Abstract: The resistance levels to phoxim, cyhalothrin and endosulfan of cotton bollworm, Helicoverpa arrnigera (Hubner), collected from Jianyang of Sichuan Province, Wuxue of Hubei Province, Hengyang of Hunan Province, Nanjing of Jiangsu Province and Hangzhou of Zhejiang Province, were determined as 8.05-38.80, 2.86-290.00 and 5.87-19.83-fold, respectively in comparison with a susceptible cotton bollwormpopulation. The Jianyang population ? and Hangzhou population (S) were crossed and backcrossed in the laboratory. The results showed that the resistance levels in the F₁ to phoxim, cyhalothrin and endosulfan were 13.16 and 16. 69, 10.43 and 19.00, and 12.42 and 10.21-fold, and the degrees of dominance in heredity of resistance to the three insecticides were estimated to be-0.2220,-0.2147 and 0.0700, respectively. It indicated that phoxim or cyhalothrin resistance was incompletely recessive, and endosulfan resistance was controlled by the semi-recessive gene. The resistance levels of progenies of F₁ breeding to phoxim, cyhalothrin and endosulfan were 17. 66, 7.57 and 9.03fold, respectively, and that in F₁ backcross with the Hangzhou population were 8. 79, 3.00 and 6.61-fold, respectively. Based on the results mentioned above, it is suggested that the gene flow between the resistant and susceptible populations would significantly reduce the resistance levels to the three insecticides.

Key words: Helicoverpa armigera, geographical population, insecticide resistance, gene flow