一、死苗现象及原因１．死苗现象　一是生理立枯死苗，多数发生在秧苗二叶一心前后，病苗先从心叶开始萎蔫，卷成筒状，然后发展至全株。秧苗死后，叶色污绿，但茎部不腐烂，发病初期根毛稀少或无，可连根拔起；二是病菌性立枯死苗，发生于立针到三叶期病苗叶片卷成针状，叶色 First, the phenomenon of dead seedlings and the reasons 1. The phenomenon of dead seedlings First dead seedlings Li Rui physiological, the majority occurred in the seedlings two leaves before and after the heart, the sick seedlings start wilting from the heart leaves, rolled into a tube, and then developed to the whole plant. After the seedling died, the leaf color was flushed, but the stem did not decay, and the root hair was sparse or absent in the early stage of disease. The second reason was that the germ was dead and withered, which occurred in the needle- Leaf color