Hypoxylon Canker and Oak Wilt in Longview Oaks

The Fungus That Waits for a Weak Oak

Hypoxylon canker is caused by fungi in the genus Biscogniauxia, still widely known by the older name Hypoxylon. Their spores are common throughout East Texas woodland and sit quietly in the outer wood of many perfectly healthy oaks. They only turn aggressive once the host loses vigor, which is why cases cluster after drought years, after construction severs roots, and in trees that have been in slow decline for a decade.

Reading Bark That Falls Away in Plates

The signature symptom is bark peeling off in irregular plates to expose a crust beneath. That crust is fungal tissue called stroma, often tan or olive when it first appears, weathering to silver gray and eventually to black. Fine brown powder collecting below the trunk is spore material. By the time broad sheets of stroma are showing, the sapwood under them has already been consumed and the stem above is structurally unsound.

How Oak Wilt Travels Between Trees

Oak wilt is a vascular disease with two routes of spread. Oaks growing near one another graft their roots underground, and the pathogen passes from tree to tree along those connections, which produces an expanding pocket of dying oaks instead of scattered single losses. It also moves overland when sap feeding beetles collect spores from fungal mats on an infected red oak and carry them to a fresh wound elsewhere.

The Pruning Calendar That Matters Most

That second route is the one a property owner controls. Any pruning cut or bark scrape on an oak becomes an entry point while those beetles are active, and spring is the riskiest stretch of the Texas year. Standard guidance is to hold non urgent oak pruning outside that window and to seal every oak wound right away, accidental ones included. Sealing wounds is advised for oaks specifically, not for trees generally.

Which of the Two You Can Still Act On

These two diseases call for opposite responses. Hypoxylon has no chemical cure, so the useful work is lowering stress on the oaks not yet affected and dealing safely with wood that has already failed. Oak wilt does have management options: trenching to sever the root grafts between trees, and preventive fungicide injection by a trained applicator. Both depend on catching it early and on a laboratory confirmed identification.