This report outlines some incidents in Canada last spring involving the drilling of maize seed treated with Clothianidin and Thiamethoxam.
There have been similar incidents in the US and Germany and this is one known problem with Neonicotinoids which needs to be addressed.

an unusually high number of reports of honey bee mortalities were received from beekeepers in corn
growing regions of Ontario and Quebec. The majority of reports were from southern
Ontario, involving over 40 beekeepers and 240 different bee yard locations.
http://www.ontariobee.com/sites/onta...ties.ENG-1.pdf