Marathon County University of Wisconsin-Extension, Cooperative Extension

Protecting From Oak Wilt

26. Mar, 2012

Oak Wilt Season Arrives Earlier Due to Warm Spring

Oak wilt is a deadly tree disease caused by a fungus. It can kill even healthy oak trees quickly and, left unchecked, can spread quickly. It can spread underground through root contact from neighboring trees, overland via sap-feeding beetles, and from infected firewood that has been transported!

Homeowners should take special care to avoid wounding oaks from now through July. In fact, any action that might provide an opening into the tree, such as carving initials into the tree or attaching a birdfeeder or clothes line, could provide an opportunity for the oak wilt fungus to invade and establish itself in the tree. If an oak tree needs to be pruned from now through July, a homeowner should consider using wound dressing or paint on the cut surface as soon as the wound is created.

Oak Wilt Spreads Above & Below Ground

Underground, most oak wilt moves from diseased trees to healthy trees through roots that have become interconnected (root grafts). Overland, oak wilt can also spread above ground by sap-feeding beetles. In the spring, fungal mats (small masses of Ceratocystis fagacearum) develop under the bark of some trees that have died from oak wilt the year before.