Now is a great time to prune or cut oaks without the risk of oak wilt infection, according to the Minnesota Department of Natural Resources. Winter is also the safest time to remove infected oaks.

Oak wilt is an invasive fungal disease spread by sap-feeding beetles that can kill all oak species. The disease is common in east-central and southeast Minnesota and is expanding north and west. In 2024, oak wilt was confirmed for the first time in Carlton and Kandiyohi counties, bringing the number of Minnesota counties with known infections to 33.

Fortunately, the public can help stop its expansion.

“Oak wilt is very expensive to treat, but prevention is often effective and much less costly,” said Brian Schwingle, Forest Health Program coordinator. “One of the best ways to help protect oaks is to do any necessary pruning or cutting in winter when the risk of infection is virtually nonexistent.”

Schwingle said the beetles that carry oak wilt spores become active in warm weather and are attracted to the sap from fresh wounds on trees, such as those made by pruning. It’s important to avoid wounding or pruning oaks April through July, the period with the highest risk of spread.  

On Jan. 22, Schwingle will lead a webinar about how to identify and prevent oak wilt as part of the Minnesota Outdoor Skills and Stewardship Series. Registration is free and the presentations are recorded.

More details about oak wilt, including identification, prevention strategies and how best to deal with infected trees and wood, can be found on the DNR’s oak wilt management webpage.