Dissipation of Fungicide Azoxystrobin in Foxtail Millet during Cultivation and Degradation in Soil

Abstract

This study investigated the dissipation of fungicide Azoxystrobin on minor crop foxtail millet and in soil. All the experiments of preparation methods were used QuEChERS modified methods and analyzed by Shimadzu LC-MS/MS 8040. For minor crop field trial, Azoxystrobin 10% wettable powder (WP) was sprayed on 4 plots according to prearranged time. Method limit of quantitation (MLOQ) of Azoxystrobin and R230310 were 0.01 mg/kg in grain and straw. The linearity (r2) of matrix matched calibration curves were ≥ 0.999. As results of samples analysis, total maximum residue amount of grain was decreased from 0.61 mg/kg (Plot 4) to 0.07 mg/kg (Plot 1) and total maximum residue amount of straw was decreased from 5.02 mg/kg (Plot 4) to 0.14 mg/kg (Plot 1). These results will contribute to establish Pre-Harvest Intervals (PHIs) and Maximum Residue Limits (MRLs) of Azoxystrobin during cultivation of foxtail millet in Korea. For the soil field trial, Azoxystrobin 10% WP sprayed 200 L/10 a for one time. For the laboratory incubation, Azoxystrobin standard solution spiked at the concentration of 0.2 mg/kg in 10 g soils which contain 75% water of field capacity and incubated at 25±2℃ in the incubator. Field and laboratory soil samples were collected according to prearranged time. The MLOQ of Azoxystrobin was 0.002 mg/kg and R234886 was 0.005 mg/kg in both soils. The linearity (r2) of matrix matched calibration curves were ≥ 0.99. The Azoxystrobin was dissipated rapidly in field soil and the half-life of Azoxystorbin was calculated 12.38. But the Azoxystrobin was dissipated slowly in laboratory soil and the half-life of Azoxystrobin was over 90 day. The residue of soil metabolite R234886 was detected less than MLOQ in both soils.

Key Words: Azoxystrobin, R230310, R234886, Minor crop, Residue, Foxtail millet, LC-MS/MS, Dissipation, Soil, Half-life