Fungicides May Cause Honey Bee Deaths: Lethal Parasite Impacts Colonies

First Posted: Jul 25, 2013 07:48 AM EDT

Honey bees are quickly disappearing from flowers and fields, succumbing to disease and colony collapse disorder. Now, scientists may have found part of the reason why these insects are dying; they've discovered that common agricultural chemicals, including fungicides, could be responsible for impairing bees' ability to fight off a potentially lethal parasite.

Honey bees are an important farm of the ecosystem, pollinating flowers that eventually fruit and produce seeds. Farmers regularly rent bees or keep bees of their own in order to help pollinate crops and produce higher yields. Over the years, though, these insects have begun to disappear. In fact, researchers found that beekeepers lost 31 percent of their colonies in late 2012 and early 2013. That's roughly double of what's considered to be acceptable in terms of losses, according to Wired.

In order to see what might be affecting these bees, researchers collected pollen from honey bee hives in fields that ranged from Delaware to Maine. They then analyzed the samples to find out which flowering plants were the bees' main pollen sources and what agricultural chemicals were being introduced into the pollen and, consequently, the honey. In addition, the scientists fed pesticide-laden pollen samples to healthy bees and then tested them for their ability to resist infection with Nosema ceranae. This parasite affects adult honey bees and has been linked to the lethal colony collapse disorder.

In the end, the researchers found that the pollen samples contained 9 different agricultural chemicals. These included fungicides, insecticides, herbicides and miticides. In addition, they discovered that sublethal levels of multiple agricultural chemicals were present in every sample; in fact, one contained as many as 21 different pesticides. The most prevalent of these were the fungicide chlorothalonil and the insecticide fluvalinate.

They didn't just find these chemicals present in the honey, though. The researchers found that bees fed pollen samples containing chlorothonatil were nearly three times more likely to be infected by the deadly parasite Nosema than bees that were not exposed to these chemicals. This is a huge finding in terms of determining exactly what may be harming these insects.

"We don't think of fungicides as having a negative effect on bees, because they're not designed to kill insects," said Dennis vanEngelsdorp, one of the researchers, in a news release. Federal regulations restrict the use of insecticides while bees are foraging, but that isn't the case with fungicides. "But there are no such regulations on fungicides, so you'll often see fungicide applications going on while bees are foraging on the crop. This finding suggests that we have to reconsider that policy."

The findings are published in the journal PLOS One.

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