| Transgenic corn hybrids expressing Bt toxins are widely deployed to control pests such as Helicoverpa zea (Boddie). However, Bt resistance can reduce the efficacy of Bt corn hybrids. Volunteer corn expressing Bt toxins may impact Bt resistance management of pests. Surveys in Mississippi revealed the occurrence of fall season volunteer corn in high densities. Helicoverpa zea larvae were found feeding during both vegetative and reproductive stages. However, Bt parentage and low to moderate water and nitrogen stresses did not significantly influence H. zea larval growth and development on Bt positive volunteer plants. Additionally, pollen mediated Bt gene flow to non-Bt refuge ears from Bt hybrids significantly reduced H. zea larval growth on cross-pollinated refuge ears. The implications of these findings are that volunteer corn in most Mississippi corn production regions will have little impact on H. zea Bt resistance management, but resistance management could be compromised in more southern regions. |
