Link Between Pesticides and Bee Deaths Becomes Clearer

The evidence linking pesticides to bee die-offs keeps building.

In late July, scientists from the US Department of Agriculture (USDA) and University of Maryland published the latest research linking honey bee deaths to pesticide exposure they receive while pollinating crops.

Although low levels of exposure may not kill bees, it  weakens their immune systems and makes them more susceptible to a deadly gut parasite called Nosema ceranae.

For this latest study, researchers collected pollen samples from crops that honey bees are known to pollinate including apples, watermelons, pumpkins, cucumbers, blueberries and cranberries. They found 35 different pesticides in the pollen, ranging from oxadiazines, neonicotinoids, carbamates, cyclodienes, formamidines, organophosphates and pyrethroids.

Scientists were able to link eight pesticides with increased risk of Nosema infestations. And they were alarmed by a significant presence of fungicides in the samples, particularly chlorothanlonil, which is commonly used on apples, reports Beyond Pesticides. Honey bees that were fed pollen containing chlorothalonil and collected at the hive entrance were almost three times as likely to become infected when exposed Nosema, compared with control bees that weren’t fed  contaminated pollen.

Perhaps even more alarming: these sorts of pesticides often don’t carry warning labels cautioning against application during crop blossoming, when bees are foraging and are most susceptible to poisoning.

Pesticides were found in every pollen sample collected in the study, even those collected from nearby wildflowers that weren’t specifically sprayed.

“It could be drift from when they sprayed their crop, but it also could be that the bees are picking it up and contaminating the pollen on the forage trip,” says the study’s co-author Dennis vanEngelsdorp, with the University of Maryland. We "need to better understand how pesticides are getting into the hive. Clearly it is not just from collecting pollen from the crops that bees are being used to pollinate.”

Bee

The study joins a growing body of evidence linking bee deaths with pesticides, particularly the relatively new class of neonicotinoid substances typically used for cosmetic purposes. The poisoning of more than 50,000 bumblebees in Oregon in June, for example, was linked to this pesticide.

“The Oregon bee poisoning is a clear warning. We have to stop pesticide use in cases where human health or food security is not at risk,” Marla Spivak, a professor from the University of Minnesota, and an authority on bee deaths, told Xerces Society. “They are long-lasting in soil and they readily move into water. If the Oregon event is an indication of what is happening more widely, we will begin to see catastrophic threats to food security and the pollination of wild plants.”

In May, the EU banned neonicotinoid pesticides for the next two years. The US so far has done little to protect bees. Legislation introduced in July calls on the Environmental Protection Agency (EPA) to suspend the use of neonicotinoids and conduct a full review of scientific research before approving any other pesticides in this class.

“One of every three bites of food we eat is from a crop pollinated by honey bees," says Representative John Conyers (D-MI),  co-sponsor of the ‘Saving America’s Pollinators Act of 2013.’ "These crops include apples, avocados, cranberries, cherries, broccoli, peaches, carrots, grapes, soybeans, sugar beets and onions. Unfortunately, unless swift action is taken, these crops, and numerous others, will soon disappear due to the dramatic decline of honey bee populations throughout the country."

Beekeepers and environmental groups have been pressuring EPA on this issue since March 2012. In May, they filed a lawsuit challenging the EPA’s failure to act.

"Pesticide manufacturers use conditional registrations to rush bee-toxic products to market, with little public oversight," said Paul Towers from the Pesticide Action Network, when the lawsuit was filed. "As new independent research comes to light, the agency has been slow to re-evaluate pesticide products and its process, leaving bees exposed to an ever-growing load of hazardous pesticides."

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