Synergistic Toxicity and Control Effect of Cymoxanil and Azoxystrobin on Pseudoperonospora cubensis

[Aims] The paper aims to provide references for effectively preventing downy mildew of cucumber. [Methods] The joint-fungitoxicity of cymoxanil and azoxystrobin against Pseudoperonospora cubensis was tested by leaf disc fl oating method, and also the control effi cacy was further confi rmedin fi eld. [Results] The mixtures of cymoxanil and azoxystrobin at the ratio of 5∶5, 6∶4 and 7∶3 had synergistic effects the synergistic ration(SR) were 2.07, 1.91 and 1.79, respectively. At the ratio of 3∶7 and 4∶6 had additive effects, the SR were 1.13 and 1.47. The control effi cacyof tankmixture of synergistic combination at the ratio of 7∶3 and 5∶5 of cymoxanil and azoxystrobin, was higher than that of respective ingredient, as well as long duration of fungitoxicity. [Conclusions] The synergistic combination ratios would be potentially applicableby tank mix.