire is fastened to line posts
required 2 to 3 times during the period of active with 1.5-2 inch barbed staples, and in the case of
shoot growth. The shoots are retained in a narrow moveable foliage wires, one legged J-nails are
(5 to 7 inch wide) vertical curtain. Up to 3 pairs used. Trellis wire is tightened with a standard
of foliage wires can be used but 1 or 2 pairs is wire stretcher and attached to the end posts with
more common. The fruiting wire is normally at patented wire fasteners. These fasteners are small
40 inches with the first pair of foliage catch wires 1/2 inch leaded sleeves that hold two wires
10-12 inches above and the second pair 10-12 together when crimped. Temperature effects,
inches above that. The single catch wire wind loads and fruit loads put a strain on wires
positioned at the top of the trellis also serves as a and they occasionally need tightened. Simple
support for bird netting. The entire canopy height ratchet type tensioners do a fine job and are
of approximately 40 inches contains plenty of leaf usually available where wire is purchased.
area for fruit maturation. The VSP trellis Excessively tensioned wires can adversely affect
described in figure 6 uses 4 inch by 8 foot CCA your entire end bracing assembly.
treated pine line posts driven 2 feet and spaced
every 30-40 feet. End bracing posts are also CCA
treated pine that measure 4-5 inches by 10 feet

16

Figure 7. H-Brace trellis brace assembly. Vine planting within the end brace assembly is possible.

The End Brace Assembly: Bracing the The main difference between the H-brace
end of your trellis is the most important and the tie-back is planting efficiency and greater
component of the trellis system. Improper bracing protection. The H-brace enables vine planting to
can lead to failure and costly repairs. Trellis the end of the vineyard row without vine training
failures can be prevented by avoiding the modifications. The tie-back assembly is equally as
following common mistakes: Inserting and strong as the H-brace, has lower up front costs but
bracing posts into deep-ripped trenches, excessive does not allow adequate training space for
tensioning of the trellis wires, tractor/implement efficient vine management. Tie-back or dead
abuse and inserting end bracing posts to depths man anchoring posts are more prone to tractor
less than 3 feet. Figures 7 and 8 describes two blight than the H-brace assembly.
end bracing assemblies.

17

Figure 8. Tie-back trellis brace assembly. No vine planting within this type of end brace assembly.

Planting - The First Year
The goal of the planting season is to es- properly maturing the crop for consistent wine
tablish a strong root system at the proper depth. quality.
This is accomplished by careful attention to a few The cuttings must be carefully protected
major points. before and during planting to avoid drying and
The fully dormant rooted cuttings should overheating. This is even more critical if the
have a substantial root system and reasonable top vines have started to grow due to overly warm
growth. They should be long enough so that two storage at some point. Generally it is best to
buds of the previous season's growth are above avoid the coldest winter temperatures. Spring
ground and the bulk of the roots begin at a depth planting (April-May) is the best time to plant in
of 12 to 14 inches (see Figure 6). The rooting Colorado. In any case the vines should be
depth is critical; shallower roots will respond too planted before high temperatures occur. Cuttings
quickly to winter and spring soil temperature should be stored in a cool place (40oF) and kept
changes and lead to winter killing or frost moist until planting can begin.
damage. Uniform rooting depth also is very The roots can be lightly pruned to fit the
important for controlling drought stress and size of the hole and to remove any dead or
decayed tissue (Figure 9C). At planting, the

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Figure 9. Grape propagation plant materials: A) Grape cutting (14 to 16 inches) with sloping cut at tip end to ensure
proper orientation. B) One-year-old own-rooted cutting as received from nursery with some shoot and root growth. C)
Properly planted rooted cutting; note that dead or damaged roots should be removed and the remaining roots prevented from
bunching. Two buds [b] are left from nursery growth.

cuttings should be set in water (i.e., in tubs or after planting, making sure that water reaches the
drums) until they are actually placed in the hole, roots. Failure to deliver water at planting and
but should not be kept in water more than one over the first few months of a vine's life
day. The vines should be set an inch or two below commonly results in an inadequately prepared
the desired 13 to 14-inch depth, then add a few vineyard and leads to poor growth and
inches of fine soil and then gently tug the vine up establishment.
to arrange the roots in a slight downward Throughout the remainder of the first
orientation. Any bunching or twisting of the roots growing season, maximum growth of the young
should be avoided to prevent the vine's self vine should be encouraged. This can be done by
strangulation as it grows. providing a balance between the water and oxygen
The vines should be irrigated immediately needs of the developing root system; over- and

19

underwatering should be avoided. The water The vine's growth and winter hardiness
status of the soil from which the limited root will be compromised if powdery mildew is not
system actually is drawing can be determined with controlled in mildew-susceptible varieties --
soil probes or with tensiometers placed at the especially the Vitis vinifera varieties. Powdery
proper location. Vines do not use a great deal of mildew occurs in all grape growing areas of
water, but irrigations must be long enough for Colorado and applications of mildew-effective
water to reach the deep roots. Once the vine is fungicides at two to three week intervals from
planted, an irrigation schedule should be June through August are wise preventative
established. Surface irrigation every 2 weeks (6-8 measures (see Disease Management, Section IV).
hour sets) is very effective for the establishment During the initial stages of acclimation, (when
year. Drip irrigation of 15 gallons per vine per green shoots begin to turn tan in color) the vines
week is also recommended for the establishment are allowed to dry to encourage good wood
year. These recommendations are for deep clay formation toward the base of the shoots. An
loam soils. More frequent irrigations may be irrigation after leaf fall is encouraged to prevent
necessary on sandy well drained soils. winter desiccation of the soil and subsequent root
Optimum growth requires the removal of injury. Mulching or throwing up a few inches of
competitive weeds. Generally, bindweed and soil over the crown of the vine can provide
alfalfa are the biggest problems and should be protection against winter injury. The vine is best
removed by mechanical or chemical means within pruned in the spring (March) to leave only one
at least a 3 foot radius of the vine. shoot with two buds (see Figure 10B) and if
growth has been encouraged, it now has a root
system that can support vigorous growth in the
most crucial year of the vineyard's life - the
training year.

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Figure 10. A) Growth at the end of the planting season. B) Above ground portion of vine following first pruning; note two
buds [b] from first year vineyard growth are retained.

What About Grow Tubes
The grow tubes or plastic shelters have stability and micro climate maintenance.
become a very popular method for training newly Growers in Washington state find the
planted vines in California and other grape plastic shelter useful, especially with young
growing regions. Colorado has also joined the interplants that are struggling. Recent
trend with several growers beginning to use the unpublished work at UC Fresno, California
tubes in 1995. The grow tubes are plastic shelters suggest the narrow tubes (less than 3-1/2)
available in various colors (white, blue, green, increase temperatures to extreme levels causing
etc.) and sizes. Typical stock sizes are from 24 to foliar burning. Colorado growers have had good
44 inches high with diameters of 2-3/4 inches to and bad experiences with the plastic shelters.
4-1/2 inches. The grow tubes have been reported Some Colorado growers excessively burnt their
to enhance growth, reduce training costs and vines with grow tubes and they claim late planting
protect vines from chemical sprays and rodents. to be the major cause. Other growers had positive
Suppliers recommend the grow tube to be placed experiences, claiming first year growth was better
over the young vine at planting. They also than they had ever seen. Removal of the tubes
recommend the grow tube be pressed into the soil was a topic of confusion. Some growers removed
2 inches and tied to the grape stake or wire for the tubes when burning was evident while others

21

waited until early fall. Growers who used the It appears that grow tubes will be used by some
tubes were planing on single trunk, not double growers in Colorado regardless of the pros and
trunk training. Double trunk training may be more cons. The tubes are expensive and more
challenging with grow tubes. Most growers felt experience under Colorado conditions is needed.
the grow tubes were beneficial but expensive. Correct grow tube use may be a cultural practice
Grow tubes normally range in price from $.40 to that can favor early vine development and
$1.40 each plus the cost of installation and enhance vine establishment; however, incorrect
removal. use could be detrimental.

The Training Year
Perhaps because there is no crop, grape of planting, the carbohydrates stored in its
growers tend to give insufficient attention to the expanded root system have prepared it with
new vines during their second year. The cost of enough energy to develop a trunk and cordon
this mistake will be felt throughout the expected arms or canes. If the vine's environment is kept
30 to 40 year life of the vineyard. The goal of the entirely weed free and the steps of training are
training year is to establish the framework of the carried out in a timely and accurate manner, the
vine so that future pruning will be efficient and vine will reach training height and be ready to
crops of the future will be properly supported. produce a modest crop the following year.
Although the vine looks like it did at the time

22

Figure 11. Grapevine training during the second season. A) Early growth (6 inches) before choosing a shoot to train. B)
Strong, well-positioned shoot tied after removal of other shoots. C) Shoot tied to form a straight trunk -- growth is 18 to 24
inches above lower wire; it will be topped at the node [n] just above that wire. Note that all lateral side shoots on the lower
two-thirds of the trunk have been removed, directing growth to the trunk. D) Growth at the end of the second season in
which the trunk and laterals were established. E) Vine pruned in March, retaining three two-bud spurs [s]. Short, lateral
canes are often retained on very vigorous vines.

A shoot is selected when it is about 6 stake at each vine is very handy for any future
inches long and all the other side shoots are retraining needs. Obviously, the training support
removed (see Figure 11C). Remove only the must be in place before growth begins the second
lateral side shoots at each leaf axil, not the leaves. season.
The chosen shoot is carefully tied to a support as As the shoot grows, it should be firmly
it grows so that a straight trunk is formed. A five tied (without crushing or breaking the tender
to six year old vine will be strong enough to tissue) a few inches behind its growing tip at
support much of its own weight if its trunk is approximate 6-10 inch intervals. This may
straight. If it is not straight, the vine will never require a tie every five to eight days if the vine is
help bear the load and will put inordinate strain on growing well. By late spring, the vine will be
the trellis system with crop weight and wind growing as fast as one inch per day. The best way
action. The system in which a permanent stake is to tie is with commercially available ties or
placed at each vine requires frequent tying to flexible tying tape.
make a straight trunk. Having a good permanent

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Figure 12. Second year training options.

Young shoots with less than 15 inches of development for cordon trained vines is delayed.
growthare very susceptible to breakage. Care A method that gives a 2-3 week advantage on
should be taken when tying and forming the trunk. cordon arm and lateral spur development is either
Each vine must be visited every week and new option 1 or option 3. Option 2 works well for the
shoots or buds arising from the crown of the trunk classic head trained cane pruned vine. Option 1
must be cut off and laterals removed up to the and option 3 are more appropriate for cordon
head training height (lower wire). All fruit trained vines. Option 1 is often referred to as a
inflorescences are removed but the leaves on the single trunk unilateral cordon. Option 3 is
newly formed trunk should be retained to referred to as a double trunk bilateral cordon.
strengthen it. Option 1 would be used in high density vineyards
Three common second year training (4 feet between vines) with low vigor vines.
options are described above (Figure 12). Previous Option 3 is better adapted for cold climates. Most
editions of this guide suggest that once the cane viticulture areas of Colorado occasionally
has grown 18 to 24 inches above head training experience temperatures cold enough to cause
height, it should be cut back to the point at which trunk injury. The double trunk system (option 3)
the vine will be headed (See figure 11). This provides for some additional protection.
forces laterals in the axils just below the cut. This Frequently, when cold temperatures are
method does work however, lateral spur growth damaging, one of the two trunks remain uninjured

24

and thus retains a partial crop. The advantage of
option 3 is quicker lateral spur development and Pest and disease control also is crucial
potential retention of a partial crop as a result of during the training year (see Pest Management /
cold injury. Nearly all vinifera vineyards in Control, Section IV). Cut worms and Lygus bugs
Colorado have multiple trunks. Multiple trunk may feed on the growing point of the vine.
training is a cold climate viticulture management Although the vine will regrow from a lateral if the
tool (see Retraining Winter Damaged vines) that apex is destroyed, valuable time and a straight
is an effective method of controlling vine vigor on trunk will be lost. At any sign of cutworm
injured vines with out of balance shoot to root damage, carbaryl baits can be sprinkled around
ratios. each vine. Lygus injury is best halted by applying
During the training season it is again an insecticide such as diazinon.
important that the vines have adequate water Powdery mildew must be controlled
available through May, June, July and August. during the training year. A main shoot heavily
Depending on the soil type and irrigation system, scarred with mildew has a much smaller chance of
water should be withheld in late August or early surviving the next winter. The normal mildew
September to encourage the formation of wood program should be followed (see pages 47-51)
and the cessation of succulent growth. Often, fruit and continued later in the summer since residue
clusters can occur on the two nodes left from the on the fruit is not a problem. Again, a post-leaf
previous year. These may aid in slowing fall irrigation is desirable.
vegetative growth in the late season. If the vine is Pruning after the training year should be
not growing well by midsummer, the clusters started after the coldest part of winter and, if
should be removed to minimize the growth possible, during March when all winter damage
difference from the more vigorous vines. can be assessed.

25

Figure 13. Vine at conclusion of third season growth on a two wire trellis.

The Third Year break off the shoots on the lower two thirds of the
The vineyard should produce a small crop trunk to encourage better growth in the head area.
in the third year, but generally it’s best not to rely Grapes from three year vines can ripen earlier
on it in for financial planning. The quantity will than the characteristic time for a mature vine and
be small, and the pattern of its maturation will be acid content can be lower. In order to get the best
unlike that of a more mature vine. Most of the use of the crop, carefully monitor acid content to
care for a third year vine is like that for a mature obtain the best possible sugar/acid balance. Do
vineyard with the following points of emphasis. It not judge future wine quality based on fruit from
may be wise to tie shoots to the wind-catch wire the third or fourth year grapes. It will probably be
when they are around 24 inches long. Wind lighter and not develop the full character that is
breakage is more significant when there are fewer present in older, more mature vines.
shoots. The use of moveable catch wires for Pruning after the third year emphasizes
canopy manipulation has provided excellent shoot both selection of two strong canes which will fill
breakage control, sunlight penetration and air as much of the trellis wire as possible and
circulation. Removing suckers is always selection of well-positioned renewal spurs
important, but is required to a greater degree with (Figure 14).
a young vine. During the third year, periodically

26

Figure 14. Vine pruned to two canes [c] and three replacement spurs [s] before start of fourth season.

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Maintaining a Vineyard

In this section, the various components of and the vines needs. These discussions are
vineyard management will be discussed separately. intended to emphasize the special concerns of high
Optimum management is based on a complete altitude arid viticulture.
understanding of your vineyard site.

Water Management
Wine grape yield and quality are water as do many tree fruits, but this should not be
determined by climate, soil and cultural taken to an extreme. As a point of reference, on a
management practices including irrigation. Poor deep, fairly heavy soil, three to five 12-hour
irrigation management can result in a water furrow irrigations are sufficient for mature vines
stressed or over vigorous condition resulting in between May and September. The last irrigation
unbalanced growth, reduced yields and inferior is timed to allow the vines to experience mild
fruit quality. stress that encourages a switch from rapid,
For practical purposes, rain can be ignored vegetative growth to the maturation of the crop
as an input to the water status of a vineyard in and the wood on the canes. If drip irrigation is
Colorado. Rains do occur, but almost never wet used, a rate of 12-15 gallons per vine per week for
the soil to a depth that can benefit a properly mature vines is typically sufficient. With drip
planted grapevine. Thus, the water supplied by irrigation, reducing the rate per vine per week by
irrigation not only keeps the vines alive, but also 40-50% approximately two to three weeks before
is the major tool the viticulturist has to optimize harvest will also encourage fruit and shoot
winter hardiness and wine quality. maturation. For example, an irrigation rate of 14
Grape vine water stress can occur if the gallons per vine per week would be reduced
supply of water to the roots is less than the (40%) to 8.4 gallons two to three weeks before
evaporative demand. The cause for the stress may harvest. It is, however, very easy to overstress
be low available soil moisture, high evaporative vines under Colorado conditions; in this case the
demand conditions, unbalanced shoot/root crop will stop maturing and the canes also will be
systems, a poorly developed root system, high salt less winter hardy. Finding the middle ground
levels or a combination of these. Unlike tomatoes between excess growth and excess stress is the
or squash, immediate signs of current season main challenge of learning to grow grapes in each
water stress are not clearly visible with individual vineyard. Parts of a given vineyard
grapevines. Symptoms are typically observed after may have different requirements. As a starting
repeated episodes of water stress, which cause point, the middle of August is an approximate
reduced shoot and fruit development. time to stop irrigating many Colorado soils so that
During the early part of the season (May- they dry to some degree through September. If
August) the vines should be given a good supply the cut-off is too early, one may see the loss of
of water to promote growth. Humidities are very leaves and a marked slowing of sugar
low in Colorado so water is transpired very accumulation by the fruit. If the cut-off has been
rapidly. Few growers can precisely control the too late, the basal portions of the canes may fail to
amount of water they apply and, even if they can, become brown and woody and fruit may retain
it is better to calibrate the irrigation through some very high acidity (some varieties will retain high
direct measure of the soil water status in the acidities under any circumstances).
rooting zone. Grape vines do not require as much Occasionally, winters are sufficiently dry

29

in Colorado to cause the killing of roots through system is closed down before a frost; in this case
desiccation. To prevent this type of winter still irrigate on the last day practical as it generally
killing, it is best to restore the water in the soil is too cool for the vines to become active again. If
with a late irrigation. This is best timed after the the crop is still present, a decline in both sugar
first frost so that there is no chance of shifting the and acid may occur through dilution in following
vines back into a vegetative pattern. Sometimes irrigation; however, the effect may only last a
the irrigation week or so.

