Oak tree on campus survives infection


Several trees on campus were treated for a fungal infection that commonly affects oak trees in the Texas Hill Country—and is almost always deadly. The condition is known as oak wilt, and two Texas live oak trees in between Doyle Hall and the Fine Arts Building tested positive for the disease.

While one tree died and was cut down, the other is still alive. Campus arborist Nicholas Arthur is optimistic about the tree’s recovery. 

“It’s unusual,” Arthur said of the fact that the tree appears to be recovering from oak wilt. “Everyone thought this tree was going to die.”

Trees suffering from oak wilt almost always die and die quickly because the fungus grows inside the tree in such a way that severely limits the ability of the tree to retain and transport water within itself. Once a tree becomes infected with the fungus that causes oak wilt, it can deteriorate and die within a matter of weeks.

“It’s a fungus, Ceratocystis fagacearum. Like any fungus, it grows in a mat of strands, hyphae, and it spreads by increasing it’s length, kind of like a plant’s roots, except much smaller in diameter,” said Bill Quinn, a biology professor. “It infects the plant at a wound site, in stems or roots, and grows into the vascular tissue, feeding itself from the water, minerals and sugars out of the phloem and xylem. This plugs up the vascular system of the plant, eventually killing the plant.”

Essentially, the fungus steals the tree’s water, starving it to death.

Furthermore, the condition is hard to diagnose, can take a few weeks to display symptoms and is untreatable. After the live oaks next to Doyle Hall started dropping leaves with a brown pattern along the veins of the leaf, a symptom known as veinal necrosis, Facilities tested both trees for the disease by taking a core sample of the wood. Both tests came back positive, but rather than treat those trees, Facilities decided to treat the healthy trees in the area because there is no cure for oak wilt.

“There is no sure-fire cure,” Arthur said in reference to oak wilt. “We don’t treat it, we manage it.”

Facilities treated trees within 100 feet of the two infected trees in order to prevent the disease from spreading. This is necessary because oak tree roots often graft to roots of nearby oak trees and form an interconnected root system, and this enables the fungus to spread from tree to tree.

As part of the treatment plan, the nearby trees were injected with Propiconazole, a fungicide in two phases of treatments.

As for the infected trees, Facilities gave them extra water and monitored their health. Texas live oak makes up 70 to 80 percent of the trees on campus, and Facilities maintains the trees for a number of different reasons. 

“The value of trees can be measured in a lot of different ways,” Arthur said. This includes energy cost savings because trees shade nearby buildings, as well as property values.

John Cotter, a global studies and environmental science and policy professor, has an office in Doyle Hall, and his window overlooks the spot where oak wilt was detected on campus. 

“Trees provide shade. That shade is really important because it saves you electricity,” Cotter said. “Plus it’s an incredible view.” 

Facilities also treated a tree in the Doyle Hall courtyard for oak wilt in spring 2011, but Arthur believes that tree was damaged during construction when the building was remodeled in 2009.  

“I think we can say now that it didn’t have oak wilt,” Arthur said of the tree in the Doyle courtyard. 

For now, Facilities is monitoring the surviving tree and the other trees in the area. 

“Live oak is the defining tree on campus,” Arthur said.