Fungicides used on apples and other crops lower the honey bees’ ability to defend against a potentially lethal parasite linked to bee colony deaths, a study found.
Commercial honey bees exposed to the fungicide chlorothalonil had a three times greater risk of being infected by the parasite linked to Colony Collapse Disorder than those not exposed to the chemical used to fight off fungus, according to research today in the journal PLoS ONE.
The findings from the study, one of the first to analyze real conditions encountered by bees as they pollinate a wide variety of crops, were surprising because fungicides aren’t designed to hurt insects, said Dennis vanEngelsdorp, a senior study author. More research is needed to better understand the effects all pesticides have on bees and how that works together to affect colony health, he said.
“This study suggests there may be some lethal effects and it may hurt the bees in the long term,” said vanEngelsdorp, a research scientist at the University of Maryland in College Park, in a July 23 telephone interview. “It may compromise their ability to fight infection. We may need to rethink how we label fungicides as safe for bees.”
Honeybees are needed to pollinate 130 different crops, representing more than $15 billion in revenue each year, according to the U.S. Department of Agriculture. Fruit-pollinated products are found in items such as Haagen-Dazs ice cream from Minneapolis-based General Mills. Lip balm made by Burt’s Bees Inc., a unit of Oakland, California-based Clorox Co., contains wax from the honeycombs of beehives.
Since 2006, the honeybee population has fallen partially because of Colony Collapse Disorder, an unexplained syndrome that has killed billions of bees. Colony Collapse Disorder has no effective antidote.
Researchers in today’s study collected pollen from bee hives from Delaware to Maine. They then analyzed the samples to determine which plants were the bees’ main pollen sources and which agricultural chemicals were found with the pollen.
The pollen samples contained on average about nine different chemicals, including fungicides, insecticides, miticides and herbicides. The most frequent pesticides were the fungicide chlorothalonil and the insecticide fluvalinate, used to control a type of mite that’s a honey bee pest.
The researchers then fed healthy honey bees the pesticide-filled pollen and analyzed their ability to fend off infection from Nosema ceranae, a parasite. Those fed the pollen containing the fungicides chlorothalonil and pyraclostrobin were less able to fend off an infection by Nosema than those not exposed to the chemicals. The insecticides used to control the mites, fluvalinate and amitraz, also hurt the bees’ ability to defend against the parasites, the authors said.
Nosema is suspected as one of the potential causes, in combination with other factors, of colony collapse disorder.