Dissipation and residue of dimethomorph in potato plants produced and dietary intake risk assessment

Late blight is a potentially devastating disease of potato. Dimethomorph has been widely used for preventing and controlling this disease. However, there is little information on dimethomorph residue in potato and the production soil. To address this issue, the present study developed a method for accurate analysis of dimethomorph using high-performance liquid chromatography. A linearity that had a determination coefficient of 0.9998 was established based on dimethomorph concentrations from 0.05 to 10.0 mg/L. The recovery rates ranged from 76.61% to 109.11%. The limit of detection and the limit of quantification were 0.02 mg/kg and 0.05 mg/kg, respectively. Potato production experiments were then carried out in three provinces of China, and dimethomorph was applied through a foliar spray. The established method was used for analysing the uptake, dissipation, and residues of dimethomorph in potato leaves and tubers and also in soils. Results showed that foliar spray of dimethomorph was translocated to tubers and generally within 2 days. The half-lives of dimethomorph in potato leaves, tubers, and soil ranged from 2.65 to 4.20, 1.79 to 3.71, and 4.62 to 9.0 days, respectively. The risk assessment of dietary exposure showed that all of the risk index values and the hazard quotient were less than 100%, indicating that foliar spray of dimethomorph on potato at 1.5 times the recommended minimum dosages poses little risk for consumption of the tubers in the three provinces of China.