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DNR urges Michiganders to hold off on pruning oak trees until mid-July

Oak wilt infected tree with bare branches
David Kenyon
Michigan Department of Natural Resources
Oak wilt infected tree with bare branches

Starting on April 15, the Michigan Department of Natural Resources is asking Michiganders to hold off on pruning oak trees in an effort to prevent the spread of oak wilt infections.

Oak wilt mainly affects red oak trees and is most commonly spread through contaminated beetles who feed off the tree's sap through its wounds.

Infected trees wilt from the top down, rapidly dropping their leaves in the process. If left untreated, the trees can die within four to six weeks after initial contact.

Oak Leaf Wilt Near Interlochen Oak Leaf Wilt, Grand Traverse Co, near Interlochen...Picnic Beattles.
David Kenyon
Michigan Department Natural Resources
Oak leaf wilt branch with sap-feeding picnic beetle near Interlochen.

Cheryl Nelson, a forest health expert with the DNR, said the best way to help these trees is to leave them alone.

“If people can avoid pruning or wounding or damaging their oak trees, especially the red oaks April 15 to July 5, that's going to be the number one thing they can do to help prevent their trees from getting oak wilt.”

Nelson said the risk of an infection outside these dates is low.

If tree owners must prune their trees during this time frame, Nelson said they can cover the wounds with tree-wound paint or latex-based paint to prevent an infection.

Oak wilt can also be spread by moving firewood from infected trees as well as from tree to tree through connected or grafted root systems.

Nelson said people who suspect their trees are infected should first report it to the DNR before they begin treatment.

Trees that are killed by oak wilt still have the ability to spread the infection.

To help slow the spread, the DNR is urging owners to burn the tree on-site, chip it or debark it before April 15. The DNR said that firewood from infected trees can no longer spread the disease once the wood has been dried for longer than a year or once all of the bark loosens.

Michiganders can report an oak wilt infection through the DNR’s interactive oak wilt map.

Editor's note: In the interest of transparency, we note the Michigan Department of Natural Resources is a financial supporter of this station.

Renae is a newsroom intern covering northwest Lower Michigan for WCMU.