The Neonicotinoid Insecticide Imidacloprid Repels Pollinating Flies and Beetles
The Neonicotinoid Insecticide Imidacloprid Repels Pollinating Flies and Beetles at Field-Realistic Concentrations
Both Diptera and Coleoptera exhibited marked avoidance of traps containing imidacloprid at a field-realistic dose of 1 µg L−1, with Diptera avoiding concentrations as low as 0.01 µg L−1. A recent meta-analysis based on 13 studies of the impacts of imidacloprid on honeybees found that field-realistic doses under laboratory and semi-field conditions had no lethal effects but reduced colony performance by 6 to 20% . If pollinators are attracted to or repelled by treated crops (compared to controls), then their level of exposure to neonicotinoids could be higher or lower than expected. Previous studies suggest that honeybees avoid imidacloprid in nectar, but the doses used were higher than naturally encountered in nectar of treated crops . Overall, Diptera, Coleoptera and Araneae exhibited avoidance of pan traps containing 1 µg L−1 imidacloprid compared to controls, with Diptera in particular exhibiting a very strong response. This avoidance response remained detectable in dipterans when using concentrations of imidacloprid as low as 0.01 µg L−1, below the lower limit of detection using most commonly available analytical methods [e.g. 19]. Our data demonstrate that arthropod sensory systems are highly sensitive to this compound. Strong repellent effects of low concentrations of a pesticide across a broad range of insects are unexpected, but perhaps may be the result of the widespread use of neonicotinoids in farmland and gardens over the previous twenty years leading to powerful selection for their avoidance.