The effects of Chlorpyrifos alone and with a fungicide on queen rearing in honey bees (Apis mellifera)

Honey bees often are exposed to pesticides when pollinating crops. Some exposure is due to systemic action of pesticides. Bees are exposed to fungicides because they are sprayed during bloom. The effects of pesticides alone and with a fungicide on the ability of honey bees to rear queens were examined. Significantly fewer queens emerged in open foraging colonies when the grafted larvae were from colonies fed pesticide alone and with added fungicide compared with larvae from open foraging colonies. There also was a significant reduction in queen emergence when larvae from open foraging colonies were reared into queens in colonies fed the treated pollens. The fewest queens emerged when larvae were grafted from and reared in colonies fed pollen with pesticide and fungicide. When nurse bees and developing queens were examined for virus, we detected deformed wing virus (DWV) in all nurse bees from open foraging colonies and those in the EFA. Most also had black queen cell virus (BQCV). Both viruses were detected in royal jelly and in queen larvae but not in the virgin queens reared in the open foraging colonies. However, most emerged queens grafted from larvae reared in colonies fed the treated pollens had DWV even when reared in open foraging colonies. When queens were reared in colonies fed treated pollen, a majority emerged with both DWV and BQCV. The results indicate that rearing queens in colonies with pollen contaminated with pesticides alone and with fungicide reduces queen emergence possibly through effects on the immune system.