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黄瓜霜霉病在黄瓜整个生长期都可发生,主要危害黄瓜叶片,使叶上出现浅绿色斑点,扩大后受叶脉限制而成为多角形褐色病斑。在潮湿环境下,叶背面病斑上长出灰紫色霉层;在高温和干燥条件下,病斑停止发展而枯干,背面不产生霉层。病班受叶脉限制往往多个病斑连成一片,常使叶片迅速变黄枯干,天气干燥时容易破裂,潮湿天气下则容易霉烂。防治方法如下:
Cucumber downy mildew can occur throughout the cucumber growth period, the main hazard cucumber leaves, the leaves appear light green spots, enlarged by the veins and become polygonal brown lesions. Under wet conditions, the leaves on the back of the disease grow purple gray mold layer; under high temperature and dry conditions, stop the development and withered lesions, the back does not produce mildew. Disease classes by the veins are often limited to multiple lesions into one piece, often leaves the rapid yellowing dry, easy to rupture when the weather dry, damp weather is easy to rotten. Prevention methods are as follows: