Joint Toxicity of Pyrethroids and Organophosphorus Insecticides to Insecticide Resistant Spodoptera litura on Cotton

摘要

The tobacco caterpillar, Spodoptera litura (Fab.) is a polyphagous lepidopterous pest causing damage to 112 crop species such as cotton, tobacco, chilli, groundnut, castor etc. throughout the country. During Khari/2005, the Guntur and Prakasam populations of S. litura have shown 20 to 550 folds resistance at LD_(50)/LC_(50) level to cypermethrin, deltamethrin, chlorpyriphos, quinalphos and triazophos, respectively (Dharma Prasad , 2006). The pyrethroids and organophosphorus combination insecticides were found to be effective against the resistant insect pest population of Helicoverpa armigera Hubner, S. litura etc. ( Martin et al., 2003). The use of synergism between pyrethroids and OP's is an additional tool in the insecticide resistance management of S. litura. Hence, the present study was taken up to study the joint toxicity of cypermethrin + chlorpyriphos, cypermethrin + quinalphos and deltamethrin + triazophos.