一、前言杨树灰斑病在黑龙江、吉林、辽宁三省多发生在大树、幼树、幼苗的叶片和枝梢上,使叶片提早脱落,嫩梢枯顶。1960年中国科学院林业土壤研究所和辽宁省固沙造林试验站曾报道过,在辽宁省沈阳、盖平、彰武等地大树、幼苗有此病发生。此病病斑颜色因树种而异,有绿褐色、灰绿色和锈褐色等,其直径大小近1厘米,后期,病斑上生黑绿色突起的小点,为病原菌的分生孢子盘。病菌使幼苗顶梢和幼嫩枝槽一开始就变黑、萎蔫,失去支撑 I. Introduction Poplar gray spot occurs in the leaves and shoots of trees, saplings and seedlings in three provinces of Heilongjiang, Jilin and Liaoning, causing the leaves to fall off earlier and tender shoots to dry top. In 1960, the Institute of Forestry and Soil Science, Chinese Academy of Sciences and the Afforestation Experiment Station in Liaoning Province reported that trees and seedlings were found in Shenyang, Gaiping, Zhangwu and other places in Liaoning Province. The disease spot color varies by tree species, there are greenish brown, gray-green and rusty brown, the diameter of nearly 1 cm in size, the lesion spots black and green protuberance dots for the pathogen conidia plate. Bacteria make seedling shoots and young twigs from the beginning black, wilting, loss of support