一、死苗类型及特点旱秧死苗主要是立枯病造成的，大体可分为以下几类。1．针腐死苗发生于立针至二叶期。病苗心叶枯黄，茎基部变褐色，根部逐渐变黄褐色，种子与茎基部交接处有霉层，潮湿时茎基部软腐易拔断。2．黄枯死苗常发生于三叶期前后，病苗最初叶尖不吐水，并逐渐萎蔫 First, the type and characteristics of dead seedlings Dry seedlings are mainly caused by dead blight, can be divided into the following categories. 1. Needle rot dead seedlings occurred in the needle to the second leaf period. The seedling heart leaves withered, the base of the stem is brown, the root gradually turns yellowish brown, the layer of mildew at the junction of the seed and the stem base is wet, the stem base is soft and easy to pull off when damp. 2. Yellow dead seedlings often occur before and after the three-leaf stage, the tip of the vaccine does not spit water, and gradually wilting