Toxicity of Insecticides to Different Generations or Different Instar of Spodoptera exigua

The toxicity of insecticides to S.exigua different in generations and instars was tested by topical application. The results that the toxicity of alpha-cypermethrin, methomyl, profenofos, and chlorfluazuron to 4th instar was decreased among second, fourth and sixth generations, and that of alpha-cypermythrin, methomyl, profenofos, and chlorfluazuron to third, fourth and fifth instar of sixth generation was also decreased. These gave a viewpoint that the resistance develops very quickly with the generations and instars increasing.