Protection Against Winter Injury A final type of winter damage may be the
There are several ways that vines may be one that causes more damage than any other type
damaged in the winter. Two that have been in Colorado. It is termed false spring damage.
mentioned are best prevented through water The parts of Colorado protected from the coldest
management. The killing of green tissues at the temperatures and rapid changes of winter temper-
first frost is best prevented by encouraging ature sometimes experience winter periods of very
hardening off of the canes. The killing of roots or mild temperature. This can lead to soil warming
above ground tissues through winter desiccation is and reduce vine hardiness. The best cure for
best prevented by a late irrigation to recharge the protection against winter injury is to grow a
soil. healthy vine. Vines that are stressed by poor
The killing of buds or canes and even cultural practices are vulnerable to winter injury.
trunks by very low temperatures is minimized by In Colorado, the bright winter days warm
the same steps described above, but is less easily the dark trunks of many vines well above air
controlled. As mentioned earlier, avoid areas temperature. This can result in damage when the
subject to sudden temperature drops and pick sites temperature suddenly declines at sunset. As with
with good cold air drainage in order to minimize fruit trees, painting the trunk with white latex
this problem. One way to prevent winter damage paint can help minimize this. Training the trunk
by extreme cold is to take the vines off the trellis on the north or northeast side of a stake also
and bury them under 6 inches or so of soil. This accomplishes the same goal of preventing heat
practice is very expensive and is not common. loading.

Frost Protection and Damage
Treatment
In Colorado, grapes actually are less Heaters: University of California tests show that,
subject to spring frost damage than in many for hard frosts, adding a small number of heaters
important grape growing regions of the world. can provide more warming than use of wind
They also are in less danger than the traditional machines without heat. For example, 8 to 12
fruit crops of the area. This is because they tend heaters per acre to support a wind machine can
to break bud two weeks later than peaches, which provide an additional 1-1/2 or 2oF more than with
reduces the time and risk of frost injury. Wind the wind machine alone, because the wind
machines are the method of choice to frost-protect machine distributes heat that otherwise would is
a large commercial scale vineyard. partly lost by updraft from the heaters.

30

Wind Machines: The theory behind wind frequently used management strategy for
machines for frost protection is based on the efficiency. Regardless of whether you rough
assumption that temperatures in and above prune or not, pruning should be completed before
vineyards are assumed to increase with height bud break which usually occurs the 3rd week in
during nights with little cloud cover and light April for the Mesa County area.
surface winds. The purpose of a wind machine is Late Pruning: Late pruning (after the
to mix air vertically and transport it horizontally buds on the apical parts of the canes have started
displacing cold air at vine height with warmer air to grow) delays the leafing out of the buds on the
brought down from above. Effective operation of retained spurs and can protect vines from early
wind machines requires that a sufficiently strong frosts. This delay may vary from three days to
temperature inversion exists. Site specific two weeks, depending on temperature. When it is
inversions can be determined by placing one very warm, the delay is short; when it is cold, the
thermometer at fruit height and the other at the top delay is longer. Shoots that grow mainly on the
of the wind machine. Late spring frost protection apical portions of the canes can be allowed to
should begin when air temperature is 31oF and grow 3 or 4 inches without injuring the basal buds
should be terminated when the air temperature or vine in general. In large vineyards, delayed
outside the treated area is at least 32oF. Wind pruning may present labor problems, especially
machine protection in early spring (just before bud during seasons when vines burst into rapid
swell) may also be beneficial. Vines are in a growth. If shoots should grow considerably more
transitional stage at this time and lose their mid- than 3 or 4 inches before pruning, the vines may
winter hardiness and become susceptible to injury be weakened and the crop reduced.
with temperatures in the low to mid-twenties. Treatment of Frosted Vines: Treatment
Delayed Pruning: Pruning grapevines in of frosted vines requires patience. Frost damage
late February or March (delayed pruning) is a to grapevines becomes apparent within a few
cultural practice normally recommended for hours, but the degree of injury to clusters cannot
Colorado conditions. The objective of delayed accurately be determined until after fruit set. In
pruning is to permit some compensation in the many frosted vineyards it is best to do nothing,
event of bud or cane/trunk injury during but in others shoot removal may be beneficial.
December, January and February. Thirty years of When vines are frozen, look to the
weather data recorded at the Orchard Mesa secondary or tertiary buds or dormant latent buds.
Research Center in Grand Junction indicate severe Some crop can be expected from varieties where
arctic cold spells (0oF or lower) occur before the these buds are fruitful, even if shoots that develop
15th of February. If pruning can be delayed until from the primary bud are frozen. Frozen shoots
after mid February, uninjured tissue (bud, cane) should be removed immediately after a freeze to
may be more available than if pruning occurs in enhance growth from secondary growing points.
the dead of winter. A decision to delay pruning When growth does occur, secondary and tertiary
must be factored in your overall management buds usually initiate shoot growth in about two
strategies because with large acreage it is simply weeks. Secondary growth is best if shoots are less
not possible to wait until March and hope to finish than 6 inches long when frozen.
before bud-break. An alternative is to prune the
hardiest varieties first and delay pruning with the
least hardy varieties.
Rough pruning, (removal of poorly
positioned canes and rank growth) in January and
February followed up by quicker less congested
pruning during normal spring pruning season is a

31

Pruning
A complete discussion of pruning is needed when pruning, i.e. It is easier to see
philosophy is not possible here. However, the what to cut out. Cordon training works well with
essential goal of pruning is to match the a vertical shoot position trellis system. Excellent
production of a vine with its growth potential. spray penetration and sunlight exposure are some
Pruning is the removal of living shoots, canes, of the benefits of cordon pruned vines trained to a
leaves and other vegetative parts of the vine. It vertical shoot positioned trellis. A cordon trained
does not include removal of flowers or fruit. The vine will have permanent cordons attached to the
purpose of dormant pruning is to balance the leaf head wire. Cordons are simply modified
surface area with the capacity of the vine to horizontal trunks with vertical spurs. Spurs
produce a mature crop. The purpose of summer provide fruiting and shoot renewal functions.
pruning is to thin out (remove shoots) and/or to Figure 12 theoretically demonstrates the second or
reduce shoot length for increased light and air third year process of cordon training an ideal vine.
exposure. The goal of second year training is to form the
Pruning in Colorado should begin in two cordon arms and if good growth occurs,
March. Thirty years of weather data at Orchard develop vertical shoots from those cordon arms.
Mesa Research Center indicate the severe cold The vertical shoots will be the fruiting wood for
temperatures of December, January and February the next season. If an arm does not extend
will be over by March. The threat of cold halfway to the next vine, a terminal (apical) bud is
temperatures (below 0oF) is minimal and any allowed to form a shoot which is trained as an
winter damage can be assessed and pruning extension of the arm.
adjustments made (see Retraining Winter One of the most critical operations to
Damaged Vines). Pruning should be complete cordon training is to remove all shoots growing
before bud swell. If pruning occurs during bud from the underside of the new cordon arm. This
swell, crop loss can occur by physically rubbing procedure directs the remaining growth upright
off the tender buds when removing unwanted and enables adequate spacing between spurs
canes. The actual removal of the unwanted (typically 4-6 inches). As the shoots grow, tuck
pruned canes can be quite abrasive to the them between the double catch wires to maintain
wanted remaining buds. Extra care should be the vertical canopy. This procedure is important
used. and must be done on a timely basis to help
stabilize the arm and prevent it from twisting
Pruning Intentions: under the weight of the shoots and prevent wind
1. To establish and maintain the vine in a form damage.
that will facilitate vineyard management. Pruning an uninjured cordon trained vine
2. To produce fruit of a desired quality. is straight forward. To prune the vine, remove the
3. To select nodes that are fruitful. shoots that grew from the cordon arms, leaving
4. To regulate the number of shoots/ clusters. short (2-3 bud) vertical spurs spaced 4-6 inches
5. To regulate the vegetative growth of the vine. evenly along the upper side of the cordon. Retain
In Colorado the two most common enough buds to balance the vigor of the vine. A
pruning systems are: A) Cordon trained, spur moderately vigorous vine such as Chardonnay
pruned and B) Head trained, cane pruned. would typically have a range of 28 to 40 buds,
A. Cordon training/spur pruning: depending on soil and site conditions.
Cordon trained vines currently represent more
than 50% of the Colorado industry. Once
established, a cordon trained vine is much easier
to prune than cane pruning. Less decision making

32

Figure 15. Cordon training, the second or third growing season depending on vine vigor.

33

The spur renewal process over the years The canes that are kept are of medium thickness,
builds short arms at each growing point along the with neither short nor long spaces (internodes)
cordon. These short arms should be replaced with between buds. The canes chosen are those
a new shoot arising at the base once the short arms positioned 4 to 8 inches below the wire. These
reach 3-5 inches in length. new canes will be trained and tied to the wire. If
part of the cane is allowed to be higher than the
B. Head trained, cane pruning: The buds on rest, it may result in a failure of the low buds to
canes that grew in the previous season are the develop. The canes are also selected to fill the
source of fruiting shoots. Each shoot will produce entire trellis system. In the case of a vigorous
two to three clusters. The level of vigor on vine, two canes are wrapped together on the lower
mature vines in Colorado usually warrants leaving wire. The upper (wind-catch) wire is present only
two canes and two to three replacement spurs; this to allow the young shoots to have support in order
means that approximately 40 to 60 buds are to prevent rolling of the cane in the wind.
retained. Figures 16 and 17 demonstrate a head Renewal spurs are chosen so that the canes they
trained cane pruned vine. produce from their two to three buds will be

Figure 16. Head trained,cane pruned mature vine showing growth at the end of the fourth season.

34

in desirable positions to form the canes to be kept portions of a shoot are brown and dead while the
in the following season. Over the years, the head thicker basal portion is healthy. The opposite is
of the vine is kept in the same spot - around 4 to 6 never true. Sometimes, the color of scraped canes
inches below the lower wire. The special is ambiguous -- neither green nor distinctly
considerations for pruning in Colorado mainly brown. If no bright green canes can be found, one
concern winter damage. If pruning can be delayed should prune the vine normally because it is
until late March and April, it often is possible to difficult to predict whether it will grow normally
identify canes that have died and to retain live or require retraining from ground level.
canes instead. However, if the vine is damaged, Extremely low temperatures can kill buds without
all above ground parts often are uniformly killing canes, and it is a good practice to cut into
affected. Live canes will have a moist, bright buds at random before pruning to determine the
green color when scraped with knife. Often, the level of damage present and to leave additional
small diameter buds if necessary.

Figure 17. Head trained, cane pruned mature fourth season vine (start of fifth season).

35

Bleeding: may be killed the next year. See figures 18 and
Near the end of winter or the beginning of 19.
spring the vine may bleed after being pruned. Steps to retrain winter damaged vines
Bleeding is the exudation of sap from cut canes that are self-rooted: If you suspect your vines
and a phenomenon that has no reported harmful have been winter injured, make an actual tissue
effects on the vine. The sap exudate comes from assessment. To help identify injured tissue, use a
the cut ends of the vessels of the xylem tissues razor blade and cut horizontally through buds.
(water and mineral conducting pipelines). Buds that are brown or black (not green) are
Bleeding may occur at any time during active typically injured. Using a knife or sharp pruning
growth if a major portion of the top growth of the shears, scrape through the bark and into phloem
vine is removed. Heavy bleeding is most and cambium tissue (typically 1/8 inch deep in
noticeable when vines are pruned at bud swell or enough). Cane tissue that is injured will generally
later. Winkler reported as much as 5 gallons of be brown. All live tissue will be moist.
sap exudate was recovered from individual vines Occasionally, trunk tissue is damaged from cold
when new cuts were made every other day. The air that stratified in a layer near the ground and
major contents of sap exudate is water, sugars, cane tissue is injured. As the vine begins to grow
mineral nutrients, solutes and the plant hormones in the spring and all carbohydrate reserves are
cytokinin and gibberellin. The significance of used up, the canes and buds begin to desiccate
these hormones and other compounds is not because of trunk injury below. Injured trunk
known. This bleeding condition depends on the tissue will have a similar dark brown oxidized
activity of living root cells. The time of cane appearance but you may have to scrape (cut)
bleeding in the spring coincides with renewal root through several layers of bark to expose live
activity and or growth. Vine root growth initiates tissue. Live trunk tissue will have more of a light-
when soil temperatures attain 48oF. green to white-cream colored appearance rather
In Colorado, we observe minimal bleeding than the definite green color of live cane tissue.
of vines pruned during mid-dormancy when root Once an overall assessment has been made
activity is non-existent. Drying or suberization of and injury is evident, retraining must begin with
the cut xylem vessels may occur during this time removal of injured tissue. If trunks and canes are
of dormancy when root activity is low and when partially injured and show signs of weak life, it
xylem vessel water movement is minimal. In is generally more productive to remove these
normal years, bleeding will not occur if you prune weak tissues. Helping the vine decide where to
your vines the first two weeks in March. Soil and put its energy by removing injured weak tissue
air temperatures in the fruit growing districts of will lead to quicker vine recovery and more
western Colorado at this time are still cool enough efficient (labor savings) retraining decisions.
to hinder renewed root activity.

Retraining Winter Damaged Vines
Unless extreme deep ground freezing
occurs, a winter damaged vine will regrow from
below ground level. Essentially, the idea of
retraining is the same as in the original training in
terms of the need to tie a shoot frequently to a
support to form a straight trunk. The difference
with an older vine is that the root system will
support extremely vigorous regrowth. Canes that
grow very rapidly tend to be winter tender and

36

Figure 18. Retraining winter damaged vines. Select and tie shoots for the development of a multiple trunk.

Healthy vines that have been in the ground vigor and depending on variety and age, there
for 2 years or more that have been injured to may be a need for 2-6 trunks the first retraining
ground level can benefit by incorpo-rating a year. The following year, half of those trunks
multiple trunk system. A multiple trunk training may be removed and eventually one or two trunks
system will help balance the root/shoot ratio and will be all that is needed to balance the root/shoot
reduce bull canes and the unwanted winter kill ratio. It is the first and second growing seasons
cycle. Vigorous bull canes are winter after winter injury that controlling vigor is vital.
tender canes and should not be selected for
retraining. Shoots that are pencil size in diameter
and have internode lengths of 2.5 to 4 inches are
preferred. Dividing the growth will help control

37

Figure 19. Retraining winter damaged vines. Dividing growth with multiple trunks will help control vigor and avoid the
winter kill cycle.

38

Management practices that
minimize winter injury
1. Site selection: Having the land and deciding to slowing down or stopping of shoot growth which
grow grapes on it is not site selection. Avoid helps the vine initiate fall acclimation responses
planting grapes in valleys or low lying areas. (lignification of tissues). Always apply a late fall
Look for a site that has good air and water irrigation to prevent mid-winter desiccation.
drainage, preferably 5% slope. Trellis modification that encourages upright
2. Varieties: Diversify, avoid planting the entire canopy development or split canopies favor
vineyard to winter tender varieties. sunlight penetration which increases the
3. Cultural management: Cultural decisions that development of sun canes rather than shade
help prepare the vine for winter or harden canes. Sun canes develop fruitful buds and
off the vine should be carefully incorporated. hardier bud and cane tissues.
Decisions that favor vigor control enhance
vine hardiness. When irrigating, always
include a dry down period (especially in deep
heavy soils). This dry down time provides a

Shoot Tying and Suckering
As young shoots reach above the second a minimum and allow for excellent sunlight
wire in spring, it is a good practice to tie two to exposure and air circulation. Suckers (shoots
three of the shoots of each cane to that wire to appearing at ground level or on the lower 2/3 of
stabilize the whole cane. This prevents it from the trunk) should be removed while green and
rolling in the wind later in the season and easily broken off. This will be necessary during
exposing the fruit to sunburning. The shoots may most seasons and can be done while passing
attach to the wire by tendrils, but not with through the vineyard to tie shoots. Sucker
sufficient support in windy sites. For this tying removal channels more energy into the fruit and
process the tape guns and temporary stapled tape facilitates many other maintenance activities. If a
mentioned before are ideal since they must be systemic herbicide such as Roundup is to be used,
removed at the next pruning. Two or three pairs it is critical that all green tissue near the ground be
of moveable catch wires can keep shoot tying to removed.

Shoot Thinning continue until soon after set. New shoots
For maximum air and sun exposure of the may be forced from buds on the cordon or
fruit and shoots, shoot thinning may be necessary. head of the wire if shoot thinning is carried
Shoot thinning is the removal of unwanted shoots. out too early. If shoot thinning occurs too
Vines typically grow more shoots than the nodes late, the energy used to develop the shoots to
left at winter pruning. These extra shoots develop be removed is lost and the redirected energy
from buds at the base of the spurs or out of old is of less benefit to the shoots in more
wood and often are not fruitful. In Colorado, it is desirable locations. Vines are commonly
not uncommon to retain some of these shoots to thinned along the cordon wire so that they
renew growth from winter injured spurs/buds that are evenly spaced at a distance of 3 to 5
never developed. Shoot thinning on moderately inches. In Australia, vines are typically
vigorous vines is typically started when new shoot shoot thinned to about 15 shoots per
growth has reached about 15 inches and can meter (5 shoots per foot).

