This study was to investigate the time dependent residual changes of systemic pesticides metconazole and myclobutanil in dropwort, and to compare the disspation rate and ratio with the initial residue based on the physicochemical characteristics of pesticides. Metconazole (20%, SC) and myclobutanil (6%, WP) were diluted 3,000 times and 1,500 times, respectively and sprayed 3 times at 7 days intervals on prior to harvest day. Residual amounts of metconazole and myclobutanil were analyzed by LC/UVD and GC/ECD, respectively. Recovery rates for residual analysis spiked with 0.4 and 2.0 mg/kg were 80.1-94.3%, and less than 10% of coefficient variation. Residual amounts of metconazole and myclobutanil were reduced from 2.15 to 0.87 and from 1.96 to 0.38 mg/kg, respectively. First order dissipation rate constants for metconazole was 0.008 and myclobutanil was 0.017. During the experimental period, the dissipation ratio versus initial residue amounts was found to be higher in myclobutanil (80.61%) than in metconazole (59.53%). Generally, pesticides with high solubility in water and low log P values are more likely to be lost due to high mobility in water or soil after spraying. The solubility of myclobutanil (132 mg/L at room temp.) was about 4 times higher than that of metconazole (30.4 mg/L at room temp.) and the log P value was 2.94 that is lower than metconazole (3.85). These results are consistent with above results, which suggests that the physicochemical properties of pesticides affect the residual characteristic.

Comparison of dissipation ratio between metconazole and myclobutanil in dropwort

254th National Meeting (2017)

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