Canker Stain
From Bugwoodwiki
Contents |
Importance
Canker stain is a deadly disease that occurs on sycamore and London planetree from New York to Georgia and west to Missouri. It poses a threat to natural stands and plantations throughout the South.
Identifying the Disease
Canker stain is hard to detect early in its development, especially under older, scaly bark (fig. 28a). It may not be noticed until symptoms appear in the crown. Long, purplish-black, lens-shaped cankers form on stems and large branches. Cankers expand laterally about 9 cm per year and lengthen up to 3 m per year. Growth follows the wood grain, often resulting in a helical-shaped canker (fig. 28b). Phloem, cambium, and sapwood mortality cause parts of the crown to wilt suddenly and then die (fig. 28e). In the South, older cankers are often colonized by L. theobromae.
|
| Figure 28a. - Diagonal line from top center to lower right of bole defines right margin of a canker satin canker. |
Identifying the Fungus
Conidia are produced on initial infection sites and in well-colonized tissue. Black perithecia with long (1 mm) necks produce hatshaped ascospores. Diseased sapwood has brown-black, wedge-shaped staining that is evident in stem cross sections (fig. 28d).
Biology
Both spore types are sticky and are spread by humans and insects. The fungus can infect even the smallest wound that exposes cambium or sapwood.
|
| Figure 28b. - The same canker shown in (a) after removing the bark. |
|
| Figure 28c. - Canker stain canker several years old with decay and woodpecker holes. |
Control
To prevent spreading canker stain to healthy trees, tools used to prune diseased landscape trees should be sprayed with a solution of rubbing alcohol and 50 percent laundry bleach. Wound dressings are of little value. Early detection and removal of diseased trees in plantations can reduce losses. “Sanitation cuts” of diseased stands should precede planting sycamore trees in adjacent areas.
|
| Figure 28d. - Wedge-shaped, dark staining extends from the dead cambium into the sapwood. |
|
| Figure 28e. - Mature Sycamore with crown dieback resulting from canker stain disease. |
References
Leininger, T.D; Solomon, J.D.; Wilson, A. Dan; Schiff, N.M. 1999. A Guide to Major Insects, Diseases, Air Pollution Injury, and Chemical Injury of Sycamore. Gen. Tech. Rep. SRS-28. Asheville, NC: USDA Forest Service, Southern Research Station. 44 p.
