Lec. 15. Pests - Definition - Categories, Causes for outbreak of pests.ppt
- 1. AEN 202 MANAGEMENT OF BENEFICIAL AND HARMFUL INSECTS (2+1) LEC No. Title 15. Pests – Definitions - Categories – Causes for outbreak of pests – Losses caused by pests Dr. N. MUTHUKRISHNAN, Ph.D., PDF (Canada) Professor (Entomology) and Dean Tamil Nadu Agricultural University Agricultural College and Research Institute Vazhavachanur, Tiruvannamalai District Mobile: 9486257548
- 2. PEST DEFINITIONS – Derived from French word ‘Peste’ - plague or contagious disease – Latin term ‘Pestis’ meaning – noxious, destructive or troublesome • Any animal which is noxious, destructive or troublesome to man or his interests • Any organism which occurs in large numbers and conflict with man’s welfare, convenience and profit • Insects become pests when sufficiently numerous to cause economic damage (Debacli, 1964) • An organism which harms man or his property significantly or is likely to do so (Woods, 1976) • All insects are NOT pests
- 3. Pest
- 4. Pests include: Insects Nematodes Mites Snails Slugs, etc. Vertebrates like rats, birds, etc.
- 5. Pests are organisms which impose burdens on human population by causing Injury to crop plants, forests and ornamentals Annoyance, injury and death to humans and domesticated animals Destruction or value depreciation of stored products.
- 7. Based on occurrence • Regular pests • Occasional pests • Seasonal pests • Persistent pests • Sporadic pests Categories of Pests Based on level of infestation • Epidemic pests • Endemic pests Based on number of host plants infested • Monophagous pests • Oligophagous pests • Polyphagous pests Based on damage potential • Key pests • Major pests • Minor pests • Potential pests
- 8. CATEGORIES OF PESTS Based on occurrence • Regular pest: • Frequently occurs on crop • Close association • e.g. Rice stem borer, Brinjal fruit borer
- 9. CATEGORIES OF PESTS Based on occurrence • Occasional pest: • Infrequently occurs • No close association • e.g. Caseworm on rice, Mango stem borer
- 10. CATEGORIES OF PESTS Based on occurrence • Seasonal pest: • Occurs during a particular season every year • e.g. Red hairy caterpillar on groundnut • Depends on climatic conditions and local agricultural practices of region concerned • Twice a year May-June and August-October • Outbreak occurs only once in Rajasthan during August- October • Mango hoppers
- 11. Based on occurrence • Persistent pests: – Occurs on the crop throughout the year – Difficult to control – e.g. Chilli thrips, mealy bug on guava • Sporadic pests: – Pest occurs in isolated localities during some period – e.g. Coconut slug caterpillar
- 12. Based on level of infestation 1) Epidemic pest: • Sudden outbreak of a pest in a severe form in a region at a particular time • e.g. BPH in Tanjore, RHC in Madurai, Pollachi 2) Endemic pest: • Occurrence of pest in a low level in few pockets, regularly and confined to particular area • e.g. Rice gall midge in Madurai, Mango hoppers in Periyakulam
- 13. CATEGORIES OF PESTS Based on the number of host plants attacked • Monophagous – Confined to a single species of plants – Mulberry silk worm-very rare monophagous pest to find – Most of monophagous pests –feed on a group of closely related plants • Oligophagous pest – Characteristically feed on a group of botanically related plants-within a single plant family – Diamond back moth –confined to plants of Cruciferae • Polyphagous pest – Accept many plants from a diverse range of plant families, even though preference still exist – Locusts, grasshoppers, hairy caterpillaers, gram caterpillar, cutworms, termites
- 14. Parameters of insect population levels General equilibrium position (GEP) Average density of a population over a long period of time, in the absence of permanent environmental changes Economic threshold level (ETL) Population density at which control measure should be implemented to prevent pest population from reaching EIL ETL- always less than EIL Provides sufficient time for control measures Index of making pest management decisions Economic injury level (EIL) Lowest population density that will cause economic damage Damage boundary (DB) Lowest level of damage which can be measured
- 16. EIL – This level or above control measures would not be useful ETL - Population density at which control measure must be taken
- 17. CATEGORIES OF PESTS BASED ON DAMAGE POTENTIAL (EIL, GEP AND DB) Key pest – Most severe and damaging pests GEP lies above EIL always - persistent pests e.g. Cotton bollworm, Diamond backmoth (DBM) Major pest – GEP lies very close to ETL or coincides with ETL e.g. Cotton leafhopper, Rice stem borer Minor pest/Occasional pest – GEP is below the ETL - Rarely cross ETL e.g. Cotton stainers, Rice hispa, Ash weevils
