Sulfoxaflor Residues in Pollen and Nectar of Cotton Applied through Drip Irrigation and Their Potential Exposure to Apis mellifera L.

Systemic insecticides have been applied through drip irrigation for controlling crop pests, but few studies have addressed potential negative effects of the application on non-target organisms. In this study, the safety of sulfoxaflor applied at 450 or 700 g a.i. ha(-)(1) through drip irrigation at different times before flowering or during flowering to honey bee (Apis mellifera L.) was studied in 2016-2017 in a cotton production field in Xinjiang, China. Results showed that sulfoxaflor residues in pollen and nectar of cotton treated with sulfoxaflor at 450 g a.i. ha(-)(1) before and during flowering through drip irrigation were either undetectable or no more than 17 μg·kg(-)(1). Application of sulfoxaflor at 700 g a.i. ha(-)(1) before flowering resulted in ≤ 14.2 μg·kg(-)(1) of sulfoxaflor in pollen and < 0.68 μg·kg(-)(1) in nectar. Sulfoxaflor applied at this higher rate during flowering had the highest residue, up to 39.2 μg·kg(-)(1) in pollen and 13.8 μg·kg(-)(1) in nectar. Risk assessments by contact exposure and dietary exposure showed that drip application of sulfoxaflor at the two rates before or during flowering posed little risk to honey bees. Thus, drip application of sulfoxaflor could represent an environmentally benign method for controlling cotton aphid.