Hypoxylon Canker on Green Ash: Signs and Management

Hypoxylon Canker on Green Ash: Signs and Management

A green ash on a floodplain in Georgia has black, crusty, carbon-like growths at the base. A chunk was removed and did not appear to originate under the bark.

Black fungal growth

Removed chunk

Diagnosis: Hypoxylon Canker

Hypoxylon spp. are secondary invaders that colonize stressed, declining trees. The crusty, black stroma (fruiting bodies) are characteristic.

Implications

• Internal decay is likely present in the lower trunk.
• Primary stressors: drought, flooding, root damage, soil compaction, old age.
• Decay fungi are slow but progressive; structural weakening occurs over years.
• Tree may fail in wind/ice storms, especially if near targets (buildings, paths).

Management

1. Promote vigor: Water during drought, fertilize based on soil test, mulch properly.
2. No cure for Hypoxylon—fungicides are ineffective once established.
3. Monitor annually for canopy thinning, dead branches, lean.
4. Consult a certified arborist for risk assessment if tree is near people/property.
5. Plan for eventual removal if decline continues.

Many trees persist for years with Hypoxylon, but safety must be the priority.