first, let's see if the plants with this symptom are distributed all over the field or scattered. Is the symptom consistent or gradually expanding? ... from the picture, it is mainly the root system problem. If the symptoms are consistent throughout the field, it is mainly to check the soil drainage problem in the field; If it is scattered and gradually spread, it is caused by root rot, and the following measures are taken: 1. Avoid flooding the whole field; 2. Pull out the diseased plants and spread quicklime on the diseased area; Sporadic occurrence can be prevented by spraying fungicides such as hymexazol, cypermethrin, carbendazim, dixone, clothianidin, etc.