The Fungitoxicity of Four Fungicides to Pseudoperonospora cubensis in Hunan Province

[Aims] The aim is to clarify the fungitoxicity of the fungicides with different action modes against Pseudoperonospora cubensis in hunan province.[Methods] The fungitoxicity of four fungicides to Pseudoperonospora cubensis of Hunan province was tested by leaf disc floating method.[Results] The results showed the fungitoxicity(ec50) in metalaxyl,cymoxanil,azoxystrobin and dimethomorph to Pseudoperonospora cubensis were 15.613-17.266,10.31313.465,3.834-5.444 and 9.122-9.915 mg/l,respectively.[Conclusions] The resistance ratio to azoxystrobin was high,and the resistance ratios to the other three fungicides were lower.however,the index of relative toxicity of azoxystrobin was significantly higher than that of the other three fungicides.