Effect of Methamidophos on Honey Bees (Hymenoptera: Apidae) During Alfalfa Pollination

Abstract

Mortality and foraging activity of honey bees, Apis mellifera L., were determined before and for 3 d after treatment of alfalfa with methamidophos applied at 14 g/ha (0.75lb/acre). In colonies at the field edge, mortality was low and, on the second day after treatment, returned to levels approximately equal to those before treatment. Flight activity at the hive entrances diminished to about 25% of levels before treatment. After spray application before dawn, many bees continued to forage actively on alfalfa, indicating that bees may not be repelled by methamidophos. Foraging virtually ceased during the afternoon. The population of bees that collected sugar syrup at uncontaminated feeding stations within the treated field was reduced to about 10% of levels before treatment. Sublethal levels of intoxication or avoidance learning (or both) might account for reduced foraging activity. Methamidophos appears to have a severe effect on honey bee foraging and pollination efficiency.