The effects of pesticides on queen rearing and virus titers in honey bees (Apis mellifera L.)

Authors: DeGrandi-Hoffman, Gloria; Chen, Yanping - Judy; SIMONDS, ROGER - Agricultural Marketing Service (AMS, USDA)

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2012
Publication Date: 1/4/2013
Citation: Hoffman, G.D., Chen, Y., Simonds, R. 2013. The effects of pesticides on queen rearing and virus titers in honey bees (Apis mellifera L.). Insects. 4(1), 71-89.doi:10.3390/insects4010071. http://www.mdpi.com/2075-4450/4/1/71

Interpretive Summary: We investigated the effects of sublethal pesticide exposure on queen rearing and virus titers of emerged queens in honey bee colonies. Queen rearing colonies were kept in an enclosed flight area and fed pollen with chlorpyrifos (CPF) alone (pollen-1) and with CPF and the fungicide Pristine® (pollen-2). The flow of CPF and components of Pristine® in the food stores and bees was examined to determine if nurse bees and developing queens had direct exposure to the pesticides. Levels of CPF and fungicide in stored pollen and nurse bees were lower than in the pollen we fed. We did not detect CPF or the fungicide in royal jelly or in the queen larvae; therefore the effects of the pesticides on queen rearing were not due to direct exposure to the compounds. We found a reduction in queen emergence when larvae from open foraging (i.e., outside) colonies were reared in colonies fed pollen-1 or 2 compared with when those larvae were reared in outside colonies. Fewer queens grafted from and reared in colonies fed pollen-2 emerged compared with pollen-1 or outside colonies. Deformed wing virus (DWV) and black queen cell virus (BQCV) were found in nurse bees from colonies fed pollen-1 or 2 and in outside colonies. However, we did not detect virus in queens that were grafted from and reared in outside colonies. In contrast, DWV was found in all emerged queens grafted from colonies fed pollen-1 or 2 either reared in outside hives or those fed pollen-1 or 2. The results suggest that sublethal exposure of CPF alone but especially when Pristine® is added reduces queen emergence possibly due to infections by virus or other pathogens in developing queens.

Technical Abstract: The effects of sublethal pesticide exposure on queen emergence and virus titers were examined. Queen rearing colonies were fed pollen with chlorpyrifos (CPF) alone (pollen-1) and with CPF and the fungicide Pristine® (pollen-2). Fewer queens emerged when larvae from open foraging (i.e., outside) colonies were reared in colonies fed pollen-1 or 2 compared with when those larvae were reared in outside colonies. Larvae grafted from and reared in colonies fed pollen-2 had lower rates of queen emergence than pollen-1 or outside colonies. Deformed wing virus (DWV) and black queen cell virus were found in nurse bees from colonies fed pollen-1 or 2 and in outside colonies. The viruses also were detected in queen larvae. However, we did not detect virus in emerged queens grafted from and reared in outside colonies. In contrast, DWV was found in all emerged queens grafted from colonies fed pollen-1 or 2 either reared in outside hives or those fed pollen-1 or 2. The results suggest that sublethal exposure of CPF alone but especially when Pristine® is added reduces queen emergence possibly due to compromised immunity in developing queens.