Quaking Aspen Canker and Borer Damage in Oregon

The canker-like growth with bore holes and insects on your 11-year-old quaking aspen (Populus tremuloides) indicates a canker disease complicated by borer infestation. Common aspens cankers in the West include Cytospora, Ceratonystis (black canker), and Hypoxylon.

What's Happening

• Cankers are fungal infections that kill bark and cambium, creating sunken, discolored, often oozing lesions.
• Borers (flatheaded or roundheaded) are secondary invaders attracted to stressed, wounded wood.
• The "rotted hardened wood" is dead sapwood colonized by decay fungi.

Immediate Actions

1. Do not chip away at the canker—you spread spores and worsen wounds.
2. Prune out the affected limb if the canker is on a branch (cut 6–12 inches below visible damage).
3. If on the main trunk: The tree may not be savable. Aspens don't compartmentalize trunk cankers well.

Professional Help Is Critical

Contact the Oregon Department of Forestry (links in original answer) for a forester visit. They can:

• Identify the specific canker.
• Assess structural risk (aspens with trunk decay fail unexpectedly).
• Advise on removal vs. management.

Prevention for Remaining Trees

• Avoid bark injury (mowers, trimmers).
• Water deeply during drought—aspens need consistent moisture.
• Thin dense stands to improve air flow.

Aspens are short-lived (60–80 years) and prone to cankers. If this tree is a hazard near structures, removal may be wisest.