Oak Wilt

What Can I do?

1. Prevent new infections

The most efficient and cost effective means of control is prevention. To prevent the introduction of oak wilt, avoid tree wounds during the infection period. Don't prune during April, May or June!! This rule of thumb also holds true for construction activities in and around oak trees. If at all possible, don't work around oak trees during those months. If work cannot be avoided, carry a can of pruning paint and immediate paint each wound created, including those on exposed roots. Even 15 minutes can mean the difference between prevention and disease.

Further reading about oak wilt protection, prevention, and treatment:

• If you are building a house or doing other construction around oaks."Are you thinking of building on a wooded lot? Protect your trees from oak wilt"
• Remain current on beetle activity and the dates when not to prune.
• Oak Wilt Management—What Are the Options?

2. Diagnose infected trees

• Become familiar with the symptoms and methods for detecting and reporting suspected oak wilt infected trees. See the U.S. Forest Service publication at and the University of Minnesota.
• Report all suspected oaks immediately to the area Forester, Parks Director or area tree inspector in your community.
• Learn how your community is dealing with the disease. Call your city, township or county and speak with the tree inspector about possible inspection and treatment programs.
• If your community does not have an oak wilt program, contact a certified arborists to work with you in managing the disease or look for disease control under the list of services provided by those arborists working in your area.
• You can also take a sample yourself and send it in for culturing.
  • For sampling procedures, U.S. Forest Service publication.
  • For instructions on submitting a sample to the University of Minnesota Plant Disease Clinic.

3. Control existing infection areas.

Vibratory Plow

If oak wilt has been diagnosed on your property, a forest pest specialist, forester or consultant trained in oak wilt management should work with you to assess the need and benefit of root graft interruption before removing infected trees. If there are healthy trees nearby that might share root grafts with an infected tree, vibratory plowing is highly recommended. The machine cuts a narrow 54 deep slit in the soil to sever the grafts. No soil is excavated from the slit and site disturbance is usually minimal. No chemicals or barriers are inserted in the slit. This plowing process is a purely a mechanical interruption of interconnected roots.

Removal of diseased wood

To prevent above ground spread it is important to remove infected trees and properly depose of the wood. If you want to keep the wood for firewood, follow these steps. All wood from the infected tree that is 4 inches or great in diameter must be chipped (wood chips from infected trees do not harbor the beetles) burned, debarked, buried or covered and sealed to the ground with 4-mil plastic sheeting as follows:

1. Stack or pile infected wood 4 inches in diameter or greater. The size of the pile does not matter, but it should be stable enough to not collapse. Trim branches that may poke holes through the plastic.
2. Dig a 4-inch deep trench completely around the woodpile.
3. Completely cover the woodpile with a single sheet of heavy (4 mil or thicker) plastic sheeting (black plastic will absorb heat better, aiding in the process), laying the sheet edges in the trench.
4. Fill the trench with soil to COMPLETELY SEAL the woodpile from beetles.
5. Keep the pile sealed until after July 1st of the following year. Then uncover to let the wood finish drying for use during subsequent winters.

Fungicide treatment

Where high value non-symptomatic red oaks occur within the plow line, it may be feasible to inject them with a fungicide in order to protect them from developing oak wilt. A forest pest specialist, forester, or consultant trained in oak wilt management should work with you to assess the need and benefit of fungicide treatment.  Systemic fungicide treatments can also be used to protect high-value red oaks in situations where plow lines cannot be installed. Treating infected red oaks that are already wilting is not recommended and is rarely effective. The fungicide propiconizole is the most widely used product. The chemical is available under several brand names and has been shown to provide disease protection for up to two years. Because the fungicide only stops the fungus from killing the tree and does not prevent root graft infections from occurring, applications may be necessary every two years for continued protection.  Fungicides can be effective in preventing and in some cases curing oak wilt in bur and white oaks.

4. Replanting

Replant with the right tree. Oaks are often found in virtually pure stands. When replanting, be sure to select a species that meets site needs and sustains diversity in the community forests. For information on selecting trees, check with your city forester for any prohibited species. Then see the University of Minnesota Extension information or for sources of nursery stockin Minnesota.