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DNR: Michigan oak trees currently at high risk for fungal disease

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Posted at 2:41 PM, Apr 15, 2020
and last updated 2020-04-15 15:26:23-04

(WXYZ) — Those with oak trees, particularly red oaks, should be wary of oak wilt spores carried by flying beetles, the Michigan Department of Natural Resources said.

From April 15 to July 15, oak trees are at high risk for oak wilt, a serious fungal disease that can weaken white oaks and kill red oak trees within a few weeks of infection.

“The guidelines against pruning oak trees during this period are a way to help prevent the spread of the disease,” said James Wieferich, forest health specialist in the DNR’s Forest Resources Division. “Unfortunately, many people learn not to prune or otherwise wound trees from mid-April to mid-July only after they lose their oaks to oak wilt.”

Once a tree is infected, the fungus can also move to neighboring red oaks through root grafts. Oaks within about 100 feet of each other, depending on the size of the trees, have connected root systems, the DNR said.

Left untreated, oak wilt will continue to move from tree to tree, killing more red oaks. As more trees die, more fungal spores are produced, which allows the beetle to carry infection to new locations.

The DNR said it's important to avoid pruning or injuring oak trees during this time period. Firewood can also harbor the fungus.

To minimize the risk of infection, the DNR restricts cutting of red oak trees on state-managed lands between April 15 and July 15.