Identification, symptoms and nature of damage of Gundhi bug, Thrips and Armyworm

1. Identification, symptoms and nature of damage of Gundhi bug, Thrips and Armyworm

2. Introduction • 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. • 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. Next Previous End (Cont.....)

3. 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 End Previous Next

4. 1. Gundhi bug (Leptocorisa acuta) • Identification • 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. Gundhi bug adult End Previous Next

5. Nature of Damage • Female lays several dark brownish eggs in long rows on underside the leaves. Gundhi bug eggs • 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. Gundhi bug Nymph Next End Previous

6. 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 Echinochloa (Sawan grass) Alternate host plant of gundhi bug End Previous Next

7. 2. Thrips (Stenctenchaetothrips biformis) 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. Rice thrips- adult Courtesy: agritech.tnau.ac.in • 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. Rice thrips-Nymph Courtesy: agritech.tnau.ac.in End Previous Next (cont...)

8. 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. Silvery streaks on rice leaves caused by thrips Courtesy: agritech.tnau .ac.in End Previous Next

9. 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. Armyworm adult Next Previous End

10. Nature of Damage • 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. Next End Previous (cont.....)

11. When high populations occur, army of swarming larvae march in the field and feed voraciously on leaves. • 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 Armyworm larva Next End Previous

12. 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. Next End Previous

13. 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. Next