Joint actions of deltamethrin and azole fungicides on honey bee thermoregulation

The effects of sublethal doses of deltamethrin, a pyrethroid insecticide, and prochloraz and difenoconazole, two azole fungicides, on honey bee thermoregulation were investigated by infrared thermography of honey bees kept at 22°C. Deltamethrin at doses of 0.5 and 1.5 ng/bee did not elicit any significant effect on bee thermogenesis whereas doses of 2.5 and 4.5 ng /bee caused a severe hypothermia. Similarly, prochloraz and difenoconazole did not elicit any significant effect on thermogenesis at doses of up to 850 ng /bee whereas they triggered hypothermia at 1250 ng /bee. When associated with prochloraz or difenoconazole at 850 ng /bee, deltamethrin elicited a joint hypothermia at doses that did not induce a significant effect on thermoregulation when used alone.