Dissipation and Residues of Pyraclostrobin in Rosa roxburghii and Soil under Field Conditions

Rosa roxburghiihas been widely planted in China. Powdery mildew is the most serious disease ofR. roxburghiicultivation. Pyraclostrobin was widely used as a novel fungicide to control powdery mildew ofR. roxburghii. To assess the safety of pyraclostrobin for use onR. roxburghiifruits, its residue rapid analysis as well as an investigation on its dissipation behaviors and terminal residues inR. roxburghiiand soil under field conditions were carried out. The QuEChERS method was simplified using LC–MS/MS detection and combined with liquid–liquid extraction purification to allow determination of pyraclostrobin levels inR. roxburghiifruits and the soil. The fortified recoveries at 0.1~5.0 mg/kg were 93.48~102.48%, with the relative standard deviation of 0.64~3.21%. The limit of detection of the analytical method was 0.16 and 0.15 µg/kg forR. roxburghiifruit and soil, respectively. The effects of different spray equipment and formulations on the persistence of pyraclostrobin inR.roxburghiiwere as follows: gaston gasoline piggyback agricultural sprayer (5.38 d) > manual agricultural backpack sprayer (3.37 d) > knapsack multi-function electric sprayer (2.91 d), suspension concentrate (SC) (6.78 d) > wettable powder (WP) (5.64 d) > water dispersible granule (WG) (4.69 d). The degradation of pyraclostrobin followed the first-order kinetics and its half-lives inR.roxburghiiand soil were 6.20~7.79 days and 3.86~5.95 days, respectively. The terminal residues of pyraclostrobin inR.roxburghiiand soil were 0.169~1.236 mg/kg and 0.105~3.153 mg/kg, respectively. This study provides data for the establishment of the maximum residue limit (MRL) as well as the safe and rational use of pyraclostrobin inR.roxburghiiproduction.Keywords:pyraclostrobin;Rosa roxburghii;soil;dissipation;residue