GELLERMAN: Since 2006 there has been a mass die-off of honeybees in the US.
The same thing was seen in Europe going back to the 1990s. And while the die-off has a name: Colony Collapse Disorder, the cause has puzzled scientists.

But there have been clues that one of the world’s most commonly used pesticides plays a role in the destruction of up to 90% of honeybee hives. Alex Lu, a professor of environmental exposure biology at Harvard University conducted a series of field experiments using the popular pesticide Imidacloprid.

Like commercial beekeepers, who feed their colonies with high fructose corn syrup, Professor Lu dosed his experimental hives with corn syrup laced with minute amounts of the pesticide. He says it’s the Imidacloprid ---given over time -- that’s causing Colony Collapse Disorder.

LU: We found that this pesticide called Imidacloprid is capable of collapsing honey bee colonies in a sub-lethal dose manner.

GELLERMAN: So it’s basically the smoking gun?

LU: It is, because the study design we created eliminated other possible risk factors. We found 15 of the 16 pesticide treated hives collapsed while none of the control hives except for one.

GELLERMAN: 94 percent of the experimental colonies fed high fructose corn syrup laced with sub-lethal doses of Imidacloprid over time died. Professor Lu says the onset of Colony Collapse Disorder coincides with the introduction of the pesticide in the US and Europe. He says it’s the chemical residue, found in corn syrup produced using genetically modified plants, that’s killing bees.

Besides corn, Imidacloprid is sprayed on 140 food crops---including potatoes and rice - and it's commonly found in pet flea collars. The US EPA has an ongoing study.
Professor Lu’s results are published in the latest edition of the Bulletin of Insectology.