Ear and shank damage by corn borers and corn earworms to four events of Bacillus thuriengiensis transgenic maize

Twenty-eight transgenic maize hybrids containing the Bacillus thuringiensis (Bt) endotoxin and several of their non-Bt isolines were evaluated for control of the southwestern corn borer, Diatraea grandiosella Dyar, the European corn borer, Ostrinia nubilalis (Hubner), and the corn earworm (CEW), Heliocoverpa tea (Boddie) in the shank and ear. The Bt hybrids represented four events (Mon810, Bt11, 176, and CBH354) from seven seed companies. The maize hybrids were grown in four locations that ranged from the northern to southern length of the Texas Panhandle. A semi-arid environment with hot days-cool nights and <220 mm of rain characterize this region. Maize in this region is irrigated with furrow or moving truss application systems. Maize was infested with each species of corn borer at the tasseling growth stage using the Davis applicator. Natural infestations of corn earworm were allowed to develop. Hybrids of events Mon810, Bt11, and CBH354 provided good control of corn borers in shanks and ears. Event 176 hybrids did not provide good control in the shanks and ears because Bt is not expressed in reproductive tissue in this event. No Bt transgenic maize hybrid provided consistent control of CEW larvae on kernels. Feeding gallery length on ears from CEW feeding was sometimes shorter in Mon810 and Bt11 hybrids than in the non-Bt hybrids. (C) 2001 Elsevier Science Ltd. All rights reserved.