根颈腐烂病是由核桃溃疡病、核桃腐烂病及苗木菌核性根腐病综合侵染而引起的 ,该病主要发生在幼树主杆地上 10 cm至地下 5cm处。发病初期主杆基部出现褐色菱形或近圆形病斑 ,呈水渍状 ,并流出褐色液体 ,后期病皮干缩下陷 ,严重时病斑不断扩大 ,环绕干基一周 ,呈烧灼状 ,并出现 Root rot disease is caused by the combined infection of walnut canker, walnut rot disease and seedling root rot. The disease mainly occurs on the stem of young tree 10 cm above the ground and 5 cm below ground. Early onset of the main rod at the base appear brown diamond or nearly circular lesion, was water-like, and out of the brown liquid, the late skin shrinkage depression, severe lesions continue to expand, around the dry week, was burning, and appeared