Pesticides hit non-pests: exposed bees forage poorly, die more often

The recent demise of many commercial bee hives has focused attention on the health of pollinators. Both domesticated and wild insects play key roles in making sure a variety of agricultural plants are pollenated and productive, so the sudden decline in domesticated bees was worrisome. Although initial evidence pointed to parasites, more recent evidence pointed the finger at insecticides.

A new study, released over the weekend by Nature, doesn't do much to clarify the cause of colony collapse. But it does show that insecticides can influence the health of a bee colony in subtle ways that could be hard to detect with standard study approaches. And it indicates that natural pollinators, which generally don't form the massive hives that domestic bees do, may be even more sensitive to these effects.

The work relied on a careful tracking of the bees, using small, indoor colonies of bumble bees, a common natural pollinator. The bees were fitted with small radio tags that could be read as the bees passed through a tube on their way in and out of the colony. On their way out, the bees would go through a chamber where they were exposed to pesticides. Ten colonies were exposed to a topical insecticide that's normally dusted on plants (λ-cyhalothrin, a pyrethroid); another 10 were exposed to a neonicotinoid called imidacloprid, which is ingested. A 10-colony control group went unexposed (except, possibly, in the environment), and another group got both insecticides.

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