1Cotton Research Laboratory, Punjab Agricultural University, Ludhiana-141 004, Punjab (India).
2Department of Entomology, College of Agriculture, Punjab Agricultural University, Ludhiana-141 004, Punjab (India).
3Punjab Agricultural University, Ludhiana-141 004, Punjab (India).
Field studies were conducted for three years (1991–93) to determine the effectiveness of ‘Dipel 8L’ (Bacillus thuringiensis Berliner (Bt) var. kurstaki serotype 3ab) against bollworm complex of american cotton (cv. LH 886). Earias species, Helicoverpa armigera (Hubner) and Pectinophora gossypiella Saunders constituted bollworm complex at Ludhiana during 1991–93 and Mukatsar in 1993 where these trials were conducted. Bt alone and as alternate sprays as well as tank mixture with some insecticides was evaluated and compared with fixed spray schedule of recommended insecticides and untreated control. Bt (750 ml/ha) in alternation with endosulfan (2.5 I/ha) or its tank mixture with fenvalerate (250 ml/ha)lendosulfan (2.5 I/ha)/quinalphos (2 I/ha) was effective and comparable with recommended spray schedule of insecticides in respect of bollworm damage and seed cotton yield. The increase in seed cotton yield with alternate sprays of Bt and endosulfan was 52.1 per cent. Bt alme did not prove better than recommended insecticidal treatment for bollworm control in cotton. The number of sprays of synthetic organic insecticides were reduced from six to three when given in alternation with Bt sprays. Thus, the use of Bt (‘Dipel 8L’) in alternation with endosulfan or as tank mixture with fenvalerate/endosulfan/quinalphos is suggested for effective management of bollworms in cotton.
