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NEWS ARCHIVE:     Age: 624 days

Protect oak trees, avoid oak wilt by waiting until after July to prune

Published by Central Office March 29, 2016

Contact(s): Kyoko Scanlon, DNR statewide forest pathologist (Fitchburg), 608-275-3275, Kyoko.Scanlon@wisconsin.gov; Don Kissinger, DNR urban forester (Wausau), 715-359-5793, Don.Kissinger@wisconsin.gov; Paul Cigan, DNR plant pest and disease specialist (Spooner) 715-416-4920, Paul.Cigan@Wisconsin.gov; or Mike Hillstrom, plant pest and disease specialist (Wisconsin Dells), 715-459-1371, Michael.Hillstrom@Wisconsin.gov

MADISON - To protect oak trees and help prevent oak wilt, the Wisconsin Department of Natural Resources advises people to avoid pruning oaks on their property from April through July.

Oak wilt can cause leaf drop and defoliation. Often leaves with the characteristic brown margins and green center can be found on the ground underneath infected trees. Oaks in the red oak group get the disease most easily while oaks in the white oak group (those with rounded leaf edges) are less susceptible.
Oak wilt can cause leaf drop and defoliation. Often leaves with the characteristic brown margins and green center can be found on the ground underneath infected trees. Oaks in the red oak group get the disease most easily while oaks in the white oak group (those with rounded leaf edges) are less susceptible.
Photo Credit: WDNR

Spring and early summer pruning makes oak trees vulnerable to oak wilt, a fatal fungal disease. Any tree damage during this time creates an opening that exposes live tree tissue and provides an opportunity for the oak wilt fungus to invade and establish itself in the tree.

Don Kissinger, a DNR urban forester in Wausau, said beyond concerns about oak wilt, there are other important reasons to avoid pruning deciduous trees in spring.

"Spring is the time when tree buds and leaves are growing, leaving the tree's food reserves low," Kissinger said. In general, the best time to prune trees is in winter.

The use of tree paint or a wound dressing is not normally recommended on pruning cuts or wounded surfaces on most trees. These products are recommended for damaged oaks from April through July. An immediate light painting of wounds on oak trees during this time helps protect against the spread of oak wilt by beetles.

"Just 15 minutes could be enough time for beetles that are carrying oak wilt spores to land on a fresh wound and infect your tree," said Kyoko Scanlon, DNR statewide forest pathologist.

Property owners with oak trees are encouraged to check with their municipality to find out if there are local oak wilt ordinances.

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

More information about oak wilt is available online. Visit sbe.wi.gov, and search for "oak wilt." Additional information about proper pruning techniques is available from community foresters or by searching for "tree pruning."

Last Revised: Tuesday, March 29, 2016

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