Hypoxylon Canker: Atlanta Diagnosis & Prevention Guide

What Is Hypoxylon Canker?

Hypoxylon canker is caused by fungi in the genus Biscogniauxia (formerly Hypoxylon) and is one of the most visible and alarming diseases on Atlanta's oaks. However, it is important to understand that Hypoxylon is a secondary pathogen — it cannot infect healthy, vigorous trees. It only attacks trees that have been severely stressed by drought, construction damage, root compaction, grade changes, or other environmental insults. When you see Hypoxylon on an oak, it is a sign the tree was already in serious decline.

How to Identify Hypoxylon Canker

Symptoms are distinctive once the fungus becomes active:

• Bark sloughing: The outer bark peels away in patches to reveal a crusty, tan, silver, or dark brown fungal layer (stroma) covering the wood beneath.
• Dark fungal mats: As the stroma matures, it darkens to a charcoal-black crust that is hard and brittle.
• Branch dieback: Individual branches or large sections of the crown die suddenly, often during or immediately following a drought period.
• Rapid decline: Affected water oaks, white oaks, willow oaks, and pecans typically die within one to three years of visible symptom onset.

Treatment & Prevention

There is no fungicide treatment for Hypoxylon canker. Once the fungus is visible on the bark, the tree cannot be saved. Prevention is the only effective strategy:

• Maintain tree health: Consistent watering during drought is the single most important preventive measure. Atlanta's periodic summer droughts are the primary trigger for Hypoxylon outbreaks.
• Protect roots during construction: Establish tree protection zones before any construction or grading activity near oaks. Root damage and soil compaction are major stress triggers.
• Proper mulching: Mulch the root zone to conserve soil moisture and reduce heat stress.
• Remove infected trees promptly: Dead and dying trees with Hypoxylon become structurally hazardous as the wood decays rapidly. A tree risk assessment can determine removal urgency.

When to Call an Arborist

If you notice bark peeling to reveal a dusty or crusty fungal layer on any oak or hardwood, contact an ISA-certified arborist for evaluation. While the infected tree cannot be saved, a professional can protect nearby trees through proactive health care and assess whether the declining tree poses a safety risk. Call EastLake Tree Services at 404-850-1174 or request a free quote.