Aerially Applied Ultra-Low-Volume Malathion Effects on Colonies of Honey Bees (Hymenoptera: Apidae)

Abstract

Thirty-two-hectare fields of Brassica napus L. (canola cultivar Westar) with an apiary of 8 or 10 colonies of honey bees, Apis mellifera L., were sprayed with aerially applied ultra-low-volume malathion at a rate of 210 ml/ha to simulate a mosquito control program. Sprayed colonies gained significantly less weight than control colonies for up to 28 d after spraying and had significantly lower populations than control colonies for up to 86 d after spraying. Trap counts of dead bees were significantly higher in sprayed colonies than in control colonies for 3-4 d after spraying. Sprayed colonies collected significantly less pollen than control colonies collected for 2-3 d after spraying. The number of foragers entering sprayed colonies was significantly less for 1-2 d; there was no change in the proportion of pollen and non pollen foragers entering colonies.