Fungicide for Plants May Hurt Honeybees

Megan McGrath
August 09,2013

A widely used chemical used to fight plant disease is hurting honeybees in an unexpected way, according to new research. As Megan McGrath reports, it may be contributing to the widespread loss of honeybees that pollinate many fruits, vegetables, nuts and other crops.

Honeybee hives in the United States and elsewhere are dying, and researchers like Dennis VanEngelsdorp at the University of Maryland are trying to understand why. “The number of colonies that die every winter has been one in three. So on average 30 percent of the colonies have died every winter over the last six winters. And that’s an astronomical number.”

VanEngelsdorp's research team examined the pollen that honeybees carried to their hives, and found that it was contaminated with high doses of 35 different pesticides. They also found that eating certain fungicides made bees more susceptible to infection by Nosema, a deadly microbe.

But fungicides are essential to US agriculture, according to pesticide industry researcher Mike Leggett, with CropLife America. "Fungicides are used, and have been used, pretty broadly, for centuries, for protection of plants from plant disease,” he said.

He also points out that many of the other pesticides VanEngelsdorp found in the pollen actually made the bees less likely to be infected with Nosema.

“I think it’s interesting research that adds to the body of research that’s available, but I’m not really sure that the conclusions reached were… you know, well-supported,” said Leggett.

Maryland farmer and beekeeper Keith Ohlinger has watched his bees die every winter. Researchers are investigating the effects of a variety of factors, including pesticides, diseases and malnutrition. Many people, including Ohlinger, think widespread bee death is caused by many different stresses at once.

“What I felt it was, was a compilation of a lot of little things. I didn’t feel that there was probably one smoking gun. But there’s a division there, some people feel that it is just one thing,” said Ohlinger.

Ohlinger does feel sure that pesticides are a part of the problem. “Maybe I’m just not educated enough, I don’t know, but my view is, if you can take a bath in it, it’s probably safe. And I don’t know many of the things that they’re putting out right now that anybody would come out of a bath in for any length of time and go, ‘Wow, that was great, I feel much better!’ You know?”

Honeybees are essential to agriculture. This makes the search for an answer to the bee die-off especially urgent for VanEngelsdorp's team.

“One in every three bites of food we eat are directly or indirectly pollinated by honeybees. So without honeybees, we wouldn’t have that variety in our diet,” said VanEngelsdorp.

Even as a third of the country's food supply depends on honeybees, a third of those bees continue to die each winter.