39

Leaf Removal
Leaf removal in the fruit zone can improve when berries begin to color). Lateral leaves may
fruit composition, spray penetration, enhance fruit develop and require the practice to be repeated
color and reduce disease by increasing the later in the season if leaf removal occurs too early.
exposure of the clusters to sunlight and air Avoid exposing shaded fruit in mid-late summer
circulation. Normally, removal of one to three as sunburn can occur. Fruit clusters exposed to
leaves per shoot is sufficient. Leaf removal trials the sun in the early season are less prone to
at the Orchard Mesa Research Center indicate sunburn. Mechanized leaf removal is currently
minimal sunburning occurs if fewer leaves are practiced throughout Europe, South Africa,
removed on the west side of the canopy. Australia, California and in some vineyards in
Afternoon sun can be extremely hot in western Colorado. The machines perform best with
Colorado. positioned canopies such as vertical shoot
The ideal time for leaf removal is 3-4 positioned trellis.
weeks before veraison (Veraison is the time

Crop Thinning
Crop thinning is a final adjustment inflorescence thinning, i.e., before flowering, is an
technique of crop regulation that results in the operation that is rapid and easily visible. Bunch
most significant fruit quality improvement. Crop thinning or cluster thinning is done after flowering
thinning adjustments may be necessary to mature and set. This operation involves removal of
the fruit earlier or change wine style. Vigorous undersized, poorly-set or immature clusters.
varieties such as Seyval blanc and Dechuanac Researchers in Italy (Ferrini et.al. 1995) have
have high initial fruit set and continue to produce recently shown the best time to cluster thin
abundant flowers late in the season which must be Sangiovese grapes was at the veraison stage.
removed for proper fruit composition and They found at that time, quality is not impaired,
maturation. The earlier the thinning, the greater clusters are more visible, thinning is faster and
the benefit to the remaining inflorescence. Early more accurate.

40

Hedging, Trimming or Topping
Hedging, Trimming or topping consists of If vine trimming is needed for increased
cutting off shoot tips during the early to mid light exposure, spray penetration, harvesting or to
summer. Late season trimming should be avoided ease the application of bird netting, etc.,
since lateral regrowth may be stimulated and alternative practices should be considered.
cause a delay in fruit maturation. Trimming to Controlling vine vigor through proper irrigation
less than 10-12 nodes may impair fruit ripening. management, fertilization, use of an improved
If trimming is not performed previous to a late trellis system, or matching variety to site are
season topping, healthy leaves could be removed better viticultural strategies than vine trimming.
from the canopy exterior exposing previously Vine trimming is a temporary band- aid solution
shaded older unproductive senescing leaves and to vineyard canopy problems.
thus lowering fruit ripening potential. Non-
positioned canopies are very prone to this
practice.

Nutrition Analyses and Foliar Sprays between soil nutrient levels and grapevine needs.
Grapevines have fewer mineral Tissue analysis (TA) is a much more
deficiencies and a lower plant food demand than effective and reliable means to determine vineyard
many other horticultural crops. Grapevines can nutrition than soil analysis. TA determines the
adapt to a wide range of soil types and, if soil concentrations of nutrients the grapevine is able to
depth, texture, and water conditions are favorable, remove from the soil. A typical complete TA will
will survive and bear salable crops in soils with assess levels of nitrogen (N), phosphorus (P),
poor fertility. potassium (K), calcium (Ca), magnesium (Mg),
Sixteen elements are known to be zinc (Zn), manganese (Mn), boron (B), iron (Fe),
necessary for normal plant growth: carbon, and sometimes sulfur (S) and sodium (Na), all
oxygen, hydrogen, nitrogen, phosphorus, expressed either as percent or as parts per million
potassium, calcium, magnesium, sulfur, zinc, (ppm). TA is another tool that helps the
boron, iron, manganese, copper, molybdenum, vineyardist establish a guideline for proper vine
and chlorine. Plants take three of these, carbon, nutrient levels.
oxygen, and hydrogen, primarily from air and Sample timing is extremely important;
water. The other 13 are absorbed from soil by the samples must be taken during bloom time, the
roots and divided into two groups, macronutrients nearer to full bloom the better. The plant part to
and micronutrients. The last seven elements listed sample is the leaf petiole, and petioles from leaves
above are micronutrients and are used in smaller opposite the blossom clusters toward the base of
quantities than the macronutrients. the shoot are preferred. Each sample should
The function of each element in the plant's represent not more than five acres; areas of
metabolism is beyond the scope of this different soil types and vine strength should be
publication; however, the vineyardist generally sampled separately. A representative sample
can determine deficiencies and/ or excesses with consists of 75 to 100 petioles (one per vine) from
the proper laboratory diagnostic methods. vines uniformly distributed over each area. Put
Laboratory soil analysis is used to appraise each sample in a new, clean brown kraft paper
vineyard problems related to Ph, salinity, and bag, label it with pertinent information -- e.g.,
certain toxicities. Soil analysis is not a reliable name, date, variety, location, and foliar sprays
means of determining nutritional problems and used or fill out an information sheet supplied by
fertilizer requirements. Field research has the laboratory. Both soil and tissue samples can
repeatedly shown inconsistent relationships be sent to the Soil Testing Laboratory, Colorado

41

State University, Fort Collins, CO 80523. most noticeable on basal to mid-shoot leaves.
Information on current costs per sample can be Newly developing leaves often have a pale green
obtained from your county Cooperative Extension color and should not be confused with nitrogen
office. deficient leaves.
Critical nutrient levels have not been Some growers confuse nitrogen deficiency
established for Colorado conditions, and with iron deficiency. In western Colorado soil pH
interpretations of the analysis can be compared is typically in the range of 7.3 to 8.4. High pH
only to other viticultural areas with similar soils like these make iron unavailable to the vine
conditions until further research has been which is often confused with nitrogen deficiency.
accomplished. Symptoms of iron deficient vines are easy to
detect. the classical symptom is a pronounced
Nitrogen intervenal leaf yellowing. The veins of a
Nitrogen is acknowledged to be one of the moderately iron deficient grape leaf remain green.
most important and most likely limiting nutrients In Colorado, Iron deficiency is typically visible by
in grapevines. Nitrogen is the essential element late June. Nitrogen deficiency on the other hand
used in greatest amounts by vines. Nitrogen is shows complete fading of green color including
needed for growth and development. Grapevines the veins. Other symptoms that point to nitrogen
use nitrogen to build essential compounds deficiency are a slow rate of shoot growth, short
including proteins, enzymes, amino acids, nucleic internodal length, and small leaves. Insufficient
acids, and pigments including chlorophyll and nitrogen can also reduce crop through a reduction
anthocynanins of fruit. in cluster, berries and berry set. Note that other
Once absorbed by the vine, nitrogen can factors such as drought, insect pests, disease and
be lost through fruit harvest and annual pruning of overcropping can also cause similar nitrogen
vegetation. Previous research has determined that deficiency symptoms.
on average, each ton of fresh grapes contains
about 3.5 pounds of nitrogen. A harvest of 5 Nitrogen and vine cold hardiness:
tons/acre would remove approximately 18 pounds The belief that any added nitrogen will
of nitrogen per acre. The depletion of nitrogen reduce cold hardiness of a vine is a
would be even greater if cane prunings are misconception. The addition of moderate
removed from the vineyard. (Canes contain about amounts of nitrogen (20-40 pounds of actual
4.5 pounds of nitrogen per ton of grape.) Most nitrogen per acre) will not reduce the vines cold
soils will eventually be depleted of readily hardiness level and will likely improve their
available nitrogen if supplemental additions are overall performance.
not made. Nitrogen depletion will occur most
rapidly with soils low in organic matter content Correcting nitrogen deficiency:
(typical in western Colorado). Soil higher in Maintaining an appropriate nitrogen status
organic matter content can more easily convert is based on past experience, vine performance and
organic nitrogen to available forms (nitrate and supplemental use of bloom-time analysis for
ammonium ions) capable of being absorbed by the nitrogen concentration. Adequate nitrate-nitrogen
vine. levels at bloom time range between 350 - 1200
ppm for most grape varieties. Site, variety and
Symptoms of nitrogen deficiency: year to year differences may exist. This data is
The classical symptom is a light green based on leaf petioles taken from opposite clusters
color of leaves, as opposed to dark green leaves of at full bloom. If nitrogen fertilization is needed,
vines receiving adequate nitrogen. If the leaves application of 20-40 pounds of actual nitrogen per
show this uniform light green color, it will be acre on sandy loam soils is a good starting point

42

for mature vineyards. Young vineyards (first and per acre would require 98 pounds of urea
second growing season) in need of nitrogen fertilizer/acre (45#/46% = 98) or 128 pounds of
fertilization typically require no more than 30 ammonium nitrate fertilizer/acre (45#/35% = 128)
pounds of actual nitrogen per acre. It occasionally or 214 pounds of ammonium sulfate fertilizer/acre
takes two years for added nitrogen to have an (45#/21% = 214).
impact on vine performance. This is because
much of a vines early-season nitrogen needs Foliar Sprays:
depend on nitrogen stored in the vine from the A properly applied foliar spray program
previous usually focuses on micronutrients and can be
beneficial. Before applying any nutrient spray, a
Time of Application: laboratory analysis of petiole samples from
Nitrogen fertilizer should be applied affected and normal leaves and a soil analysis
during periods of active uptake to minimize loss should be performed and evaluated. This allows
through soil leaching. This includes the period you to base your decision with more evidence
form bud break to veraison, and if leaf fall has not than just visual symptoms. Foliar spray products
occurred, immediately after fruit harvest. are not cheap and may be of little benefit if
Nitrogen is very mobile in the soil and applying improperly applied. Micronutrients can be
nitrogen while the vine is dormant and not extremely toxic even in small amounts. They can
actively absorbing nutrients should be avoided. kill vines if applied in excess. Some nutrient-
Multiple applications of nitrogen are deficiency symptoms can be confused with factors
preferred over one mega spring application. other than nutrient supply. Care should be taken
before applications are made to verify visible
Applying Nitrogen: symptoms by tissue analyses.
Apply nitrogen within 1 -2 feet of the vine Consider your foliar spray program as a
or where absorption can be aided by irrigation. supplement to basic root feeding. The micro-
Nitrogen should be immediately incorporated into nutrients most commonly applied in foliar form
the soil by discing, irrigating or if planned are manganese, zinc and iron. Boron also can be
accordingly, apply it before a rain. Incorporating considered, but deficient levels are not common in
nitrogen into the soil minimizes volatilization and Colorado soils. Macronutrients generally are not
hence loss. Application can be achieved by effective or practical as foliar fertilizers and
banding, injecting through the drip system or hand should be soil-applied either by spreader, hand, or
tilling the soil around the vines. Banding with a drip system. Correcting a deficiency and
modified tractor-mounted fertilizer spreader controlling growth are major concerns in
works well for large vineyards without drip Colorado, and trying to achieve this with a
injection capability. Incorporating nitrogen by combination tank mix of N, P, K, Mn, Zn, Fe, and
hand tilling a ring 15 - 20 inches from trunks is B may lead to increased vigor problems and,
practical for small vineyards. hence, increased winter damage. Witches brew
tank mixes of pesticides and foliar nutrients
Calculating Actual Nitrogen: should be avoided as phytotoxicity and berry
There are several forms of nitrogen scarring have been reported in California. The
fertilizer commercially available such as Urea following is a brief summary of materials, rates,
(46%), ammonium sulfate (21%) or ammonium and trial studies for Mn, Zn, and Fe as foliar
nitrate (35%). Recommendations for actual nutrients. The information was gathered from the
nitrogen must be translated into rates based on Wine Advisory Board Research Report (Oregon)
commercial formulations. for example, a and the UC-Davis publication #4087, Grapevine
recommendation for 45 pounds of actual nitrogen Nutrition and Fertilization.

43

Zinc deficiency may be corrected by Manganese deficiency rarely is a problem,
applying a foliar spray two or three weeks before but can occur in soils with high Ph values such as
bloom (10 to 15 cm shoot growth or near tight those in many Colorado vineyard sites. A Mn
cluster stage); this helps improve berry set. The deficiency has little practical effect on vine yields
vines should be sprayed with enough volume to since it appears in late season on older leaves that
wet the flower clusters and the underside of the contribute little to vine function. The symptoms
leaves. Treatments applied with a dilute sprayer begin on the basal leaves as a chlorosis between
(100 to 150 gal/acre) result in more Zn absorption the veins. The only effect appears to be a
than a concentrate sprayer application (20 to 30 reduction in leaf chlorophyll. Manganese sulfate
gal/acre) when comparable rates of Zn are used. at 2 to 3 lbs per 100 gal of water applied as a
A number of products containing 50 foliar spray at the loose cluster stage has corrected
percent Zn are available under various trade the deficiency in some California vineyards.
names. These products (basic zinc sulfates) will Higher rates should be avoided as it may cause
be neutralized to prevent foliage burn. Zinc minor leaf burn. Manganese chelate products
sulfate (36 percent Zn) alone has no neutralizer have been used as foliar sprays with some
and must be used with caution to prevent foliage success.
burn. Studies in California have shown that Iron deficiency is considered one of the
neutral zinc products containing 50 to 52 percent most difficult nutritional problems to correct.
Zn to be the most effective on a label rate per acre Foliar spray treatments of Fe chelates at
basis. Chelated Zn (EDTA 14 percent Zn) manufacturer recommended rates or of ferrous
materials are available, but are a little more sulfate at 4 to 6 lbs per 100 gal of water result in a
expensive on a cost per acre basis than the basic temporary correction, at best. Because Fe is
zinc sulfates. The zinc sulfates are fully soluble in nonmobile in plants, a spray benefits only existing
the spray tank, whereas basic zinc sulfate is not foliage. If chlorosis is severe and persists,
and requires good agitation to remain in repeated applications at 10 to 20-day intervals
suspension. Soil application beneath drip may be necessary. Experience in Colorado has
irrigation emitters may be more effective since it found that soil treatments with Fe chelates work
provides more concentrated placement with more best and tend to last longer; however, they are
continuous wetting for zinc movement into the expensive.
root zone. Deficiencies were nicely corrected in a
drip irrigation trial where rates of liquid zinc
sulfate (12 percent Zn) at 4 to 9 fl. oz. per vine
and liquid zinc chelate (EDTA 6.5 percent Zn) at
0.25 to 1.8 fl. oz. per vine were tested. However,
a foliar spray treatment in this moderately
deficient trial vineyard was equal to the best drip
soil treatments (zinc sulfate) and would be the
most cost-effective treatment.

44

Estimating Grape Yields for several reasons such as diseased vines, winter-
Crop estimation, also called crop injured vines, etc. For these reasons, each year
prediction, is the process of projecting as growers need to physically count the missing
accurately as possible the quantity of crop that vines, subtract that number from the maximum
will be harvested. Why estimate the crop? number to get an accurate count of the bearing
Obviously, growers need to know how much crop vines. If 10% of the 871 vines/acre (i.e. about 87
they produce. Also, growers would like to know vines) were missing or nonbearing then the actual
whether their vines are overcropped or number of bearing vines/acre is 871-87 = 784.
undercropped in order to conduct the necessary 2) Number of clusters per vine: this
adjustment. This is especially important in cold number will depend on how many nodes (buds)
areas such as Colorado where winter freeze and are left after pruning. The number of clusters per
spring and fall frosts could change the crop vine can be counted as soon as they are visible
quantity each year. (i.e. two weeks before bloom) or as late as berry
The formula described below is the most set (i.e. BB size stage). The advantage of doing
popular and easy to understand system to estimate an early count is that clusters are readily visible
yield. This system is used successfully in other and are not obscured by leaves. The number of
winegrape growing regions of the country. This vines on which to count clusters depends on
system provides only an “estimate” of yield which vineyard size and uniformity. For example, in 1
should never be considered “final”. Components to 3 acre-vineyards with vines of a uniform age,
of yield vary each year depending on the year, size, and pruned to the same bud number, only 45
site, variety, and cultural practices. The following of the vines need to be counted. For practicality,
formula can be used to estimate crop with 10 to 20 vines could be used; however, bear in
reasonable accuracy: mind that the higher the number of vines selected
for cluster count the more accurate the yield
PY = (NV x NC x CW)/2000 estimate will be. In larger, non-uniform
vineyards, more vines should be selected. All the
Where PY = predicted or estimated yield clusters on the sample vines should be counted.
(in tons per acre) Also, the vines should be selected methodically,
NV = actual number of vines/acre e.g. select every 10th vine in every other row.
NC = number of clusters per vine 3) Cluster weight: this is the component
CW = cluster weight (in pounds). of yield that varies the most from year to year. It
is influenced by environmental conditions. For
According to the formula, the grower example, wet weather during bloom could cause
needs to measure the following 3 parameters each poor set and may lead to low cluster weight; also
year: the actual number of vines per acre, the a dry summer tends to reduce berry size and thus
number of clusters per vine, and the cluster may decrease average cluster weight. Other
weight. These parameters are discussed below factors that may affect cluster weight include
with examples. cultural practices (irrigation, fertilizers), diseases,
1) Actual number of bearing vines per insects, and birds. Cluster weights at harvest are a
acre: the maximum number of vines per acre is key part of any yield prediction program. The
determined by the row and vine spacing. For goal of obtaining cluster weight at harvest is not
example, a vineyard spacing of 5 x 10 feet will to predict the yield that year, but to provide
have 871 vines per acre. Almost always the records for yield prediction in subsequent years.
“actual number” is lower than the “maximum Clusters can be collected from picking bins after
number” of vines per acre due to vines missing harvest. This is an easy way to sample clusters
from the bin but not as accurate as sampling

45

clusters from the vines. The same vines used for Even with thorough sampling, accurate vine
cluster counts could be used for cluster weights. counts, and many years of average cluster weight
Clusters from each sample vine are picked and data the actual crop tonnage at harvest can vary.
then weighed. The average cluster weight is However, accuracy with this system is very good
obtained by dividing the total cluster weight per and usually falls between 75 - 100%.
vine by the number of clusters per vine. Growers
who do not have these data (but hopefully will in
the future!) could use estimates of cluster weights
shown in Table 5 on the next page (source: CSU-
OMRC and Washington State University).

