霜霉病主要危害黄瓜幼苗和成株的叶片,开始产生水渍状斑点。因受叶脉限制,斑点呈多角形的黄褐色病斑。在潮湿条件下,叶背病斑长有紫黑色霉。此病一般从下部叶片向上蔓延,严重时病斑互相连合,最后整叶片枯黄卷缩。霜霉病是由鞭毛菌亚门假霜霉属真菌侵染引起,冬天温室黄瓜传播到春大棚黄瓜上或葫芦瓜上,再传播到露地春秋黄瓜上。总之,只要黄瓜生产周期不断进行,霜霉病就不断发生。霜毒病病原菌以无性繁殖阶段的孢子囊在各茬黄瓜上传播。其发生、发展与温度、湿度关系极为密 Downy mildew mainly cucumber seedlings and adult leaves, began to produce water-like spots. Due to the limitations of the veins, spots were polygonal brown spots. In humid conditions, the leaf spot disease purple long black mold. The disease generally spread upward from the lower part of the leaves, serious when the lesion interconnected, and finally the whole leaf curled yellow. Downy mildew caused by fungal infection of Flammulina subtilis pseudo-mold fungus caused by the winter greenhouse cucumber spread to the spring or greenhouse cucumber on gourd melon, and then spread to the open field cucumber. In short, downy mildew continues to occur as long as cucumber production cycles continue. Frost and disease pathogenic bacteria in the vegetative stage of the sporangia in each stubble cucumber spread. Its occurrence, development and temperature, humidity is extremely close relationship