Susceptibility of conventional and transgenic cotton bolls expressing the Bacillus thuringiensis CryIA(c) partial derivative-endotoxin to fall armyworm (Lepidoptera : Noctuidae) and beet armyworm (Lepidoptera : Noctuidae) injury

摘要

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