- 18. Sporadic pests GEP generally below EIL & ETL Sometimes crosses ETL and cause severe loss in some places/periods e.g. Sugarcane pyrilla, White grub, Hairy caterpillar Potential pests Normally do not cause economic damage GEP always less than EIL If environment changed may cause economic damage e.g. Tobacco cutworm
- 19. Pest outbreak Sudden increase in the number of an insect pest Causes for pest outbreak: 1. Deforestation 2. Destruction of natural enemies 3. Intensive and extensive cultivation (Monoculture) 4. Introduction of new crops, improved strains and use of high yielding varieties 5. Improved agronomic practices (Excessive use of ‘N’ fertilizers 6. Introduction of new pest in new areas / environment 7. Accidental introduction of foreign pests 8. Indiscriminate use of pesticides (Resurgence) 9. Large scale storage of food grains – stored product pest problems
- 20. CAUSES OF PEST OUTBREAK • Deforestation and bringing under cultivation – Pest feeding on forest trees - forced to feed on cropped- Biomass/unit area more in forests than agricultural land – Weather factors also altered - Affects insect development • Destruction of natural enemies – Due to excess use of insecticides, natural enemies – killed- affects natural control mechanism and pest outbreak occurs – Synthetic pyrethroids kill NEs
- 21. CAUSES OF PEST OUTBREAK • Intensive and Extensive cultivation – Monoculture (Intensive) leads to multiplication of pests – Extensive cultivation of susceptible variety in large area – No competition for food -multiplication increases – Stem borers in rice and sugarcane
- 22. CAUSES OF PEST OUTBREAK • Introduction of new varieties and crops – Varieties with favourable physiological and morphological factors cause multiplication of insects – Succulent, dwarf rice varieties favour leaf folder. – Cambodia cotton favours stem weevil and spotted bollworm – Hybrid sorghum (CSH 1), cumbu (HB1) favour shoot flies and gall midges
- 23. CAUSES OF PEST OUTBREAK • Improved agronomic practices – Increased N fertilizer - High leaf folder incidence on rice – Closer planting - BPH and leaf folder increases – Granular insecticides - Possess phytotonic effect on rice • Introduction of new pest in new environment – Pest multiplies due to absence of natural enemies in new area – Apple wooly aphid Eriosoma lanigerum multiplied fast due to absence of Aphelinus mali (Parasitoid)
- 24. • Accidental introduction of pests from foreign countries (through air/sea ports) • Diamondback moth on cauliflower (Plutella xylostella) • Potato tuber moth Phthorimaea operculella • Cottony cushion scale Icerya purchasi on wattle tree • Wooly aphid - Eriosoma lanigerum on apple • Psyllid - Heteropsylla cubana on subabul • Spiralling whitefly - Aleurodicus dispersus on hort. Crops • Tomato pin worm Tuta absoluta • Papaya mealybug, Paracoccus marginatus • Coconut rogous spiraling whitefly, Aleurodicus rugioperculatus • Tapioca mealybug Phenacoccus manihoti • Maize fall armyworm Spodoptera frugiperda
- 25. • Indiscriminate use of insecticides (Resurgence of pests) – Tremendous increase in the population of pests due to application of sub-lethal dose of insecticides – Insecticides applied for control one insect - tend to offer favourable physiological conditions for sucking insects – Deltamethrin, Quinalphos, Phorate - Resurgence of BPH in rice – Synthetic pyrethroids - Whitefly in cotton – Carbofuran - Leaf folder in rice • Large scale storage of food grains serve as reservoir for stored grain pests – Urbanisation - changes ecological balance – Rats found in underground drainage
- 26. Losses caused by pests Crop loss from all factors 500 million US $ annually world wide Estimated crop loss due to insect pest – 2,92,400 million rupees Insect pests - 15.6% loss of production Plant pathogens - 13.3% Weeds - 13.2% Yield loss: Reduction in yield caused by a single pest Direct loss: Refers to decrease in productivity (quantity) & consumer value (quality)
- 27. Estimated crop loss in various crops in India Estimated annual crop loss in India by insect pests = Rs.29,240 crores (Dhaliwal and Arora) Crop Yield loss (%) Wheat 3.0 Rice 10.0 Maize 5.0 Sorghum 5.0 Cotton 18.0 Pulses, groundnut 5.0 Sugarcane 10.0 Fruits 25.0 Coffee 8.0 Coconut 5.0
- 28. Crop losses due to insect pests in India • 15.7 per cent which account for annual losses of US$ 36 billion (Dhaliwal et al., 2019)