1 玉米圆斑病的发病症状该病由碳色长蠕孢菌侵染所致,目前世界上报道的圆斑病有三个生理小种。我国1978年前没有圆斑病菌生理小种的报道,1978年后玉米自交系上发生的圆斑病菌有两个生理小种,即生理小种1号和2号,主要危害果穗和苞叶。病菌先侵染苞叶并向果穗内蔓延,危害籽粒和穗轴并多从果穗顶部开始,先是花丝腐烂,苞叶褪绿干枯呈 1 Symptoms of corn spot disease The disease caused by the infection of C. longum, there are three physiological races currently reported in the world. There was no report of physiological races of C. punctatus before 1978 in our country. There were two physiological races of S. melliferae occurring on post-1978 maize inbred lines, ie, physiological races 1 and 2, with the major damage to ear and husk . Bacteria first invade the husk and spread to the ear, endangering the grain and cob and more from the top of the ear, the first decayed filamentous, husk dry blew