后霉病是我省油菜上的主要病害之一，每年都有不同程度的发生。随着旱地连作油菜面积的扩大，病害呈逐年加重的趋势。一、特征与症状霜霉病是一种真菌性病害，整个生育期间地上各部分均可发病。叶片感病后，初现淡黄色斑点，病班扩大受叶脉限制是不规则形黄褐色斑块，叶背病班 After mildew disease is one of the major diseases in our province rape, each year to varying degrees. With dryland even rapeseed area expansion, the disease showed a trend of increasing year by year. First, the characteristics and symptoms Downy mildew is a fungal disease, the entire reproductive period of the ground can be part of the disease. After the onset of the leaves, pale yellow spots appear, the disease is limited by the expansion of the veins is irregularly shaped brown patches, leaves back disease classes