EFFECTS OF TRANSGENIC BACILLUS-THURINGIENSIS CORN-FED PREY ON MORTALITY AND DEVELOPMENT TIME OF IMMATURE CHRYSOPERLA-CARNEA (NEUROPTERA, CHRYSOPIDAE)

Laboratory feeding experiments using transgenic Bacillus thuringiensis variety kurstaki (Berliner) corn plants hate been carried out to stud y the effects of B. thuringiensis-fed herbivores (i.e., prey), on the predator Chrysoperla carnea Stephens. Host plants were a transgenic B. thuringiensis-expressing (CrylAb) corn hybrid and the corresponding u ntransformed, B. Thuringiensis-free corn hybrid. Two different prey sp ecies were used in the experiments, the European corn borer, Ostrinia nubilalis (Hubner) (lepidopterous target pest), and Spodoptera littora lis (Boisduval) (lepidopterous nontarget pest for B. thuringiensis). T he objectives were to quantity the effects of B. thuringiensis-fed pre y on chrysopid immature development and to determine whether observed effects were caused by sick, suboptimal prey (indirect effects) or ass ociated with B. thuringiensis-related causes (direct effects). Mean to tal immature mortality for chrysopid larvae raised on B. thuringiensis -fed prey was 62% compared with 37% when raised on B. thuringiensis-fr ee prey. There was no significant difference in mortality between chry sopid larvae reared on B. thuringiensis-fed O. nubilalis or B. thuring iensis-fed S. littoralis, Similarly, no significant difference in mort ality was detected when chrysopid larvae were raised on B. thuringiens is-free O. nubilalis or B. thuringiensis-free S. littoralis. Developme nt time of chrysopid larvae was prolonged when B. thuringiensis-fed O. nubilalis was given to the predators but not for B. thuringiensis-fed S. littoralis. Although some unnoticed adverse effects in S. littoral is may have occurred because of the B. thuringiensis corn, our results suggest that the reduced fitness of chrysopid larvae was associated w ith B. thuringiensis. The prolonged development time of chrysopid larv ae raised on B. thuringiensis-fed O. nubilalis was probably because of a combined effect of B. thuringiensis exposure and nutritional defici ency caused by sick prey.