Abstract: Transgenic cotton has been engineered to produce insecticidal toxins from [WTBX]Bacillus thuringiensis (Bt) to resist cotton bollworms, [WTBX]Helicoverpa armigera (Hübner) has been commercially cultivated in China since 1997, and it has been intensively planted in Xinjiang fore more than 10 years, where cotton was cultivated in large area, and the crop systems were quite different from other areas. Therefore, it was suspected that the current results about the impact of Bt cotton planting on the seasonal population patterns of cotton bollworms may not reflect the actual situation in Xinjiang. The monitoring of cotton bollworms with light trapping was carried out in a high Bt density region in Markit County and in a low Bt density region in Awat County, Xinjiang during the period from 1999 to 2010. The analyzed results indicated that the population size of cotton bollworms was decreased only in the high Bt density region, but the change in the low Bt density region was not significant. There was a significant negative correlation between the percentage of Bt cotton planting and the light-trapped H. armigera moths. The population size of H. armigera moths of all three generations was decreased with the time of planting Bt cotton, the population size and light-trapped moths of the second generation were dramatically decreased compared with those of the overwinter and first generations, and the relative abundance of the second generation was also decreased gradually. These results demonstrated that cotton bollworm population was suppressed by high Bt density cultivation at present, especially for the second generation.

Key words: Helicoverpa armigera, dynamic change of population, light trapping, Bt cotton, Xinjiang