Study: Disorientation from pesticides a clue to bee disorder

Study: Disorientation from pesticides a clue to bee disorder

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Widely used insecticides interfere with the homing instincts of bees, international researchers suggested Thursday, linking a class of agricultural pesticides to the growing threat to beehives known as colony collapse disorder.

Since 2006, U.S. beekeepers have reported unusually severe winter losses of honey bee colonies 33 or greater with about a third of the losses directly attributed to the syndrome.

Explanations have ranged from poor nutrition to diseases to mite pests, which have devastated wild honeybees. Also mentioned in the new study, which looked at both honeybees and bumblebees, are pesticides, including the "neonicotinoid" insecticides that are among the most wide ly used agricultural pesticides worldwide.

"Certainly, it looks like these insecticides are one important mechanism in the problem," says entomologist Dave Goulson of the United Kingdom's University of Stirling, who was senior researcher on the bumblebee study, one of the two bee studies released by the journal Science. "What we are seeing are subtle effects of non-lethal doses of these agricultural chemicals," he says.

In their study, Goulson and colleagues dosed some bumblebee hives with the insecticides, but not others. They placed the hives in enclosed fields where their bees could forage naturally. After six weeks, they found that the dosed hives were 8 to 12 smaller than the others and, more important, that they produced only 15 as many queen bees, an average of two compared with nearly 14 in undosed hives, important for the hive producing future generations of bees.

"The bumblebee fin ding is really important" because reproduction is a key element in deciding whether or not to approve a particular insecticide, says entomologist Jeffery Pettis of the U.S. Department of Agriculture. "The queen bees are what lead the bees to start out of the hive foraging, as well, something that directly affects survival."

In the second study, led by Mickal Henry of France's Institute for Agricultural Research (INRA), researchers individually tagged honeybees and released them from hives in fields of scorpion weeds. Some received doses of neonicotinoid insecticides equivalent to exposures seen on farms, while others didn't. Dosed foraging honeybees, which are supposed to bring nectar back to the hive, died roughly two to three times more often than other bees wi thout returning home. "They failed to return," Henry says. "Clearly the homing task seems to have become more challenging for them."

Colony collapse disorder is marked by bees emptying out of hives and not returning. Bee colony losses have alarmed U.S. farmers, who rely on about 2.68 million managed bee colonies to pollinate crops, a $ 15 billion industry, according to the U.S. Department of Agriculture.

"Ironically, we have moved to neonicotinoids because they are safer for people. We may be seeing unintended consequences of solution to an earlier problem," says entomologist James Frazier of Penn State University in State College, Pa.

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