Effects of aldicarb and its biologically active metabolites on bees

Alkali bees, Nomia melanderi Cockerell, and alfalfa leafcutting bees, Megachile rotundata (F.), were relatively tolerant to aldicarb and its sulfoxide and sulfone in acute and chronic oral feeding studies. Eggs and young larvae of the leafcutting bee were highly tolerant to these chemicals. The immediate hazard of nectar contamination in alfalfa flower of plants treated with 3.4 kg (AI)/ha is minimal to both leafcutting and alkali bees and is reduced to no-effect levels within 3 or 4 weeks. There were no adverse effects of aldicarb and its metabolites to bees 1 or more years after treatment because soil residues were minimal and, apparently, only the low-toxicity aldicarb sulfone was present. Proper application of aldicarb to alfalfa seed fields in eastern Washington should not cause measurable losses of alfalfa leafcutting or arkali bees, the major pollinators of this crop in the Pacific Northwest.