Wisconsin Ag Connection - Oak Wilt Disease Starting to Show Up in Southern Wisconsin

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Oak Wilt Disease Starting to Show Up in Southern Wisconsin
Wisconsin Ag Connection - 07/23/2008

The first signs of oak wilt, a tree-killing fungal disease, are now appearing in infected trees in counties in the southern two-thirds of Wisconsin. Oak wilt plugs the water- and nutrient-conducting channels in the tree, and affects trees in both the red oak and white oak groups.

"The first symptoms of oak wilt are branches with wilted leaves and leaves on the ground in summer when you wouldn't expect to see them," said Kyoko Scanlon, a forest pathologist with the Wisconsin Department of Natural Resources Division of Forestry. "These are not the brown, dry leaves you see in the fall. These are partially green to bronze-green and are not completely dry."

Once a tree is infected with oak wilt, water and nutrients can't move upward from the root system, causing the tree's leaves to wilt and fall and eventually killing the tree. Oaks in the red oak group, including northern red, northern pin, and black oaks, are particularly vulnerable to this disease. Once symptoms become visible, a tree loses most of its leaves, typically from the top down, and dies very quickly, often within a few weeks.

"Anyone with an oak tree that is rapidly losing its leaves may want to have the tree examined for oak wilt by an arborist or forester or send in a sample for a laboratory test," said Don Kissinger, a DNR urban forester. "A person should take immediate steps to protect other nearby oaks on the property if they value those trees."

The University of Wisconsin's Plant Disease Diagnostic Clinic can help verify the presence of oak wilt. A sample must be sent to the clinic and a small fee is charged for the service. The clinic can be reached at 608-262-2863.

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