Comparing effects on honeybees and bumblebees after application of contaminated dust in semi-field and field conditions

In 2013, the European Food Safety Authority (EFSA) has highlighted several data gaps regarding the exposure and risk of pesticides to honeybees, bumblebees and solitary bees, including the risks from exposure to contaminated nectar and pollen. This study aims to contribute data, results and conclusions to obtain more information on exposure and risks of flowering oilseed rape seed treated with the neonicotinoid clothianidin, to pollinators. Semi-field and field trials were conducted at five different locations across Germany, using the Western honeybee ( Apis mellifera L.), the buff-tailed bumblebee ( Bombus terrestris L.) and the red mason bee ( Osmia bicornis L.) as study organisms. Highest amounts of clothianidin residues were measured in single samples of mud cell walls (7.2 μg kg -1 ) and pollen (5.9 μg kg -1 ) from solitary bee nests. Residues in nectar from honey sacs, honeybee combs and bumblebee nests (2.2, 2.9, and 3.0 μg kg -1 respectively) showed no clear differences in the amount of residues, neither did residues in pollen (1.5, 1.8, and 1.3 μg kg -1 respectively). These results suggest differences in the risk profiles of those three bee species. Keywords: clothianidin, residues, honeybees, bumblebees, solitary bees, field, semi-field