Degradability of Strobilurin Fungicides in Water and Soils

The degradability of strobilurin fungicides in the environment is critical to assessing its environmental risk.A laboratory experiment was performed to examine the influences of temperature,pH and light on the degradation of three strobilurin fungicides(azoxystrobin,kresoxim-methyl,and JS399-19)in water and soils.The results showed that the degradation of azoxystrobin and JS399-19 was relatively slow,while kresoxim-methyl degraded quickly in water at pH5.0,7.0,and 9.0 under 25 ℃.The half-life times of three strobilurin fungicides ranged from 2.64 hours to more than 1.0 year.The hydrolysis of three strobilurin fungicides was controlled by both water pH and their chemical structures.The hydrolysis rate was greater at 50 ℃ than 25 ℃,showing a positive correlation with temperature.The half-life times of kresoxim-methyl,JS399-19,and azoxystrobin in three different kinds of soil were less than 1.0 day,107 to 330 days,and 223 to 407 days,respectively.The photolysis rate constants of kresoxim-methyl,azoxystrobin,and JS399-19 were 0.666 4,0.561 1,and 0.023 5 h-1,respectively.Our results indicate that azoxystrobin and JS399-19 have long retention in water and soil,and more attention should be paid to their residues in the environment.