If you live anywhere in the Midwestern or Eastern United States, its time to stop pruning your oak trees for the year. Why, you ask? With the onset of spring, the worry of oak wilt grows anew.
Caused by a fungus, oak wilt has existed in the aforementioned regions of the United States for some time. Red, black and pin oak are most susceptible to oak wilt, though white and bur variants are not immune. Black, pin, or red oak usually die within the same summer they are infected. White oak and bur oak can often take a number of years before they succumb to this disease.
Oak wilt can spread from infected trees to their healthy neighbors in two ways: a small beetle that carries spores of the fungus from a diseased tree to a healthy one with an open wound during the growing season, and through root grafts connecting nearby oaks. For example, if a red oak is infected and there is another red oak within 50 to 100 feet, there is a good chance that the roots of these trees are grafted and the fungus can move from the diseased tree to the healthy tree.
Good indicators of wilt include leaves turning a bronzed brown along the rim of the leaves. This does not mean that no green can be present on the leaves–a green leave with a brown rim could still be a symptom of infection. You’ll generally first spot leaves like this on the ground, as defoliation starts at the top of the tree, and is difficult to see when the leaves are intact.
So what does this have to do with oak pruning? Open wounds. The best way to prevent the spread of oak wilt is to prevent any wounding to oak trees during the growing season. If a tree is wounded from storm damage or pruning is required during the growing season, treat the wounds immediately with a wound dressing such as acrylic paint. Do not purchase pruning paints/sealants, as such products slow the tree’s ability to seal over the wound.
Oak wilt is an insidious killer, and has already claimed a tragic number of our nation’s precious hardwoods. Holding off on your pruning plans could go a long way towards preserving more of our oaks for the future.
A humble homesteader based in an undisclosed location, Lars Drecker splits his time between tending his little slice of self-sustaining heaven, and bothering his neighbors to do his work for him. This is mainly the fault of a debilitating predilection for fishing, hunting, camping and all other things outdoors. When not engaged in any of the above activities, you can normally find him broken down on the side of the road, in some piece of junk he just “fixed-up.”
Tom says
In Wisconsin, prune in any month with a R.
John says
So when do I prune my oaks?