Development of 40% Fluopicolide· Pyraclostrobin Suspension Concentrate and Its Controlling Efficacy to Potato Late Blight in the Field

【Objective】 The objective of this study is to screen the optimum ratio of the mixtures of fluopicolide and pyraclostrobin which has a high inhibitory activity to Phytophthora infestans and processed it into aqueous suspension concentrate(SC),and to evaluate the control efficacy of the SC sample to potato late blight in the field.【Method】 The inhibitory activity of the mixtures of fluopicolide and pyraclostrobin at different mixing ratios against P.infestans was determined by leaf disc test and the synergistic ratios were calculated according to Wadley formula.The combination with higher synergistic interactions was screened and wetting-dispersing agents were selected by flowing point test and viscosity curve.The samples with different contents of adjuvants were processed by wet grinding.The rheological feature of the samples was adjusted and the formulation was optimized step by step.The sample was processed by wet grinding and the control efficacy was tested to potato late blight in the field after the final formula was determined.【Result】 Synergistic interactions against P.infestans of the mixtures of fluopicolide(F) and pyraclostrobin(P) were found at the ratio of 10﹕1 and 1﹕4(F﹕P) and the synergism ratios were 1.56 and 1.66,respectively.The optimal formulus of 40% fluopicolide.pyraclostrobin SC was established as follows: fluopicolide≥8%,pyraclostrobin≥32%,1% Terwet1004,2% Tersperse2700,2% Morwet D425,0.5% magnesium aluminosilicate,4% glycol,3% SAG630,water≤47.5%.The control efficacy of the sample of 40% fluopicolide.pyraclostrobin SC applied at the doses of 480,360,and 288 g a.i./hm2 against potato late blight in the field was 94.38%,92.20%,and 88.22%,respectively.【Conclusion】 Fluopicolide and pyraclostrobin used in combinations had synergistic interactions against P.infestans in some degree.The sample of 40% fluopicolide.pyraclostrobin SC was processed based on the selected formula had small particle size,high suspensibility and good storage stability and exhibited excellent efficacy in controlling potato late blight in the field.