Susceptibility of Helicoverpa armigera from different host plants in northern China to Bacillus thuringiensis toxin Cry1Ac

► Moths emerging from Bt cotton were more tolerant to Bt toxin than moths emerging from wheat and corn. ► There is significant variation in susceptibility to Bt toxins among H. armigera populations derived from different host crops. ► Susceptibility to Cry1Ac changed from year to year. ► Corn could be used as refugia to minimize the evolution of resistance to Bt cotton.