Farmers have been using this insecticide for over a decade. See this abstract from scientific article.
Experimental results show that the environmental release of particles containing neonicotinoids can produce high exposure levels for bees, with lethal effects compatible with colony losses phenomena observed by beekeepers.I wonder why it took so long to determine this link, and if their is a significant testing of insecticides before being released to the market--I doubt it. Also, it makes one speculate as to other, but yet unknown, deleterious effects this insecticide might be having on the environment and humans.