Black Canker (Target Canker)

Concentric rings create a target pattern on cankers. Prune affected branches and sterilize tools. The pathogen (Ceratocystis fimbriata (black canker); Cytospora notastroma (target canker)) favors moist conditions and enters through wounds or natural openings. You are most likely to see symptoms during the growing season when conditions shift between wet and warm. On susceptible hosts, the damage can progress quickly if left unchecked.

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.