Identification, symptoms and nature of

damage of Gundhi bug, Thrips and Armyworm

Introduction

(Cont.....)

Damage by several insect pests is one of the major factors

responsible for lower rice yields. Intensive cultivation of rice

has aggravated the problems of various biotic constraints like

insects, diseases, and weeds.

Rice (Oryza sativa L.) is the staple food crop of humid and sub-humid

Asia, cultivated in 112 countries covering every continent and is

consumed by 2500 million people in the developing countries. Rice is

grown on an area of 44.3 million hectares in different agro-climatic regions

of the country with a production of 89.09 million tonnes. However, India’s

productivity is much lower than neighbouring countries.

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Rice gundhi bug, thrips and

armyworm are important

pests of rice and inflict heavy

yield losses during certain

years. Their effective

management thus becomes

essential to ensure good

harvest to the farmers.

Pest problem being discussed with farmer

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Identification

Gundhi bug adult

1. Gundhi bug (Leptocorisa acuta)

Gundhi bug adults are slender yellowish

green bugs with long antennae and legs.

Nymphs resemble adults except for

presence of wings. These bugs produce

typical dirty smell in the field and hence

this pest is known as “gundhi bug”. The

smell helps in detecting presence of this

pest in the field.

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Nature of Damage

Gundhi bug eggs

Gundhi bug Nymph

Female lays several dark brownish

eggs in long rows on underside the

leaves.

Both nymphs and adults suck juice from

developing grains during milky stage of

the crop.

The affected grains remain chaffy and

black spot develops on them due to

fungal infection at the point of puncture.

Under severe infestation several empty

grains can be found in affected panicles. Next

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Echinochloa (Sawan grass)Alternate host plant of gundhi bug

Staggered planting intensifies its

incidence in an area as bugs get grains

in milky stage for longer period of time

and they migrate from field to field.

Sawan grass (Echinochloa) weed is its

alternate host plant and it should be

destroyed in order to reduce incidence

of this pest.

Economic threshold level:

1 bug/hill

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2. Thrips (Stenctenchaetothrips biformis)

Rice thrips- adultCourtesy: agritech.tnau.ac.in

Rice thrips-NymphCourtesy: agritech.tnau.ac.in

(cont...)

Identification

Thrips are minute thin black-brown

insects which jump on disturbance.

These can be found by removing the

leaf sheath at its junction with stem.

Both nymphs and adults damage the

crop during seedling stage in the nursery

as well in the main field.

They suck sap from leaves resulting in

yellowish streaks on them. Later, the

leaves curl longitudinally from margins

inwards leading to sharply pointed leaf

tips resembling needles. Next

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Silvery streaks on rice leaves caused by thrips Courtesy: agritech.tnau .ac.in

Infestation at panicle stage causes

unfilled grains or spikelet sterility.

Sometimes, complete panicle remain

chaffy and are confused with white-ear

damage of the stem borer.

However, thrips damage can be

differentiated from that of stem borer

damage in the sense that while white-ears

can be easily pulled out but panicles

affected by thrips can not be removed with

that ease. Besides, panicles damaged by

thrips have some black spot at their

puncture points.

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Armyworm adult

3. Armyworm (Mythimna separata)

Identification

The armyworm, also called climbing

cutworm or ear-cutting caterpillar, was

named so because of larvae’s habit of

appearing in army-like enormous

numbers.

Adults are dirty brown stout moths and

larvae are also brownish in colour.

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Nature of Damage

(cont.....)

Only larvae damage the crop. Though sporadic in occurrence, this pest

may cause heavy losses during sudden outbreaks.

Larvae are nocturnal in nature and hide in loose soil, under trash, in

stubbles and in whorls during day time. During night they become

active and feed on foliage.

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When high populations occur, army of

swarming larvae march in the field and

feed voraciously on leaves.

Armyworm larva

Absence of standing water in the field

facilitates their migration. Severely attacked

field gives a grazed appearance. The larvae

cut the ear-heads in addition to damaging the

foliage.

Economic threshold level (ETL): 1 larva/hill

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Let us sum up

Gundhi bugs produce typical foul smell in the field and hence this pest is

known as “gundhi bug”.

Both nymphs and adults of gundhi bug suck juice from developing grains

during milky stage of the crop.

Echinochloa weed is alternate host plant of gundhi bug and it should be

destroyed in order to reduce incidence of this pest.

Both nymphs and adults of thrips suck sap from leaves causing

yellowish streaks on them. Later, the leaves curl longitudinally from

margins inwards leading to sharply pointed leaf tips resembling needles.

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Panicles damaged by thrips have black spots at their puncture points.

The armyworm, also called climbing cutworm or ear-cutting caterpillar, is named

so because of larvae’s habit of appearing in army-like enormous numbers.

Absence of standing water in the field facilitates migration of armyworms.

Severely attacked field gives a grazed appearance.

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