Late-instar European corn borer (Lepidoptera : Crambidae) tunneling and survival in transgenic corn hybrids

Field studies were conducted in 1996 and 1997 to determine injury by and su rvival of late-instar European corn borer, Ostrinia nubilalis (Hubner), on genetically altered Bacillus thuringiensis Berliner corn, Zea,mays L. Cry1A b events 176, Bt11, MON810, and MON802; Cry1Ac event DBT418; and Cry9C even t CBH351 were evaluated. Plants of each corn hybrid were manually infested with two third-, fourth-, or fifth-instar O. nubilalis. Larvae were held in proximity to the internode of the plant above the ear with a mesh sleeve. Lan ae were put on tie plants during corn developmental stages V8, V16, R1, R3, R4, R5, and R6. This study shows that not all B. thuringiensis hybrids provide the same protection against O. nubilalis injury. Hybrids with B. t huringiensis events Bt11, MON810, MON802, and CHB351 effectively protected the corn against tunneling by late-instar O, nubilalis. Event 176 was effec tive in controlling late-instar O. nubilalis during V12 and V16 corn develo pmental stages; however, significant tunneling occurred by fourth instars d uring R3 and R5. Event DBT418 was not effective in controlling late-instar O. nubilalis during corn vegetative or reproductive stages of development. Whether the B, thuringiensis hybrids satisfied high- and ultrahigh-dose req uirements is discussed.