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Thinking about those construction or landscaping plans for this spring? If so, remember to avoid damaging oak trees. Be careful with that lawnmower! Human-caused wounds is one of the most common ways to spread oak wilt. The moist wounds attract spore-carrying sap beetles which carry disease spores from infected trees.

The standard time to avoid oak injury is May through July. In most years, the spore generating fungal pads have dried-out by then, but not always. Last year, fungal pads were active into September.

Oak wilt is firmly established in the Shakey Lakes region of Menominee County. Additional oak wilt epicenters are scattered along the Menominee River and in the Iron Mountain area. In 2004, a new eradication effort began. It will likely be continued this summer.

Last fall, about 50,000 feet of root-breaking trench was plowed. A hundred epicenters were treated. Identification and treatment of oak wilt pockets will need to continue for at least another year or two if we hope to achieve a good measure of control.

When an oak wilt pocket is identified, both overland and underground disease spread must be stopped. Overland spread can be controlled by removing and properly disposing of infected trees. Underground spread is treated by a vibratory plow that severs roots down to five feet. Root systems must be broken due to the root-grafting habit of red oaks, which would otherwise spread the disease from tree to tree.

Oak wilt can be recognized by rapid wilting of leaves beginning at the top of the tree. Oaks killed last year will display spore pads that rupture the bark, usually evidenced by a slight swelling and a vertical crack. The spore pads are often called pressure pads due to this behavior.

The combination of drought and attacks by two-lined chestnut borers can sometimes be mistaken for oak wilt, especially on sandy soils. However, the dying process is usually longer and recently dead trees do not form the spore pads.

Gypsy moths can mask the leaf effects of oak wilt when the trees are defoliated in June. Many oak areas were loaded with gypsy moth egg masses in the fall of 2004.

The disease can easily be transported in logs and firewood. Harvested oak from infected stands should either be processed immediately or tightly covered by tarps. Oak wilt is one more reason why the movement of firewood should no longer be done without consideration for the potential of spreading insects and diseases.

If construction or landscaping is absolutely necessary during the spring and early summer, oak wounds should immediately be painted. Any commercial wound paint will work, but immediate means within minutes. Letting the task go until the next day can significantly increase the risk of infection. Oak wilt prevention is one of the few reasons that tree wounds should be sealed. It is not a normally a beneficial practice.

Should your oak trees display symptoms of oak wilt or if you would like more information, contact Bill Cook at cookwi@msu.edu or 906-786-1575. His office is at the U.P. Tree Improvement Center near Escanaba.

The oak populations in the Upper Peninsula are vulnerable to this disease. Oaks are about the only trees that produce hard mast along the Menominee River. The acorns are a valuable commodity for many species of wildlife. Oaks also have other important ecological roles and are popular trees among landowners for many reasons. Please make every effort to help control the spread of oak wilt.

Trailer
Bill Cook is an MSU Extension forester providing educational programming for the entire Upper Peninsula. His office is located at the MSU Upper Peninsula Tree Improvement Center near Escanaba. The Center is the headquarters for three MSU Forestry properties in the U.P., with a combined area of about 8,000 acres. He can be reached at cookwi@msu.edu or 906-786-1575.

Prepared by Bill Cook, Forester/Biologist, Michigan State University Extension, 6005 J Road, Escanaba, MI 49829
906-786-1575 (voice), 906-786-9370 (fax), e-mail: cookwi@msu.edu

Use / reprinting of these articles is encouraged. Please notify Bill Cook.
By-line should read "Bill Cook, MSU Extension" Please use the article trailer whenever possible.

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Last update of this page was 5 November, 2018