To protect oak trees, and help prevent oak wilt, the Department of Natural Resources advises area residents with oak trees on their property not to prune them from April through July.

Oak wilt is a fatal fungal disease of red oaks. The risk of oak wilt spreading above ground is highest April through July.

Oak Wilt was first confirmed in Lincoln County in 2012 - between Tomahawk and Lake Nokomis. The DNR has since confirmed several other oak wilt disease centers in that area.

“Oak wilt has been killing oaks immediately north of Tomahawk for several years and it has a firm foothold,” said Brian Schwingle, DNR forest health specialist. “It is extremely important for Tomahawk and Lake Nokomis area residents to prevent infection on their land by not pruning or damage oaks from April through July.”   

Any action that provides an opening into the tree, such as carving initials into the tree, accidentally cutting exposed roots with a lawn mower, or attaching a birdfeeder or clothes line, could provide an opportunity for the oak wilt fungus to invade and establish itself in a forest, Schwingle noted.
Builders and developers also need to be very careful, as many oak wilt infections occur through inadvertent damage to roots, trunks, or branches during the construction process.

While using paint or a wound dressing is not normally recommended on pruning cuts or wounded surfaces on most trees, oaks are an exception from April through July. An immediate light painting of wounds on oak trees is recommended during this time to help protect against the spread of oak wilt by beetles.

While the risk of spreading oak wilt is low after July, homeowners could avoid pruning or wounding oaks until November, to be on the extremely safe side.

More information about oak wilt and other forest pests is available on the Wisconsin DNR website. Visit dnr.wi.gov and search the words "oak wilt."