• Paula Johnston, certified arborist with Oak Wilt Specialists of Texas, measures the diameter of a live oak tree to determine how much treatment solution will be needed. — Standard-Radio Post/Scott Allen
  • Veinal necrosis, a symptom of oak wilt, is seen on a leaf that fell off of a local tree.
  • An old keg is modified to do fungicidal injections on an oak wilt-infected tree on Lindy Segall’s land.
  • A motte of live oak trees clustered just inside Gillespie County shows the varying stages of oak wilt. The trees that show no color are in the later stages of the disease. — Standard-Radio Post/Scott Allen

Oak wilt spreads again in Gillespie County

Beetle-induced disease can affect live oaks over 100 feet away

Oak wilt, the disease that has wiped out more than a million trees in 76 Texas counties, is on the rise again in Gillespie County and surrounding areas.

Caused by the Ceratocystis fagacearum fungus, this infectious vascular disease can remain in trees for up to seven years, according to the Texas A&M Forest Service.

Lindy Segall, Fredericksburg resident who owns land out near Hye, recently discovered a few of his trees on his fence line have contracted oak wilt from a neighboring infection center.

Segall is in the process of selling the land, but wants to rid any disease beforehand.

“I think what might’ve happened is someone was cutting cedars a few years ago and they nicked some of the oaks when they were hauling out the cedars,” Segall said. “And if you don’t paint over that, you know what happens.”

If the disease doesn’t get better, Segall said he’ll have to cut down trees every 18 months, since the disease moves 75-100 feet a year.

He is currently working with the Oak Wilt Specialists of Texas to flush his trees of any oak wilt. Water he’s using is coming from the Real Ale Brewery in Blanco.

“The water we’re using consists of a beer by-product from Real Ale Brewery,” Segall said. “The water is full of post-fermented bacteria that was left over from the beer-making process. I get to use it because the gentleman who keeps his cattle on my property has connections with them.”

Trained professionals should be contacted to help with oak wilt, Segall added.

“Be careful what you use on trees,” Segall said. “Don’t use Round-up and other pesticides. Also, don’t ever use weed and feed. It may kill your weeds, but it can also kill your trees. I’ve lost a few trees from it.”

 

Local impact

Twenty-two states in the U.S. have been affected by oak wilt, most of them in the central and northeast areas.

“The first case was in the 1940s up in Wisconsin,” said Robert Edmonson, Texas A&M Forest Service project biologist for the Johnson City Region. “They found it in other northern states. It was in 1966 that we had a positive of a sample in Dallas County. There was suspicion that there was oak wilt out in the Hill Country in the mid-1950s, but we were also undergoing a tremendous drought during that time.”

In a 2007 study by texasoakwilt.org, Gillespie was shown as one of the most affected areas in Texas.

“As far as intensity goes, Gillespie County is one of the counties where oak wilt is absolutely more prevalent,” Edmonson said. “Gillespie, Kerr, Kendall and Bandera counties are all pretty bad.”

Oak wilt doesn’t exist much in the eastern states, Edmonson said, which includes East Texas.

 

How it starts

The Nitidulid beetle (a bug the size of a pinhead) is a sap-feeding insect that’s known to transmit the oak wilt fungus. These bugs can fly for a distance of one mile, according to TexasOakWilt.org.

And every oak tree species is susceptible.

An infection starts when sap-feeding beetles pick up spores from infected red oaks and carry them to fresh wounds on other oaks. Once a tree becomes infected, the disease can spread to adjacent oaks through root connections. Trees die because the wilt invades and disables the water-conducting system. 

Although the disease was discovered less than 75 years ago, local scientists believe it has been around for a while.

“It’s still here and it’s not going anywhere,” Edmonson said. “Oak wilt has been present in Central Texas for forever, probably. Is it getting worse? Yeah. There are more disease centers discovered every day and existing centers are expanding.”

New oak wilt disease centers are started when a contaminated beetle finds a fresh wound on a healthy tree. And due to the amount of rain since early 2015, there has been an unusually high number of beetles.

“A perfect storm of weather events, if you will, had to occur for the extremely high number of disease centers and a high activity of beetles to be present,” said Paula Johnston, certified arborist with Oak Wilt Specialists of Texas. “We had a lot of rain, a mild winter, followed by more rain.”

 Typically, Johnston says the areas with greater human activity are more susceptible to wilt.

 A new infection center gets started because sap-feeding beetles are hungry.

“They are attracted to the fruity odor, they feed from the fungal mat, and the spores are sticky and stick to the beetle. The beetle also eats tree sap, especially oak sap,” Edmonson said. “If they happened to have visited a fungal mat first and get spores on their body and then visit a free wound on an oak tree, that’s how the fungus gets introduced.”

 

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