To assess the ecological effects of Bt-maize expressing the Cry1Ab protein on larvae of Chrysoperla carnea, an important predator in maize, we examined a) the performance of three prey herbivores (Rhopalosiphum padi , Tetranychus urticae and Spodoptera littoralis ) on Bt transgenic and non-transgenic maize plants, b) the intake of the Bt-toxin by the three herbivores and c) the effects on C. carnea when fed each of the prey. The intrinsic rate of increase (rm) was used as a measure of performance for R. padi and T. urticae . No difference in this parameter was observed between herbivores reared on Bt or non-transgenic plants. In contrast, a higher mortality rate and a delay in development were observed in S. littoralis larvae when fed Bt-maize compared to those fed the control plants. The intake of Bt-toxin by the different herbivores was measured using an immunological assay (ELISA). Highest amounts of Cry1Ab toxin were detected in T. urticae , followed by S. littoralis and only trace amounts detected in R. padi . Feeding C. carnea with T. urticae , which were shown to contain the Bt-toxin, or with R. padi , which do not ingest the toxin, did not affect survival, development and weight of C. carnea. In contrast, a significant increase in mortality and a delay in development were observed when predators were fed S. littoralis larvae reared on Bt-maize. A combination of prey quality and Bt-toxin may account for the negative effects observed on C. carnea when fed S. littoralis . The relevance of these findings on the ecological risks of Bt-maize on C. carnea>/i> are discussed.
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA