Woodpecker Damage and Falling Limbs: Is Your Tree a Hazard?

When Woodpecker Holes Signal Structural Decay

A large tree with extensive woodpecker holes, a nesting cavity, and sudden large limb failure (limbs falling without visible holes) shows classic signs of advanced internal decay.

Why Limbs Fall Without Warning

• Decay fungi hollow out the heartwood, leaving a thin shell of sound wood.
• Limbs appear healthy (even blooming) but lack structural strength.
• Woodpeckers excavate easily in soft, decayed wood—confirming internal rot.
• Dark fluid streaking the trunk suggests wetwood (bacterial flux) or fungal metabolites.

Hazard Tree Criteria (ANSI A300)

A tree is hazardous if it has a structural defect likely to cause failure that could strike a target (people, structures, vehicles). Key thresholds:

• Sound wood thickness < 1 inch per 6 inches of stem diameter.
• Advanced decay (soft, punky wood) combined with cracks, weak unions, or large dead limbs.
• Fungal conks (mushrooms/brackets) on trunk or root flare.

Immediate Actions

1. Restrict access to the fall zone.
2. Hire a certified arborist for a Level 2 or 3 risk assessment (resistograph, sonic tomography).
3. Contact your state forestry agency for a free forester visit—they can confirm hazard status.

Do Not

• Fill cavities with cement or foam (traps moisture, accelerates decay).
• Assume fertilizing will “fix” structural decay.

Find an arborist: ISA Certified Arborist Search