This study investigated the long-term potential risk to honey bee colonies under natural field conditions by assessing hive health over four years of consecutive exposure to corn and oilseed rape crops grown from thiamethoxam-treated seeds. To quantify exposure, pollen and nectar collected from honey bees after foraging on flowering corn (pollen only) and oilseed rape (pollen and nectar) were analyzed for residues of thiamethoxam and its primary metabolite CGA322704. Residues of thiamethoxam and CGA322704 in corn pollen collected from honey bees were low; = 50% of the samples had quantifiable levels of thiamethoxam or CGA322704; maximum concentrations were 2 �g/kg for parent and the primary metabolite. For oilseed rape pollen and nectar, thiamethoxam was detected more frequently in nectar (83% of samples) compared to pollen (50% of samples), however maximum residues were also low, 1 �g/kg in pollen and 3 �g/kg in nectar. No quantifiable residues of CGA322704 were detected in oilseed rape pollen and nectar. Throughout the study, mortality, foraging behavior, colony strength, colony weight, brood development, and food storage levels were similar between treatment and control colonies. Detailed examination of brood development throughout the years demonstrated that colonies exposed to the treated crop overwintered successfully and had a comparable health status to the control colonies in the following spring. These data confirm low exposure with no resulting impact on honey bee health from potential residues in nectar and pollen following the use of thiamethoxam as a seed treatment on corn and oilseed rape.

Honey bee field studies: Assessing hive health after four consecutive years of exposure to flowering crops grown from thiamethoxam-treated seed

246th National Meeting (2013)

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