See:
Poplar (Populus spp.) - Canker
Cause The canker disease caused by the fungus Cryptosphaeria ligniota has been reported in both Oregon and Washington and is an important killer of aspen. The fungus can infect aspen, bigtooth aspen, eastern cottonwood, Lombardy poplar, and purple willow. Cankers are associated with trunk or branch wounds. Perithecia develop in bark once it has been dead for one year. Spores are shed during late spring and summer rains. Mortality usually occurs in small trees after only a few years and before the canker girdles the stem. Large trees may be killed more slowly as the canker affects their branches. Especially on large trees, branches may be infected first, from which the fungus can spread to the stem.
Other canker diseases include sooty-bark, black, and Cytospora cankers. Cytospora commonly shows up as a secondary invader of the already dead tissue.
Symptoms Cankers with orange-brown margins may only be 2 to 5 inches wide but expand along the trunk up to 10 feet. Discolored bark may extend well below the cankered area. These long narrow cankers, which may extend the length of the trunk, develop black dots (perithecia) in the bark after a year. A red heartwood stain and advanced, brown-mottled trunk decay occur in the cankered area. Dead bark adheres tightly to cankers.
Cultural control
- Keep trees in good vigor and avoid wounding.
- Remove and destroy cankered trees.
- Partial harvest of stands is strongly discouraged.
Reference Rocky Mountain Region, Forest Health Protection. 2010. Field guide to diseases & insects of the Rocky Mountain Region. Gen. Tech. Rep. RMRS-GTR-241. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 336 p.