4) Example of predicted yield of
Chardonnay for 1997 harvest at OMRC:
-spacing = 5 x 10 feet or 871 vines/acre
-missing/nonbearing vines = 1% or about 9
vines/acre
-actual number of bearing vines = 871 - 9 =
862 vines/acre
-average cluster count = 45 clusters/vine
-average cluster weight (based on 1996 harvest) =
0.3 lbs.
-predicted yield = (862 x 45 x 0.3)/2000 = 5.8
tons/acre

46

Table 5. Average cluster weights for wine grape varieties in Washington and Colorado.

Variety Cluster Wt. (lbs.) in WA Cluster Wt. (lbs.) At OMRC*
Whites:
Chardonnay 0.3 - 0.45 0.3
White Riesling 0.25 - 0.3 0.34
Gewurztraminer 0.25 - 0.3 0.2
Semillon 0.4 - 0.5 0.46
Muscat blanc 0.4 - 0.5 0.57
Viognier – 0.27
Sauvignon blanc 0.25 - 0.3 –
Pinot blanc – 0.3
Chardonel – 0.23
Seyval Blanc – 0.24
Vignoles – 0.18

Reds:
Merlot 0.3 - 0.45 0.36
Cabernet Sauvignon 0.3 - 0.4 0.37
Cabernet franc 0.4 - 0.45 0.29
Pinto noir – 0.34
Shiraz – 0.28
Sangiovese – 0.61
Dolcetto – 0.4
Malbec – 0.36
Norton – 0.12
Lemberger 0.4 - 0.5 –

*Cluster weights taken at OMRC are based on 1996 harvest data.

Harvest Timing begins to increase rapidly. This stage is called
The greatest potential of any wine grape veraison. From that point on, if nothing else is
variety is realized only when it is harvested at the limiting, the sugar content will increase over time
proper time. The maturity of grapes is usually and do so more rapidly at higher temperatures.
based on three parameters: sugar content, acid The best way to measure sugar is with a hand-held
content and Ph. All of these change over time, refractometer which uses the degree to which light
and the rate at which they change is based largely is bent by the dissolved sugar in the juice to give a
on the temperature regime in which the grapes quick visual measure of the dissolved soluble
exist. Each parameter and its means of solids. The scale on these instruments is given in
o
measurement is discussed below. Brix or oBalling which for practical purposes can
Sugar Content: Grape sugar content be considered to be percent sugar by weight.
remains low until a midseason point, usually in These really are worth their approximate $150 to
July or August in Colorado, at which time it $250 cost since they can measure the sugar

47

content of the juice of single berries. to 3.4, but it is difficult to measure pH accurately
A hydrometer is a less expensive device enough using specially treated papers. A pH
which, when floated in a cylinder of juice, sinks meter, an electronic device, is a rather expensive
to a level dependent on the juice density which piece of equipment, but it is standard in any
also corresponds to sugar content. Around 50 to commercial winery lab. Most home winemakers
100 ml (2-3 fl. oz.) of juice are required to do this function without a pH meter.
test. Sampling: Sampling is critical in
The alcohol content of a dry, finished wine determining crop maturity. You can determine
is approximately 0.55 times the sugar content at the sugar content of a single berry with a
harvest. White wine grapes are usually harvested refractometer, but there is a wide variation in
between 18 and 24 percent sugar depending on maturity between berries even on the same cluster.
the intended style of the wine. Red wine grapes To make an accurate estimate of the sugar, acid
are generally harvested at 21 to 25oBrix. and pH of a crop, draw a representative sample
Acidity: The organic acid content in taken from as many parts of the block, as many
grapes (mostly malic and tartaric acids) increases vines, and as many clusters in different sun
through the early season until a point near exposures as possible. Younger vines and vines
veraison. From that point on, acid is lost through that are somewhat more water stressed will have
the grape skins by evaporation, and that process higher sugar and lower acid. Clusters exposed to
occurs more rapidly at high temperatures. Acidity the sun will be higher in sugar and lower in acid
is more difficult to measure, but choosing the best than those on the inside of the canopy. Often
time to harvest depends upon having a good there are two size classes of berries (especially on
estimate of acidity. A sample of juice of known cultivars such as Chenin blanc) that differ greatly
volume (usually 10 milliliters) is diluted with in maturity. In order to get a good estimate for
distilled water to make 40 milliliters. This picking, it is recommended that at least 200
mixture is then stirred while adding a base berries be plucked with an effort to spread the
(sodium hydroxide or NaOH) of known strength sample across all the variations which might exist.
(usually 0.1 Normal). In the example described It is easier to sample exposed clusters and exposed
here, the number of milliliters of base required to berries, so one tends to overestimate sugar content
raise the pH of the juice to 8.2 is divided by 10. and underestimate acidity. It is also important
This results in a number called the percent acid that the grapes be squeezed to approximately the
(grams/ 100 ml). The standard strength base can same degree to which they will be when actually
be purchased and the pH 8.2 end point can be pressed since higher sugar juice is released with
determined by a color change of an indicator only mild crushing. Unless it is very hot, weekly
solution. If measured in that manner, it is not sampling is sufficient to follow trends in maturity.
necessary to have a pH meter available. The A few samples carefully collected on a weekly
desired acid content of a wine varies greatly with basis are better than many inaccurate ones
the intended style of the wine; high acids (above collected on a daily basis.
.9 percent) can be useful in sweet finished wines
and for those who have a taste for high acid dry
wines. Acids that are too low are of greater
concern (i.e., below .7 percent for white and .6
percent for red).
pH: The pH of a wine is only indirectly
related to acidity; pH tends to increase after
veraison. But, if pH becomes too high, the wine
will not be stable. The optimum pH range is 3.0

48

Pest Management/Control
All too often in the past, only limited provides the greatest control probably will be the
attention has been given to options for pest poorer choice if satisfactory control at lower
management. With the increasing concern for environmental or monetary cost is available
chemical toxicities and consumer risk and the through other options. Remember, the goal
decreasing number of chemical control options, should always be satisfactory control at the least
the wise grower will consider all of the available combined environmental, health, and monetary
options and their cost (risk) : benefit relation- cost.
ships. Sometimes an option may provide a lower Color identification sheets for some
level of pest control that may in fact still be diseases and insects are appended to this guide.
satisfactory; conversely, an option that

Disease Management
Climatic conditions have a large role in Powdery Mildew: Grape powdery
disease development and occurrence. The warmer mildew (caused by the fungus Uncinula necator)
and wetter the climate, the more numerous and is an important disease in almost all grape
severe disease problems are likely to be for the growing regions of the world, but it is the most
grape grower. Colorado generally has an arid to important in relatively dry climates. Under
semiarid climate, with 7 to 20 inches annual Colorado conditions, powdery mildew is the most
precipitation in areas where grapes might be common and most destructive single grape
grown. Thus, even in the wetter areas (i.e., 15 to disease. Uncinula necator originated in North
20 inches precipitation per year), disease America and thus the native grapes are generally
problems should be manageable with advance less severely damaged by mildew infection.
planning and attention throughout the growing Grapes which originated elsewhere in the world,
season. particularly the V. vinifera cultivars, are often
Of the eight grape diseases reported or highly susceptible and easily damaged by
suspected in Colorado, two (grape powdery powdery mildew since they were selected for
mildew and crown gall) are very common centuries in the absence of that pathogen. Hybrid
throughout the state. Three others (Botrytis bunch cultivars vary in their mildew susceptibility.
rot, sour bunch rot, and Verticillium wilt) occur Powdery mildew fungi infect a wide
with varied frequency and distribution. Oc- variety of crops, but each species can be quite
currence of one virus disease, grape leafroll, has specific. The mildew that infects grapes does not
been confirmed in several western Colorado infect any other Colorado crop and the powdery
vineyards planted with non-certified nursery mildews of other crops (e.g. apples, cucurbits,
stock. Suspected observations of two other roses...) do not infect grapes. Powdery mildews
diseases (Eutypa dieback and nematode-vectored are unique among fungal pathogens in that they do
fanleaf degeneration) have been reported but not not require free moisture for spore germination or
yet confirmed. Occurrence of downy mildew, for penetration of the host plant. The spores are
Phomopsis leaf spot, and black rot is highly spread by wind. After arriving on the plant
unlikely in western Colorado and not too likely surface they germinate and grow a short distance
even in eastern Colorado, although some of the before forming a structure called an appressorium.
Front Range areas might have sufficient summer From that structure a small peg is formed that
humidity and rainfall to allow them to occur. penetrates the cuticle and epidermal cell wall. A

49

specialized feeding structure called a haustorium obligate parasite -- it can only live and grow on
develops inside the penetrated cell, but that is the the host grape tissue. It overwinters in two ways.
extent of fungal development inside the plant. Mycelium can enter the developing buds and
After an infection is established the continuing remain alive inside of the bud scales to grow
growth of the fungal colony is on the surface of again the following spring. When the necessary
the plant. Hyphae radiate from the first mating types are present, the fungus can also
penetration site and periodically penetrate more survive in its resistant, sexual spore bearing
cells to establish more haustoria for nutrient structures called Cleistothecia. These small (the
uptake. As the colony develops, columns of size of a pinhead) structures can sometimes be
barrel shaped spores are produced. When found on leaves and fruit late in the season. They
colonies grow large enough to be visible or when have appendages with hooked ends which can
multiple colonies are present, the infected plant catch on the bark of the cordon or trunk.
surface develops a white to gray, felt-like to Cleistothecia which remain on the vine can
powdery appearance. The entire process from mature and produce ascospores there in the spring,
infection to sporulation can take anywhere from 5 and these can be forcibly ejected following rains
to 21 days, depending on temperature. Powdery to infect the emerging grape shoots. It is not clear
mildew grows most rapidly at moderate how much overwintering inoculum in Colorado
temperatures (70F) and is very slow at extremely comes from cleistothecia and how much from
high temperatures (90F). Mildew responds to infected buds.
leaf temperature, not air temperature and Whether originating from infected buds or
transpiring leaves are usually much cooler than from Cleistothecia, even a small population of
the surrounding air. powdery mildew can build up through the season
Almost any green tissue of a grapevine is because of the relatively short infection cycle
susceptible to mild infection including tender described earlier. To the grower, powdery mildew
parts of the shoot, blossoms, leaves, berries, the infection often appears to have occurred suddenly,
rachis and pedicles. Immature tissues are always but actually it was building logarithmically long
more susceptible. Severe shoot and leaf infection before it was found. It is for this reason that
can reduce yield, reduce overwintering hardiness powdery mildew control methods must be
or stunt growth, but the most common form of practiced pro-actively -- long before infections
mildew damage concerns the fruit. When berries can be found in the vineyard.
are infected, the epidermis under the colony The key to a successful powdery mildew
develops a network of russeted scars. This can be control program is the assumption that mildew is
unsightly (a problem for table grapes). More always present in the vineyard and must either be
importantly, if the berry is still expanding the prevented from spreading or repeatedly killed-
damaged portion of the skin fails to grow and the back so the epidemic does not develop to levels
berry cracks. This enhances secondary infection that will damage the crop. Begin spraying as soon
by fungi and acid bacteria. Even without as practical after buds emerge in the spring and
cracking, severe fruit infection reduces yield, and continue steadily until veraison. Overall mildew
the presence of mildew spores and mycelium can pressure varies from year-to-year based on
impart off-tastes to the wine. Berries are overwintering conditions and on the temperature
susceptible to infection from before bloom until pattern of the given season, but any grower who
veraison. When berries have around 11% sugar, neglects to maintain a good mildew program will
they can be considered safe from further infection eventually suffer severe damage.
and the mildew present on the berries will soon There are currently three registered classes
die. Even so, the rachis remains susceptible. of fungicides for powdery mildew control on
Like all powdery mildews, Uncinula is an grapes. Each has its own advantages and

50

weaknesses so that the optimal control program enzymes which are inhibited by the fungicides.
often uses 2 or 3 classes at one point or another All of those available for use on grapes inhibit the
during the season. Each class is described below: same enzyme in the ergosterol biosynthesis
Sulfur: Elemental sulfur is the oldest known pathway which is important because strains which
fungicide and was the mainstay of mildew control become tolerant to one DMI fungicide are also
until recent times. It is recognized as suitable for more tolerant to other DMI products (cross
organic production. Sulfur particles on the plant resistance). These fungicides are all applied in
slowly sublimate (change from solid directly to water and move to a certain extent from cell-to-
gas) and generate sulfur compounds which can cell in the plant and with the transpiration stream.
kill germinating spores of powdery mildew. The systemic movement is not sufficient to move
Sulfur is a completely preventive fungicide and is fungicide to new tissues, but it does help
only effective immediately in the vicinity of the overcome small inconsistencies in spray coverage.
particle. Excellent coverage is necessary for DMI fungicides can be very potent tools for
control with sulfur. Sulfur is available either as a powdery mildew control and are particularly
dust (use rates 5-15 lbs/acre) or as a wettable valuable during bloom and immediately after
powder for water application (use rates 2-6 when berry tissue is expanding so rapidly that
lbs/acre). Dusts have the advantage of potential sulfur protection is difficult to maintain. DMI
high speed application and penetration of dense fungicides can kill a young mildew colony (1-3
canopies but they have the disadvantages of days), but are not able to kill established,
substantial drift which can damage neighboring sporulating infections. Although they have this
crops and irritate neighbors. Sulfur dust should be curative action, they should be approached as
applied on a 7-10 day cycle. Wettable sulfur can protective fungicides and used on a 14-18 day
be used on a slightly longer spray interval (7-14 spray schedule. Tolerance to DMI fungicides is
days) and does not have problems with drift. It well documented, but is not a dramatic all-or-
takes longer to apply and can be more difficult to nothing type of resistance. Even so, it is best to
deliver to all parts of the canopy. With either kind limit the total number of DMI sprays used in a
of sulfur, high temperatures (90F) can speed spray program, to use other fungicides as part of
sublimation to the point that leaves are damaged. the program, and to avoid using DMI fungicides
Very low temperatures (55F) do not allow later in the season when the selection pressure is
enough sublimation to be effective. Sulfur is applied to a large mildew population. As new
highly susceptible to rain wash-off and must be classes of systemic fungi-cides are introduced, the
re-applied after any significant rain. When using same general guidelines should apply. Do not rely
sulfur for mildew control, the basic goal is to keep on a single mode-of-action throughout the season
a coating of relatively fresh sulfur on the entire and use potent systemic treatments early to mid-
vine as consistently as possible. The faster the season before larger mildew populations are
vine is producing new, unprotected tissue, the present.
more frequent the sulfur applications must be to Impact Fungicides: A class of powdery
reestablish the protective barrier. Sulfur does not mildew control tools has been introduced recently
kill established mildew infections, it simply slows that is described as impact fungicides. These are
the progress of the epidemic. materials that are capable of killing mildew spores
Sterol Inhibitors: There is a class of and mycelium during direct contact of the spray
synthetic, systemic fungicides variously referred solution or suspension. These materials are
to as SIs (Sterol inhibitors), EBIs (Ergosterol almost strictly curative in their activity because
biosynthesis inhibitors), or DMIs (Demethylase they have no effect on new spores that arrive after
inhibitors). All these names are more or less
specific descriptions of the kind of fungal

51

Standard Fungicide Programs

The most highly recommended fungicide programs for grape
powdery mildew control are as follows:

Standard DMI program:
1. Wettable or dusting sulfur starting at budbreak and
continuing on a 10-14 day pattern (7 days for dust) until
bloom or 10 shoot growth.
2. DMI applications every 18 days from bloom or 10
shoot growth until the total, annual dosage/acre has been
applied (usually around 3 sprays).
3. Sulfur applications on a 10-14 day interval (7 day
interval for dust) until veraison.

Standard Sulfur Program:
1. Wettable sulfur starting at budbreak.
2. Dusting or wettable sulfur on a 7-14 day cycle until
veraison.

Older recommendations (first written in 1905) began the
program at 6 or 12 inches of shoot growth, but recent research indicates
that much better control is usually achieved by starting the spray
program earlier.

These programs are commonly modified by grape growers
for various reasons.

