一白粉病的发病症状白粉病主要发生在植株叶片上,严重时可侵染到植株的幼芽、嫩梢和花蕾等部位。植株在初发病时,嫩叶正反面出现近圆形或不规则形的白色粉斑(即病菌无性时代的分生孢子),并略显褪绿或呈畸形。在适宜的条件下,粉斑迅速扩大并连接成片,使得叶面布满白色粉状霉斑, A powdery mildew disease symptoms Powdery mildew occurs mainly in the leaves of plants, severe infection can plant buds, shoots and buds and other parts. Plants at the beginning of the disease, the young leaves appear on the front and back of nearly circular or irregular white spots (ie germ germ-free era of conidia), and slightly chlorotic green or deformity. Under suitable conditions, the spots rapidly expand and connect into pieces, making the foliage covered with white powdery mildew,