Fusarium canker of yellow-poplar is caused by the fungus Fusarium solani, which also causes cankers on sugar maple, sweetgum, and true poplars (Populus). The fungus enters the tree through broken branches, dead water sprouts, or bark wounds, especially those made by ambrosia beetles (which are possibly vectors). First, small vertical cracks form in the bark. These cracks become cankers up to a foot in length; separate cankers often merge. Infected tissues commonly ooze in the fall. Foliage does not appear to be damaged in the early stages of the disease, but as the cankers enlarge and kill more bark, the crown of the tree begins to thin and die back. Cankers that form during the growing season (April to July) usually callus over with no canker activity the spring of the following year. Cankers that form in September may be still active 2 years later. |
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