苹果、梨、桃树等，常因定干过低，生长过旺，或因过度轻剪而导致下垂枝的背上枝太多，使果园郁闭，通风透光不好，在土壤湿度过大时导致根颈腐烂。根颈腐烂病发生后，叶片发黄，但不明显。扒开根颈处土壤，即可发现根颈上有绿白色菌落，皮层已经彻底腐烂，木质部已变黑。... Apples, pears, peaches, etc., often due to dry set too low, over-growth, or excessive shear caused by drooping branches back branches too much, so that the orchard closed, poor ventilation and light in the soil humidity is too large When the root neck decay. After the root rot rot disease, leaves yellow, but not obvious. Peeling open the neck of the soil, you can find a green-white colonies on the neck, the skin has been completely decay, xylem has become black. ...