Sooty-bark Canker

Quaking aspen (Populus tremuloides) occasionally develops cankers that appear sooty or darkened on the bark. Limited information is available about symptoms, conditions, or management for this disease in the PNW. The disease status and economic significance remain unclear, warranting observation but not urgent intervention in most landscape situations.

Prune out cankered branches at least six inches below visible symptoms, making cuts into healthy wood. Sterilize your tools between cuts. Canker pathogens typically enter through wounds, so minimize pruning injuries and avoid working on trees when bark is wet. Maintain tree vigor through proper watering and avoid stress from drought or compacted soil, which makes trees more susceptible.