Biological Properties and Fungicide Toxicity on Pathogen of Coix Leaf Spot

  Objective  Biological properties of Curvularia coicis Castellani, which causes coix leaf spot (CLS) on Chinese pearl barley, and the control efficacy of 3 fungicides on the disease were studied.

  Method  Effects of temperature, pH, light, and carbon and nitrogen sources on the mycelial growth of the pathogen as well as the toxicity of mefentrifluconazole, pyraclostrobin, fludioxonil, and their binary compounds toward the pathogen were determined.

  Result  The optimum conditions for the mycelial growth of C. coicis were found to be 25 ℃, pH 8, starch for carbon, and peptone for nitrogen with no specific preference for light exposure. All 3 tested fungicides exhibited inhibitory effects on the pathogenic growth as indicated by the toxicity indices of mefentrifluconazole at 234.83-fold, pyraclostrobin at 97.84-fold, and fludioxonil at 84.97-fold of that of carbendazim. In combination of the agents, only mefentrifluconazole and pyraclostrobin were shown synergistic in the antifungal efficacy with the best mixing ratio of 5∶5 with a toxicity index of 221.85.

  Conclusion  Temperature, pH, and carbon and nitrogen sources significantly affected C. coicis growth. Mefentrifluconazole, pyraclostrobin, and fludioxonil were strongly antifungal against the pathogen. But application of combinations of these agents require further evaluation.