Oak tree. Wiki­media Commons


Oak wilt, a fungal disease that can infect and kill certain oak trees in a matter of weeks, is a growing problem across Michigan and the eastern United States, according to Plant Pathol­ogist David Roberts from Michigan State University’s College of Agri­culture and Natural Resources.

Roberts will present about the disease, its spread, and how to prevent or contain the infection of oak trees March 1 from 5 – 7 p.m. at the Hillsdale Com­munity Library. The talk is spon­sored by ReLeaf Michigan, a non­profit tree orga­ni­zation, and will educate home­owners and attendees about how to protect local oak trees that are sus­cep­tible to oak wilt.

Oak wilt has a con­firmed presence in Michigan, and is spread through the root systems of infected trees or by sap beetles, which feed on the fungus and spread the disease to new trees through wounds in the bark that can be caused by pruning trees, Roberts said. He said about 90 percent of oak wilt cases are due to root graft, when the root systems of two trees nat­u­rally grow together.

Roberts said transport of firewood or timber from infected trees can also spread the disease to dif­ferent loca­tions.

Pre­ven­tative mea­sures, such as avoiding pruning oak trees while the beetles are active from approx­i­mately mid-April to mid-July, help prevent the spread of oak wilt, according to Hillsdale College Hor­ti­cul­tur­alist and Hillsdale County Shade Tree Com­mittee member Angie Girdham said.

“The silver lining with oak wilt is that proper tree care man­agement tech­niques goes a long way in con­trolling the spread,” Girdham said in an email. “The biggest factor is pruning at the correct time of year to prevent the trans­portation of the disease by the beetles that move the spores into fresh wounds.”

Red oaks, which are espe­cially sus­cep­tible to oak wilt, can die within two to three weeks of becoming infected, according to infor­mation from the Michigan Department of Natural Resources. Roberts said the primary symptom of oak wilt is pre­mature leaf fall, but since man­aging the disease can be an expensive process, anyone who sus­pects an oak wilt infection should consult an arborist to confirm the diag­nosis.

Once a tree is infected with oak wilt, there is no way to cure the tree, making it all the more important to prevent the spread of the disease, Roberts said. Pre­ven­tative mea­sures include digging trenches around infected trees to prevent the spread of oak wilt through the tree’s root system or injecting trees with a fungicide.

City Forester Gary Sta­chowicz said he is not aware of any cases of oak wilt in Hillsdale County. He said the city’s trees are pre­dom­i­nantly maple, but include a small number of both white and red oaks along the road, and there are more oaks in the city’s parks and cemetery.

“The idea is to educate as much as pos­sible to slow the spread of the disease,” Sta­chowicz said.

Sta­chowicz said the two-hour pre­sen­tation is free of cost, and is open to anyone in the com­munity. He said he has also invited tree cutting busi­nesses and tree com­panies from Jackson, Michigan, to attend the oak wilt pre­sen­tation.

“Anybody who is inter­ested in learning more about oak wilt is welcome to attend the pre­sen­tation,” Sta­chowicz said.

According to the DNR, a 2011 Forest Inventory and Analysis data and with the current average stumpage price for red oaks indicate that the value of red oak timber in Michigan is approx­i­mately 1.6 billion dollars. Girdham said one of the most valuable trees on campus is a large White Oak near Howard Music Hall valued at $39,025.50.

Based on a 2013 survey of campus trees, there are approx­i­mately 19 oak trees on campus, although the city’s oak trees and trees in the arboretum, Hayden Park, or at Hillsdale Academy were not included in the survey. There have been no known cases in any oaks at Hillsdale College, according to Arb Program Coor­di­nator Laurie Rosenberg.

“As far as I know, we do not have any oak wilt on any of the trees at the arboretum yet,” Rosenberg said in an email. “We are very careful about trimming them and pro­tecting them from damage, which is about all you can do to prevent the disease from having an entry point into the tree.  I am also shifting any future plantings of oaks to white oak species, which are less sus­cep­tible to the fungus.”

Although official rec­om­men­da­tions from the DNR advise against pruning oak trees from mid-April to mid-July, Roberts said the sap beetles that spread the fungus can become active anytime tem­per­a­tures rise above 45 degrees for several days, although the risk for trans­mitting oak wilt is not high during short stretches of warm weather toward the end of winter.

“One of the major pur­poses of having ReLeaf Michigan and Hillsdale offer this pre­sen­tation is to educate our property owners and the local tree trimming com­panies of this awful pest and the steps each of us can do to prevent it from moving into our com­munity,” Girdham said in an email.

  • Angela Girdham

    Just as an FYI…there is a sen­tence in the fifth para­graph that doesn’t cor­rectly explain the pruning window. While the beetles are active April to July; pruning should stop the end of March and not start up again until November.