ANN ARBOR, Mich. (Michigan News Source) – With temperatures dropping and leaves falling, the Michigan Department of Natural Resources (DNR) is cautioning oak tree owners to consider the opportunity to prune their possible infected trees.
The tree disease was first identified in the 1940s and was widespread across Michigan’s Lower Peninsula and along the Wisconsin border in the Upper Peninsula according to the DNR.
”Red oaks are most susceptible and can die within weeks of infection,” according to the DNR, “These trees have leaves with pointed tips and include black oak, northern red oak and northern pin oak. Trees in the white oak group have rounded leaf edges and are less susceptible. Affected trees will suddenly wilt from the top down, rapidly dropping leaves, which can be green, brown or a combination of both colors.”
During the high-risk season from April 15-July 15, if oak trees are pruned there is a higher likelihood of becoming infected by oak wilt fungus. Fresh bark damage from pruning or other wounds attract beetles which can help spread the fungus.
“Beetles that can carry the disease from tree to tree are not very active now, and the trees are not vulnerable to infection,” said Simeon Wright, forest health specialist with the DNR Forest Resources Division.
Even after infected trees are cut ahead of the winter time, their trimmed appendages can still offer a home for the beetles. Scientists encourage mitigating this spreading of beetles by covering the wood with a plastic tarp and burying its edges underground to inhibit beetle access. The wood should be sarcophagic for at least six to twelve months, or until the bark falls off.
A recent resident report found the fungus in an Ann Arbor nature area, the first time a detection was made in the area’s history. City officials have already made a tentative plan for the removal of infected and nearby trees to reduce further infestation including work below and above the ground.
According to the City of Ann Arbor, the work will take place in the Bird Hills Nature area.
Work belowground will entail “Trenching a perimeter around the infected and potentially-infected stand of red oaks. Trenching will sever the root systems through which the infection spreads.” While work above the surface will feature “Removing all the red oaks within the trenched perimeter. Currently, the recommended trenching perimeter would result in approximately fifty-five (55) red oaks being cut and removed. This will result in the loss of significant tree canopy in the remediation area.”
Ann Arbor anticipates completing the trenching portion of the project in November and the tree felling portion by the end of January 2024.