Monitoring Of Resistance Development To Bt Cotton In Field Populations Of Helicoverpa armigera (Lepidoptera: Noctuidae)

In order to maintain continuing success of Bt cotton, F₂ screen was conducted from 2003 to 2005 to monitor resistance to Cry1Ac-expressing cotton in field population of Helicoverpa armigera in Qiuxian County (Hebei, China). Results showed that resistance allele frequency to Bt cotton ranged from 0.0119 to 0.0297 with an overall frequency of 0.0146 for the 3-year period. This study indicated that introduction of Bt cotton expressing multiple Bt toxins and integration of Bt technology with other tactics are necessary for preventing further increases of Bt resistance in this key pest.