Abstract:

To scientifically evaluate the safety of pyraclostrobin on three minor crops (wampee, guava, and pitaya), one-year residual field trials in four sites were conducted on pyraclostrobin 30% suspension concentrate (SC) based on guidelines for field trials of pesticide residues in crop. The dissipation dynamics, final residues, and dietary risk assessment of pyrclostrobin SC on wampee, guava, and pitaya were carried out based on ultra-high performance liquid chromatography tandem triple quadrupole mass spectrometer (UPLC- MS/MS). The sample was extracted with acetonitrile (ACN), purified by PSA, and determined by UPLC- MS/MS. The results showed that when the spiked levels of wampee whole fruit, wampee pulp, guava, pitaya whole fruit and pitaya pulp was from 0.01 to 5.0 mg/kg, the recovery ranged from 104% to 107%, 80% to 96%, 93% to 100%, 83% to 91%, and 90% to 107%, with the relative standard deviation ranging from 0.9% to 3.8%, 2.7% to 5.3%, 3.0% to 10.7%, 1.1% to 4.3%, 2.2% to 6.3%, respectively. The limits of quantification were all 0.01 mg/kg. The initial concentration of pyraclostrobin in wampee, guava, and pitaya was from 2.8 to 4.8, 0.36 to 1.0, 0.48 to 1.40 mg/kg, and the half-lives ranged from 8.8 to 11.4 d, 5.6 to 13.9 d, 3.0 to 3.8 d, respectively, when pyraclostrobin 30% SC was applied at the dosage of 250 mg/kg, thrice. The finial residues in whole wampee and pulp, guava, whole pitaya and pulp was from 0.24 to 2.8, 0.016 to 0.73, 0.20 to 0.46, 0.12 to 3.6, <0.010 to 0.072 mg/kg, when the pre-harvest intervals was 7 and 10 days in wampee and guava, 5 and 7 days in pitaya, respectively. The dietary risk assessment showed there was no unacceptable risk to the health of the general population, when the risk quotient (RQ) of pyraclostrobin was 77.0%. The research results provided support and reference for scientific and rational use of pyraclostrobin 30% SC on three minor crops, and establishing their maximum residue limit (MRL) values.

Key words: pyraclostrobin, wampee, guava, pitaya, pesticide residues, dissipation dynamics, dietary risk assessment