白菜霜霉病又叫白霉、霜叶病 ,是白菜及十字花科蔬菜重要病害之一。一、发病症状幼苗期到开花、结荚期都可受害。成株期叶片上病斑呈水渍状 ,淡绿色 ;后受叶脉限制呈多角形 ,黄褐色 ,背面病斑上有白色霉层。发病严重时病斑连片 ,叶枯黄。包心后从外叶向内叶层层发展 ,病叶干枯 Cabbage downy mildew, also known as white mold, cream leaves disease, cabbage and cruciferous vegetables is one of the important diseases. First, the symptoms of seedling to flowering, podding can be harmed. The lesions on the leaves of adult plants showed water stains and light green color. After being restricted by the veins, the lesions were polygonal and brownish-brown with a white mold layer on the back of the lesion. When the disease is severe contiguous, yellowish leaves. After the heart from the outer leaf to the inner leaf layer development, diseased leaves dry