Hypoxylon Canker
caused by Hypoxylon

Fungi in the genus Hypoxylon generally cause a white rot of hardwood slash. However, some species are known to cause severe cankering of stressed hardwoods. Cankering caused by this fungus contributes to the premature death of trees stressed by drought, construction damage, or other problems. Rapidly rotting tissue leads to structural weakening, which causes serious hazard to people or property in high-use areas.

Identification:

The fungus is usually visible as a definite fruiting layer that has dislodged the bark. Fruiting layers vary in color. Hundreds of small, black fruiting bodies are imbedded in this layer.

Injury:

The fungus invades the tree's cambium, and the fruiting layer exerts sufficient pressure to dislodge the bark. Careful observation is sometimes needed to see the fruiting layer, since it can resemble the bark of some trees, such as hackberry.

Biology and History:

Weakened trees are most often attacked by Hypoxylon. The fungal spores enter wounds, germinate, and grow into the cambium, severely cankering and often girdling the tree very quickly. Concurrently, white rot of the sapwood under the canker begins. Fruiting structures eventually cover the cankered area and rupture the bark. Spores are produced at a rapid rate and are wind borne to new hosts.