近几年来,全国玉米黑穗病的发生一年比一年重。轻的年份发生率为2-3%;中等年份发生率为10% 左右;最严重的年份发生率高达60-70%。那么,是什么原因造成玉米黑穗病如此一年比一年重呢?笔者分析认为主要有以下几种原因: 一、玉米重茬、迎茬增。旱田主要是大豆、玉米轮作,大豆种植效益低的年份,下一年玉米面积增大,不是重茬就是迎茬。玉米丝黑穗病菌孢子年年往地里撒, 一年比一年增多,菌原增加,病害不加重发生才怪呢? 二、干旱或低温延迟出苗时间。春季干旱或低温, In recent years, the occurrence of corn smut in the whole country has been heavier and heavier year after year. The incidence of light years is 2-3%; the incidence of middle age is about 10%; the most serious year the incidence of up to 60-70%. So, what causes corn smut so heavier than a year? The author analyzes mainly for the following reasons: First, corn stubble, growing stubble. Dry land is mainly soybeans, corn rotation, soybean planting low benefit of the year, the corn area increases, not the stubble is stubble. Spores of corn ear smut spores year after year, an increase year after year, increased bacteria, disease does not aggravate it strange? Second, drought or low temperature delayed emergence time. Spring drought or low temperature,