UNIT-4
MAJOR INSECT PEST OF AGRONOMICAL CROPS
A. CEREAL CROPS
1. MAJOR INSECT-PESTS OF RICE
a. Rice yellow stem borer (Scirpophaga incertulas; Lepidoptera: Pyralidae)
Life cycle:
Eggs 5-7 days- Larva 3-6 weeks - pupa 8-14 days - Adult
Damage:
Caterpillars of yellow stem borer are destructive in nature causing direct damage. to plant.
Eggs are laid on the tip of the leaves. After hatching caterpillar enter into the rice stem after wandering 1-2 hours on rice plant. It feeds on soft part of stem for about a week and hollows out stem completely.
Damage at vegetative stage causes death of central whorl and symptom is known as "Dead heart", while damage at reproductive stage of plant cause the death of emerging panicle known as "White head". This could be easily pulled out.
MANAGEMENT:
Remove the plant having symptoms of dead heart, destroy egg masses and remove infested seedlings from nursery to prevent the population buildup of rice borers in furthergeneration.
Collect and destroy all the rice stubbles at the time of first plowing after harvesting to prevent incidence of insects to the next year.
Generally early planting of rice escape from borer infestation.
Grow rice varieties such as IR-20, Taichung-176, chinung-142, Palung, Khumal-4,
Chandina which are moderately resistant to stem borer complex.
Spray Bacillus thuringiensis (Bt) based formulations such as DIPEL or BIOLEP@
3 g per litre water during evening hours, repeat application at 10 days interval. Trichogramma can be very effective and economical control as it can eliminate
the pest in the egg stage.
Spray pesticides like Dursban 20% EC (chlorpyrifos) @ 2 ml per liter water three times at 30, 50 and 75 days after transplanting if more than 10% dead hearts appear in the fields or apply Carbofuran @ 1-2 kg a.i per hectare in the rice field.
b. Brown Plant hopper (Nilaparvata lugens; Homoptera: Delphacidae)
Excess population causes ,hopper burn" usually observed in patches of the ripening phase of the crop. It also transmits Grassy stunt" virus disease. Its activities in rice field starts from the middle of August and under favorable environmental conditions of drought.
Life cycle
Eggs 6-9 days Nymph 10-18 days Adut
Damage:-
BPH sucks cell sap from leaf sheath. Infestation during early stage of plant
growth reduces the number of tillers, plant height in genera
Under severe infestation leaves appear dry and brown. Heavy infestation produce symptoms of "hopper burn" i.e. leaves become dry and brown after insect feeding and patches of burned plants are often lodged. The infested crop usually looks sick showing like the deficiency of nitroge
BPH transmits the grassy stunt, ragged stunt and wilted stunt viral disease to rice plants. Attack may occur at any stage of the crop but mostly at 70 days old plant.
Cond...