一、症状 小麦白粉病主要发生在叶面上,也可发生在植株叶鞘、茎秆和穗上,一般叶正面的病斑比背面多,下部叶片较上部叶片被害重。其症状特点是病部表面覆有一层白粉状霉层。病部最先出现分散的白色霉斑,逐渐扩大并相互联合,呈长椭圆形的较大霉斑,严重时可覆盖叶片大部,甚至全部,霉层增厚可达2毫米左右,并逐渐呈粉状。后期霉层由 First, the symptoms of wheat powdery mildew occurs mainly in the foliage, but also occurs in the plant leaf sheath, stalk and ear, the general leaf front than the back of the lesion, lower leaves than the upper leaves were killed. Its symptoms are characterized by the appearance of a layer of moldy mildew on the surface of the diseased part. The first appearance of the diseased part is the scattered white mildew, which gradually expands and coalesces with each other. The mildew is oblong, and can cover most or even all of the leaves in severe cases. The thickening of the mold layer can reach about 2 mm and gradually increase Was powder. Late mold layer by