Symptoms mainly harm the leaves. When the disease occurs, there are yellow and wet spots on the leaf margins and tips. There are light-brown or oblong to long-term lesions at the junction of disease and health. Parallel to the veins, the symptoms of the old leaves are particularly obvious. Leaf margins and tip lesions are 7 to 13 cm long and 1 to 2 cm wide. Symptoms of severe lesions are 13 to 15 cm long with brown markings. Lesions on the leaves are contiguous and become brownish yellow spots. Plant growth Affected, reduce the ornamental value. Pathogens and Occurrence The pathogen of the disease is a microorganism called Cercospora, which is wintered on the diseased part or the diseased body. During the second year of spring and summer, the conidia are transmitted through wind, rain, air and water splashes, which may occur. Subinfection and reinfection. When the humidity is high, it is easy to attack, and it can be affected from the seedling stage to the elongation period of adult plants. The optimum temperature for the germination of germs is 25 to 28Â°C. High temperature and humidity are conducive to the reproduction and transmission of pathogens. They are easy to attack in rainy and low-lying areas in spring and summer. In the Pearl River Delta, from April to September, the incidence of heavier, summer and autumn heat and drought, suddenly thunderstorms or typhoon storm weather can easily lead to serious illness. Prevention methods (1) Keep the fields and basins moist, pay attention to drainage in summer and autumn rainfall, increase phosphorus and potassium fertilizers, and compound fertilizers; control the water and fertilizers in winter, and use appropriate moisture, promote dormancy, spray pesticides to kill bacteria, or cut off diseases The dead leaves are concentrated and burned. (2) Spray control at the early stage of disease, 50% carbendazim wettable powder 600 to 800 times liquid, 50% thiophanate-methyl, sulfur suspension 600 to 800 times, 50% benomyl powder 800 to 1000 times liquid, 50% Wanning wettable powder, 70% thiophanate-methyl wettable powder 800 to 1000 times liquid, 50% Wanning+37% Wilt gram wettable powder (1:1) 800 to 1000 times liquid , 70% chlorothalonil + 40% benzoate (1:1) WP, alternately sprayed 3 to 4 times, sprayed once every 7 to 8 days, have better control effect.
Fresh taro,Fresh carrot,other vegetables
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