崇明地区大白菜苗期病害主要是霜霉病。一般发病率在20～30％,病重的苗床因发病率高达90％以上,要在苗床内用药剂将病菌彻底铲除,是十分困难的。大白菜移栽后,这些病苗往往成为田间的发病中心,加重后期霜霉病的发生,严重影响大白菜产量和品质。针对霜霉病在大白菜苗期的侵染特点,笔者于1989～1991年用甲霜灵拌种防治大白菜苗期霜霉病的试验、示范,取得了良好的效果。这一技术已作为高产栽培技术中的主要措施在本地区全面推广。现将试验、应用情况报告如下。 Chongming area cabbage seedling disease is mainly downy mildew. The general incidence of 20 to 30%, the incidence of sick seedbed as high as 90% or more, in the seedbed with drugs to eradicate the bacteria, it is very difficult. After transplanting Chinese cabbage, these seedlings often become the center of disease in the field, aggravating the occurrence of downy mildew in the later stage, seriously affecting the yield and quality of Chinese cabbage. In view of the infection characteristics of downy mildew in Chinese cabbage at seedling stage, the author tried to test and demonstrate downy mildew prevention and treatment of Chinese cabbage seedlings with metalaxyl in 1989-1991 and achieved good results. This technology has been widely promoted in the region as a major measure of high-yielding cultivation techniques. Now test, application report is as follows.