DMI program modified for resistance management:
Alternation: sulfur sprays inserted between the DMI

52

the spray dries. Any type of impact fungicide is or stress it so that it becomes non-winter hardy.
based on emulsions of either plant oils or Injuries for gall initiation are most common in the
paraffinic mineral oils. The mineral oils are not nursery and during planting, but winter freeze-
very compatible with a spray program that also cracking of trunks provides another potential entry
includes sulfur. Under some conditions, a sulfur point in Colorado.
treatment as much as two weeks before or after an Crown gall has been controlled on some
oil application can lead to severe burning of hosts by use of another bacterium that produces an
leaves. The other type of impact fungicides are antibiotic that inhibits some strains of the
potassium salts of naturally occurring fatty acids. pathogen. Unfortunately, the common grape
These materials are compatible with the use of strain (biovar 3) is not sensitive to this antibiotic.
sulfur and can be particularly useful for rescue Thus the biological control option (strain K84 of
applications when mildew infection is flaring up A. radiobacter) is not effective in controlling
in isolated areas or because of failure of the grape crown gall. An eradicant chemical such as
previous preventive control program. A spray kerosene or Gallex can be used on the gall itself to
program (10-14 day interval) using only curative kill gall tissues, but treated vines should be
fatty acid products has been shown to give season- checked for gall recurrence over the next year or
long mildew control. Fatty acids are also two since new galls can develop at treated sites.
attractive alternatives when conditions are too hot Use of management practices that reduce
for sulfur or if the winemaker is concerned about winter injury can be helpful because the
sulfur residues carrying over to the must at development of crown gall is frequently
harvest. Oils (and to a lesser extent fatty acids) associated with the occurrence of freeze injury.
effect the appearance of the waxy surface of the Freeze cracking injury in the field allows the
berries. This does not effect their resistance to formation of galls on mature vines; this
other diseases or resistance to water, but it is occasionally kills the trunk outright, and the vine
generally considered unsuitable for table grape must be retrained from root suckers. Thus, in
production. sites prone to severely cold winter temperatures,
Crown Gall: Crown gall, a bacterial growers should consider burying young vines in
disease caused by Agrobacterium tumefaciens, the fall to reduce freeze injury and possible
can be a significant problem in some Colorado hilling of trunks in the fall to protect the crown
grape plantings. Galled vines frequently have tissues (and to protect replacement buds from
poor shoot growth and fruit production, and freezing just in case they are needed for trunk
portions of the vines above the galls often die renewal the next season). Any galled wood
prematurely. Vinifera grapes appear to be most should be removed from the vineyard and burned.
susceptible to crown gall attack and damage, but Recent research also has shown that the
some V. labrusca cultivars (e.g., Niagra, pathogen can become systemic within grape tissue
Dutchess, and Isabella) also can become heavily and can be introduced into previously non-
infected. Hybrids that are often infected include infested soil by planting infected grape plants.
Aurore, Chancellor, and Cayuga White. In This points out the need to plant only pathogen-
Colorado, Merlot appears to be more susceptible free vines, especially in new planting ground.
to crown gall than Riesling. Such a practice should help minimize crown gall
The bacterium lives in soil but, when occurrence in replanted ground and avoid the high
present at a plant wound, it invades the host cell incidence of disease that has often been
and transforms it into an undifferentiated gall type experienced in new plantings.
of growth. The galls interfere with normal sugar Botrytis Bunch Rot: Botrytis bunch rot or
and water transport in the host and, depending on grey mold generally is present in all vineyards,
the location and size of the gall, can kill the plant but only occasionally causes problems in Colo-

53

rado vineyards. Varieties with tight clusters vineyards planted in soils in which susceptible
(Chenin blanc, Muscat blanc, Gewurztraminer, crops (e.g., sweet cherry, apricot, tomato,
Pinot noir, Rougeon, Sauvignon blanc, and strawberry) have been grown.
Riesling) are usually the only ones damaged in Symptoms of Verticillium wilt mimic
Colorado and usually only in seasons with cool, those of drought stress. Shoot wilt, collapse, and
unusually wet summer weather. Both yield and death can be extremely rapid by mid-summer, and
quality can be reduced. Table grapes can lose leaves and young berries just dry up and remain
substantial fruit quality in the field, in storage, or attached to the dead cane. The diagnostic
in transit, but wine grapes suffer even more symptom, however, is the greyish to brownish
serious damage to quality because of the chemical discoloration of the vascular elements within the
changes within the grapes brought about by base of the collapsing cane. This discoloration,
infection. Wines made from diseased fruit tend to best seen by cutting the bottom portion of the cane
be less clear, have off-flavors and do not age well. on a diagonal (an oblique cut), appears as greyish
Affected bunches also can be affected by to brownish streaks associated with or within the
the vinegar bacterium, Acetobacter sp., and a vascular bundles.
common saprophytic fungus, Aspergillus niger in The reason for the drought stress type
what is known as sour bunch rot (see next entry). symptoms and the vascular tissue discoloration is
Control can be obtained through two non- that the Verticillium fungus colonizes and plugs
chemical management options. Leaf removal up the vascular tissues. Thus, as the need for
around the developing fruit clusters will increase water transport increases with increasing summer
air circulation and decrease humidity levels within temperatures, the infected vine simply cannot
the canopy. This will reduce the liklihood of supply enough water to the heavily colonized
bunch rot getting started. Secondly, varieties with canes fast enough to keep up with demand. As a
very tight clusters may be cluster thinned by result, the affected canes simply wilt and die.
removing selected berries when young; this opens This disease is mostly a problem in young
up the clusters to allow more air movement plantings between their second and sixth leaf. By
through them and thus reduce the potential for the sixth leaf, vines that exhibited symptoms
bunch rot. earlier but did not die recover and are not affected
Sour Bunch Rot: Sour bunch rot may thereafter. At that point, the disease generally is
cause damage to varieties with tight clusters no longer a problem within the vineyard.
(Chenin blanc, Muscat blanc, Gewurztraminer, Although early fruit production can be reduced
Pinot noir, Rougeon, Sauvignon blanc, Riesling) and full production delayed by the disease, no
in seasons where hot August weather is effect on yield has been shown in vineyards that
accompanied by rains. Broken berries attract the no longer show symptoms of Verticillium wilt.
vinegar fly that carries the vinegar bacterium, Thus specific control measures for the disease do
Acetobacter sp. The berries rot and develop an not appear warranted other than avoiding any sites
objectionable vinegar order. The fungus where the disease has actually killed grapevines.
Aspergillus niger is often involved in the Eutypa Dieback: Eutypa dieback is also
complex. This disease has no real control except known as dying arm (formerly dead arm). It
by avoiding berry breakage by birds or other is one of the most destructive diseases of woody
factors. To date, it has not occurred in sufficient tissues of commercially grown grapes. The causal
abundance in Colorado to adversely effect wine fungus, Eutypa lata (synonym = E. armeniaca),
quality. and the disorder are most common in areas of
Verticillium Wilt: Verticillium wilt is higher rainfall and severe winters, but can be
caused by the fungus Verticillium dahliae. It expected in areas where the annual precipitation is
occurs only sporadically in Colorado, primarily in above 10 inches per year. Occurrence in areas

54

with less than 10 inches precipitation per year is certified nursery stock could import a potential
unlikely, but since many of the grape plantings virus problem that could spread within vineyards
within Colorado are likely to be within areas and last in the soil even after the diseased vines
where apricots are grown, the possibility of the are removed. NON-CERTIFIED VINES or
disease does exist. vines from questionable sources SHOULD NOT
Characteristic symptoms of Eutypa BE PLANTED OR USED FOR
dieback begin with early season growth, when PROPAGATION.
shoot growth is 10 to 20 inches in length. Grape Leafroll Disease : Grape leafroll,
Affected shoots are deformed and discolored, with which results from infection with the grape
much dwarfed internodes, and the leaves smaller leafroll virus, causes chronic damage to affected
than normal, cupped and chlorotic. The leaves vines. Leafroll infection does not kill affected
often develop small necrotic spots and tattered vines, but yield loss of 20 percent has been
margins with age. The diagnostic feature of reported to occur each year for as long as the
Eutypa infection on arms with such symptoms is a diseased vines were maintained within the
wedge-shaped zone of dark-brownish dead vineyard. The disease is widely distributed
sapwood extending into the wood when the wood because of past propagation from diseased mother
is cut in cross-section. vines, but was not known to occur within
Control is available through a drenching Colorado vineyards before the 1989 season.
spray of benomyl applied at pruning to any large However, one confirmed occurrence in an entire
wounds or cuts on woody tissues (i.e., not the planting of Lemberger and a second in a second
annually produced canes, but rather any tissue that leaf Cabernet franc planting in Mesa County
is two years old or older). This material is illustrates the need to order only certified virus-
effective in preventing spores from germinating free grapevines.
and gaining a foothold for infection; thus, it must The disease is characterized by the
be in place before the spores arrive. Applications occurrence of colored leaves (yellow for light
must be sufficiently drenching to be absorbed and fruited varieties or red to red-purple for dark
taken up into the vascular tissue to be effective, fruited varieties) with green veins and downward
and they must be applied as soon as possible after rolled leaves. These symptoms develop in late
the wound or cut is made. Manual treatment of summer beginning with the leaves at the base of
such wounds at the time of pruning will have the the cane and proceeding toward the tip. However,
highest probability of success. In Colorado's since similar symptoms also can be produced (to
more arid climate, those chances should be some extent) by cane or vine injury (from cane
relatively high. borers, crown gall, mechanical damage, crown rot,
Virus Diseases: The two virus diseases etc.), careful examination must be made to rule
known or suspected to occur within Colorado are out these other possible causes. General size of
grape leafroll and fanleaf degeneration. In both infected vines and plant structures (leaves, shoots,
cases (the same is true for most other virus canes, trunk, and root system) is slightly smaller
diseases) problems can be avoided by planting overall than that of healthy vines. In addition, the
only certified clean stock such as that grown in disease delays fruit ripening and reduces fruit
the Pacific Northwest and in certified programs in cluster size and fruit sugar content; fruit color,
California. The various viruses, in addition to the especially in the red or black cultivars, is pale.
symptoms for which they are generally known, Control of the disease is relatively simple -
appear to reduce the winter hardiness of the vines. - removal of the affected vines. No vector for the
In addition, some grape viruses are spread by causal virus is known, and natural spread in
dagger nematodes that occur within our fruit commercial vineyards is slow. This strongly
producing soils. Thus importation of non- suggests that the primary source of infection is the

55

diseased budwood from which vines were discoloration of early spring vegetative structures
propagated. Leafroll is an avoidable disease if (leaves, shoots, tendrils, and inflorescences). The
care is taken to plant only virus-free vines. discolorations range from scattered yellow spots
Fanleaf Degeneration: Fanleaf to rings or lines to extended leaf mottling to total
degeneration, the oldest known virus disease of yellowing. Affected vines are easily spotted
vinifera grapes, varies with cultivar tolerance to within the vineyard in early spring, but are less
the virus. Sensitive cultivars are severely affected obvious by summer in areas with hot summer
with infection causing decreased yields (up to 80 weather whey they begin to produce normal,
percent losses) and fruit quality, progressive vine green foliage.
decline and shortened productive vineyard life, The third symptom syndrome,
reduced graft take and rooting ability of cuttings, veinbanding, consists of mid- to late-summer
and lower tolerance of adverse weather conditions discoloration in mature leaves and severely
(e.g., winter hardiness, heat and drought tolerance, reduced fruit yield (to virtually zero). No shoot or
etc.). leaf malformations are produced, but chrome
Diagnosis is complicated by the fact that yellow flecks develop along the main veins of
the virus can cause any of three distinct symptom some (but not all) mature leaves. The flecking
syndromes. These focus primarily on leaf shape then spreads somewhat into the interveinal areas
and color patterns, shoot growth patterns, and fruit of the affected leaves. Fruit set is poor and the
production effects. clusters are straggly.
The first symptom syndrome, infectious Grape fanleaf virus (GFLV) is spread
malformations, includes the most severe primarily by a dagger nematode, Xiphinema index.
symptoms and is the best known of the symptom The virus has no known natural weed hosts -- only
syndromes. Its most obvious effects are grapes. However, the nematode can acquire the
malformations of the leaves and shoots that virus in a single, brief feeding on an infected vine
appear in the spring and continue throughout the and can remain inoculative for up to eight months,
season, with a slight lessening in severity of the even in the absence of host plants. Added to this
leaf symptoms severity during the summer. is the ability of grape roots to remain viable (and,
Leaves are variously deformed, often thus, as sources of inoculum) for many years after
asymmetrical and puckered, with the leaf base the mother vine is removed. This makes control
tending to be more flattened (less of an angular extremely difficult once the nematode and
notch at the leaf base) and the veins less separated infected grape roots are present within a planting.
to give the leaves a more open, fan-like The best control for fanleaf degeneration is
appearance (from which the disease derives its to plant only certified virus-free stock. Once the
name). The leaves also may have a chlorotic nematode and infected grape roots are present, the
mottle. Shoots are commonly malformed with ecological cycle of the nematode / virus / grape
shortened internodes, a zigzag or snake-like complex must be broken. This usually requires a
growth pattern, double nodes, abnormal prolonged fallow period with rigorous weed
branching, and fasciations. Fruit set in vines with control or eradication of the vector nematodes
such symptoms is poor, and the fruit bunches are with soil fumigants or both. Soil fumigation (at
fewer and smaller than normal with shot berries high rates) works better in shallow than in deep
and irregular ripening. soils, as some nematodes can survive below the
The second symptom syndrome, yellow depth the fumigant penetrates. Rootstocks
mosaic, exhibits little or no malformation of resistant to either the virus or the vector nematode
shoots or leaves, but it does result in small fruit or both are being developed and should be
clusters with some shot berries. Its main considered for use in renovated vineyard plantings
characteristic is the bright chrome yellow with a history of fanleaf degeneration.

56

Insect Mite Pest Management
Insect and mite pest problems have not sufficient size to enter. Entry of the larvae into
been severe enough in Colorado to require a the berries of some grape varieties causes the
regularly scheduled spray program. However, berries to turn red in response; this can be helpful
with the continued increase in acreage planted to in identifying the problem early. Full-grown
grapes, this could change. Grape pests known to larvae pupate on the ground or on the leaves, and
occur within Colorado vineyards or orchards a second generation of moths becomes active in
include: grape leafhopper, grape berry moth, late July. This second generation usually is the
grape cane borer, grape mealybug, grape most injurious. Eggs are laid on the berries, and
skeletonizer, sphinx moth, thrips, cutworms, emerging larvae invade the fruit. Pheromone
cottony maple scale, thrips, and mites. Phylloxera traps are available that can help determine periods
is not known to occur currently in Colorado. when adult moths are flying and laying eggs.
With proper care in selection of plant sources and Insecticide applications are suggested for
careful examination of all materials before approximately 10 days after flight periods begin.
planting, it is hoped that this pest can be kept out Concord growers have had good success in
of Colorado. Leafminers are an occasional controlling the problem with sprays of carbaryl
problem in backyard grape plantings but have not (Sevin) at those times. Vinifera grape growers
been a problem in commercial plantings to date. should watch for this problem to determine if they
Climbing Cutworms: Several species of need such sprays.
climbing cutworms may be found chewing on Grape Leafhopper: Although this
grapes in Colorado. These pests hide in the soil distinctive, orange and white mottled leafhopper is
or debris beneath the grape trellis by day and usually encountered at some level in vineyards, it
move up the vine at night to feed on buds just as seldom reaches sufficient populations to
they are swelling and pushing in the spring. Their materially damage the vines. The nymphs of this
feeding leaves small (1/16 to 1/8 inch) tunnels pest suck the juice from the leaves and cause them
into a bud; this kills the bud and results in crop to become blotched with white spots. Infested
loss. Sprinkling a suitable carbaryl (Sevin) bait vines may show a lack of vigor. Its droppings are
around the trunk of each vine usually will stop undesirable on table fruit and, if enough stippling
this damage. If the worms are living on the trunk of leaves occurs due to its feeding, the crop could
itself, a spray may be necessary. be delayed in maturity.
Grape Berry Moth: Grape berry moths Adult grape leafhoppers overwinter
can be important pests of grapes in Colorado and beneath leaves and trash near vineyards. In May
can cause serious fruit losses in some areas. The the adults migrate to the grapes, feed, and lay eggs
larval stage of this insect enters young berries and just under the lower leaf surface. After hatching,
causes them to wither as they mature. The insect the young nymphs feed on the leaf undersurface
typically is found in American grapes such as and cause the typical leafhopper damage. There
Concord and in hybrids, but also can be found in can be a partial second generation late in the
vinifera grapes. summer.
There are two generations of the moth Grape leafhoppers are relatively easy to
each year, with peak flights in mid-June and late- control with insecticides when the nymphs are
July. Adult moths emerge in late May from present. These include carbaryl (Sevin),
overwintering pupae and lay eggs singly on small azinphosmethyl (Guthion), methomyl (Lannate)
developing grapes or cluster stems. If the berries and diazinon. There also are some natural
are too small, the larvae will make webs on the controls (e.g., an Anagrus wasp that parasitizes
cluster stems and feed there until the berries are of leafhopper eggs).

