Mature White Oak Hypoxylon Canker: Stress Management

Diagnosing Black Streaking

Mature white oak with dead limbs, black streaking (missing bark to black cambium) 2–3" wide from base to top—resembling lightning strike but without lightning—has Hypoxylon canker. This fungus attacks stressed oaks (drought, compaction, construction damage, root disease).

Critical Facts

• Secondary invader—exploits existing stress.
• Extensive infection = beyond repair—remove to reduce spores.
• Localized branches—prune out, may slow advance.

Prevention for Nearby Oaks

1. Water 1 inch weekly during drought (pan method).
2. Fertilize 10-10-10 at 1 lb/inch trunk diameter.
3. Avoid root wounds, compaction, grade changes.

Why It Matters

Hypoxylon signals severe stress. Protecting nearby oaks requires addressing the underlying stressors (likely last year's drought). The canker itself is a symptom, not the primary cause.