霜霉病主要为害叶片。发病初时趁早晨有露水时观察,可见叶背叶脉间出现水渍状绿色斑点,很快扩展为淡褐色多角形病斑。潮湿时病斑背面长满一层灰色霜霉状霉层。几天内,病斑即可连片,病叶干枯,霉状物也变为黑褐色。 Downy mildew is the main damage leaves. At the beginning of the onset, when the dew was observed in the morning, a greenish spot of water stain appeared between the leaf blade veins and quickly expanded into a light brown polygonal lesion. The back of the lesion is covered with a layer of gray moldy mildew on the wet surface. Within a few days, the lesion can be contiguous, sick leaves dry, mildew also turned dark brown.