The document defines a pest as any organism that interferes with human health, food supply, or quality of the environment. It notes that approximately 1 million insect species have been named, with 500,000 being herbivorous plant-eating insects and 3,500 of those causing problems for humans. Pests are classified based on their population levels relative to economic thresholds and whether they are occasional, key, or potential pests. The document also describes different types of insect damage and symptoms caused by biting/chewing and piercing/sucking insects.

1. Pest
 A pest is anthropocentric and circumstantial
term; one man’s pest might be another’s pet.
Derived from French -‘Peste’ and Latin - ‘Pestis’
meaning plague or contagious disease
Any organism that interferes with our health and
comfort, the quality and quantity of our food
supply, our forest and building, our domestic
animal and many other aspects of quality of our
environment
Potential agricultural pests are:- insect, pathogen,
weed & rodent
Approximately one million insect species named.
500,000 (50%) are herbivores that eat plants and
compete with us.
3500 (0.7% of herbivores) cause us problems.
200 insect species are serious pests.

2. Introduction
 General equilibrium position (GEP): Average
density of a population over a long period of time,
around which the pest 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

3. 1. Based on population level in EIL
Occasional pests: GEP is below the EIL usually; Rarely they
cross EIL; Can be controlled by spraying e.g. Rice hispa
 Key pests: 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
 Potential pests: They are not pests at present; GEP always less
than EIL; If environment changed may cause economic loss e.g.
S. litura in hilly region.
2. Based on hosts association
Monophagous insects: mulbery silk worm
Oligophagous insects: PTM, DBM,
 Polyphagous insects: locusts, bollworm etc.

4.  Done in order to apportion loss occasioned by
particular insect pests and to know when to initiate
control measures.
Estimated by sampling.
Pests are usually sampled so that their abundance can
be predicted, losses attributable to them measured and
the damage they cause prevented.
Sampling may be direct wherein insects are counted
directly on the plant parts (e.g. flea beetles on okra
leaves); or indirect where insect populations are
estimated via the damage they cause (e.g. stem borers).

5. Direct damage is when the harvestable part of a crop
is affected (e.g. cowpea pod)
Indirect damage is when the non-harvestable portion
of the crop is affected (e.g. maize leaf)
Types of insect damage
1. Biting and chewing insects
holing of leaves thereby reducing photosynthetic areas
 boring of the stem causing reduction in plant vigor
 scrapping of leaf surface causing burning of leaves
 rasping of leaf edges
 mining of leaves
 cutting of roots
 destruction of buds or growing points
 flower abortion
 premature fruit fall

6. 2.Piercing and sucking insects
cause loss of vigor due to removal of sap (wilting)
sucking of sap from leaves or stems
 staining or discoloring of seeds
transmission of diseases
Indirect Effect
make crops much more difficult to cultivate
may make crops develop spreading habit which
makes weeding and spraying difficult
contamination of produce thereby reducing quality
and marketability

7. Chewing type of symptoms
 Defoliation: Large caterpillars, Sawflies,
Slugs, Grasshoppers
Shot holes: Small caterpillars, Leaf
beetles
 Notched margins: Black vine weevil,
Two banded Japanese weevil, Fuller
rose beetle, rhododendron root weevil
 Skeletonization: Elm leaf beetle,
Japanese beetle

8. Foliage Discoloration Symptom
 Stippling:
• Fine: Spider mites, Eriophyd
Mites
• Medium-Coarse: Lace bugs, Plant
bugs, Leaf hoppers
• Coarse: Holly Leaf Miner
 Streaking: Thrips
 Mining:leafminer (serpentine
mines)
 Yellowing: Aphids, Whiteflies,
Mealybugs

9. Leaf / Trunk / Branch
Distortion Symptom Types
Leaf cupping:
Boxwood psyllid,
Aphids
 Leaf or twig galling:
Gall wasps and flies
 Bark ripping or
cracking: Moth and
Beetle borers

10. Shoot / Twig / Branch
Dieback Symptom Types
Shoot dieback: Pine
tip moths
Branch dieback:
Boring beetles and
moths, Twig girdler,
Twig pruner, Root
feeding beetle larvae,
Scale insects

11.  Honey dew and Sooty
mold: Aphids, Soft scale
insects, Leaf/Tree/Plant
hoppers, Whiteflies,
Psyllids, Mealybugs
Fecal spots: Thrips,
Some plant bugs, Leaf
beetles
Silk: Tent caterpillars,
Web worms, Leaf tiers

12.  Spittle: Spittlebugs
 Pitch / Gum masses
or Sap flow: Larvae of
some Moths (peach tree
moth), Beetles, and
Midges
 Frass: bark eating
caterpillers, stem borers

13.  Protective coverings:
Bagworms, Case bearers
Fluffy white wax: Mealybugs,
Some aphids, Some scale insects,
Some planthoppers
Soft or hard white, brown, gray
to black wax covers: