Economic threshold for chemical control of spotted bollworms (Earias vittella and E. insulana) and pink bollworm (Pectino phora gossypiella) on tree cotton (Gossypium arboreum)

An experiment was conducted during 1991-93 to study the control of spotted bollworms [Earias vittella (Fabr.) and E. insulana (Boisd.)] and pink bollworm [Pectinophora gossypiella (Saund).] based on bollworm population or infestation level in fruiting bodies of tree or desi cotton (Gossypium arboreum L.). Fenvalerate (50 g al/ha) alternated with quinalphos (0.5 kg ai/ha) was used in all the treatments. Six sprays of these insecticides in the recommended criterion (spray at 10-day intervals starting from squaring on 25% plants till Z weeks before the first picking) on cotton controlled the bollworms most efficiently, as the highest seed-cotton yield (1 718 kg/ha) as well as net income (Rs 23 375/ha) were obtained under this treatment. Insecticidal sprays at 5% incidence in freshly shed fruiting-bodies (5 sprays) was the next in effectiveness. Sprays done at stage of 2 larvae/plant and 10% incidence in intact fruiting-bodies on plant were found the least effective.