Dissipation of difenoconazole in rice, paddy soil, and paddy water under field conditions

An analytical method for determining the residue of a broad-spectrum fungicide, difenoconazole, in soil and rice crop matrices is described. Mean recoveries and relative standard deviation (RSD) in paddy soil, water, rice plant, rice hull, and husked rice matrices at three spiking levels ranged 71.8–115.8% and 1.6–7.8%, respectively. The half-life of difenoconazole was determined at three different field sites in Guangxi, Hubei, and Zhejiang provinces in China via a dissipation experiment, in which a 30% aqueous suspension concentrate of difenoconazole and propiconazole (15% difenoconazole, 15% propiconazole) was applied at high dosages. The half-lives of difenoconazole in water, rice plant, and soil in Guangxi were 0.30, 2.59 and 23.26 days, 2.50, 1.77 and 2.82 days in Hubei, and 2.71, 1.39 and 6.61 days in Zhejiang, respectively. Difenoconazole concentrations in soil, rice hull, and husked rice samples were below the detection limit at pre-harvest intervals of 30, 40 and 50 days after fungicide application. The concentration in straw at pre-harvest intervals of 30, 40 and 50 days in the three experimental locations ranged from 0.037 mg kg−1 and 2.53 mg kg−1.

► Developed a gas chromatography- mass spectrometry method for determining difenoconazole. ► Investigate degradation dynamics of difenoconazole in the open field. ► Suggest the pre-harvest interval of difenoconazole in rice.