稻瘟病(Pyricularia oryzae)是我县水稻上的主要病害。特别是早稻叶稻瘟发生面大,流行频率高。为了探索有效的预测方法,笔者对本县1981—1990年有关早稻叶稻瘟发生的历史资料进行了系统的研究分析,发现叶稻瘟流行程度与田间发病始期和6月上旬雨量关系密切。见表1。将叶稻瘟流行程度分5级,并依轻发生中偏轻发生、中等发生、中偏重发生、大流行等次序分别以1、2、3、4、5代表,对表1中数 Pyricularia oryzae is a major disease on rice in our county. In particular, rice blast occurred in large area, high prevalence. In order to explore effective prediction methods, the author systematically studied the historical data of rice blast from early stage in 1981-1990 in the county, and found that the prevalence of leaf blast was closely related to the onset of field and the rainfall in early June. See Table 1. The epidemic degree of leaf blast was divided into 5 grades, and the occurrence of mild to moderate occurrence of light, moderate occurrence, the partial emphasis occurred, the sequence of 1, 2, 3, 4, 5, respectively,