Harvard scientists recently tested the effects of the pesticide imidacloprid on bee colonies in situ, meaning out in the field instead of in a laboratory. At each site, four hives were treated with four different amounts of the pesticide. Beginning with the hives that received the highest doses, and continuing to the hives that received low doses, the bees died in a fashion symptomatic of colony collapse disorder (CCD).Reactions: The scientists say their findings show that even low doses of imdacloprid, similar to those used in real agriculture, can cause CCD. The pesticide's manufacturer, Bayer, says the low doses used in the study remained too high to be realistic. The EPA still considers CCD to result from a mix of factors, possibly including pesticide exposure as just one factor. That may still be a reasonable summary of the balance of current evidence, but the new study strengthens the case that pesticides -- imidacloprid in particular -- have a big role.