Stock, age, and seasonal differences in insecticide sensitivity of the honey bee, Apis mellifera

Honey bee losses due to acute and sublethal doses of insecticides have been well documented  in the recent literature. Little information exists, however, on the variation of susceptibility to insecticides between stocks, age, and season. We tested the insecticide sensitivity of Carniolan, Italian and Russian stocks of honey bees in both young (3 day old) and old bees (14 days old), as well as throughout the year (spring, summer, and fall) by using topical bioassays with remethrin, phenothrin, etofenprox, allethrin, dibrom/naled, malathion. There were significant differences in the LD₅₀ values against pyrethroids, but not the organophosphates in different stocks of young bees in the spring. Our hypothesis is that as workers transition to foragers at 14 days old, the higher metabolic rate of foragers will decrease insecticide sensitivity. Experiments will be on going through the summer and fall. Results of this study will be used to make recommendations about which stocks are most suited in environments where exposure to insecticides may be at a high risk.