The susceptibility to insecticides and inhibitory activities of OP insecticides to α-Naphthyl acetate(α-NA) esterase of cotton aphid on five plants were measured in order to understand the insecticide resistance mechanism of the aphid for developing integrated management.The cotton aphids,Aphis gossypii(Glover) fed on Chinese prickly ash,hibiscus,pomegranate,Chinese ilex and cotton were collected.The tolerance to pesticides of aphids varied with the host plants they fed on.There was difference in the frequencies of α-NA esterase activity...