一、青枯病和蒸苗１、青枯病：多发生于三叶期前后，发病初幼苗顶端无水珠，叶片打绺，叶片逐渐变青绿色后变灰绿色，根变褐，根毛少，苗基部变褐腐烂，病株渐枯死呈青灰色。２、蒸苗：生理性病害。叶片迅速卷缩打绺，呈灰绿色以后变成黄褐色，叶上部枯死，苗基部不腐烂，... First, bacterial wilt and steamed wilt 1, bacterial wilt: Occurred before and after the three-leaf stage, the early emergence of seedling no water at the top of the bead, the leaves fight, the leaves turn greenish green, brown, root hair less Browning and decay of seedling base, the diseased plants gradually withered blue-gray. 2, steaming Miao: physiological disease. Leaves quickly curled up, gray-green later into brown, leaves the upper part of the withered, seedling base is not rotten, ...