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Pest - Definition, Categories, Causes For Outbreak, Losses Caused By Pests
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Lecture 11: PEST - DEFINITION, CATEGORIES, CAUSES FOROUTBREAK, LOSSES CAUSED BY PESTS
PEST - Derived from French word ‘Peste’ and Latin term ‘Pestis’ meaning
plague or contagious disease
- Pest is any animal which is noxious, destructive or troublesome to man or his
interests
- A pest is any organism which occurs in large numbers and conflict with man’s
welfare, convenience and profit
- A pest is an organism which harms man or his property significantly or is likely to
do so (Woods, 1976)
- Insects are pests when they are sufficiently numerous to cause economic damage
(Debacli, 1964)
- Pests are organisms which impose burdens on human population by causing
(i) Injury to crop plants, forests and ornamentals
(ii) Annoyance, injury and death to humans and domesticated animals
(iii) Destruction or value depreciation of stored products.
- Pests include insects, nematodes, mites, snails, slugs, etc. and vertebrates like rats,
birds, etc.
Depending upon the importance, pests may be agricultural forest, household,
medical, aesthetic and veterinary pests.
CATEGORIES OF PESTS
Based on occurrence following are pest categories
Regular pest: Frequently occurs on crop - Close association e.g. Rice slem borer,
Brinjal fruit borer
Occasional pest: Infrequently occurs, no close association e.g. Caseworm on rice,
Mango stem borer
Seasonal pest: Occurs during a particular season every year e.g. Red hairy caterpillar
on groundnut, Mango hoppers
Persistent pests: Occurs on the crop throughout the year and is 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
Based on level of infestation
Pest epidemic: 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
Endemic pest: Occurrence of the 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
, Parameters of insect population levels
General equilibrium position (GEP)
The average density of a population over a long period of time, around which
the pest population over a long period of time, around which the pest population tends
to fluctuate due to biotic and abiotic factors and in the absence of permanent
environmental changes.
Economic threshold level (ETL)
Population density at which control measure should be implemented to
prevent an increasing pest population from reaching the ETL.
Economic injury level (EIL)
The lowest population density that will cause economic damage
Damage boundary (DB)
The lowest level of damage which can be measured. ETL is always less than
EIL. Provides sufficient time for control measures.
PEST CATEGORIES ACCORDING TO EIL, GEP AND DB
(i) Key pest
- Most severe and damaging pests
- GEP lies above EIL always
- Spray temporarily bring population below EIL
- These are persistent pests
- The environment must be changed to bring GEP
below EIL
e.g. Cotton bollworm, Diamond backmoth
(ii) Major pest
- GEP lies very close to EIL or coincides with
EIL
- Economic damage can be prevented by timely
and repeated sprays e.g. Cotton jassid, Rice
stem borer
(iii) Minor pest/Occasional pest
- GEP is below the EIL usually
- Rarely they cross EIL
- Can be controlled by spraying e.g. Cotton
stainers, Rice hispa, Ash weevils
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