1960年3月,作者在明尼苏达州中部的颤杨(populus tremuloides)树上发现了一种不知病原的溃疡病。随后,在这个州另一些地方的颤杨上也看到了类似的溃疡病。这种溃疡病在主干上普遍只发生一处,但个别地在一株颤杨的树干及其较大的枝条上也可看到5—10个溃疡病斑。典型的溃疡是呈输纹型,与在栎属植物上由 Str-umella coryneoides Sacc.et.Wint.引起的溃疡相同。这种溃疡病斑的长度相当于它的宽度的2—3倍,轮纹 In March 1960, the authors found a pathogen-free ulcer disease in the populus tremuloides tree in central Minnesota. Subsequently, a similar ulcer disease was seen on viburnum in other parts of the state. This canker disease occurs most commonly on the trunk, but 5-10 ulcer lesions can also be seen individually on the trunk of a viburnum and its larger branches. A typical ulcer is lenticular, identical to the ulcer caused by Str-umella coryneoides Sacc. Et. Wint. On Quercus plants. This ulcer lesions the length of its width is equivalent to 2-3 times the wheel pattern