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What are the control methods for soybean downy mildew?

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Soybean downy mildew damages seedlings, leaves and seeds. After the first true leaf unfolds, chlorotic patches appear along both sides of the veins. On the leaves of mature plants, round or irregular yellow-green specks with indistinct edges appear on the surface, later turning brown, and a grayish-white mold layer forms on the underside of the leaves. The surface of diseased seeds is covered with a grayish-white layer of mycelium containing large numbers of the pathogen's oospores. The pathogen overwinters as oospores on seeds and in diseased leaves, becoming the primary infection source for the following year. The disease begins to appear in mid-to-late June each year, with the peak period from July to August, and in rainy years it often becomes severe. Control

Soybean downy mildew damages seedlings, leaves and seeds. After the first true leaf unfolds, chlorotic patches appear along both sides of the veins. On the leaves of mature plants, round or irregular yellow-green specks with indistinct edges appear on the surface, later turning brown, and a grayish-white mold layer forms on the underside of the leaves. The surface of diseased seeds is covered with a grayish-white layer of mycelium containing large numbers of the pathogen's oospores. The pathogen overwinters as oospores on seeds and in diseased leaves, becoming the primary infection source for the following year. The disease begins to appear in mid-to-late June each year, with the peak period from July to August, and in rainy years it often becomes severe.

Control methods:

(1) Agricultural control. Select disease-resistant varieties, carefully sort the seeds, remove diseased seeds, and practice a 2-3 year crop rotation.

(2) Chemical control. Use 40% fosetyl-aluminum wettable powder, or 25% metalaxyl wettable powder, for seed dressing at 0.5% of seed weight. When the disease occurs in the field, spray with a 300-fold fosetyl-aluminum solution or an 800-fold metalaxyl solution, using about 40 kg of spray solution per 667 sq m.

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