Health Canada: Evaluation of Canadian Bee Mortalities that Coincided with Corn Planting in Spring 2012

(except from conclusion)...The information evaluated suggests that planting of corn seeds treated with the nitro guanidine insecticides clothianidin and/or thiamethoxam contributed to the majority of the bee mortalities that occurred in corn growing regions of Ontario and Quebec in Spring 2012. The likely route of exposure was insecticide contaminated dust generated during the planting of treated corn seed. The unusual weather conditions in the spring of 2012 were likely also a contributing factor.

Measures have been implemented to reduce honey bee exposure to dust generated during planting of treated corn seed, including communication of best practices to reduce the exposure of honey bees, labelling of treated seed, a treated seed dust standard, and development of technical solutions to reduce dust, including developments in the areas of seed coating quality, seed flow lubricants, planting equipment, and disposal of treated seed bags. Please refer to “Pollinator Protection: Reducing Risk from Treated Seed” ( pollinisateurs/index-eng.php) for details.

Additionally, the nitro-guanidine neonicotinoids have been placed under re-evaluation (REV2012-02, eng.php) and further regulatory action will be taken if required. 

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