我县地处鄂西北山区,常年玉米种植面积达25万亩左右。自1971年以来,由于大量从省外引种和玉米南繁,致使大斑病发病面积扩大,危害程度逐年加重。1972年全县发病面积约2.7万亩,为轻病年;1973年是重病年,发病面积达4.5万亩,其中发病严重的1.7万亩左右;1974年为中等发病年,发病 My county is located in northwest Hubei mountainous area, perennial corn planting area of ​​250000 acres. Since 1971, due to the large number of introduced from outside the province and the south of corn, resulting in an increase of the incidence of the Great Spot disease, the degree of harm increased year by year. In 1972 the county incidence area of ​​about 2.7 million mu, light years; 1973 is a serious illness, the incidence of 4.5 million mu, of which about 17000 acres of serious disease; 1974 for the second year of onset, the incidence of