By applying bioassay and biochemical analyses, the susceptibility to insecticide of four cotton aphid Aphis gossypii （Glover）populations feeding on Chinese prickly ash, hibiscus, pomegranate and cotton, the activities of their α-naphthylacetate （α-NA） esterase and the inhibition by monocrotophos ofα-NA esterase activity were tested. The results showed that the cotton aphid populations collected on four host plants had different sensibility to insecticide. The specific activity of α-NA esterase of A. gossypii on cotton was 1.30-fold to 2...
