What Is Killing Oak Trees in Michigan?

The No. 1 killer of oak trees in Michigan is caused by oak wilt disease. For several years, this disease has continued to move through Michigan at an alarming rate — with April through July being the time of the year when oak trees are most at risk. In this blog, we’ll share the history of this disease, how it affects oak trees and its impact throughout the state.

What Is Oak Wilt and Where Did It Come From?

Oak wilt, or ceratocystis fagacearum or Bretziella fagacearum, is a fungal disease and is fatal to Michigan’s oak trees. While the disease’s effects can be problematic in Michigan’s white oak trees, oak wilt is fatal to red oaks.

Experts believe the fungus originated somewhere in Latin America in the early 1900s and then came to the U.S. and spread rapidly. Cases were first reported and began killing oak trees in Michigan in the 1970s. The disease infects trees either through the root system or when it is carried to the tree via beetle.

What Happens When a Tree Has Oak Wilt?

Once infected with oak wilt, an oak tree’s leaf tips will turn brown because the tree’s water system gets blocked by the fungus. This discoloration spreads to the base of the leaf, killing it and causing it to fall to the ground. Underground, oak wilt creates a fungal mat that could lead to the discoloration of any sap the tree may produce.

If left untreated, oak wilt leads to tree death in red oak groups of trees in a matter of months (the underground spore mats can travel to nearby trees). White oaks tend to fight off the disease easier, but there can be tree damage left behind.

Oak Wilt in Michigan

The Michigan Department of Natural Resources confirms oak wilt exists in 61 of Michigan’s 83 counties. Oaks make up about 10% of the forest in Michigan and oak wilt has the potential to impact 149 million red oak trees across the 20 million acres of forest land that occurs in Michigan, the DNR reports.

How To Prevent Oak Wilt

To stop oak wilt from killing your oak trees, avoid inflicting fresh wounds on your trees in the warmer months (April through July), including pruning, adding climbing spikes, nailing signs or hanging lanterns, as this can result in more new tree infections. Also, beetles carrying fungal spores are attracted to these fresh wounds, making the trees even more vulnerable.

Oak wilt can be treated with fungicide to an extent — the fungicide won’t get rid of oak wilt, but it will help symptoms subside in the short term. The fungicide’s effectiveness also depends on how much the disease has already spread.

Worried your oaks may have oak wilt? Don’t leave your trees vulnerable to fungal infection. For more information on prevention or a free estimate on treatment, contact us.

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