Don't prune or injure oak trees during greatest risk period
Have an oak tree on your property? To keep it healthy, don’t prune it from mid-April through the summer. That’s a key time for infection with oak wilt, a serious disease that can weaken white oaks and kill red oak trees within weeks.
Oak wilt, caused by a fungus, has been reported throughout the Midwest, including Michigan, said Ryan Wheeler, invasive species biologist with the Michigan Department of Natural Resources.
Red oaks are most susceptible to the disease. These trees have leaves with pointed tips and include black oak, northern red oak and northern pin oak. Trees in the white oak group have rounded leaf edges and include white oak and swamp white oak. They are less susceptible.
Symptoms most often appear from June until September.
"Affected trees will suddenly begin to wilt from the top down, rapidly dropping leaves, which can be green, brown or a combination of both colors," Wheeler said.
Oak wilt is spread above ground mainly by sap-feeding beetles that carry the disease spores from an infected tree, or wood cut from an infected tree, to fresh wounds,