If you have severe problems with canker disease on certain of your trees, replacement with less susceptible species may be the best solution. Poplar, willow, aspen and spruce are among the most susceptible to canker diseases. Repeated abrasion may result in girdling and death. Barriers to prevent this type of injury can extend a tree's life. Bark mulch or gravel around the base will eliminate the need for mowing close to the stem while providing an attractive alternative to grass.
Infections occur through bark wounds or at junctions of dead and live branches.
Once established, the fungi grow slowly through bark during fall and winter while the host is dormant. During the growing season, vigorous trees respond by forming callus tissue in rolls around the edges of affected areas. This alternating growth of fungus and tree results in the target-like appearance. The cankers are shallow and bark on the advancing margins is frequently discolored. Diffuse cankers are usually lethal, and diseased branches should be removed immediately.