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PRUNE TREES IN WINTER TO HELP PREVENT OAK WILT

Contact(s): Don Kissinger: 715.359-5793, Kyoko Scanlon 608.275-3275, Paul Cigan 715.416-4920 or Mike Hillstrom 715.459-1371.
February 1, 2016

MADISON - Now is a good time for tree pruning, while temperatures remain cold, according to Wisconsin Department of Natural Resources tree health experts.

"The best time to prune trees in Wisconsin is during winter when a tree is dormant," said DNR Urban Forester Don Kissinger. This is because:

An oak dying from and an oak killed by oak wilt
Photo Credit: WDNR

• Insects and diseases that attack open wounds on pruned trees aren't active in winter, and
• Without leaves on the trees it is easier to see and prune broken, cracked or hanging limbs.

"Pruning oak trees during winter is a good practice to help prevent introduction of oak wilt," said Kyoko Scanlon, DNR Forest Pathologist. Oak wilt is a fatal disease of oaks. During the winter, beetles that carry oak wilt spores to healthy oak trees are not active.

To help reduce the spread of oak wilt another way, do not move firewood. "Several recent oak wilt finds in northern Wisconsin were probably the result of infected firewood brought from areas with oak wilt," according to Paul Cigan, DNR Forest Health Specialist for northwest Wisconsin.

• Keep oak firewood where it is cut for one year, or until the bark is naturally loose, to prevent the spread of oak wilt.

"Oak wilt is still uncommon in much of northern Wisconsin", said Mike Hillstrom, DNR Forest Health Specialist for central Wisconsin. Taking precautions to prevent the spread of oak wilt will help keep it that way.

For additional information online, search the DNR website dnr.wi.gov for keywords "oak wilt".

Pruning tips

Trees should be pruned throughout their entire life to maintain strong structure and remove dead wood. "Pruning should not remove more than 25 percent of the live crown of a tree. The lower third of trunks of deciduous trees should be free of limbs," Kissinger said. The DNR pruning brochure offers more detailed, step by step tips for tree pruning. Find it by searching the DNR website dnr.wi.gov for "tree pruning [PDF]".

Certified arborists who offer pruning and other tree care services can be found at waa-isa.org/arborists/search.asp (exit DNR).