Oak Wilt: Plant Rant

Raise your hand if you have red oaks in your yard or neighborhood. Okay, now raise your hand if you have heard of oak wilt. If you love oak trees or have them in your area you should know about it.

Oak wilt, scientifically known as Ceratocystis fagacearum, is a fungal ailment that progresses through the tree's vascular system, which comprises the water-conducting tissues. It has the potential to cause the demise of robust red oak trees, and although white oaks can also succumb to it, they exhibit greater resistance and are less susceptible to fatal outcomes. The fungus spores are transported to trees by tiny beetles that feed on sap from freshly inflicted wounds. These sap beetles serve as carriers, transmitting the disease from infected trees to recently wounded or pruned ones. Once the beetles have fed and the fungus infiltrates the vascular tissue, the tree initiates a defense mechanism by sealing off the disease's spread, resulting in the wilting of branches. Furthermore, the disease can spread from already infected oak trees by traversing through root connections between trees of the same species. This is why oak wilt spreads so efficiently among neighboring trees.

One straightforward measure that can significantly deter the spread of oak wilt is refraining from pruning during the summer months. This precautionary action prevents the creation of fresh wounds that might attract sap beetles carrying the oak wilt fungus. The ideal time for pruning is between November and March. Additionally, it is crucial not to transport firewood since oak wilt can be disseminated through the movement of beetles on wood.

Oak wilt in action.

Submitted by naturalist Cathy Wesley, September 2023