Screening of the Fungicides against Phytophthora Blight of Pepper

The toxicity of 10 fungicides(dimethomorph,cupric hydroxide,copper oxychloride,metalaxyl,thiram,fosetyl-aluminium,oligosacchari,propamocarb,chlorothalonil and mancozeb) to Phytophthora capsici Leonian were determined by inhibiting mycelium growth and germination of zoosporangia of the fungus in vitro,respectively.The results showed that dimethomorph had substantial inhibitory activity against mycelium growth with EC50 1.06 μg/mL and cupric hydroxide was effective on inhibiting germination of zoosporangia with EC50 1.68 μg/mL.Mancozeb had a little less inhibitory activity against mycelium growth and germination of zoosporangia,while propamocarb had almost no activity on the two phases of the pathogen.The screening of culture medium to produce zoosporangia indicated that rice bran agar culture medium was optimal for production of zoosporangia of the oomycete and P.capsici.Zoosporangia produced by the culture medium were enough in quantity,bigger and almost in the same size.