Abstract: The resistance and rehabilitation of sensitivity to pyrethroids and the variation of acetylcholinesterase in cotton bollworm Helicoverpa armigera were studied by bioassay and biochemistry method. The results showed that the resistance of cottonbollworm to pyrethroids was unstable and the sensitivity to the insectcides increased with the time after withdrawal of stress. The rehabilitation of sensitivity in the first generation of cotton bollworm fed at the insectary was more rapid. The results of affinity tests between special inhibitors and acetylcholinesterase of the cotton bollworm confirmed that variation of acetylcholinesterase was taken place during the decrease of resistance to pyrethroids in cotton bollworm, and it might have a significant impact on the stability of this resistance.

Key words: Helicoverpa armigera, pyrethroid, acetylcholinesterase, resistance