Status of Insecticide Resistance in Guntur and Prakasam Population of Spodoptera litura on Cotton

Experiments were conducted to assess the status of insecticide resistance in Spodoptera litura (Fab.) on cotton in Guntur and Prakasam districts of Andhra Pradesh during Kharif 2007 and 2008. In addition to the relative resistance, relative levels were worked out in comparison with baseline data. The Guntur population of S. litura developed 6.3 and 5.4; 3.0 and 2.9; 1.7 and 1.4; 16.2 and 14.4; 1.14 and 1.11 folds resistance at LD50 and 11.3 and 7.06; 4.2 and 3.2; 1.07 and 1.06; 34.8 and 26.9; 3.5 and 2.9 folds resistance at LD90 level to chlorpyriphos, quinalphos, endosulfan, cypermethrin and methomyl during Kharif 2007 and 2008, respectively. While the corresponding values for Prakasam population of S. litura were 5.7 and 2.6; 1.7 and 1.7; 1.4 and 1.3; 15.4 and 11.3; 1.11 and 1.03 at LD50 and 8.6 and 3.7; 1.9 and 1.19; 1.05 and 1.04; 30.9 and 25.6; 3.1 and 2.6 folds resistance at LD90 respectively.