黄瓜霜霉病是保护地黄瓜发生最普遍、为害最严重的病害。黄瓜霜霉病主要为害叶片,因受叶脉限制呈多角形的黄褐色病斑,在潮湿条件下,叶背病斑上长有紫黑色霉。黄瓜霜霉病的发生发展与温湿度有密切关系,特别是湿度。其发生条件有三:(1)温 Cucumber downy mildew cucumber protection is the most common occurrence, the most serious damage to the disease. Cucumber downy mildew is the main damage to the leaves, due to the limitations of the veins polygonal brown spots, in wet conditions, leaf back spots on the long purple black mold. The occurrence and development of cucumber downy mildew and temperature and humidity are closely related, especially humidity. The occurrence of three conditions: (1) warm