Seed treatment with neonicotinoid insecticides does not affect the foraging behavior of honey bees

The widespread use of neonicotinoid insecticides in the agricultural ecosystems is said to be one of the causes for the alarming bee decline observed around the world. However, the evidences against neonicotinoids are inconclusive. In this study, we assessed the impact of neonicotinoids (imidacloprid, and thiamethoxam), when applied as seed treatment and foliar sprays, on the foraging activity of honey bees. When applied as seed treatment, residues of the tested molecules in the pollen and nectar samples were present below quantifiable levels (< LOQ). At 3 days after spraying, residues of imidacloprid and thiamethoxam were 0.86 and 0.96 mg/kg in the leaf samples, 0.15 and 0.23 mg/kg in the pollen samples, and 0.07 and 0.07 mg/kg in the nectar samples, respectively. Further, the foraging activity of the bees did not appear to be impacted when neonicotinoids were applied as seed treatment. Contrarily, foliar application of the neonicotinoides significantly reduced the foraging activity between 1 and 3 days after application. Nonetheless, the foraging activity was comparable to the control levels 7 days after spraying. It appears that there is little short-term impact of neonicotinoids on the foraging activity of bees, especially when applied as seed treatment.