Residual behavior and risk assessment of the mixed formulation of benzene kresoxim-methyl and fluazinam in cucumber field application

Benzene kresoxim-methyl (BKM) is a new strobilurin fungicide mixed with fluazinam (Flu) into 40 % suspension concentrate (SC) formulation to improve fungicidal efficacy and to reduce the risk of resistance on cucumber. However, the fate of the fungicide residues in a cucumber plantation remains unclear. Thus, an efficient method of ultra-performance liquid chromatography combined with a modified quick, easy, cheap, effective, rugged, and safe sample preparation was developed to simultaneously determine the BKM and Flu residues in cucumber and soil samples to investigate their residual behavior and risk assessment in the cucumber plantation. This analytical method revealed that the detection limits of BKM and Flu were 1.64 × 10(-3) and 1.82 × 10(-3) mg L(-1), respectively, and their average recoveries in the cucumber and soil samples were 77.5-106.9 %. The respective half-lives of BKM and Flu were 2.2-3.4 and 1.0-2.5 days in cucumber; in soil, the half-lives of BKM and Flu were 2.6-5.0 and 2.4-5.3 days, respectively. Seven days after application, the terminal residues of BKM and Flu in cucumber were less than 0.02 mg kg(-1). The residual profiles of BKM and Flu suggested that these fungicides could rapidly degrade in cucumber plantations. Their hazard quotient values were all less than 1 on the preharvest intervals of 3, 5, and 7 days, indicating that the dietary risk of BKM and Flu 40 % SC with the recommended usage on cucumber is negligible.