Hypoxylon Canker: A Fatal Stress Disease of Post Oaks

White, ash-like bark that sloughs off to reveal dusty brown then silver-gray cankers indicates Hypoxylon canker, a fungal disease attacking drought-stressed post oaks. The fungus produces spores that spread to other trees. Cankers can expand 3 feet per season; large oaks may die within 1–2 years.

No cure exists. Management: water deeply during drought, avoid root damage and soil compaction, prune only in dormancy, and remove severely infected trees to reduce spore load. Lightly infected trees may benefit from aeration and fertilization. Prevention through stress reduction is the only effective strategy.