Are fungicides hurting honeybees? eVGN August 2013

According to USDA’s Agricultural Research Service (ARS), honeybees that consume pollen that contains low levels of commonly used fungicides might be more susceptible to infection by a gut parasite.

Researchers from the University of Maryland and ARS collected pollen samples from honeybees pollinating apples, watermelons, pumpkins, cucumbers, blueberries or cranberries. They analyzed the pollen to determine how much fungicide, insecticide, miticide and/or herbicide the bees were exposed to while pollinating each of the crops, according to ARS.

In many cases, the pollen that bees brought back came primarily from plants other than the targeted crop. Some pollen samples contained few pesticides, but the average number seen in a pollen sample was nine different pesticides. Fungicides were the most frequently found chemical substances in the samples. The most common was chlorothalonil, widely used on apples and other crops. The most common miticide was fluvalinate, which beekeepers use to control varroa mites. Neonicotinoid insecticides were only found in pollen from bees foraging on apples, according to ARS.

Honeybees that were fed pollen that contained chlorothalonil, collected at the hive entrance, were almost three times more likely to become infected when exposed to the parasite Nosema, compared with control bees. The fungicide pyraclostrobin, which was found less frequently in the pollen samples, also increased bees’ susceptibility to Nosema infection, according to ARS.