Again, I don't profess to be a bee expert, but John mentioned a study. The U.S. Department of Agriculture just released a fairly significant paper, and in it they're very clear that this is multifactorial. Pesticides are one very small component. In fact, I think they said it's one of the least significant components, and that hive health through nutrition could probably solve most of the issues they're experiencing, at least in the U.S.
On May 7th, 2013. See this statement in context.