Effect of peach bagging on deposition, distribution and residues of six typical pesticides

In this study, the QuEChERS method was modified for simultaneous determination of imidacloprid, azoxystrobin, fenbuconazole, difenoconazole, chlorpyrifos and β-cypermethrin residues in peach leaf, peach fruit and soil by ultra-performance liquid chromatography/gas chromatography tandem mass spectrometry. The results showed that the average recoveries of the six pesticides in three matrices were between 72% and 111% with the relative standard deviations (RSDs, n = 5) between 0.90% and 18% at spiking levels of 0.05-20 mg/kg (peach leaves), 0.05-2 mg/kg (peach fruits) and 0.05-5 mg/kg(soil). In the non-bagging treatment group, pesticides were mainly deposited in peach leaves after application, followed by soil and peach fruits, which accounted for 57%-69%, 25%-39% and 3%-6%, respectively. Moreover, the ultimate residues of the six pesticides on the 14th and 21st days after the second application were (0.07 ± 0.01)-(0.77 ± 0.13) mg/kg and <0.05-(0.27 ± 0.05) mg/kg, accounting for 15%-60% and 9%-34% of the corresponding MRL values, respectively. Fruit bagging significantly decreased the initial deposits and ultimate residues of six pesticides in peach fruits. In the bagging treatment group, the percentage of initial deposition of the six pesticides on peach fruit were <1%, and the ultimate residues at 14 and 21 days was lower than 10% of MRL value regulated by China. This study clarified the effects of fruit bagging on deposition and residues of six pesticides, and provided a theoretical basis for guiding the safe use of fruit bagging measures in peach orchards.