Impact of Mediterranean Fruit Fly Malathion Bait Spray on Honey Bees

Abstract

During a Mediterranean fruit fly eradication program (1980–1982) in northern California, two field studies were conducted to evaluate the impact of malathion bait spray on honey bees. Significant mortality of adult bees was associated with weekly applications, eventually reducing colony populations to levels that would cause economic loss and threaten winter survival of colonies. Flight activity was reduced greatly for 1 day after each predawn application. Brood mortality was not observed. Residual levels of malathion were 1.71 ± 0.37 ppm (range, 2.24–7.64 ppm) in trapped pollen and 2.22 ± 0.13 ppm (range, 0.78–5.28 ppm) in bees collected from entrance traps attached to hives within spray zones.