Keys to Hypoxylon by Trees Are Key published on 2019-06-20T15:08:57Z Trees Are Key Let's take a look at a canker that seems to have become more popular in the last decade. The hypoxylon canker, has been renamed Biscogniauxia (instead of Hypoxylon) atropunctatum, but everyone still refers to it as hypoxylon. Hypoxylon canker is a fungus that causes cankers and death of oak and other hardwood trees. Species Spotlight This week's species spotlight features the Water oak, Quercus nigra, a deciduous, Texas native. This large tree grows to 90 feet or more with a trunk to 3 feet in diameter, with a dense, round crown of dark green foliage. Its wood is heavy, hard, and strong, light brown in color, with lighter-colored sapwood.