Symptoms, also known as spot disease or leaf spot disease, mainly damage the leaves. The spotted leaf was irregular to a round shape with a reddish-brown color at the beginning, and then turned grayish to gray with a slightly raised edge. A small black spot was scattered on the surface of the spot, that is, a pathogenic conidia. In severe cases, leaf spots are densely covered or commissures, causing partial or total dryness of the leaves.
The pathogen Phyllosticta batatas (Thum) Cooke said that the sweet potato leaf spot mildew is a fungus of the fungus Subphylum fungus. Conidiophore nearly spherical, with orifice, diameter 100-125um; conidiophore short, oval or elliptic, unit cell, colorless, size 2.6-a 101.7-5.8 (μm).
Transmission routes and disease conditions Northern mycelia and conidia were found in the soil that fell from the body of the disease, and conidia spread and spread throughout the following year. In southern China, in the warm regions where annual sweet potatoes were planted, pathogenic bacteria spread and spread without any significant wintering period. Conidia were initially infested and reinfested by rain spattering. During the growing season, frequent rainwater, high humidity in the air and in the field, or low waterlogging in the field, are easily affected.
Control methods (1) Dispose of the diseased body and remove it immediately after harvest. (2) Avoid continuous cropping seriously. (3) Choose high-lying plots to plant the land. After the rain, clear the gutters and lower the temperature. (4) Frequently or severely, timely spraying 70% thiophanate-methyl wettable powder 1000 times liquid plus 75% chlorothalonil wettable powder 1000 times or 30% green leaf dan wettable powder 600 times continuously in the beginning of the disease. , 80% spray grams WP 600 times, 50% benomyl WP 1500 times, 40% more. Sulphur suspension 500 times, about 10 days 1 time, continuous control 2-3 times, pay attention to spray evenly enough.
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