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Control efficacy of an extract of cultured Xylogone ganodermophthora on powdery mildew caused by Podosphaera xanthii on watermelon in Korea
H. J. KANG (1), Y. Kim (1), T. Kim (1), C. U. Han (1), T. k. Jeong (1), S. Y. Nam (2). (1) Watermelon Research Institute CBARES, Eumseong-gun Chungcheongbuk-do, Korea; (2) Watermelon Research Institute CBARES, Eumseong-gun Chungcheongbuk-do, South Korea

<i>Xylogone ganodermophthora</i> (Xg) is an ascomycetous fungus that causes yellow rot on cultivated <i>Ganoderma lucidum</i>. Previously, we reported the <i>in vitro</i> antifungal activities of an Xg culture extract against several watermelon pathogens, including <i>Phytophthora capsici</i>, <i>Fusarium oxysporum</i>, <i>Sclerotium rolfsii</i>, and <i>Podosphaera xanthii </i>(Px). In 2014, we carried out greenhouse experiments to evaluate the control efficacy of a water extract of cultured Xg on watermelon powdery mildew (WPM). The test material (stock solution) was prepared by autoclaving an Xg culture in water at a ratio 800 g of culture per 6 L of water and then filtering it through filter paper. In the first trial, application of the solution (diluted 100- and 1,000-fold) at 7-day intervals suppressed the formation of conidiophores and conidia significantly. In the second trial, the 100-fold diluted solution was applied to watermelon plants 14 times before harvest (no fungicide was used). Near harvest time, more than 90% leaves of the plants were infected with Px. However, the farmer harvested 93.5% marketable fruits. These results suggest that a water extract of cultured Xg could be used as an environmentally friendly agent for the control of WPM in greenhouses.

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