Comparison of the Effect of Insecticides on Bumble Bees (Bombus impatiens) and Mosquitoes (Aedes aegypti and Culex quinquefasciatus) by Standard Mosquito Research Methods

Mosquito control districts in the United States are limited to two main classes of adulticides, pyrethroids and organophosphates, to control mosquitoes. Two adulticides used to control domestic mosquitoes are Fyfanon EW (malathion, organophosphate) and DeltaGard (deltamethrin, pyrethroid). While the effect of these pesticides on European honeybees (Apis mellifera L., Hymenoptera: Apidae) has been investigated, effects on native pollinators need additional research. The purpose of this study was to investigate the acute nontarget effects of these pesticides on Bombus impatiens Cresson (Hymenoptera: Apidae), a native North American bumble bee species, and compare these effects to wild and laboratory strains of mosquitoes (Aedes aegypti (L.) and Culex quinquefasciatus Say, Diptera: Culicidae) through field and laboratory assays. Bombus impatiens was found to be resistant to Fyfanon EW ((x) over bar = 6.7% mortality at 50-mu g malathion per bottle) at levels that caused significant mortality to study mosquitoes (86.2 >= (x) over bar >= 100% mortality) in laboratory bottle bioassays. Comparatively, B. impatiens demonstrated greater mortality to DeltaGard (93.3%) at 2.5-mu g deltamethrin/bottle than any mosquito colony assayed (14.1 >= (x) over bar >= 87.0% mortality). Only DeltaGard was tested in field applications. In the field, we observed acute effects of DeltaGard on mosquitoes and B. impatiens at 25- and 75-m distance from a truck-mounted ultra-low volume fogger, although treatment effects were not significant for B. impatiens. Additional wild-caught nontarget mortality to DeltaGard field trials was also evaluated. This study indicated that common mosquito control adulticides do cause nontarget mortality to B. impatiens but that impacts are variable depending on pesticide and further studies are needed.

Automated summary

This study investigated the acute nontarget effects of two common mosquito control adulticides on native North American bumble bees and found that Bombus impatiens exhibited resistance to Fyfanon EW but higher mortality rates with DeltaGard. Field and laboratory assays demonstrated varying impacts of these pesticides on B. impatiens, highlighting the need for further research.