57

Grape Flea Beetle: These bluish-black infestations is important and simple. Mealybugs
shiny beetles feed on the interior of developing prefer vigorous vines and can be detected in
primary grape buds and, in this way, prevent spring and summer by the presence of honeydew
development of primary grape canes. They and/or sooty mold on the trunk and below the
overwinter in trashy or wooded areas and emerge vine. The presence of honeydew should trigger a
in the spring to feed and lay eggs on the vines. closer examination of the vine for eggsacs,
The eggs hatch to produce light brown larvae that crawlers, and adults. In mid-summer, fruit
feed on the upper leaf surfaces. Mature larvae clusters that touch old wood should be examined
drop to the ground to pupate in the soil, and a closely for evidence of honeydew, and black sooty
second generation of adult beetles emerges in July mold. It s common for mealybug populations to
to August. explode mid-summer and then decline just as
Control is obtained primarily through rapidly due to the presence of natural predators. If
insecticide applications to kill the feeding larvae. control is necessary, it is best achieved with a
Methoxychlor is labelled for this use on grapes. dormant spray which can be followed by a
summer treatment. It is important to note that
Mealybugs summer treatments are only effective if applied
The grape mealybug Pseudococcus before the insects are half grown and their waxy
maritimus has been identified in vineyards of covers are still permeable.
western Colorado by B.C.Kondratieff and W. Mealybugs have two generations a year.
Cranshaw (Technical report #TR94-1 Department The first overwinters as eggs or as nymphs; the
of Entomology, CSU 1994). Populations have second is produced in mid-summer and, in turn,
increased during the last three years and it has lays the eggs that constitute the overwintering
become a production threat to vineyards of generation for the next season. In spring the
western Colorado. young nymphs move to the base of the spurs and
Mature, fully grown mealybugs are 3/16 then out onto the green portions of the vine to feed
of an inch long, pinkish red, covered with a white on foliage and fruit. After maturation in early
powdery wax. Filaments of wax extend from the June, most females return to protected areas to lay
sides and rear of the oval, somewhat flattened eggs that hatch about a month later (early July).
bodies. Eggs are yellowish to orange, laid in a The second or summer generation nymphs then
cottony eggsac under bark or in protected move out to the green portions of the vine to feed,
locations. Newly hatched nymphs (crawlers) are and it is primarily this brood that produces the
brownish and lack the powdery wax cover. bulk of the fruit damage. As the second
Mealybugs overwinter as eggs in their cottony generation females mature, some may deposit
white ovisacs, or as young crawlers beneath the their eggs on fruit and leaves; most, however,
loose bark of the vine. In spring the eggs hatch return to old wood or protected locations to lay
and the crawlers move to the base of the spurs and their overwintering eggs.
out onto the new growth. Once mealybugs reach Achemon Sphinx Moth: Caterpillers of
maturity in mid June most females return to the the Achemon Sphinx moth have caused
vine trunk and lay eggs in the protected regions occasional damage to grapes in Colorado. The
beneath the loose bark. The second generation larvae are voracious feeders and can quickly
will hatch a month later and will be responsible defoliate sections of a vineyard if large numbers
for a noticeable population explosion. It is this are present.
brood which will cause the majority of the This pest is related to a better known
damage as well as lay the eggs that will cousin, the tomato hornworm. The adults, also
overwinter. known as hawkmoths, approximate the size of a
Vineyard monitoring for mealybug hummingbird and have a similar, darting,

58

hovering flight as they fly and feed on flowers at perhaps better known as the branch and twig
dusk. The achemon sphinx moth has about a 3 to borer, is at most only a minor pest in Colorado's
4-inch wingspan, a body and forewings that are a vineyards; its presence is suspected in Fremont
marbled brownish-gray with well-defined dark County, but this has not yet been confirmed by
brown spots, and hindwings that are a rich rosy examination of actual insect specimens. It is a
pink with a brown border and dark spots. The wood-boring beetle, Malalqus confertus LeConte,
larvae are green or reddish, about 2.5 to 3 inches that also attacks other woody plants such as fruit
in length. and ornamental trees and shrubs.
Control is rarely needed, but applications On grapes, it derives its common name
of Bacillus thuringiensis (Dipel, Biobit, from its method of feeding and the resulting
Thuricide) are very effective against sphinx moth damage; the adult beetle burrows into weak grape
if made before the larvae become too large. Other canes at a crotch or bud axil and proceeds to mine
insecticides are also effective if applied at early out the woody tissue. This causes shoot wilting
stages. and flagging and, occasionally, partial breakage at
Thrips: Thrips are primarily a problem the feeding point when shoot growth reaches 8 to
for table grape production, and then only rarely in 10 inches in length. These broken shoots often
Colorado. Feeding by western flower thrips remain hanging down from the spur after
during bloom and early postbloom can result in breakage. Such wilted or wilted and broken
scarred fruit that is not salable. Feeding by large shoots should be closely examined for any
numbers on young shoots in the spring can stunt evidence of feeding holes or, possibly, the feeding
these shoots and may thus require control. adult beetle.
Thrips are small insects with fringe-like The adult blackish brown beetle is small to
wings (instead of the membranous wings of many medium sized, 0.3 to 0.6 inches in length,
other insects). Adults generally are about 1/16 of cylindrical in shape with an obviously narrowed
an inch in length and can occur in three color waist between the abdomen and thorax. The
phases: light, intermediate, and dark. The dark eggs are smooth, white, and cylindrical with a
form predominates in early spring while the light slightly pointed end. The larvae also are whitish,
and intermediate forms are most common later. but covered with fine hair and heavy bodied with
The light form is the most numerous. The two a curved C-shape that is larger toward the head
nymphal stages last one to two weeks, during end. The larvae also can do equally serious
which they feed on both stem and flower or fruit damage to vines through their feeding on both
tissues. It is this feeding that produces the fruit dead wood and living tissue; they plug their
scarring. Two additional stages (prepseudopupal feeding channels with excrement and chewed
and pseudopupal) occur in the soil debris. The wood frass.
emerging adults feed primarily on pollen so far as The eggs are laid singly in cracks and
is known. There are five to seven generations per crevices of the roughened trunk or arm bark
year, with a population peak coinciding with during late spring/early summer (approximately
grape bloom. The western flower thrips over- May in Colorado). The larvae emerge two to four
winters in the adult and nymphal stages. weeks later and establish themselves within the
Thrips populations can be determined by wood of the vine trunk or arms. They feed for the
counting adults or nymphs knocked out of the next 10 months or so, and then burrow toward the
flowers or fruit clusters. Generally, if more than tip of the arm (usually in mid-spring) where they
10 adults are observed per cluster, control sprays prepare a hollow cell and pupate for one to two
may be needed on those cultivars more weeks before emerging as adults.
susceptible to damage. Chemical control can be obtained through
Grape Cane Borer: Grape cane borer, two to three applications of carbaryl (e.g., Sevin)

59

at seven to ten day intervals when adults are emergence from overwintering pupae occurs in
emerging, but this should be considered only as a late April to mid-May, and the first generation
last resort. Satisfactory control usually is larvae are usually found in early May to late June.
obtained through attention to vineyard and area The second generation runs from late June to late
sanitation. Newly hatched larvae enter dead or August or early September.
dying areas on grape trunks and arms, so much of Control is readily obtained with chemicals
the problem can be controlled by keeping vines used for lepidopterous larvae on grapes. A
healthy and by removing any dead or dying stomach poison, such as cryolite, is preferred
portions. Prunings should be collected and because of its long residual activity and low
burned before bud-break in the spring in order to toxicity to natural enemies. Application of
eliminate overwintering larvae before they pupate. Bacillus thuringiensis (Biobit, Dipel, Thuricide)
Brush and wood piles should not be allowed to also gives good control of grape leaf skeletonizer
accumulate near vineyards and also should be if treatments are properly timed.
burned before mid-March. Cottony Maple Scale: Scale insects are
Grape Leaf Skeletonizer: Grape leaf rarely observed on grapes in Colorado. The only
skeletonizer is reported to occur within Colorado, species observed on grapes here thus far has been
but damage from this pest is not common. The one incidence of cottony maple scale. The main
bulk of the damage is due to vine defoliation by problem caused by this pest is the production of a
the larvae. Under certain conditions, it can feed great quantity of honeydew which, in turn, makes
on the fruit and this injury then leads to bunch rot the grapes sticky and sooty in the same way that
that usually destroys the entire fruit cluster. grape mealybug does.
Adult skeletonizer moths are about 5/8- The adult female cottony maple scale is
inch long and have a wingspan of 1 to 1.3 inches, about 1/5-inch long, flattened, oval or oblong, a
a characteristic bluish-black to greenish-black pale or dark brown with a large cottony egg sac
color, and comb-like bristles along the antennae. that is about two to three times as long as the
The caterpiller larvae are strongly gregarious and body. They could be confused with grape
habitually feed side-by-side during their first three mealybug if care is not taken in examining the
instars and sometimes in the fourth instar. The insects. As the scale female continues to lay eggs,
larvae display a unique swarming behaviour even the egg sac enlarges; it remains for some time
at time for the first three molts; they move away after the female has died and the crawlers have
from their feeding site (often to an undamaged dispersed to the undersides of leaves. In late July
leaf or to the stem or shoot), form a round or early August, they mature; the males develop
assembled mass, and then molt. The larvae wings and mate with the wingless females. The
become increasingly banded in appearance with mated females then crawl back to young canes for
successive molts with band colors of brown to overwintering.
blackish purple; body color between the bands is Control is best accomplished through
initially pale brown, but finally a bright yellow dormant sprays such as those for grape mealybug.
just before the larvae spins its silken cocoon. The Eight-spotted Forester: Larvae of the
larvae also have many long, dark hairs on the eight-spotted forester moth feed on grape leaves
body that seem to be poisonous; workers who and can defoliate vines when quite numerous.
brush against the hairs often develop skin welts Serious injury, however, usually is rare in
similar to those produced by contact with stinging Colorado. Fully grown larvae are about 1 inch in
nettle. length and have distinct markings of orange,
The skeletonizer overwinters in the pupal yellow, black, and white. After feeding is
stage and has two complete (and sometimes a completed, larvae drop to the ground to pupate.
third partial) generations each year. Initial The adults are black with white and yellow spots

60

on the wings. color, and knotted roots. These symptomatic
Mites: Mites have not been observed as a conditions are often confused with water stress
major problem in Colorado vineyards. They do and nutrient deficiencies. Unfortunately
best in dry, dusty conditions so that raising of dust nematodes do not cause specific symptoms on
in the vineyard in mid-summer should be avoided. above ground tissues and thus nematode detection
The McDaniel and two-spotted mites without laboratory analyses is impossible.
overwinter primarily as adult females in soil and Nematodes can also transmit a variety of viruses
trash near the base of woody plants. The extent to (e.g. tomato ringspot virus, grape fan leaf virus).
which the mites may survive the winter on the The following is a list of potentially
trunk or branches of fruit trees or vines is damaging nematode genera found in orchard/
unknown for western Colorado. It is generally vineyard soils of western Colorado (Mesa, Delta
thought that any mites on the trunk migrate down counties). The listed nematodes were identified in
to emerging cover-crop vegetation early in the 1963, 1985 and 1992 by the Colorado Agriculture
season. At this time mite populations exhibit a Experiment Station.
preference for herbaceous plants and seem to Helicotylenchus spp. (the spiral nematode),
attack fruit plants only secondarily, later in the Meloidogyne spp. (the Root-knot nematode),
summer. Because the two-spotted mite spends Paratylenchus spp. (the pin nematode),
half the growing season on the cover crop, Pratylenchus spp. (the root lesion nematode),
considerable control can be achieved through Tylenchorhynchus spp. (the citrus nematode),
cultural practices such as minimizing or Xiphinema spp. (the dagger nematode).
eliminating weeds around and under the vines. Currently, none of the above mentioned genera
Each adult female produces 40 to 100 have been specifically connected with declining
eggs, and the average adult life span is 15 to 30 vine growth in Colorado vineyards, however poor
days but may be up to two months. Unfertilized vine growth could be associated with these multi-
females produce only male young. Under average host parasitic roundworms.
growing conditions, probably 10 generations of The intent of this Guide is not to give a
mites are produced in a season. As temperatures description of the life cycles and associated
become cooler in the fall and the days shorter, the symptomatic injuries of each genera of nematode
females turn orange and congregate in branch but to inform the vineyardist of the problems that
crotches and under bark scales. Mite populations may occur. Since many vineyard sites in
experience considerable mortality over winter. Colorado are being planted in orchard ground, it
The injury caused by mite populations is would be of benefit to get a laboratory analysis of
largely confined to foliage feeding. This feeding the species present and the population levels.
causes collapse of plant cells and loss of vigor in Various laboratories throughout California and the
the vine. When infestations are heavy, the mite northwestern states offer a nematode detection
populations retard fruit color development to such service.
an extent that fruit quality may be downgraded.
High mite populations also can affect bud
formation.
Nematodes: Nematodes are microscopic,
multicellular, unsegmented, parasitic round
worms that live in the soil and feed on roots of
various plant species. Some general symptoms of
nematode injury to grapevines are overall vine
decline, yield reduction, weak vigor, greater
sensitivity to stress, poor root development, off-

61

Methods for controlling nematodes are bromide and 1,3-D, when properly applied, give
mainly limited to resistant rootstocks (see table 3), effective control, but nematode populations
preplant fumigation and clean nursery stock. frequently recolonize quickly following
Cover crops have been demonstrated to reduce incomplete fumigations.
nematode population levels. Research trials at the It is important to recognize that fumigants
University of California Kearney Field Station has are not only becoming less available (EPA
shown that the cover crop Cahaba white vetch registrations canceled) but also upset the total
exhibits nematode resistance and nematicidal microflora and fauna of the soil. The need for
properties. well balanced healthy soil, thus a healthy root
Soil fumigation studies in California have system, is significant for wine productivity and
determined that the preplant fumigants methyl longevity.

Weed Management
It is beneficial to take steps to reduce In Colorado native bindweed is the most common
perennial weed infestations before planting. This problem weed, and in orchards it is usually
will greatly help to control these perennial weeds managed with herbicides containing 2,4D (e.g.,
later. Annual weeds also can be controlled prior Dacamine, Weedar). This herbicide is NOT
to planting if proper steps are taken in the REGISTERED for use in vineyards and is very
preparation period. detrimental to grapes by causing grotesque leaf
Most weeds between grape rows can be distortion and reduced growth. Vine death can
controlled by cultivating, disking and mowing; result from 2,4-D applications. Spray drift and
however, weeds in the row are more difficult to contaminated tailwater can cause damage in
manage. Special hydraulic oes that retract to miss vineyards that have not been sprayed directly.
the vines (e.g., Clemons, Weed Badger) can be Glyphosate (Roundup) provides excellent
used to mechanically remove these weeds as can control of weeds in the vine row and can be
hand hoeing. Most growers, however, prefer the applied next to the trunks IF suckers have been
partial use of chemical herbicides. Several removed and IF applied before canes drop
herbicides are compatible with grapes, including towards the ground. Vines can be killed if the
soil active types (dichlobenil, diuron, herbicide is sprayed on green tissue! During
napropamide, oryzalin, simazine, trifluralin) and retraining of damaged vines, special precautions
foliar active types (glyphosate and paraquat). All must be taken to avoid spraying the shoots at
must be used carefully and in accordance with ground level.
their label requirements.

62

Bird Control
Birds of many species (e.g., starlings, vineyard row (posts, trellis, vines, etc.) and tied.
robins, blackbirds, and finches) are attracted to The plastic netting can be virtually a bird-proof
ripening grapes. This leads to both crop loss and enclosure when anchored to the ground or
bunch rot. A flock of 20,000 blackbirds in a two gathered under the vines and tied. the plastic
acre vineyard for 30 minutes can cause very netting is lightweight (approx. 3 lbs. per 1,000 sq.
significant damage. The problem is severe in ft. of 3/4 inch mesh size) and can be applied by
small vineyards and in those with neighboring hand or by machine. Most growers complain
trees. There are numerous noise and decoy severely when applying or removing the netting
methods available to keep birds away, for by hand, expecially if the wind is blowing. The
example, scare eye balloons, mylar reflective tape, netting snags and hangs up on what seems like
plastic bags, electric fencing, recorded distress everything in the vineyard (twigs, leaves, posts,
calls, 12 volt programmable electronic bird wire, your shoes, watch, etc.). Machine
deterents and propane canons. However, the most applicators make applying and removing the
reliable method is plastic netting. Plastic bird 5,000 ft. X 17 ft. wide rolls an easy task. One roll
netting typically comes in 5,000 ft. rolls that are of 3/4 inch mesh by 5,000 ft. X 17 ft. wide
14 or 17 ft. wide and are 3/4 inch mesh. The typically costs about $700.00.
plastic bird netting is draped over an entire

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Wine Grape Varieties for Colorado
Variety selection based on your palate is and enologically. Many of these varieties are of
not good viticultural judgement in Colorado or the European wine grape species, Vitis vinifera
any wine growing region. Unestablished markets which is generally recognized as producing the
and unsuitable climates are two very important best wines. Others are hybrids between Vitis
reasons worth considering before selecting a vinifera and native American grape species such
variety to plant in Colorado (see table 6, Relative as Vitis labrusca, Vitis rupestris, Vitis aestivalis,
Cold Hardiness of Grapevines Grown in and Vitis riparia. These hybrids were bred for
Colorado). The climate of a region and particular resistance to disease and pests and for increased
site strongly influence the survival, the maturation winter hardiness. Generally hybrids are
of grapes and the quality of wines which come somewhat more winter hardy than Vitis vinifera
from them. Planting varieties without established varieties and many bear prolific crops. The wine
markets could leave the grower out in the cold quality of the hybrids is often very good but
with no home for his crop. Since the 1990 edition sometimes is described as lacking a distinct
of this guide, more wineries have opened and new character. Currently, the market for hybrids is
markets established. This increased market has extremely limited and most wineries are only
been favorable for some varieties and not so for interested in Vitis vinifera grapes. All of the
others (see Figure 4). Research trials at OMRC varieties listed below are grown in well drained
have demonstrated several varieties can be grown moderately fertile clay loam textured soils.
quite well viticulturally

