一白菜霜霉病发生的条件白菜霜霉病的流行与气象条件有密切的关系,一般在晚秋高温潮湿、雨水过多或前期干旱,后期降霜多的情况下,都容易大发生。在华北地区8月下旬开始发生(7月中下旬播种的,早熟品种),东北地区亦于8月下旬开始发生(采种株于6月上旬开始),普遍发生多于莲座期。菜株生长衰弱,以及结球的品 A cabbage downy mildew conditions Cabbage downy mildew epidemic and meteorological conditions are closely related, generally in late autumn and winter high temperature and humidity, excessive rainfall or pre-drought, late frost and more cases are prone to occur. In North China began in late August (sowing in early July mid-late, early maturing varieties), the northeast region also began in late August (seed plants began in early June), the general occurrence of more than the rosette period. Vegetable growth is weak, and the ball of the goods