What’s Killing the Bees

New studies show that a widely used insecticide can threaten the health of bumblebee colonies and interfere with the homing abilities of honeybees.

Science Daily quotes bee researcher Dave Goulson as saying, "Some bumblebee species have declined hugely. For example, in North America, several bumblebee species which used to be common have more or less disappeared from the entire continent. In the UK, three species have gone extinct."

Investigators have long suspected pesticides, but haven’t found the connection–until now. Science Daily quotes researcher Sasha Vignieri as saying, "It’s been difficult to make direct connections between pesticides as they would be encountered in natural conditions, and the negative impacts we’ve seen in laboratory studies."

In a new study, scientists exposed developing colonies of bumblebees to low levels of a pesticide called imidacloprid, which is found in brand names pesticides such as Gaucho, Prestige, Admire, and Marathon. The doses were comparable to what the bees are often exposed to in the wild. The exposed bees had trouble finding their way back to the hive and often died before being able to do so.

Other research shows that honey bees "self-medicate" when their colony is infected with a harmful fungus, bringing in increased amounts of antifungal plant resins to ward off the pathogen (but they don’t seem to be able to defeat that lethal pesticide).

Researcher Michael Simone-Finstrom says, "The colony is willing to expend the energy and effort of its worker bees to collect these resins. So, clearly this behavior has evolved because the benefit to the colony exceeds the cost."

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