White Wine Varieties - Vitis vinifera moderate trunk damage. It matures fairly late, but
Chardonnay. This grape makes the reaches 20-22o Brix in the Grand Valley and
renowned white wines of Burgundy. It is one of usually retains 10 g/l TA. This is a suitable
the most winter hardy members of V. vinifera and balance for a wine that can be bottled with
generally of the highest commercial value. residual sugar. Colorado Riesling is characterized
Chardonnay reaches high sugars (22-24o Brix) in by its ability to develop the floral bouquets like
Colorado with desirable high acidity (8-10 g/l TA) those found in German Rieslings. Riesling vines
Currently, Chardonnay is the most widely planted are moderately vigorous with small to medium
wine grape in Colorado representing 30% of the clusters (.15 - .25 lb.). Because it ripens late, this
entire acreage and has an established market. variety should be planted in sites with longer
Chardonnay is an early ripening variety typically growing seasons. Riesling currently tends to
harvested the first two weeks in September. command a lower price per ton than Chardonnay
Mature clusters are small to medium sized (.2 - .4 while yields are comparable.
lb.) and amber colored with good sunlight Pinot blanc. This variety is moderately
exposure. Chardonnay is a moderately vigorous hardy in Colorado and matures early. It is a low
grower. The only drawback to Chardonnay is its to medium vigor vine that has very desirable sugar
slightly earlier budbreak that can result in crop : acid balances with potential as a varietal or
reduction by frost as the variety has poor blended wine. Pinot blanc clusters are small (.2 -
fruitfulness in secondary buds. .3 pound) and tight and thus subject to occasional
Riesling (White Riesling, Johannisberg bunch rot. Because of its low - medium vigor this
Riesling). This major variety of Germany has a variety is well suited for higher density plantings.
medium to hardy winter hardiness rating. Several
vines survived the 1989 freeze of -22oF with

65

Gewurztraminer. This early ripening, in other grape growing regions. Clusters are
orange-skinned variety is most famous in Alsace, medium sized (.2 - .5 lb.). Because of its higher
France. It is winter hardy and can bear a large vigor, Sauvignon blanc would benefit from a
number of clusters. Gewurztraminer is a medium lower density planting.
vigor, small (.2 - .35 lb.), tight clustered variety. Semillon. Semillon is widely planted in
Picking costs are often higher for this variety the Sauterne or Graves region of France where it
because of the difficulty removing the short is used to blend and soften Sauvignon blanc
stemmed clusters. This variety can be harvested wines. Semillon is moderately vigorous and
at desirable balances (i.e., 19-20o Brix, 7-8 g/l produces medium to large clusters (.3 - .75 lb.).
TA) with careful monitoring of its maturity in The berries are large and amber-yellow in color
September. The variety has shown significant when ripe. Semillon is medium-tender in
promise to produce its distinctive aromatic hardiness. The canes are larger in diameter than
qualities. It tends to command a somewhat higher the others mentioned above. Semillon is slow to
price than Riesling. leaf out in the spring. This variety would also be
Muscat blanc (Muscat Canelli). This more adapted to a low density planting.
aromatic, early ripening variety has potential to do Siegerebe. An aromatic (similar to Muscat
well in Colorado although it is less winter hardy blanc), orange-skinned, early maturing variety
than the preceding four varieties. As with that is typically harvested the second week in
Gewurztraminer, careful monitoring can allow August with low acids of 6-8 g/l TA. Siegerebe is
harvest with sufficient sugar and desirable acid a cross between Gewurztraminer and Madelaine
levels. Muscat blanc is a medium to high vigor Angevine. This variety is highly susceptible to
vine with medium sized clusters (.40 - 1.00 lb.) bird damage. It is not vigorous and thus is
and medium-large berries. Presently there are suitable for high density plantings. Although
relatively few producers of the variety in the U. S. somewhat unknown on the market, this
although the market is expanding. moderately hardy variety could become very
Pinot gris. Pinot gris also know as Pinot important for Colorado.
grigio in Italy, when ripe is a grayish-rose colored Rkatsiteli. Rkatsiteli originated in Russia
variety similar to Gewurztraminer. Pinot gris and Bulgaria. It has a low to moderately vigorous
evolved from Pinot noir and thus retains similar growth habit and has performed well in western
low to medium vigor growth characteristics. The Colorado. It's upright growth and small diameter
small clusters (.15 - .25 lb.) ripen early with good reddish canes are distinct. The fruit clusters are
sugar, acid and ph balances. Pinot gris is a new loose, slender, small to medium in size (.2 - .4 lb.)
variety to Colorado that shows good winter and produce wine and floral bouquets similar to
hardiness. Although the market potential is not Riesling. The berries have an elliptical football
known the grape is very versatile, and can shape and mature late in the season. Rkatsiteli
accommodate several winemaking styles (i.e. would be very adaptable to a high density planting
barrel fermentation, malo-lactic, sur lie aging etc.) on a more vigorous site.
Pinot gris has an established market in Oregon Rkatsiteli has a medium hardiness level.
and is becoming popular in Ohio. Availability of this variety is limited.
Sauvignon blanc. A popular variety Muller-thurgau. Muller-thurgau is widely
traditionally blended with Semillon in France to planted in Germany and was developed in 1924
make a dry dinner wine. Sauvignon blanc is a from a cross of Riesling and Sylvaner at the
vigorous variety and has a medium winter Geisenheim institute in Germany. The wine is a
hardiness level. Sauvignon blanc ripens early pleasant neutral wine and would be best utilized
about the same time as Chardonnay. The grape for blending. In Colorado, Muller-thurgau
produces distinct flavors of hay or grass common appears less hardy than Riesling. It has a low to

66

moderately vigorous growth habit and ripens Several Colorado growers have planted this
earlier than Riesling. variety and produced some good wines with fine
Viognier - Nationally, Viognier plantings floral bouquets. The vine has a moderately
total less than 600 acres. Viognier comes from vigorous growth habit and has a medium-tender
the northern Rhone Valley in France and has hardiness level. It produces good quality fruit and
recently become a popular variety in the US. ripens during mid-season. The clusters are loose
and small - medium (.2 - .4 lb.) in size.

White Wine Varieties -- Hybrid
Cultivars
Aurore. A popular hybrid in the eastern growth habit and its winter hardiness level
U. S., it matures very early and is subject to low appears better than Chardonnay (based on 3 years
acidity unless harvested at fairly low sugar. data). Chardonel breaks bud later than
Wines are fairly neutral and would be better Chardonnay and produces medium sized clusters.
utilized for blending. It is winter hardy, but not Thinning may be necessary during years of good
immune from damage. fruit set.
Seyval blanc. This hybrid grape has a Cayuga White. Cayuga, also developed at
very vigorous growth habit and is well suited for Cornell University, was released in 1972 as a
low density plantings and improved trellising for grape that would produce a European style white
better canopy management. Seyval produces a table wine. Cayuga is a cross of Seyval and the
fresh, crisp wine that is used to blend or with American species Schuyler. Cayuga grows well in
improved winemaking techniques (oak Colorado, producing vigorous growth with large
fermentation, sur lie aging, etc.) made into a (.3 - .85 lb.) loose clusters and big round golden
richer, longer-lived varietal wine. it is one of the berries. Cayuga is winter hardy. It is slow to
most winter hardy varieties planted in Colorado. break bud but ripens early. This hybrid produces
Seyval quite frequently needs cluster thinning to fruity wines that are slightly low in acidity (5-7 g/l
achieve high sugars (21-23o brix) and good acids. TA) but full bodied. Approximately 3 acres are
This medium sized loose clustered variety ripens currently planted to this promising variety.
early. Seyval would be well adopted to colder Vignoles. Vignoles also know as Ravat 51
sites. is widely planted in New York, Ohio and
Vidal blanc. This vigorous cultivar Michigan. Vignoles wines are usually very high
appears to be very hardy. The crop ripens late and in acid and quite often made into a sweet reserve
generally retains at least 1 percent TA, which is desert style. The growth habit of Vignoles is
difficult to utilize in a dry wine style such as that moderate and upright. Vignoles ripens very early,
for which the variety is gaining a good reputation the clusters are small, the berries are large and
in the eastern U. S. fleshy, not juicy. Vignoles is new to Colorado but
Chardonel. Chardonel, a hybrid appears to be winter hardy and might prove to be
developed at Cornell University, is a cross of a good late harvest style wine.
Seyval blanc and Chardonnay. Chardonel was
developed for its superior wine quality, high
productivity and cold hardiness. Chardonel looks
promising for Colorado. The wine is delicate with
light fruitiness and good body with very little
flavor characteristics of interspecific hybrid
grapes. Chardonel has a moderately vigorous

67

Red Wine Varieties - V. Vinifera normal Colorado conditions. Unfortunately, clean
Merlot. The Merlot grape produces one of the virus free Lemberger stock is unavailable and this
best wines from Colorado and is the second most should be considered before planting.
widely planted grape in Colorado representing Cabernet franc. Cabernet franc is
18% of the entire acreage. In most years, becoming popular with Colorado winemakers as a
Colorado Merlots are deep colored, very fruity blending wine. The wine is similar to Cabernet
and full bodied. It is often used as a blend to form sauvignon yet softer and more subtle and retains
a soft velvet-like quality to the finish of wines that the distinctive Cabernet aroma. Cabernet franc
might otherwise be harsh. Merlot has a moderate does not develop deep skin color. It has a
growth habit and is medium tender in hardiness. moderately vigorous growth habit and appears
It has small to medium (.2 - .4 lb) clusters that are slightly more winter hardy than Cabernet
loose to well-filled and have long stems. Hand sauvignon. The clusters are loose filled and small
harvesting goes quickly as stems are easily cut. to medium (.2 - .4 lb.) in size. It ripens later than
Merlot ripens fairly early and can achieve Merlot but earlier than Cabernet sauvignon. At
excellent sugar acid balances (24o brix, 8 g/l TA). harvest clusters often appear immature because of
Merlot has an established market in Colorado and the poor skin color, however fruit compositions
continues to be popular with winemakers. achieve excellent balances. Cabernet franc is well
Cabernet Sauvignon. The cool nights of know in the scientific community as a sensitive
Colorado and late-season ripening characteristics indicator plant for diagnosing leafroll virus.
of this variety tend to produce outstanding color When inoculated with the virus, it visibly
retention and an excellent balance of sugar, acid expresses symptoms (red leaves, green veins)
and Ph. This leads to a well-proportioned, full- much more profoundly than other varieties.
bodied wine. It's winter hardiness level is equiva- Sangiovese. This vigorous variety is one
lent to that of Merlot, its traditional blending of the most widely planted grapes in Italy where it
partner. This variety has a vigorous growth habit is a major component of Chianti wines.
and small to medium (.2 - .4 lb.) conical shaped Sangiovese is new to Colorado and its becoming
loose clusters. It is very easy to pick and because quite trendy in California. This variety ripens
of its late ripening would be a candidate for very late in Colorado and produces light colored
planting in sites with longer growing seasons. fresh fruity wines. The clusters are large and
Pinot noir. This variety, one of the loose filled with light red-colored large berries.
famous red Burgundies, is mentioned because it is Hardiness levels (based on 3 years data) appear
generally considered to be the most winter hardy equivalent to Merlot. The vines produce heavy
red variety. Pinot noir is a low vigor vine with crops that may require cluster thinning to achieve
small tight-filled clusters (.1 - .2 lb.). This variety sugars of 20-22o brix. Sangiovese would be a
adapts well to high density plantings. match for a low density planting on sites with the
Unfortunately it has yet to demonstrate an ability longest growing season.
to develop adequate color and character in Shiraz-Syrah. Syrah is a very dark
Colorado. One should not rule it out with future skinned grape that ripens late and in Colorado
experience; however, at this time the variety is produces wines with good acid, color and tannins.
best suited to sparkling cuvee' or blanc d'Noir The clusters are long, loose-filled and conical in
wine styles. shape weighing about (.2 -.45 lb.) each. The
Lemberger. This loose-clustered dark hardiness level of this moderately vigorous variety
pigmented variety shows promise for Colorado is similar to Merlot and Cabernet. Syrah, also
with very favorable sugar, acid and Ph parameters. known as Shiraz in Australia would be well suited
It is increasingly popular in Washington state and for the warmest sites with a longer growing
has moderately high winter hardiness under season.

68

Red Wine Varieties - Hybrid Cultivars Norton/Cynthiana. Norton also known as
Chancellor. Also known as Seibel 7053, Cynthiana produces very good wine with a deep
produces relatively full-bodied wines, is a loose- blue-black red color. The small to medium
filled clustered variety that ripens mid season. It clustered high acid variety was first discovered by
is a medium hardy variety. Dr. D.N. Norton of Virginia. Norton is an
Rougeon. A very hardy variety that American species Vitis aestivalis and is very
produces an early well-balanced crop with winter hardy. It's canes are very red in color with
excellent color. The loose-filled clusters are small buds. Norton blooms late and appears to
medium sized (0.35 lb.) and the berries are blue- have medium vigor.
black in color. This variety survived the 1989
freeze of -22oF with little trunk damage.
Dechaunac. Also known as Siebel 9549,
is very prolific, colors very early, but ripens late
season and may require thinning to mature the
fruit. This variety is extremely hardy, surviving
the 1989 freeze of -22oF with no cane or trunk
damage and very little latent bud damage. This
variety can produce up to 60 lbs./vine and should
be considered for low density plantings.

69

Table 6.

Relative Cold Hardiness1 of Grapevines Grown In Colorado
Very Hardy Hardy Medium Medium Tender
Concord Aurore Cabernet franc Cabernet Sauvignon
De Chaunac Baco noir Chancellor French Columbard
Niagara Cayuga Chardonnay Merlot
Norton/Cynthiana Chardonel Dolcetto2 Muscat blanc
Rougeon Delaware Gewurztraminer Sangiovese
Foch Lemberger Sauvignon blanc
Seyval blanc Pinot blanc Semillon
Pinot gris Shiraz
Pinot noir Viognier
Riesling
Rkatsiteli

Siegerebe
1
Hardiness is based on visual assessment and differential thermal analysis of vines grown in a
deep clay loam soil at Orchard Mesa Research Center.
2
Dolcetto is grafted to 1616 couderc rootstock.

70

Table Grape Varieties

Successful table grape cultivation in Colo- hardiness and sets loose clusters. It survived the
rado requires optimum cultural practices; but, eight winters prior to 1989, but was winter killed
with certain considerations, they can be grown to ground level by the -22oF temperatures during
with the same management skills as wine grapes. January of 1989.
The intent of this section in the Colorado Grape Other seedless varieties (e.g., Concord
Grower's Guide is to provide the grower with Seedless, Thompson Seedless, Flame Seedless)
additional information for table grapes that has have been tested at OMRC. However, their
not been addressed previously in the text. performance has been poor and they cannot be
Varietal selection is extremely important recommended for commercial production. There
and involves considerations of winter hardiness are many seeded varieties (e.g., Concord, Niagra,
and marketability. Information concerning per- Steuben, Golden Muscat, etc.) that can be suc-
formance of specific cultivars in Colorado is cessfully cultivated in Colorado; all have more
limited although some information does exist. A intense marketing challenges when competing
summary of vegetative growth and fruit character- with the more desirable seedless varieties.
istics for 15 of the most popular seedless table Pruning and improving grape quality are
grape cultivars that are currently available is two additional areas that should be modified from
provided in Tables 7 and 8. The following wine grape production. Pruning and training table
descriptions are of several varieties grown at grapes depends on variety and the overall objec-
Orchard Mesa Research Center that appear well tive of the operation. Pruning and training table
suited for the wine grape growing regions of grapes can be identical to that of wine grapes, but
Colorado. often should be modified to help equalize
Himrod. This white variety is a cross production for large average crops of high-quality
between Ontario X Sultanina (Thompson fruit. Most varieties mentioned above are vigo-
Seedless) and has excellent quality fruit which is rous and should be trained to a pruning system
juicy and sweet with pleasant flavor. This that allows for that vigor such as the Geneva
vigorous vine is moderately hardy; it survived the Double Curtain, Four Arm Kniffen and/or
1989 freeze of -22oF with little trunk damage. Umbrella Kniffen. These systems require more
Himrod tends to shed individual berries when trellis expense but may be better suited for the
picked; this should be considered before planting more vigorous varieties.
large acreages. Quality of table grapes can be improved
Interlaken. A second white variety that is by blossom thinning (i.e., removal of flower
also a cross between Ontario X Sultanina. This clusters before bloom and of immature clusters), a
vigorous vine bears heavy crops early in the cultural practice not typically performed on wine
season, has good flavor and is somewhat less grapes. Like pruning, thinning concentrates the
hardy than Himrod. activities of the vine into the remaining parts and
Lakemont. A third white variety of the strengthens the vine by limiting the crop without
same parentage as Interlaken (Ontario X Sultanin- diminishing the leaf area. Girdling, also called
a). It produces large compact clusters with quality ringing, is an old practice that improves set, in-
that approaches that of Himrod and ripens a week creases size of berries and advances maturation; it
or two later. It has moderate to low winter har- should NOT be performed in Colorado due to the
diness. increased risk of Crown Gall infection.
Suffolk Red. A large-berried, red seedless
grape with good quality. It has low winter

71

Table 7. Vegetative growth characteristics of seedless table grape cultivars.

Ripening Vine Yields/ Winter
Variety Season Vigor Vine Hardiness

Canadice Early Medium High High

Challenger Mid Season Medium Medium Medium

Concord
Seedless Late Mid Medium Low High

Glenora Mid Season Medium Low Low

Himrod Early Medium Low Medium

Interlaken Very Early Medium Medium Low

Lakemont Mid Season High High Low

Mars Early Medium Medium Medium

NY 63878.1 Mid Season Medium High Medium

Reliance Early High Medium High

Remaily Late Mid Medium High Low

Romulus Late Medium Medium Medium

Suffolk Red Mid Season High Low Low

Vanessa Mid Season Medium Medium High

Venus Very Early High High Medium

72

Table 8. Fruit characteristics of seedless table grape cultivars.

