ECONOMIC THRESHOLD FOR CHEMICAL CONTROL OF SPOTTED BOLLWORMS (EARIAS-VITTELLA AND E-INSULANA) AND PINK-BOLLWORM (PECTINOPHORA-GOSSYPIELLA) ON TREE COTTON (GOSSYPIUM-ARBOREUM)

An experiment was conducted during 1991-93 to study the control of spo tted bollworms [Earias vittella (Fabr.) and E. insulana (Boisd.)] and pink bollworm [Pectinophora gossypiella (Saund).] based on bollworm po pulation or infestation level in fruiting bodies of tree or desi cotto n (Gossypium arboreum L.). Fenvalerate (50 g ai/ha) alternated with qu inalphos (0.5 kg ai/ha) was used in all the treatments. Six sprays of these insecticides in the recommended criterion (spray at 10-day inter vals starting from squaring on 25% plants till 2 weeks before the firs t picking) on cotton controlled the bollworms most efficiently, as the highest seed-cotton yield(1 718 kg/ha) as well as net income (Rs 23 3 75/ha) were obtained under this treatment. Insecticidal sprays at 5% i ncidence in freshly shed fruiting-bodies (5 sprays) was the next in ef fectiveness. Sprays done at stage of 2 larvae/plant and 10% incidence in intact fruiting-bodies on plant were found the least effective.