March 29, 2012

New Studies Give More Evidence Of Pesticides Harming Bee Populations

Scientists reported in the journal Science on Thursday that even low doses of widely used pesticides can harm bumblebees and honeybees.

British and French researchers looked at bees and neonicotinoid insecticides in two studies, which is a class of pesticides that was introduced in the 1990s and has become one of the most commonly used pesticide in the world.

Bee populations have been dropping rapidly throughout the world, and scientists fear pesticides are partly to blame for it.

During the two studies, one team from University of Stirling exposed developing colonies of bumblebees to low levels of neonicotinoid called imidacloprid, and then placed the colonies in an enclosed field site where they could fly around and collect pollen under natural conditions.

At the beginning and end of the experience, the team weighed each of the bumblebee nests to see how much the colony had grown.

They found that the treated colonies, compared to the control colonies that were not exposed to the pesticide, had gained less weight, suggesting less food was coming in.

On average, the treated colonies were eight to 12 percent smaller than the control colonies at the end of the experience.  The treated colonies also produced about 85 percent fewer queens.

In the second study, researchers tagged free-ranging honeybees with radio-frequency identification microchips glued to the bee's back.  This allowed them to track the bees as they came and went from hives.

They gave the bees a low dose of the neonicotinoid pesticide thiamethoxam and compared them to a control group of bees that was not exposed to the pesticide.

They found that the treated bees were two to three times more likely to die while away from their nests, most likely due to the pesticide interfering with the bees' homing systems.

Mickael Henry of the French National Institute for Agricultural Research (INRA) and leader of the second study said the findings raised important issues about pesticide authorization procedures.

"So far, they (the procedures) mostly require manufacturers to ensure that doses encountered on the field do not kill bees, but they basically ignore the consequences of doses that do not kill them but may cause behavioral difficulties," he said in a statement.

Eric Mussen, a bee expert for the University of California, Davis, told RedOrbit in an email that the insecticide in the study is just one of many devices used by man to help kill off honeybees.

“The neonicotinoids are simply one of a number of types of insecticides that can outright kill or, at sublethal doses, negatively impact honey bees and other bees, as well,” Mussen, Ph.D, an extension apiculturist at UC Davis who was not a part of the research, told RedOrbit.

“We have a lot of research ahead of us to determine what synergisms are occurring in our
beehives,” Mussen told redOrbit. “Once we have that knowledge, then the commercial crop producers will do what they can to help protect our bees.”


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