Berry Cluster Cluster
Variety Color Flavor Size Size Compactness

Canadice Red Good Medium Medium Tight

Challenger Red Good Large Medium Loose

Concord
Seedless Blue Fair Small Small Loose

Glenora Blue Good Medium Medium Compact

Himrod White Excellent Medium Medium Loose

Interlaken White Good Medium Medium Compact

Lakemont White Good Medium Large Compact

Mars Red Good Medium Small Compact

NY 63878.1 Red Excellent Medium Medium Compact

Reliance Red Good Medium Medium Loose

Remaily White Fair Large Large Compact

Romulus White Fair Small Large Compact

Suffolk Red Red Excellent Large Medium Loose

Vanessa Red Good Medium Medium Compact

Venus Blue Good Large Large Tight

73

Vine Sources (1995)
In the United States there are hundreds of grapevine nurseries and thousands of retail outlets for
grapevines. The following is a representative sample of suppliers from coast to coast that have good varietal
selection and certified stock availability.

Arroyo Seco Vineyards Inc. (V) FPMS* (V)
P. O. Box 395 Foundation Plant Materials Service
Greenfield, CA 93927 University of California
408-674-2318 Davis, CA 95616
916-752-3590
Bien Nacido Vineyards (V)
1253 Coast Village Road, Suite 102 Ge-No's Nursery (V)
Santa Barbara, CA 93108-3790 8868 Rd. 28
805-969-5803 Madera, CA 93637
209-674-4752
Borri Nurseries Inc. (V)
1150 Felta Road Grafted Grape Vine Nursery (A, FH, V)
Healdsburg, CA 95448 2399 Wheat Rd.
707-433-6045 Clifton Springs, NY 14432
315-462-3288
Concord Nurseries Inc. (A, FH, V)
10175 Mile Block Road Inland Desert Certified Grape Nursery (V)
North Collins, NY 14111-9770 Route 1, Box 1315
716-337-2485 Benton City, WA 99320
509-588-3405
Duarte Nursery, Inc. (V)
1555 Baldwin Road Meyer Orchards Nursery (V)
Hughson, CA 95326 3785 Gibson Rd., NW.
209-531-0351 Salem, OR 97304
1-800-GRAFTED 503-364-3076

Fairacre Nursery (A, FH, V) Sonoma Grapevines Inc. (V)
Rt. 1, Box 1068 1919 Dennis Lane
Prosser, WA 99350-9788 Santa Rosa, CA 95403
509-786-2974 707-542-5510

The codes after the source name show whether they carry Vinifera varieties (V), French-American
Hybrids (FH), or American varieties (A).
FPMS is a service unit created to provide virus-indexed plant materials for research and commercial
use. Private individuals or companies can contract with FPMS on a fee-for-service basis to have special
grape varietal selections heat treated and virus tested as necessary to qualify them for Foundation stock
status. Contracts and fee schedules are available from FPMS upon request.

74

Sources for Vineyard Supplies
A. M. Leonard, Inc. Horticultural and Viticultural tools
P.O. Box 816
Piqua, Ohio 45356
1-800-543-0633

Barnel International, Inc. Horticultural and Viticultural tools.
1075 NW Murray Rd., Suite 256
Portland, OR 97229
1-800-877-9907

Fruita Cooperative Fertilizer
1650 U.S. Highway 6 50
Fruita, CO 81521
970-858-3667

Grand Junction Pipe Supply Irrigation piping and supplies
2868 Highway 6 24
Grand Junction, CO 81501
970-243-4604

Munroe Pump Pumps
735 South 9th
970-242-6810

Orchard Valley Supply Complete vineyard materials, supplies and
Vineyard Orchard Supply equipment.
Route 1, Box 41-B
Fawn Grove, PA 17321
Phone: 717-382-4612
FAX: 717-382-4612

Rears Manufacturing Co. Vineyard equipment
2140 Priarie Rd.
Eugene, OR 97402
1-800-547-8925

T. G. Schmeiser Co. Vineyard drill, Till and Pak, Culti-Plow, and
Box 1047 land levelers.
Fresno, CA 93714
1-209-268-8128

75

The Grower Supply Center Complete vineyard materials, supplies, and
2415 Hartford Road equipment.
Fallston, MD 21407
410-931-3111

United Fruit Growers Pruning equipment, fertilizer, insecticides,
144 Kluge Ave. hand tools.
Palisade, CO 81526
970-464-5671

Waterford Corporation Trellis supplies and installation.
404 N. Link Lane
Box 1513
Fort Collins, CO 80522
970-482-0911

Western Implement Tractors, implements, hand tools, posts, wire,
2919 North Avenue etc.
970-242-7960

Wildlife Control Technology Inc. Bird netting
2501 N. Sunnyside Ave #103
Fresno, CA 93727
1-800-235-0262

76

Vineyard Development and Production Cost Assumptions
Projecting the true costs of establishing or $8.00 per hour. This wage rate is determined as
maintaining a vineyard is extremely difficult. the net cost to growers for hired labor which is
This is particularly true in the case of small paid a cash wage of $6.00 per hour with an addi-
acreages where various compromises can be made tional $2.00 per hour for payroll expenses (social
to trade labor costs for equipment costs. Many security, taxes, workmens compensation
experienced growers, researchers, extension staff, insurance, withholding taxes, record keeping,
consultants, and retailers were involved in the etc.). The cost of an irrigation system can vary
following cost estimate study. A number of broad widely -- from $500 for a gated pipe system to
assumptions were made to provide a common $1500 / acre for an automated, microsprinkler or
basis for these costs. First, we assumed that we pressure compensating emitter system. The
were establishing a new vineyard on open ground automated drip irrigation system itemized is based
with no improvements. All prices for capital on a horizontal stainless steel sand media filter
improvements and equipment are new and in 1996 with automatic backflush, a centrifical sand
dollar values. Next, we assumed that certified separator, a flow meter, a computerized controller
virus free #1 self rooted Chardonnay vines or a and a chemical injector.
similar variety were planted with a production life Weed control costs are shown using a in the row
expectancy of 30 years following a four year hydraulic grape hoe. In addition to mechanical
establishment period. The sample vineyard is cultivation, herbicide application such as
planted at a density of 871 vines per acre. The glyphosate was figured for controlling the
spacing is 5 feet between vines and 10 feet be- persistent bindweed. The production costs are
tween rows. The trellis system is a six wire shown on a per acre basis (Table 10) and assume a
vertical shoot positioned system with one stake at yield of 4 tons per acre.
each vine and 4 inch by 8 foot line posts every 30 These general assumptions were used to develop
feet. The traditional 3 post H-brace system was the vineyard establishment and production costs
used at both ends of every row for anchoring the that follow. The example cost sheets (Tables 9
trellis. and 10) are intended to itemize the major cost
We assumed that labor used in wine grape factors and indicate their relative importance.
establishment and production is valued at

77

Table 9. Vineyard establishment costs: Mesa County, Colorado, 1996, includes new equipment, drip
irrigation, 6 wire vertical shoot positioned trellis and 1 metal stake per vine.

Item 10 Acres
Equipment
Tractor (40 HP) 20,000.
Truck (3/4 ton) 17,000.
Sprayer (200 gal vineyard airblast) 8,000.
Weed Sprayer (100 gal) 2,000.
Trailer 1,000.
Disk 3,000.
Hydraulic grape hoe (Clemons, badger, etc.) 4,000.
Chopper 1,500.
Auger 1,500.
7' Blade 800.
Springtooth 1,200.
Shop tools 2,500.
Pruning Shears 80.
Misc. Equipment (staples, strainers, tie tape etc.) 1,000.
$63,580.

Capital Improvements
Shop Storage Building (33' x 45' metal building) 9,000.
Irrigation System (automatic, drip), @ $1,500/A 15,000.
5' Grape Stakes, steel epoxy coated 16 gauge, 871/A @ 1.40 ea. 12,194.
Treated Posts, 4 x 8' and 4 x 10' 200/A @ 6.25/post 12,500.
Wire 12.5 gauge high tensile, 4000' roll (12 rolls/A) 6 wire trellis 7,800.
1 yr, #1 self rooted cuttings, 871/A @ $.80/vine 6,968.
$63,462.

Overhead, Labor ($8/hour) Materials
Layout Mark, (5 Hr/A) + $50 rental 450.
Preplant weed control, (1 Hr + $70 material) /A 780.
Preplant Land Prep., chisel, plow, disk 2X, float, $135/A 1,350.
Post Driving, $2/post @ 200 posts/A 4,000.
Trim plant @ 21 Hr/A 1,680.
String wires, staple set stakes @ 40 Hr/A 3,200.
Train and Prune @ 25 Hr/A-2nd yr + 12 Hr/A-3rd yr 2,960.
Cultivate, 5X @ 4 Hr/A (all years) 1,600.
Mildew Control, 4X @ (1 Hr + $16 material) /A 960.
Fuel and Repair, $90/A/yr all years 900.
Water and Taxes, $55/A/yr 550.
$18,430.

TOTAL $145,476.
Per Acre $14,547.

78

Table 10. Estimated annual per acre vineyard production costs.1 (5 x 10 spacing, 871 vines/A)

Item Detail (per Acre) Cost/Acre

Fuel and Repair $90 $ 90.00

Water Taxes $55 55.00

Mildew Control 6X @ (1 Hr + $16 mat.) 144.00

Herbicide 1X @ (2 Hr + $60 mat.) 76.00

Pruning $.22/vine 192.00

Brush disposal 1 Hr 8.00

Canopy positioning 8 Hr 64.00

Suckering 6 Hr 48.00

Mechanical weed control (Hydraulic hoe) 5X @ 2 Hr ea. 80.00

Irrigate .5 Hr/week (4 months) 64.00

Picking $94/ton 376.00

Fertilizer, Ammonium Sulfate + micronutrients 50.00

Cultivate, mowing/discing 3 X @ 1.5 Hr each 36.00

Miscellaneous Labor Supplies 50.00

TOTAL per acre $ 1,333.00

1
Based on 1996 data and labor costs of $8.00 per hour.

79

Useful Books and Publications
Below is a list of books and publications that growers should consult as additional background
reference material to the Colorado Grape Growers Guide.

General References
From Vines to Wines. 1985. J. Cox. Garden Way Publishing, Pownal, VT. 253 pp.

General Viticulture. 1974. A. J. Winkler, J. A. Cook, W. M. Kliewer, and L. A. Lider. Univ. of Calif.
Press, Berkeley. 710 pp.

Grape Growing. 1976. R. J. Weaver. John Wiley Sons, Inc., New York. 371 pp.

Grape and Wine Production in the Four Corners Region. 1980. E. A. Mielke, et. al. Technical
Bulletin No. 239, University of Arizona. 116 pp.

Grape Production in Colorado: An Evaluation of Grape Varieties for Wine Production and of Grape
Production Risks and Profit Potentials. 1985. R. Hamman and R. Renquist. Report prepared for the
Colo. Dept. of Agric. 12 pp.

Knowing and Making Wine. 1981. Emile Peynavd. John Wiley Sons Inc., New York, NY. 391 pp.

The New Frank Schoonmaker Encyclopedia of Wine. 1988. Alexis Bespaloff. William Morrow and
Company, Inc., New York, nY. 624 pp.

Oregon Winegrape Growers Guide, 4th Edition 1992. Ted Casteel. The Oregon Winegrowers
Association, 1200 NW Front Avenue, Suite 400, Portland, Oregon 97209. 258 pp.

Proceedings of the Second International Symposium for Cool Climate Viticulture and Oenology. 1988.
New Zealand Soc. for Viticulture and Oenology, Auckland, New Zealand. 365 pp.

The Production of Grapes and Wine in Cool Climates. 1987. David Jackson and Danny Schuster.
Butterworths of New Zealand. 192 pp.

Rootstock Seminar, A Worldwide Perspective. 1992. Proceedings American Society for Enology and
Viticulture, June 1992. Reno, Nevada. 84 pp.

Sunlight into Wine, A Handbook for Winegrape Canopy management. 1991. Richard Smart Mike
Robinson. Wine titles, Australian Industrial Publishers Pty. Ltd. 88 pp.

Viticulture Volume 2 Practices. 1992. Coombe, B. G. and P. R. Dry. Winetitles 2 Wilford Avenue,
Underdale SA 5032 Australia. 376 pp.

80

Frost Winter Hardiness/Injury
Minimizing Winter Damage: Site selection, vineyard establishment, and maintenance. 1979. W. Wolfe.
Proc. Wash. St. Grape Society. 9:67-75.

Pruning Effects on Cold Hardiness and Water Content During Deacclimation of Merlot Bud and Cane
Tissues. 1990. R. A. Hamman Jr., A. R. Renquist, and H. G. Hughes. Am. J. Enol. Vitic. 41(3):251-
260.

Seasonal Carbohydrate Changes and Cold Hardiness of Chardonnay and Riesling Grapevines. 1996. R.
A. Hamman, Jr., I. E. Dami, T. M. Walsh, and C. Stushnoff. Am. J. Enol. Vitic. 47(1): (in press).

Vine Hardiness: A part of the problem of hardiness to cold in N.Y. vineyards. 1971. N. Shaulis. Proc.
New York St. Hort. Soc. 116:158-167.

Wine Grape Performance of 32 Cultivars in Western Colorado 1982-1986. 1993. R. A. Hamman Jr.
Fruit Varieties Journal 47(1):59-63.

Pest Management
Compendium of Grape Diseases. 1988. R. C. Pearson and A. C. Goheen, eds. APS Press, The Am.
Phytopath. Society, 3340 Pilot Knob Road, St. Paul, Minnesota, 55121. 93 pp. [Cost $20.00]

Grape Pest Management. Revised 1991. D. L. Flaherty, et. al., eds. Pub. No. 3343. Div. of Agric.
Sci., Univ. of Calif. 416 pp.

Insect and Mite Pests Associated with West Slope Wine Grapes. 1994. B. C. Kondratieff W.
Cranshaw. Technical Report TR94-1. Agricultural Experiment Station, Colorado State University. 12
pp.

Phylloxera Issue. 1990. B. Strik, ed. The Wine Advisory Board Research Report (Special Report)
Special Issue (Sept.): 1-17. Published jointly by the [Oregon] Wine Advisory Board and Oregon State
Univ. Ext. Service, Corvallis, OR. 17 pp. (+ 4 pp. insert with color photos.)

Vineyard Pest Management: Alternatives for the future. 1992. Publication compiled for the American
Society for Enology and Viticulture workshop May 1992. Napa Valley. 33 pp.

Economic/Cost Analyses
Cost Analysis of Selected Wine Grape Vineyard Production Practices in Washington. 1983. D. Kirpes,
R. Folwell, and M. Ahmedulla. EB 1200. Wash. St. Univ. Coop. Ext., Pullman, WA. 16 pp. [Cost
$0.50]

The Economics of Establishing and Operating a Concord Grape Vineyard. 1990. J. G. Schimmel, R. J.
Folwell, and R. Wample. EB1572. Wash. St. Univ. Coop. Ext., Pullman, WA. 10 pp (+ 13 tables).
[Cost $0.50]

Wine Grape Vineyard Development in Washington and Economic Perspectives. 1986. S. Lutz, R.
Folwell, M. A. Castaldi. EB 1398. Wash. St. Univ. Coop. Ext., Pullman, WA. 56 pp. [Cost $1.25]

81

Viticulture Trade Magazines Grape and Wine Resources on the
Internet
Grape Grower
Published monthly, Munford Publications, Inc., 1. U. C. Davis
4974 E. Clinton Way, Suite 123, Fresno, CA http://pubweb.ucdavis.edu/Documents/wine/venl.
93726-1558, 209-252-7000 html

Practical Winery Vineyard 2. Food Science Technology Department
Published bimonthly, 15 Grand Paseo, San http://aruba.nysaes.cornell.edu/fst
Rafael, CA 94903, 415-479-5819
3. The Wine Research Extension at Cornell
Vineyard Winery Management http://aruba.nysaes.cornell.edu:/FST/MARKET/w
Published bimonthly, J. William Moffett ineries.html
Box 231, Watkins Glen, NY 14891
607-535-7133 4. All About Wine
http://www.aawine.com/index2.html
The Wine Spectator
Published biweekly, M. Shanken 5. CSIRO Grapevine
Communications, Inc. http://cgswww.adl.hort.CSIRO.au/
Opera Plaza, Suite 2040, 601 Van Ness Ave., San
Francisco, CA 94102 6. Virtual Vineyards
1-800-752-7799 http://www.virtualvin.com

Wines Vines 7. Not Just Cows List of Agricultural List Servers
Published monthly, The Hiaring Company http://www.lib.lsu.edu/sci/njc.html#1 listserv
1800 Lincoln Ave., San Rafael, CA 94901-1298
415-453-9700 8. What is Sustainable Agriculture
http://www.sarep.ucdavis.edu/sarep/concept.html
Wine Business Monthly
867 W. Napa St, Sonoma, CA 95476 9. Organically-Grown Grapes
707-939-0822 http://www.fetzer.com/
707-939-0833 (Fax)
10. Wine Business Monthly
http://smartwine.com

11. Wine Wizards
http://www.wines.com

82

Figure 6. Seven wire vertical shoot positioned trellis, Cordon training.

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