LARVAL SURVIVAL AND DEVELOPMENT OF THE FALL ARMYWORM (LEPIDOPTERA, NOCTUIDAE) ON NORMAL AND TRANSGENIC COTTON EXPRESSING THE BACILLUS-THURINGIENSIS CRYIA(C) PARTIAL-DERIVATIVE-ENDOTOXIN

Survival and development of fall armyworms, Spodoptera frugiperda (J. E. Smith),on leaves and bells of normal (variety DP 5415) and transgen ic cotton plants, Gossypium hirsutum L., expressing the Bacillus thuri ngiensis Berliner (Bt) CryIA(c) partial derivative-endotoxin (variety NuCOTN 33(B)) were examined. No significant differences were observed in larval survival between the 2 varieties at 2, 4, 6, 8, 10, and 12 d after exposure. In addition, no significant differences were observed between varieties in the number of larvae that pupated and eclosed as adults. However, larval weights of fall armyworms were significantly higher at 6 and 12 d after exposure on DP 5415 leaves than NuCOTN 33(B ) leaves, and time to pupation and adult eclosion were significantly s horter on DP 5415 leaves than on NuCOTN 33(B) leaves. No significant d ifferences between varieties were observed for sex ratio, but neonate survival of the subsequent generation was significantly lower from ins ects reared on NuCOTN 33(B). Larval survival to pupation and adult ecl osion for larvae fed a combination of DP 5415 foliage (early instars) and bells (late instars) were significantly higher than for larvae fed NuCOTN 33(B) foliage and bells. The effects of a single generation se lection of fall armyworms on NuCOTN 33(B) leaves were also measured. F all armyworms originally reared on DP 5415 and NuCOTN 33(B) were fed e ither normal (DP 5690) or transgenic Bt cotton (NuCOTN 35(B)) leaves. Larval survival at 2, 4, 6 d after exposure and adult survivorship wer e not significantly affected by 1 generation of rearing on transgenic Bt cotton. Single generation exposure to NuCOTN 33(B) did not affect l arval weights of the subsequent generation when reared on transgenic B t cotton.