Effects of novel pesticides on bumble bee (Hymenoptera: Apidae) colony health and foraging ability

Two experiments were conducted testing for lethal and sublethal effects of the transgenic proteins Cry1Ac and chitinase, and the chemical seed and soil treatment imidacloprid on humble bees (Bombus occidentalis Greene and B. impatiens Cresson, Hymenoptera: Apidae). In the first experiment, B. occidentalis colonies were exposed to realistic residue levels of Cry1Ac, chitinase, and imidacloprid found in pollen. There were no effects on pollen consumption, bumble bee worker weights, colony size, amount of brood, or the number of queens and males produced. In the second experiment, using B. impatiens, we tested the effects of Cry1Ac and two levels of imidacloprid. Similar colony health measures were collected as in the first experiment, but in addition foraging ability of individual bees was tested on complex artificial flowers. There were no differences in colony characteristics among treatments. However, bees in the high-imidacloprid treatment had longer handling times on the complex flowers than bees in the other treatments. No lethal, sublethal colony, or individual foraging effects of these novel pesticides were found at residue levels found in the field, suggesting that humble bee colonies will not be harmed by proper use of these pesticides. Use of an artificial flower foraging array proved to be a sensitive method for detecting sublethal response of bees to pesticides.