GREENHOUSE AND FIELD EVALUATIONS OF TRANSGENIC CANOLA AGAINST DIAMONDBACK MOTH, PLUTELLA-XYLOSTELLA, AND CORN-EARWORM, HELICOVERPA-ZEA

Canola (Brassica napus L.) cultivars Oscar and Westar, engineered with a Bacillus thuringiensis (Bt) cryIA(c) gene, were evaluated for resis tance to lepidopterous pests, diamondback moth, Plutella xylostella L. (Plutellidae) and corn earworm, Helicoverpa tea (Boddie) (Noctuidae) in greenhouse and field conditions. In greenhouse preference assays co nducted at vegetative and flowering plant stages, transgenic plants re corded very low levels of damage. A 100% diamondback moth mortality an d approximate to 90% corn earworm mortality were obtained on transgeni c plants in greenhouse antibiosis assays. The surviving corn earworm l arvae on transgenic plants had reduced head capsule width and body wei ght. Mortality of diamondback moth and corn earworm were 100% and appr oximate to 95%, respectively, at different growth stages (seedling, ve getative, bolting, and flowering) on the transgenic plants in greenhou se tests. In field tests conducted during 1995-1997, plots were artifi cially infested with neonates of diamondback moth or corn earworm or l eft for natural infestation. Transgenic plants in all the treatments w ere highly resistant to diamondback moth and corn earworm larvae and h ad very low levels of defoliation. Plots infested with diamondback mot h larvae had greater damage in both seasons as compared with corn earw orm infested plots and plots under natural infestation. After exposure to defoliators, transgenic plants usually had higher final plant stan d and produced more pods and seeds than non-transgenic plants. Diamond back moth injury caused the most pronounced difference in plant stand and pod and seed number between transgenic and non-transgenic plants. Our results suggest that transgenic canola could be used for effective management of diamondback moth and corn earworm on canola.