Susceptibility of conventional and transgenic cotton bolls expressing the Bacillus thuringiensis CryIA(c) ∂-endotoxin to fall armyworm (lepidoptera: noctuidae) and beet armyworm (lepidoptera: noctuidae) injury

Document Type

Article

Publication Date

12-1-1998

Abstract

Fifth-instar fall annyworms, Spodoptera frugiperda (J. E. Smith), and third-instar beet armyworms, Spodoptera exigua (Hübner), were caged on conventional 'DP 5415' and transgenic Bacillus thuringiensis (Bt) 'NuCOTN 33B' cotton bolls of various ages to define the period of boll susceptibility to larval injury. Larval mortality, incidence of feeding, and boll penetration were examined on both cultivars. There was no significant linear relationship between incidence of feeding and boll age for either species caged on DP 5415 and NuCOTN 33B. However, a significant linear relationship between larval mortality and boll age was observed for both species caged on NuCOTN 33B (mortality increased as bolls matured), but no such linear relationship was found on DP 5415. A significant linear relationship between boll penetration and boll age was observed for both species caged on NuCOTN 33B (boll penetration decreased as bolls matured). Similarly, a significant linear relationship between boll penetration and boll age was observed for beet armyworms caged on DP 5415 (boll penetration decreased as bolls matured), whereas no relationship was found for fall armyworms caged on DP 5415. Fall armyworms penetrated ≥60% of DP 5415 bolls regardless of their age, but these bolls were tolerant (≤10% boll penetration) to beet armyworms at 390 heat units. The NuCOTN 33B bolls were tolerant to fall armyworm damage at 864 heat units, but these bolls were tolerant to beet armyworm damage at 361 heat units. These data suggest that fall armyworms and beet armyworms are able to successfully penetrate bolls of 350 heat units at unacceptable (≥10%) levels.

Publication Source (Journal or Book title)

Journal of Agricultural and Urban Entomology

First Page

163

Last Page

171

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