in this presentation the main focus is given on what basis we identify the plant damage by different insects whether in field conditions or in stored conditions. i hope that you will find it helpful while going through it.

1. Topic: Diagnosis Of Pests On The Basis Of
Plant Damage
NAME: Bhumika Kapoor
Regd. NO. : J-12-AGRI-457
COURSE: RAWE- 423
DIVISION OF ENTOMOLOGY

2. WHAT IS A PEST ???
• PEST- derived from French word ‘PESTE’ and Latin
term ‘PESTIS’ meaning “ PLAGUE OR CONTAGIOUS
DISEASES”.
• A Pest is any organism which occurs in large numbers
and conflict with man’s welfare, convenience and
profit.
• Pests include insects, nematodes, mites, snails,
slugs, etc. and vertebrates like rats, birds.

3. •Pest epidemic : for eg. BPH in Tanjore.
•Endemic pest: for eg. Rice gall midge in Madurai.
•Key Pest : For Eg. Cotton Bollworm And Diamond Back Moth
•Major Pest: For Eg. Cotton Jassid, Rice Stem Borer
•Minor Pest/ Occasional Pest: For Eg. Rice Hispa, Ash Weevils
•Sporadic Pest: For Eg. White Grub, Hairy Catterpillar
•Potential Pest: For Eg. S. Litura Is Potential Pest Of North
India.

4. A SYSTEMATIC APPROACH TO
DIAGNOSING PLANT DAMAGE
The Factors causing plant damage can be grouped into two
major categories :
• Living Factors: living organisms such as pathogens (fungi,
bacteria, viruses, nematodes) and pests (insects, mites,
mollusks, rodents...).
• Nonliving Factors: mechanical factors (i.e. breakage,
abrasions, etc); physical, environmental factors (extremes
of temperature, light, moisture, oxygen, lightning); and,
chemical factors (chemical phytotoxicities, nutritional
disorders, etc).

5.  Plant Identification And Characteristics. Establish what the “normal”
plant would look like at the time of year. Describe the “abnormality”:
Symptoms & Signs.
 Examine The Entire Plant And Its Community. Determine the primary
problem and part of the plant where initial damage occurred.
 Look For Patterns: On more than one plant? On more than one plant
species?
• Non-uniform damage pattern-(scattered damage on one or only a few
plant species) is indicative of living factors (pathogens, insects, etc.).
• Uniform damage pattern over a large area (i.e. damage patterns on
several plant species) and uniform pattern on the individual plant and plant
parts indicates nonliving factors (mechanical, physical, or chemical factors).
Delineate Time-development Of Damage Pattern:
• Progressive spread of the damage on a plant, onto other plants, or over an
area with time indicates damage caused by living organisms.
•Damage occurs, does not spread to other plants or parts’’ of the affected
plant.’ Clear line of demarcation between damaged and undamaged tissues.
These clues indicate nonliving damaging factors.

6. The location of the feeding damage on the plant caused by the insect’s feeding, and the
type of damage (damage from chewing or from sucking mouth parts) are the most
important clues in determining that the plant damage is insect-caused.
FEEDING HABITS
oCHEWING INSECTS eat plant tissue such as leaves, flowers, buds, and twigs.
The damage they cause (leaf notching, leaf mining, leaf skeletonizing, etc.) will help in
identifying the pest insect. Chewing insects can be beetle adults or larvae, moth larvae
(caterpillars), and many other groups of insects.
POTATO LEAF BETTLECAULIFLOWER CATERPILLER

7. oSUCKING INSECTS insert their beak (proboscis) into the
tissues of leaves, twigs, branches, flowers, or fruit. Damage caused by
these pests is often indicated by discoloration, drooping, wilting, leaf spots
(stippling), honeydew, or general lack of vigor in the affected plant. Aphids,
scale insects, squash bugs, leafhoppers and plant bugs are examples of
piercing-sucking insects.
APHIDS DAMAGE ON MUSTARD LEAF HOPPER DAMAGE ON GRAPES

8. Many insects feed within plant tissue during a part or all of
their destructive stages.
•BORERS: The larvae may bore into the terminal shoots
and cause death of the shoots as in the case of the cotton
bollworm, Earias spp.
COTTON BOLLWORM SUGARCANE BORER

9. •WORMS OR WEEVILS : The larvae bore into flower
buds and cause shedding. Such larvae are usually called
bud worms as in the case of the moringa budworm and
jasmine budworm, mango nut weevil, etc.
MANGO NUT WEEVIL RICE WEEVIL

10. • LEAF MINERS : When the larvae, being very
small, live in between the two epidermal layers of
the leaves and feed on the food material inside.
Some of the common examples are the citrus leaf
miner, the cashew and mango leaf miner, and the
buprestid leaf miner, etc.
CITRUS LEAF MINER TOMATO LEAF MINER

11. • GALLS: Mostly some species belonging to the
families Cecidomyiidae, Cynipidae, Aphididae, Psyllidae
and Aleyrodidae and the order Thysanoptera (thrips) are
known to cause plant galls on the different parts of
plants.
GALL BY FIG THRIPS BLOSSOM MIDGE ON MANGO

12. Subterranean insects are those insects that attack plants
below the surface of the soil. Many soil insects are host
specific and most of them damage the crops in their larval
stage as in wireworms, chafers, cutworms, flea beetles, etc.,
and only a few spend their life-cycle in the soil entirely.

13. The infestation may continue from the material stored earlier
and be carried over to fresh material stored later in a godown
or storage house as in the grain weevil, Sitophilus oryzae, which
infests single grains and the flour moth, Cadra cautella which
webs together the grains with silken threads and feeds on them.
GRAIN WEEVIL INDIAN MEAL MOTH

14. • Injury By Egg-laying: for eg: grapevine stem girdler
• Use Of Plant Parts For Making Nests: for eg: the leaf cutter
bee, Megachile anthracina.
• Insects As Disseminators Of Plant Diseases: for eg: aphids,
thrips, etc
WHITEFLYLEAF CUTTER BEESTEM GIRDLER