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Watch for oak wilt signs to help stop the spread of this tree-killing disease

Published by Central Office August 22, 2017

Contact(s): Todd Lanigan, DNR forest health specialist, 715-839-1632; Don Kissinger DNR urban forester, 715-359-5793

MADISON -- Each year, a tree-killing fungal disease strikes and kills thousands of oak trees in Wisconsin's forests, woodlots and urban areas. Oak wilt is common in southern and central Wisconsin and is becoming increasingly abundant in northern counties. It is difficult to control once the disease takes hold and prevention steps need to be taken to slow the spread.

"We are observing oak wilt in more places this year, probably due to the storms we had in the spring," said Todd Lanigan, a forest health specialist with the Department of Natural Resources Division of Forestry. "The first symptoms of oak wilt are branches with wilted leaves dropping in summer. These are not the brown, dry leaves you see in autumn. These are partially green to bronze-green and are not completely dry."

Oak wilt is confirmed in all Wisconsin counties except Ashland, Bayfield, Calumet, Door, Douglas, Forest, Iron, Kewaunee, Manitowoc, Sheboygan and Taylor counties.

Oaks in the red oak group, including northern red, northern pin, and black oaks, are particularly vulnerable to oak wilt.

"Oak wilt is fatal for the infected tree. Landowners need to know what to watch for to take immediate steps to protect nearby oaks," said Don Kissinger, DNR urban forester. "Trees that die of oak wilt can still spread the disease for approximately a year after they die. It is important to know the signs and have a certified arborist or local forest health specialist help manage and contain the spread of oak wilt."

Wisconsin communities may be eligible to participate in a cost-sharing program to help combat oak wilt. The Urban Forestry Grant Program is not available to individual property owners; however, they can work with their municipalities to take steps to protect their oaks. Grant applications are due October 1. If a community is interested in applying for a grant, contact the local DNR urban forestry coordinator for more information.

"It is important to know the signs and have a certified arborist or local forest health specialist help outline management options, such as applying a fungicide," said Don Kissinger, DNR urban forester.

What to watch for:

Leaves infected with oak wilt drop rapidly and appear bronze-green.
Leaves infected with oak wilt drop rapidly and appear bronze-green.
Photo Credit: DNR

Helpful tips:

The University of Wisconsin's Plant Disease Diagnostic Clinic can help verify the presence of oak wilt. Instructions for collecting and mailing samples to the clinic are available at (exit DNR), or by calling 608-262-2863.

Other diseases and insect infestations can mimic oak wilt. Additional information about oak wilt and other forest health issues can be found at, keyword "forest health."

Last Revised: Tuesday, August 22, 2017

Contact information

For more information about news and media, contact:
James Dick
Director of Communications