TOXICITY OF BACILLUS-THURINGIENSIS CRY1AB TOXIN TO THE PREDATOR CHRYSOPERLA-CARNEA (NEUROPTERA, CHRYSOPIDAE)

Laboratory feeding studies were carried out to determine the effects o f the Bacillus thuringiensis (Berliner) Cry1Ab toxin on developmental time and mortality of Chrysoperla carnea (Stephens) larvae. A bioassay technique was developed that allowed for incorporation of the Cry1Ab toxin into a liquid diet that was then encapsulated within small paraf fin spheres. Because only 2nd and 3rd instars can penetrate the surfac e of the paraffin spheres, 2 different methods were used to rear chrys opid larvae through the Ist instar. The Ist method used small foam cub es soaked in non-encapsulated, liquid diet (with or without Cry1Ab). T he 2nd method used Ephestia kuehniella (Hubner) eggs as prey during th e first instar (no Cry1Ab exposure). After reaching the 2nd instar, al l larvae received encapsulated, artificial diet with or without Cry1Ab , respectively. When reared only on artificial diet containing Cry1Ab toxin, total immature mortality was significantly higher (57%) than in the respective untreated control (30%). Also, significantly more chry sopid larvae died (29%) that received Cry1Ab later during their larval development compared with the respective control (17%). Although mort ality was consistently higher, no or only small differences in develop mental times were observed between Cry1Ab-treated and untreated C. car nea larvae. C, carnea larvae required significantly more time to compl ete larval development when reared on artificial diet only than when r eared first on E. kuehniella eggs followed by encapsulated artifical d iet or on only E. kuehniella eggs, regardless of exposure to Cry1Ab. T hese results demonstrate that Cry1Ab is toxic to C. carnea at 100 mu m g/ml of diet by using encapsulated artificial diet.