Status of OP and Pyrethroid Resistance in Spodoptera litura (Fab.) on Cotton

Experiments were conducted during kharif, 2005 to study the status of OP ann dyrethroid resistance in Spodoptera litura (Fab.) on cotton in Guntur and Prakasam districts of Andhra Pradesh. In addition to the relative resistance, resistance levels were worked out in comparison with baseline data. Very high levels of resistance was shown by S. litura to pyrethroids than to OP insecticides where the Guntur strain of S. litura has developed 557.9, 728.5, 86.9, 22.8 folds resistance at LD₅₀/LC₅₀ level and 472.3, 453.8, 121.3, 11.3 and 32.2 folds resistance at LD₉₀/LC₉₀ level, respectively, to cypermethrin, deltamethrin, chlorpyriphos, quinalphos and triazophos. While the Prakasam strain has recorded 174.3, 416.4, 130.7 and 13.6 folds at LD₅₀/LC₅₀ and 412.2, 362.5, 173.0, 8.8 and 28.5 folds resistance at LD₉₀/LC₉₀, respectively.