An article posted today on Salon.com said the maker of imidacloprid, Bayer CropScience, found the pesticide in the nectar and pollen of flowering trees and shrubs at concentrations high enough to kill a honeybee in minutes. That December 2007 revelation, plus beekeepers' own experiences in fields treated by the pesticide, have scientists taking a new look at imidacloprid's role in sudden, unexplained bee die-offs that have been reported around the world for the past 10 years.

Scientists have pondered whether there is a single cause of Colony Collapse Disorder or whether the phenomena results from a variety of factors, such as the combined effect of disease, pests and pesticides, as was reported in March by the BBC. Salon reporter Julia Scott spoke to UC Davis Cooperative Extension entomologist Eric Mussen about the pesticide implicated in today's article.

He told Scott that he wasn't surprised about Bayer's research conclusions and that he has seen UC studies with similar results, such as one at UC Riverside that found imidacloprid in the nectar of a eucalyptus tree bloom at concentrations of 550 ppb a year after it was applied.

"From some of the data on the trees, it appears as though there are situations where honeybees can get into truly toxic doses of the material," Mussen was quoted in the article. "This (is) the first time that we've had something you put in a tree that could stay there for a long time."

Still, Mussen said, he doesn't believe imidicloprid or a related pesticide clothianidin carry all the blame for CCD.

"Could it be part of the story? I'm sure. I think any of the pesticides the bees bring back to the beehive is hurting the bees," Mussen was quoted.