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一、霜霉病的发病症状。葡萄霜霉病主要危害葡萄叶片,也危害新梢、幼果等幼嫩组织。叶片发病时,初期呈现半透明边缘不清晰、油渍状小斑点,后扩展为黄色至褐色多角斑点,并能愈合成大斑。潮湿时病斑背面产生白色霜状霉层。病斑最后干枯,叶片吊落;新梢、卷须、穗抽发病时,开始为水渍状半透明油渍状斑点,后发展为微凹陷,黄色至褐色病斑。病梢生长停滞,扭曲,枯死;幼果染病后病部褪色,变硬下陷,使果实的含糖量降低,品质变劣。
First, the symptoms of downy mildew. Grape downy mildew is the main hazard grape leaves, but also endanger shoots, young fruit and other young organizations. Leaf onset, the initial semitransparent edge is not clear, small spots of oil-like, after the expansion of the yellow to brown polygonal spots, and can heal into large spots. Damp fungus mildew on the back of damp spots. Lesions last dry, leaves hanging; shoots, tendrils, spike pumping onset, began to water-like translucent stain-like spots, after the development of micro-depression, yellow to brown lesions. Stasis growth stagnation, twisting, dead; young after the disease faded discoloration, hardened subsidence, so that the fruit sugar content decreased, the quality of the worse.