Hypoxylon canker is a disease caused by the fungus Biscogniauxia atropunctata. It is often one of several factors ultimately responsible for tree death. Hypoxylon damages tissues in the inner bark and sapwood that are used by the tree to move water from soil to the leaves. Vigorous, healthy trees are colonized by the fungus, but only damaged or stressed trees develop cankers and are killed. Outbreaks of this disease follow severe drought.
Tree Species Affected
Hardwoods, especially the red oak group
Symptoms and Signs
Early symptoms
- Noticeable thinning of the crown
- Small patches of brown leaves
- Branch dieback
Later symptoms
- Large areas of bark fall off the branches and trunk, revealing a thick, dusty fungal mat with tan spores.
- The fungus turns silver or grey as it matures, giving the appearance of thick paint on the side of the tree.
- Old infections may appear black. Black zone lines may appear in the sapwood as rapid decay occurs, leaving the tree in a very brittle state.
Recommendations
Unfortunately, there is no treatment for Hypoxylon canker. Once a tree is showing symptoms of the disease, it is too late—the tree will die. Healthy trees are often already colonized by the Hypoxylon fungus, so removing infected trees may not protect nearby trees. However, in high traffic and residential areas, remove infected trees as soon as possible to avoid damage caused by falling limbs.
Firewood from trees infected with Hypoxylon canker is safe to burn. Firewood movement should only occur locally to prevent the spread of invasive forest pests.
Prevention
Maintaining tree vigor is the best way to prevent Hypoxylon canker.
- Practice good forest management.
- Avoid damaging trees during construction and logging activities.
- Water high-value trees during drought periods.