Saving a Mature Post Oak with Hypoxylon Canker

A massive, old post oak shows exactly half its canopy dead—every branch on one side of the main fork (12 feet up) is dead, the other side alive. The owner wants to save this beloved tree.

Diagnosis: Hypoxylon Canker

This fungal disease attacks stressed trees. The dead side is infected; the fungus girdles branches, cutting off water and nutrients.

Treatment Plan

1. Prune dead wood: Remove all dead limbs back to healthy tissue.
2. Fertilize: Apply 10-10-10 fertilizer at 1 lb per inch of trunk diameter, scattered under the canopy and watered in deeply.
3. Water deeply: Provide 1 inch of water weekly during dry periods (use a pan under sprinkler to measure).

This boosts the tree's vigor, helping it compartmentalize the disease. Monitor for further dieback.