Research conducted by Pioneer Hi-Bred International Inc. showed significantly lower levels of black cutworm Agrotis ipsilon (Hufnagel) feeding and cutting on Herculex I (CrylF) as compared to the isoline control. The objective of this study was to determine any effect that alternate host availability may have on the damage potential of black cutworms in Herculex I corn. The research was conducted in field and greenhouse experiments, and the alternative weed host was conventional corn (Pioneer 34M94). Treatments consisted of two corn types (Herculex I or its non-transformed isoline) with and without alternate host removal. Plants were infested with 3rd instar black cutworms at the VI or V2 stage. Plants were sampled daily for cutting or tunneling above and below the soil surface. Weeds were removed at the V2 or V3 stage. The experiment concluded when all corn plants were cut or when plants reached the V4 stage. Analysis showed significant differences between isoline and Herculex I. No significant difference in Herculex I treatments with and without weed removal was recorded in the field experiments. In the greenhouse trials after weed removal, significantly more Herculex I plants without alternate hosts were cut than when the weed hosts remained. Pathogens, such as insect viruses, have been used for insect control as alternatives to chemical control. Black cutworm is highly susceptible to Agrotis ipsilon multicapsid nucleopolyhedrovirus (AgipMNFV). The objective of this study was to test black cutworm susceptibility to this pathogen after feeding on Herculex I. Third instar black cutworm were fed Herculex I and isoline for 24 hours. Larvae were then given the LD₅₀ dose of AgipMNPV on a small diet cube. After 24 hours, larvae that had consumed the entire cube were placed on diet and after 9 days were evaluated for virus symptoms. Of the exposed larvae, those fed the Herculex I diet had significantly higher rates of virus infection than those fed the isoline diet.