Trimming Oak Trees- A Chore That Can Wait

Katie Hafner, NFWF Soil Conservationist

The presence of oak wilt (OW) had been confirmed in 61 counties in Michigan alone. Oak wilt is a fungal disease that affects oak trees not only in Michigan, but all around the US. It is a fatal disease that affects mainly oaks in the red oak family: red oak, black oak, pin oak (the oaks with the pointy leaves). White oaks can also contract the fungus but are more likely to live. In the last 50 years, oak wilt has spread greatly in Michigan counties- including those in mid-Michigan. OW is present and spreading in Clinton County. Suspect trees should be located and reported to the MDNR using this online tool. While always fatal, the spread of this disease can be slowed by following a few guidelines.

Photo provided by: Michigan Oak Wilt Coalition

Do not prune/cut/trim live oak trees from April 15-July 15 as this is the high-risk period to for the fungus to spread.

During the spring and summer months, when oaks are damaged, sap beetles are attracted to the sweetness of the open wound on the tree. If those beetles are carrying the OW fungus, that tree will most likely be infected. From that point on, the tree is terminally ill and death is almost certain. Leaves will begin to “wilt” turning brown and falling as early as 2 weeks after infection. Death can occur as soon as 5-6 weeks.

In addition to spread by the sap beetles, infected trees that touch roots with healthy trees underground, spreading the fungus.

The easiest and cheapest way to control oak wilt is to prevent it.

The Michigan Oak Wilt Coalition has some great articles, photos, and guides. Their website also has contact information for OW certified foresters who can assist in determining whether or not trees are infected. In addition, MSU offers many articles on OW. The Clinton Conservation District is also here to help.

Stay tuned! The Clinton Conservation District is planning a fall workshop focusing on oak wilt. This field-based event will feature industry educators that can help you diagnose OW and give options for treatment, as well as the current extent of spread in the county and surrounding areas. Please email info@clintonconservation.org with interest in this event so we can keep you informed.