Paul Cigan of the Wisconsin DNR tells DrydenWire.com that the fatal Oak Tree disease 'Oak Wilt' is spreading throughout northwest Wisconsin.
Oak wilt, a devastating oak disease, continues to spread throughout Northwest WI. With spring just around the corner, WI DNR Forestry officials are advising landowners to take extra care to avoid injuring or cutting their oaks from April through July to prevent them from dying. First detected in Washburn County in 2014, where it was found killing a large red oak on a private residence in the city of Spooner, oak wilt has continued to spread well beyond Spooner. Last year, the disease was found killing red oaks in 5 new townships across Washburn County, with another 5 townships added to the list across Burnett, Sawyer, and Rusk Counties the same year. Movement of diseased firewood, spring oak injury and cutting, and storm damage are believed to be the primary causes of disease spread in the Northwoods.
“Oak wilt fungal mats form under the bark of oaks in the fall or spring after fatal wilt. Disease spores are carried away by sap beetles to fresh oak wounds, spreading the disease. Keeping diseased firewood stacked and covered tightly to the ground line with plastic for one year after tree death prevents beetles from spreading the disease. First known infection in Minong Township, October, 2016 (Washburn Co.).
(“Applying pruning paint to oak pruning wounds and stumps immediately after injury during April – July may reduce the risk of oak wilt infection.” Photo Credit: WI DNR)
(“Sap beetles spread oak wilt from fungal mats to fresh oak wounds” Photo Credit: WI DNR)
The Wisconsin DNR also published the following on their website:
News Release - 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.
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 infect the tree.
(Just 15 minutes could be enough time for beetles that are carrying oak wilt spores to land on a fresh wound and infect a tree. Photo Credit: George W. Hudler, Cornell University)
"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 Paul Cigan, DNR forest health specialist in Hayward.
Property owners with oak trees are encouraged to check with their municipality to find out if there are local oak wilt ordinances.
The use of tree paint or a wound dressing is not normally recommended on pruning cuts or wounded surfaces on most trees. But for damaged oaks, these products are recommended 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.
Don Kissinger, a DNR urban forester in Wausau, said there are also other important reasons to avoid pruning deciduous trees in spring beyond concerns about oak wilt.
"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.
It's worth protecting
Oak wilt and other diseases also move easily on or in firewood logs year-round. To protect trees in general, don't move firewood long distances, or only use firewood labeled as Wisconsin certified.
Oak wilt is found in all Wisconsin counties except Ashland, Bayfield, Calumet, Door, Douglas, Forest, Iron, Kewaunee, Manitowoc, Sheboygan and Taylor counties. Several of these counties have the highest abundance of healthy and productive oak forests in the state. Taking recommended precautions with living oak trees and keeping firewood local to prevent the spread of oak wilt will help keep them that way for years to come.
More information is available online. Visit the DNR website, dnr.wi.gov, and search for "oak wilt" or "firewood." Additional information about proper pruning techniques is available from community foresters or by searching for "tree pruning."
Last Update: Mar 24, 2017 8:04 am CDT
