Tips for helping to prevent oak wilt disease

It’s best to avoid cutting, pruning or damaging oak trees this time of year to prevent the spread of oak wilt disease.

Oaks are most vulnerable to the disease during the growing season, especially from April 1 to July 15.

“Disease prevention is key,” said Ben Walker, a silviculturist with the Chequamegon-Nicolet National Forest. “Once oak wilt becomes established, it can kill otherwise healthy trees in as little as three to four weeks.”

Oak wilt is a fungal disease spread by sap-feeding beetles and underground root grafts. Through mid-July, the beetles fly and feed on new cuts and wounds on oak trees. They can pick up fungal spores from an infected tree and carry them on their bodies to healthy trees.

Oak wilt can be very difficult and costly to control once a tree is infected. Underground spread through root grafts is common and many oaks can be lost quickly. Once established in an area, if not controlled quickly, spread to other nearby areas is almost inevitable.

Transporting firewood also creates a chance for fungal mats under the bark to carry oak wilt to new locations.

Silviculurists recommend using local firewood and following Wisconsin firewood rules.

While oak wilt has been established in the forest’s Lakewood- Laona Ranger District in northern Oconto County for more than 20 years, it was discovered more than 100 miles away in the Great Divide and Washburn ranger districts in Bayfield and Sawyer counties in 2018. Chance for control and containment in the northwest counties stand a better chance since infections are relatively new and more localized.

Oak wilt can reduce property values and recreational opportunities, while the forest products industry can also see reduced timber values.

“All landowners can help with prevention,” Walker said. “The most important thing we can do is protect oak trees during the growing season.”


Conservation Corner is a weekly article produced by the Forest County Land &Water Conservation Department. For more information contact Steve Kircher, County Conservationist-Land Information/GIS Director at 715-478-1387 or by e-mail at .