Majestic and long-lived, the mighty oak tree is a backyard favorite, providing shade and an easy-to-climb tree for children. But a fungus is giving some oaks the deadly disease known as oak wilt. Here's how to identify, prevent, and control this aggressive pathogen on your trees.
Oak wilt identification commonly begins with noticing a distinct color change in the foliage. Starting from the canopy, or top, of the tree, the bright green color of the leaves will quickly change to a sickly yellow-green. This will progress down the tree.
The leaves will then begin to wilt, changing color again to bronze. Within a month, a red oak will have lost the majority of its leaves, while a white oak will take longer, even years, for partial or total defoliation. White oaks may even manage to survive. Red oaks have bristles at the tip of their pointed leaves which is one way that they can be differentiated from white oaks, which have rounded, blunt leaves.
Extreme care must be taken to not wound the bark of oak trees. This means not nicking it with the lawn mower or weed eater, or pounding nails into it for a tree house. Any opening in the bark, the tree's protective "skin," could allow the oak wilt fungus an entry. It could also attract wood-boring beetles that will exacerbate the problem.
This also means that the tree not be pruned between the time the sap starts running in early spring until after Labor Day. Any pruning that needs to be done should be in late fall or early winter when the tree heads into its dormant period. While wound paint isn't normally recommended after pruning, the tree service will generally apply this paint to avoid leaving an opening for disease. Once a tree is infected, there is no cure. No chemical treatment or fungicide currently exists.
Even though an infected tree cannot be saved, the other oaks that are in close proximity have a chance if the proper steps are taken. Diseased trees must be removed from the property before the fungus has a chance to spread. But, oak tree roots will frequently graft with one another. This can provide an underground "highway" for the disease to travel. Cutting infected trees down before the other trees have been protected can further spread the spores.
To protect living trees, a tree service will come in with a special plow and will cut a 5-foot deep protective barrier around the remaining healthy trees, severing their connected roots. Where this isn't possible, the diseased stump will be removed and treated chemically. The tree service typically chips or burns the diseased wood onsite so as not to spread it elsewhere. For extra precaution, the soil will be sterilized by solarization. This is done by covering the area with black plastic sheeting.
Companies like Corner Landscaping & Tree Service can inspect your trees and answer any questions you might have about oak wilt and protecting your property.