Baseline susceptibility of Helicoverpa armigera to Bt toxin (Cry1Ac) in cotton field of Xinjiang.

【Objective】It aimed to test the baseline susceptibility of Xinjiang populations of Helicoverpa armigera to the insecticidal protein Cry1Ac.【Method】Helicoverpa armigera were collected from eight cotton areas and tested log dose probit analysis.【Result】The results show that the mean lethal concentrations(LC50) is 0.033 μg/mL,ranging from 0.022 μg/mL to 0.048 μg/mL;LC90 is 0.899 μg/mL,ranging from 0.526 μg/mL to1.333 μg/mL. The detection concentration(LC99)is 1.020 μg/mL.All populations were very susceptible to Cry1Ac.The analysis of 95% fiducial limits showed that the susceptibility of Helicoverpa armigera collected from the eight major cotton fields have no significant response to Cry1Ac protein.【Conclusion】The data acquired can be used as a benchmark for monitoring resistance H.Armigera to Bt cotton in future.