Cytospora canker of poplar and willow
From Bugwoodwiki
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USDA Forest Service. 1979. A guide to common insects and diseases of forest trees in the northeastern United States. Northeast. Area State Priv. For., For. Insect and Disease Management., Broomall, PA. p. 123, illus.
Cytospora canker is caused by the fungus Cytospora chrysosperma (the sexual stage is Valsa sordida). Poplars, aspens, and willows are the most commonly affected trees.
Cytospora canker is confined to weakened trees. The fungus enters the tree through a wounded or weakened twig and kills the twig back to a larger branch or the trunk. Brownish, circular-to-oval cankers with sunken bark are formed in the smooth bark of branches and trunks. The diseased area gradually enlarges, and frequently stems are girdled and killed. When the older trunk or large branches are attacked, the inner bark blackens and gives off a disagreeable odor. Severely attacked trees 3 to 6 inches in diameter die in 2 or 3 years.
The fungus produces small fruiting bodies in the diseased bark. Spores are splashed by rain or carried by wind, birds, or insects to other trees.
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 Photo by USDA Forest Service - Rocky Mountain Region Archive, USDA Forest Service, Bugwood.org |
