The big, beautiful live oaks that line your street and shade your home aren’t indefensible. There’s a silent killer that at this very moment could be creeping down your block, one yard at a time.
Considered an epidemic throughout Central Texas, oak wilt is one of the most destructive tree diseases in the United States. The infectious disease spreads in the spring, killing trees that share its name, with red oaks and live oaks most susceptible.
“Live oaks are just phenomenal trees that we’re blessed with here in the Hill Country; oak wilt is just its Achilles heel,” said Texas Forest Service Forester Eric Beckers, who is based in Austin.
“It’s an incredibly valuable tree. It’s a great survivor against everything that gets thrown at it from wind damage to drought to insects and other diseases, but it’s a poor survivor with oak wilt.”
Oak mortality has been noted since the 1930s, but oak wilt wasn’t confirmed as the cause until the late 1970s. It has since been found in 73 counties — principally in Central Texas though it’s crept as far as Amarillo and Houston.
An infected oak can spread the disease to surrounding oaks via their interconnected root systems. When that happens, the only way to stop further spread is by digging trenches to break the root connections.
Oak wilt also can be spread from February through June via sap-feeding beetles, which eat spore mats produced by infected red oaks. The disease is spread when those insects fly off to feed on a healthy red oak or live oak with a fresh wound.
Diseased live oaks do not produce the same spores but they can become infected by them.
“We’re talking about trees that have been in the landscape for a century or more. We don’t replace those trees overnight,” Beckers said, adding that the death of such majestic trees can lead to drops in property values. “Preventing oak wilt is the key.”
A wound is created any time bark is removed and wood is exposed, Beckers said. That can happen with the simplest of tasks — planting flowers, pruning or even pushing a lawn mower over a bare tree root.
That bare wood produces sap, which attracts the sap-feeding beetles, Beckers said, stressing the importance of avoiding wounds in the spring, painting tree wounds year round and destroying diseased red oaks.
“You don’t want to have to manage oak wilt. That means you have it. You want to prevent it from happening,” Beckers said, explaining that there was no cure for the disease. “Oak wilt is a bear. It’s very difficult to stop.”
For more information about oak wilt and maps detailing which counties are affected, visit www.texasoakwilt.org.
