Hypoxylon Canker on Pin Oak: Stress-Induced Decline

A large pin oak in southeast Kansas shows dying limbs, brown leaves, and round gray patches on limbs after two years of drought.

Diagnosis: Hypoxylon Canker

This fungal disease (Hypoxylon spp.) is a secondary invader—it attacks trees already stressed by drought, root disease, compaction, or construction damage. The gray patches are fungal mats under sloughed bark.

Management

• No cure for infected wood. Remove severely infected trees to reduce spores.
• Prune localized infections (cut 1 ft below visible canker) during dry weather; sterilize tools.
• Boost tree vigor: Fertilize with 1 lb 10-10-10 per inch trunk diameter, scattered and watered in. Repeat in spring.
• Irrigate deeply during dry periods.
• Prevent wounds and root damage.

Key Point

Hypoxylon doesn't spread to healthy trees. Keeping oaks vigorous is the best defense.