Effects of Bt corn pollen on honey bees: emphasis on protocol development

Laboratory feeding studies showed no effects on the weight and survival of honey bees feeding on Cry1Ab-expressing sweet corn pollen for 35 days. In field studies, colonies foraging in sweet corn plots and fed Bt pollen cakes for 28 days showed no adverse effects on bee weight, foraging activity, and colony performance. Brood development was not affected by exposure to Bt pollen but significantly reduced by the positive insecticide control. The number of foragers returning with pollen loads, pollen load weight, and forager weight were the most consistent endpoints as indicators of foraging activity. Using variances of measured endpoints, experimental designs required to detect a range of effect sizes at 80% statistical power were determined. Discussed are methods to ensure exposure to pollen, duration of exposure, positive controls, and appropriate endpoints to consider in planning laboratory and field studies to evaluate the nontarget effects of transgenic pollen.