†Department of Statistics and Mathematics, Agricultural College, Bapatla522101, Guntur District, Andhra Pradesh, India.
Department of Entomology, Agricultural College, Bapatla522101, Guntur District, Andhra Pradesh, India.
Experiments were conducted to assess the status of insecticide resistance in Spodopera litura (Fab.) on cotton in Guntur and Prakasam districts in Andhra Pradesh during 2003–2004. Guntur strain of S. litura showed 89.9, 49.6 and 31.3 folds at LD50 and 72.7, 39.8 and 31.8 folds resistance to chlorpyriphos at LD90 respectively at 24, 48 and 72 h after treatment. Correspondingly Prakasam strain of S. litura showed 97.2, 61.1 and 37.2 folds at LD50 and 94.0, 48.6 and 27.0 folds resistance at LD90 level to chlorpyriphos.
Guntur and Prakasam strains showed 2.3 and 2.2: 1.7 and 1.2 and 1.4 and 0. folds at LD50 level and 4.9 and 3.7: 2.8 and 1.6 and 2.2 and 1.1 folds resistance to methomyl at LD90 level, respectively at 24, 48 and 72 h after treatment. The two strains showed 40.8 to 77.2 and 24.0 to 70.8 folds resistance at LD50 and LD90, levels to quinalphos; resistance levels ranged from 102.0 to 200.5 folds and 62.6 to 181.4 folds at LD50 and LD90 levels against fenvalerate.
Insecticide resistance, Spodoptera litura, chlorpyriphos, methomyl, quinalphos, fenvalerate, Bacillus thuringienis
