一、玉米大斑病玉米大斑病又名玉米叶枯病、玉米条斑病,是玉米上的重要病害之一。主要侵害玉米的叶片、叶鞘和苞叶,以叶片受害最重。在大田,一般先从下部叶片开始发病,逐渐蔓延到上部叶片。发病初期,叶片上首先出现水渍状青灰色斑点。以后逐渐沿叶脉向两端扩展,形成中央黄褐色? First, the big spotted corn disease Big spotted disease, also known as corn leaf blight, corn streak disease, is one of the important diseases on corn. The main damage to the corn leaves, leaf sheaths and bracts, leaves the most affected victims. In the field, generally the first start of the disease from the lower leaves, and gradually spread to the upper leaves. Early onset, the first spot on the leaves appear water stains like gray spots. After gradually expanding along the veins to both ends, the formation of central brown?