REGION– Spring is pruning season for many tree species, but if you have an oak tree, put down your saw by mid-April.
To stop the spread of oak wilt, a fungal disease that can kill red oak trees within weeks, the Michigan Department of Natural Resources is urging homeowners not to prune any oak trees from April 15 to July 15.
Despite warm days in late winter, the risk of infection through sap-feeding beetles is still very low through April 15. Risk is highest from mid-April to mid-July, and recent research at Michigan State University indicates that in Michigan, oak infection risk peaks in May and June.
Oak wilt infection can occur when sap-feeding nitidulid beetles become contaminated with viable oak wilt spores and carry them to fresh wounds on other vulnerable oaks. Before April 15, this is unlikely to occur even if the beetles are active on warm days.
Oak wilt also can be spread by moving firewood cut from infected trees. It also spreads from tree to tree through connected, or grafted, root systems.
“After a tree is infected, there is no cure for oak wilt, so it is important to prevent infection in the first place,” said Simeon Wright, forest health resource analyst with the DNR’s Forest Resources Division.
Trees killed by oak wilt require special management. If you suspect a tree has succumbed to oak wilt, you can help slow the spread by burning it on-site, chipping it or debarking it before April 15. Once the wood has been dried for longer than a year and/or all the bark loosens, the firewood can no longer spread oak wilt.
If an oak tree is damaged during the high-risk period from April 15 to July 15, landowners can immediately cover all wounds with tree-wound paint or latex-based paint. Painting tree wounds is not recommended for other trees species as it can reduce the effectiveness of the healing process.
Symptoms of oak wilt most often appear from late June until September. Affected trees will suddenly begin to wilt from the top down, rapidly dropping leaves, which can be green, brown or a combination of both colors. Left untreated, oak wilt will continue to move from tree to tree through grafted root systems, killing more red oak over an increasingly large area when oak trees grow close together.
Contact a local DNR forest health specialist by email at DNR-FRD-Forest-Health@Michigan.gov for more information or to ask a question.
Visit MichiganOakWilt.org for a listing and more information.
