The only effective method of avoiding canker in poplar trees is to plant resistant varieties.避免杨树溃疡病的唯一有效方法是种植抗病品种。I remember that solitary white poplar by the lake.我记得湖畔那株孤零零的白杨树。Brought up in town, the boy finds it difficult to separate a poplar from a willow.那男孩是在城里长大的，所以觉得很难区别杨树和柳树。The canal is bordered by poplar trees.运河的两边是杨树。