一、前言 山杨灰斑病广泛发生在黑龙江、山东和新疆各地,对山杨为害很大。1983年在黑龙江省林口县青山林场山杨次生林中的幼树上发现有灰斑病。该病主要为害幼树幼苗的嫩梢和叶片,严重时嫩梢枯顶正株叶片枯死。 在野外调查的基础上,进行了病原菌的分离培养、病原菌的生物学特性、病原菌的 I. Introduction Populus gray spot disease occurs widely in Heilongjiang, Shandong and Xinjiang, a great harm to Aspen. In 1983, gray leaf spot was found on young trees in the secondary forest of Populus euphratica in Qingshan Forest Farm, Linkou County, Heilongjiang Province. The disease mainly affects young shoots of young shoots and leaves, severe shoots dry top leaves. On the basis of field investigation, the isolation and culture of pathogenic bacteria, the biological characteristics of pathogenic bacteria,