Survivorship and development of fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), on conventional and transgenic maize cultivars expressing Bacillus thuringiensis Cry9C and Cry1A(b) endotoxins

Abstract

Growth and development of fall armyworm, Spodoptera frugiperda (J. E. Smith), were compared in two laboratory trials between individuals offered transgenic maize seedlings, conventional maize seedlings, or artificial diet. Transgenic maize seedlings in the first and second trials expressed Cry9C (Event CBH 351) and Cry1A(b) (Event MON 810) Bacillus thuringiensis (Berliner) ( Bt ) endotoxin genes, respectively. Significant differences were observed in both trials between fall armyworm fed transgenic and conventional maize for larval and pupal survival, weight, and development time. Survivorship of fall armyworm larvae was 28 v - v 70% on both transgenic cultivars, compared to 62 v - v 97% recorded on both conventional cultivars and artificial diet. Fall armyworm fed Cry9C transgenic maize had lower larval and pupal weights relative to those fed conventional maize, but the difference was significant only for pupae, whereas those fed Cry1A(b) transgenic maize had significantly lower larval weights, while pupal weights were similar. Developmental periods of larvae fed transgenic or conventional maize were similar in the trial involving Cry9C maize, and longer for larvae fed transgenic maize in the trial involving Cry1A(b) maize. Pupal developmental periods were longer for larvae fed either Cry9C or Cry1A(b) transgenic maize relative to conventional maize, but the difference was significant only in the former case. Estimation of Bt endotoxin concentration in plant tissues via enzyme-linked immunosorbent assays revealed that endotoxin expression was ∼10 times greater in Cry9C maize relative to Cry1A(b) maize. Results are discussed in reference to implications for biological control of pests, such as fall armyworm, that are not targets of Bt transgenic maize.