Frequency of Alleles Conferring Resistance to Bt Proteins in Helicoverpa Zea in Texas and the Mid-South

An F₂ screen was conducted on populations of Helicoverpa zea collected in an intensive Bt cotton and Bt corn production area of Texas, to estimate the Cry1Ac, Cry2Ab2, and Vip3A resistance allele frequency. Our study reflected a very high occurrence of Cry resistance alleles, which represents a challenge in management efforts to delay the evolution of Vip resistance in H. zea.