一、玉米主要病害1.玉米大斑病玉米大斑病主要发生在气候较凉爽的玉米种植区,特别是东北、华北北部、西北、西南及其他海拔较高的地区发生严重。病害主要发生在玉米抽雄以后,下部叶片首先发病并迅速向上部叶片扩展。症状:大斑病菌侵染玉米叶片、苞叶和叶鞘。叶片受侵染后,出现点状水浸斑,沿叶脉扩展并不受叶脉限制,很快形成长梭形、中央灰褐色的大斑。田间湿度大时,在病斑表面产生灰黑色霉状物。传播途径:通过分生孢子或者菌丝形 First, the main maize diseases 1. Maize big leaf spot The maize leaf spot occurs mainly in the cooler climate of corn growing areas, especially in the northeast, northern North China, northwest, southwest and other areas with high altitude serious. Disease occurs mainly in maize tasseling, the lower part of the first incidence of leaves and rapid expansion of the upper leaves. Symptoms: S loci infect corn leaves, husk and leaf sheath. After the leaves were infested, a spot-like dipping spot appeared, spreading along the veins and not restricted by the veins, quickly forming a long fusiform, central taupe large spot. When the field humidity is high, gray-black moldy substances are produced on the surface of the lesion. Route of transmission: through conidia or mycelial shape