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白菜霜霉病在包头市年年发生,为害严重。1964年、1973年、1975年、1978年曾四次大流行。发病率高达80—90％,病情指数50—80％,一般年份减产10—20％,严重年份减产40—50％。 一、白菜霜霉病大流行的气象指标:在包头市,1963—1979年的十四年中,白菜霜霉病大发生4年,小发生4年,中发生6年。比较各年8月中旬至9月下旬的气温变化对霜霉病的影响不如相对湿度大,如下图所示。 据调查资料明确的白菜霜霉病大流行的气象指标为:8月中旬降雨多、湿度大,8月下旬、9月上旬平均气温18℃左右,旬平均相对湿度达70％,一次连阴雨五天,昼夜温差11℃左右,霜霉病就流行。
Cabbage downy mildew occurs in Baotou every year, serious damage. 1964, 1973, 1975, 1978, there were four pandemic. The incidence of up to 80-90%, the disease index 50-80%, 10-20% reduction in the general year, 40-50% reduction in severe years. First, the cabbage downy mildew meteorological indicators: In Baotou City, 1963-1979 fourteen years, cabbage downy mildew occurred four years, a small occurrence of four years, occurred in six years. Comparison of temperature changes from mid-August to late September in each year is not as good as the relative humidity in terms of downy mildew, as shown below. According to the survey data clear cabbage downy mildew meteorological indicators are: more rainfall in mid-August, humidity, late August, early September the average temperature of about 18 ℃, ten-day average relative humidity of 70%, once again with the rainy five days , Temperature difference between day and night about 11 ℃, downy mildew on the popular.