Tree disease

Hypoxylon Canker

KillerSeriousManageableMostly cosmetic

A fungus that lives quietly inside many healthy oaks and takes over when drought, root damage or construction weakens the tree. Bark sloughs off to show a crusty fungal mat. It does not start the decline. It finishes it.

DiebackBark sloughingCrown thinning

Trees it affects: Laurel oak (among the most affected), Water oak, Live oak, Other hardwoods

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Affects: Laurel oak (among the most affected), Water oak, Live oak, Other hardwoods
When it shows: Follows hot, dry weather and stress events such as root damage or construction.
What we do first: Find the stress: drought, root damage, compaction or construction.

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What you see

Signs in the field

Early crown thinning and branch dieback
Bark sloughing off the trunk and limbs
A crusty fungal mat under the bark: tan to olive green and powdery when young, then silvery gray, then brown to black
Dead branches first, then the fungus running down the trunk

Often confused with

Bot canker and Diplodia dieback Bacterial leaf scorch Wood decay and conks

Why it matters

Once the fungal mat shows on the trunk, the tree is unlikely to survive. A girdled, crown-dead oak becomes a structural risk over walks, roads and homes.

Stress opens the door

The fungus is already inside many healthy oaks. Drought, root damage, soil compaction, wounding and a poor site let it take over. That is why the defense is vigor, not a spray.

What we do

How Ptolemy handles it

Field condition first, then the recommendation. Treatment, removal and diagnosis calls are made by an ISA Certified Arborist, and the serious ones are confirmed in a lab.

Water during hot, dry spells, avoid compaction and wounding, and protect the root zone during construction.
Remove dead and infected wood, and hazardous trees, promptly.
A tree risk assessment where an affected oak stands over people, roads or homes.
No fungicide is registered for it, and we do not sell one.

Next step

Seeing hypoxylon canker on your property?

ReadOur written protocolsEvery serious threat has its steps written down before it is needed.ReportReport a concernSend a photo and where it is. A photo is a reason to look, not a diagnosis.RequestThe free master planWe map every palm and tree and write one 10-year plan, with an estimated budget each year.

Or call (239) 467-0142. The serious calls are confirmed in a lab before anyone acts.

FAQ

Questions about hypoxylon canker

Can Hypoxylon canker be treated?

No product is registered for it. The defense is keeping oaks vigorous: water in drought, no compaction, no root damage. Infected wood and hazardous trees come out.

Why did it show up now?

The fungus lives quietly in many healthy oaks. It takes over after a stress, most often drought, root damage or construction near the tree.

Is an infected oak dangerous?

It can be. Once the fungus girdles the crown, dead limbs and the trunk can fail. Trees over targets get a risk assessment.

Built on

Our own field records, our written specs, and these public references:

UF/IFAS FOR338/FR407, Biscogniauxia (Hypoxylon) Canker or Dieback in Trees

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