ATTENTION ALL MOTORIZED TRAIL MAINTAINERS: and PROPERTY OWNERS:
DO NOT PRUNE OAK TREES BETWEEN APRIL 15 AND JULY 15.
Click here for an online map showing active areas of Oak Wilt à OAK WILT MAP
Help prevent the spread of oak wilt:
Know what to look for;
- Avoid pruning or wounding oak trees between April 15 and July 15;
- Use caution when grading and performing routine maintenance on Michigan’s Trails System
The following guidelines against pruning and preventing damage to oak trees can help prevent the spread of the disease.
| Oak trees have a reputation for being mighty, but these majestic trees need our help in spring and early summer to prevent the spread of a microscopic killer. From April 15 to July 15, oak trees are at high risk for oak wilt, a serious fungal disease that can weaken white oaks and kill red oak trees within weeks of infection. During this time of year, flying beetles can carry oak wilt fungus spores from tree to tree and the fungus can infect trees through wounds left by pruning or storm damage. The fungus can move from an infected oak to neighboring oaks through root grafts. Depending on tree size, adjacent oaks may be connected to other trees, or grafted, through root systems. Roots of large trees can reach 100 or more feet. Left untreated, oak wilt will continue to move from tree to tree, killing more red oak over an increasingly larger area. As more trees die from oak wilt, more fungal spores are produced, which allows the beetle to carry infection to new locations. Trees in the white oak family are more likely to survive an infection because they are capable of compartmentalizing the fungus. |
- Red oaks are especially vulnerable; can die within weeks of infection
| Trees in the red oak family are most susceptible to oak wilt. These trees have leaves with pointed tips and include black oak, northern red oak, and northern pin oak. Trees in the white oak group have rounded leaf edges and include white oak and swamp white oak. They are less susceptible. Symptoms most often appear from late June through September. Affected trees will suddenly begin to wilt from the top-down, rapidly dropping leaves, which can be green, brown or a combination of both colors. If you have an oak tree on your trail that gets damaged during the risk period from April 15 to July 15, immediately cover all wounds with tree-wound paint or latex-based paint. |
- Contact a local DNR forest health specialist for more information 517-284-5866.
- Contact your local Forestry Assistance Program forester for a site visit in select counties.
- Seek verification from Michigan State University. Find instructions at canr.msu.edu/pestid or call 517-355-4536.
- Get help from an oak-wilt qualified specialist. Visit MichiganOakWilt.org for a listing and more information.
