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霜霉病.一种真菌病害,病菌在白菜种株上越冬,也可在种子或土壤中越冬,靠风雨传播。初发病时,叶上出现水渍状小斑点,后扩大为多角病斑,由黄变淡褐色,叶背面出现白色雾状物,严重时叶片枯黄。天气时冷时热、连续几天西南风、空气湿度大、播种过早、病菌严重的地块、连作和低洼地等,都有利于此病的发生和导致病情加重。为防治霜霉病,播种时用种子重量0.4％的代森锌(80％)拌种。在发病初期喷20％乙磷铝可湿性粉剂300—500倍液,或65％代森锌可湿性粉剂500倍液。
Downy mildew, a fungal disease that infects cabbage plants and overwinters in the seed or soil, spreading by wind and rain. Initial onset, the leaves appear water-like small spots, after the expansion of polygonal lesions, from yellow to light brown, white back of the leaf appeared mist, yellow leaves in severe cases. When the weather is cold and hot, a few days southwest wind, air humidity, sowing premature, severe germ plots, continuous cropping and low lying, etc., are conducive to the occurrence of the disease and lead to aggravating. In order to prevent downy mildew, sowing seeds with seed weight 0.4% of the zinc (80%) seed dressing. Early in the incidence of spraying 20% phosphorus aluminum phosphorus wettable powder 300-500 times, or 65% dextrins zinc WP 500 times.