Resisting resistance to Bt -corn

Zea mays L. These genes, which are called cry genes, code for crystal protein toxins (Cry toxins) that are toxic to some insects but not to mammals. The present generation of Bt -corn protects the plant from damage by the larvae of European corn borer, Ostrinia nubilalis (Hübner) [Lepidoptera: Crambidae] (Ostlie et al. 1997, Rice and Pilcher 1998), and southwestern corn borer, Diatraea grandiosella Dyar [Lepidoptera: Crambidae] (Porter et al. 2000). Because these species are two of the most significant pests of corn in the U.S. corn belt, Bt -corn can in principle provide farmers with significant economic benefits. These perceived benefits have resulted in a rapid adoption by U.S. farmers (Table 4.1). Other moth pests, especially the noctuids fall armyworm Spodoptera frugiperda (J. E. Smith), corn earworm Helicoverpa zea (Boddie), black cutworm Agrotis ipsilon (Hufnagel), armyworm Pseudaletia unipunctata (Haworth), and stalk borer Papaipema nebris (Guenée), are not effectively controlled by Bt -field corn. Moreover, this generation of Bt -corn has no effect on non-moth pests, such as mites and beetles. Consequently, Bt -corn does not eliminate the need for farmers to remain vigilant in monitoring insect pests, and in some cases may not affect insecticide use patterns.