![]() ![]() It is unknown whether the fungus remains active in the wood. It is interesting that cankers can be rendered completely inactive by excision of the diseased bark . This accounts for the flaring, cobra-like margin. Callus is produced by the host in response to the canker, but largely on the sides rather than the top and bottom. Thus, snapping at such a canker would usually be fatal.Ĭanker margins grow approximately 1.3 cm per year , but faster vertically than horizontally . Sixty percent of cankers occur in the lower 2.5 m . The pathogen itself penetrates the wood and causes some wood decay and other decay fungi may infect the stem through the canker. Larger trees may snap due to distortion associated with the canker and/or wood decay behind the canker. Small trees, less than ~12 cm DBH, can be killed directly by the disease. ![]() This is consistent with the fact that a dead branch stub is usually present at the canker center. The pathogen is thought to invade these dead or moribund branches, or their stubs, then progress into the stem and initiate a canker. Epicormic branches frequently die after the crown closes and they receive less light. Increased light after cutting stimulates epicormic branching on the stems. The disease often is most frequent in stands that have had some type of partial cutting . A smaller number of infections occur via wounds. The stub often persists at the center of the canker face. Infections typically occur through dead and dying branch stubs, usually small ones . Thick, white to buff mycelial fans are produced beneath the bark at the advancing margin of the canker. Perithecia are produced on parts of the canker older than 4-5 years, or may be confined to the center of the canker . This gives the bark a blackened appearance. The pathogen, Eutypella parasitica, produces black perithecia embedded and slightly protruding from bark on old cankers (see featured image above). However, in North American urban areas, it can be quite common in Acer platanoides, a species native to Eurasia . Acer saccharum (sugar maple) is infected more commonly than other native species. The host range is primarily restricted to maples. Eutypella cankerĮutypella canker is a persistent perennial canker and an important disease of sugar maple in the midwestern and northeastern United States and in southern Ontario and Quebec. It probably fruits mostly in certain years when weather is right, and then in the dormant season when we’re not around to see it. The canker face is usually free of bark, making it rather attractive, but it may have bark on aspen. The canker persists for many years without killing its host. Back and forth the combatants go, creating this work of art that takes years to develop.
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