前言 近年白菜霜霉病仍然是白菜产量不稳定的主要因素之一。内蒙古、黑龙江、山东、河北时有发生,流行年份,为害严重。包头、呼和浩特市1975、1977、1978年曾三次大流行,发病率高达80-90%,病指50-80,减产50%左右,使生产遭受巨大损失,严重影响蔬菜供应。 对白菜霜霉病的研究四十 Introduction Cabbage downy mildew in recent years is still one of the main factors of unstable cabbage production. Inner Mongolia, Heilongjiang, Shandong, Hebei, sometimes, popular years, serious damage. Baotou and Hohhot had three pandemics in 1975, 1977 and 1978 with the incidence rate as high as 80-90% and the disease index of 50-80, with a reduction of about 50%, causing huge losses in production and seriously affecting the supply of vegetables. Study on cabbage downy mildew forty