Abstract: Collected from cotton fields with low level application of insecticide and rearedwith artificial diet at constant temperature, the larvae of cotton bollworm (Helicoverpa armigera Hiibner) were separately treated with fenvalerate and four other insecticides bytopical application in the laboratory. Results showed that the resistance of the larvae has respectively reached 311.0-fold (F₁₅) to fenvalerate, 10.8-fold (F₁₂) to methomyl, 3.5-fold (F₁4 to parathion-methyl, 5.2-fold (F₁₃) to phoxim, and 4.8-fold (F₁₂) to mixture ofparathion-methyl and phoxim. The R-fenvalerate strains have distinct cross-resistance to deltamethrin (41.8 fold) and cyhalothrin (28.1 fold). The results of enzymic inhibitor and activity respectively determined with methods of bioassay and biochemistry distinctly showedthat the rise of resistance to fenvalerate was mainly associated with the increasing activities of two kinds of esteraes (mixed-function oxidases and carboxylesterase) in the larvae of cotton bollworm.

Key words: Helicoverpa armigera (Hiibner), fenvalerate, insecticide resistance, resistance mechanism, cross resistance