What Is Hypoxylon Canker?

A Central Texas Homeowner’s Guide to a Dangerous Tree Disease

Hypoxylon canker is a fast-spreading tree disease that poses a serious threat to the health of hardwood trees across Central Texas. This fungal infection, often affecting oaks, begins silently and becomes active when trees are stressed—quickly leading to severe internal decay, dieback, and eventual death. If left untreated, it can spread to neighboring trees and result in costly removals and landscape damage.

At Leaf Tree Services, our ISA Certified Arborists regularly identify and respond to Hypoxylon canker in Round Rock, Georgetown, and Austin. This guide explains what it is, how to recognize it, and the best steps to protect your property.

What Causes Hypoxylon Canker?

The disease is caused by Hypoxylon atropunctatum, a fungus that naturally exists in the wood of many healthy trees. However, when a tree becomes stressed, the fungus activates and begins to attack the vascular system—compromising the tree’s ability to move water and nutrients.

Common stress factors include:

• Prolonged drought or dehydration

• Soil compaction from construction or foot traffic

• Mechanical injury or root damage

• Improper or excessive pruning

• Poor drainage or root rot

Once triggered, the fungus quickly spreads through the sapwood and begins to rot the tree from the inside out, leaving it structurally unstable and prone to failure.

Trees at Risk in Central Texas

Hypoxylon canker primarily affects hardwoods. In our region, the most commonly infected species include:

• Live oaks, post oaks, blackjack oaks, and red oaks

• Pecan trees

• Hickories

• Elms

• Sycamores

Because oak trees are so prevalent in Central Texas neighborhoods and parks, the spread of Hypoxylon canker can lead to significant community-wide losses.

How to Identify Hypoxylon Canker

Early detection is critical. Unfortunately, the initial signs are subtle and often overlooked. Watch for:

• Thinning foliage or sudden leaf drop in early summer

• Patches of bark flaking off, revealing dusty gray, olive-green, or tan spore masses beneath

• Sunken, dark lesions along the trunk or large limbs

• Sudden limb dieback from the top down

• Dry, brittle wood or fine sawdust collecting around the base of the tree

If you notice these symptoms, it’s essential to call a Certified Arborist for a full tree health assessment.

Can Hypoxylon Canker Be Treated?

There is currently no chemical treatment or fungicide to cure Hypoxylon canker. Once infection reaches the trunk or major limbs, the tree cannot be saved.

Removal and Containment

If the fungus is found early in small branches, complete removal of the infected limbs may help slow its progress. However, if the trunk is affected, the entire tree should be removed to prevent the spread of spores to nearby trees—especially other oaks.

Proper containment requires:

• Professionally removing infected wood

• Immediate disposal of contaminated material (never leave on site)

• Sanitizing tools to avoid unintentional transmission

At Leaf Tree Services, we follow ISA guidelines to reduce the risk of cross-contamination and safely remove affected trees.

How to Prevent Hypoxylon Canker

Because there’s no cure, prevention and proactive care are your best defenses. Healthy trees are much less likely to succumb to infection.

Our arborists recommend:

• Avoiding unnecessary root disturbance, especially during landscaping or construction

• Using bio-identical root stimulators to improve resilience and overall tree health

• Pruning properly and only when necessary, especially avoiding large cuts in hot, dry months unless urgent

• Watering during drought periods, particularly young or newly planted trees

• Mulching around the base (but not against the trunk) to retain soil moisture

• Annual health evaluations to catch signs of stress early

Protect Your Trees in Central Texas

Hypoxylon canker is serious—but with early detection and expert guidance, you can minimize the damage and protect your property. Read more about tree maintenance to avoid tree disease. At Leaf Tree Services, we help homeowners, HOAs, and commercial property managers develop tree health plans tailored to Central Texas conditions.

Our ISA Certified Arborists will assess your trees, recommend necessary removals, and put a prevention plan in place to keep your landscape safe and strong.

Frequently Asked Questions

Q: What does Hypoxylon canker look like? A: You may notice peeling bark with gray or olive spore layers beneath, dead limbs, and thinning leaves. The wood underneath often looks dry and streaked.

Q: Can Hypoxylon canker spread to nearby trees? A: Yes. If not removed, spores can spread through wind, insects, or contaminated tools—especially to nearby oaks.

Q: Will my tree die if it has Hypoxylon canker? A: If the trunk is infected, the tree will eventually die. Immediate removal is advised to prevent spread and reduce safety hazards.

Q: Can I prune off the infected parts myself? A: No. DIY removal can worsen the issue by spreading spores. Professional handling is critical for safety and containment.

Q: How do I protect the other trees on my property? A: Keep trees healthy with deep watering, root stimulator applications, and annual arborist inspections. Don’t ignore signs of stress.