Neonicotinoids, the class of chemical pesticides most commonly blamed for CCD, were introduced into widespread use around the time CCD appeared. I don't think a

Neonicotinoids, the class of chemical pesticides most commonly blamed for CCD, were introduced into widespread use around the time CCD appeared. I don't think anybody has definitely proven causation (and see the various posts, even today, about problems in deriving causation from correlation). But there appears to be neurobiological evidence for some link between the way the pesticides work and the way bees behave. As far as likely suspects for the cause of CCD go, it's high on the list.