Residues, dissipation, and safety evaluation of pymetrozine-clothianidin mixture in strawberry.

The residue detection method and field dissipation dynamics of the pymetrozine-clothianidin mixture in strawberries were investigated combining QuEChERS pretreatment and LC-MS/MS analysis to provide a reference for the safe use of pymetrozine and clothianidin mixture on strawberries. Good linearity (R2 > 0.999) was obtained for pymetrozine and clothianidin within the range of 0.005–1 μg mL−1. Method validations indicated that the recovery for pymetrozine and clothianidin was 84.2–101.4%, intra-day and inter-day repeatability ranged from 1.8 to 8.1% and from 4.1 to 7.0%, respectively. Following application of the recommended dose in field trials, pymetrozine and clothianidin dissipation followed first-order kinetics with half-lives of 6.8–13.9 days in strawberries at four locations. Moreover, owing to risk quotient < 100%, a mixture pesticide of 30% suspension concentrates (25% pymetrozine + 5% clothianidin) was unlikely to give rise to vital health concerns to humans following the recommended application guidelines. This study can be utilized in safety assessment and developing spray schedules for this mixed pesticide in strawberries.