Diagnosing Walnut Canker in a Declining Tree

Symptoms of Walnut Canker

A 30-foot walnut dying from the top down with rotten trunk sections, falling limbs, and bird nesting in dead wood suggests walnut canker (Thousand Cankers Disease or Botryosphaeria canker). Nearby trees with similar symptoms support a disease diagnosis.

Recommended Action

1. Contact state forester: Request a free on-site evaluation (available in most states).
2. Sanitation pruning: Remove and destroy (burn/chip) all dead/diseased limbs. Disinfect tools between cuts.
3. Avoid wounding: Prevent further bark injury.
4. Consider removal: If main trunk is extensively decayed, the tree may be a hazard.

No Chemical Cure

Fungicides are ineffective once cankers are established. Management focuses on slowing spread and reducing hazard.