Oak Wilt is a fungal disease

Oak wilt is a fungal disease attacking oak trees in eastern and central U.S. It causes rapid death of trees in the red oak group and a slower decline of trees in the white oak group. Oak wilt will spread quickly to other trees through insect vectors and root grafts. For this reason, it is important to identify and treat any trees with the fungus in order to minimize threat of infecting healthy trees.

✓ What trees are affected?

  • All Oak trees, especially oaks in the red oak group (red, black, pin, etc.)

✓ Symptoms

  • In red oak group trees: Leaves will begin to wilt and turn bronze/yellow in the top of the tree. The foliage will continue to decline on branches inward and downward till the entire canopy is dead. A brown streaking may be present in the outer ring of sapwood. This process only takes a few weeks and the tree will be completely devoid of leaves by mid-summer.
  • In white oak group trees: The disease moves much slower in white oaks. Due to the white oak group’s ability to decompartmentalize, it takes years for the fungus to spread throughout the tree. Symptoms of oak wilt on white oaks include branch die back and overall tree decline. These symptoms are very similar to that of oak decline, construction damage, soil compaction and root rot. It is necessary to have a pathology lab verify oak wilt for positive identification. Some species, such as white oak and bur oak, will contract the disease and then recover.

✓ Solution

There is no control for oak wilt. The only solution is early detection and prevention of the spread. When oak wilt is identified, tree removal is the only option. This disease will spread to other oak trees by way of root grafts under ground and insect vectors. Insects carrying the disease are attracted to other stressed or injured trees, including trees wounded by pruning cuts. Therefore, avoid pruning any oak trees during the spring and summer months.

Sanitation is also very important. Any pruning equipment used on an infected tree should be sterilized before it is use on healthy trees. All infected material should be hauled off site and destroyed; any residual wood could potentially infect other trees. If any trees are in the vicinity of an infected tree, consider root pruning areas that may contain root grafts. This is sometimes not practical in urban environments with underground utilities and irrigation.