It's big. It's nasty. And its tendrils suck the life out of trees

Armillaria ostoyae is a parasitic fungus with long
black tentacles that spread out and attack vegetation. Once inside
the tree, it leaves a mycelial fan, white branching filaments that
cover the insides of the bark like paint, depriving the tree of
water and nutrients.

Armillaria ostoyae is a parasitic fungus with long black tentacles that spread out and attack vegetation. Once inside the tree, it leaves a mycelial fan, white branching filaments that cover the insides of the bark like paint, depriving the tree of water and nutrients. (Debora Lyn Porter)



Estimated read time: 3-4 minutes

SALT LAKE CITY — It is big, nasty with long black tendrils that suck the life out of trees.

University of Utah scientists have dubbed it the "humongous fungus" and studied a 3 1/2-square mile specimen in eastern Oregon that weighs 35,000 tons and is possibly the largest living organism on earth.

In just two years, it was responsible for causing $1.5 million in damage to Georgia's peach trees.

Its scientific name is Armillaria ostoyae and it can infect and kill 600 types of woody plants — and the fungus itself is extremely hard to kill.

"Once it gets started, it is very hard to root it out," said Debora Lyn Porter, lead author of the research paper and a doctoral student in the university's mechanical engineering program.

She noted that farmers are hacking down the growing tendrils, but they keep coming back.

The Utah study, published in the newest edition of the Journal of Mechanical Behavior of Biomedical Materials, looked at what makes the fungus so hardy, and there is hope the research results will provide farmers and forestry officials some relief.

Specifically, the study probed the biomechanical structure of the tendrils, or what are known as rhizomorphs.

Armillaria ostoyae is a parasitic fungus with long
black tentacles that spread out and attack vegetation. Its cordlike
structures, called rhizomorphs, seek out and attack trees by
sucking out their nutrients. They are fungus is known to infect and
kill over 600 types of woody plants, posing a substantial threat to
forests and the agriculture industry.
Armillaria ostoyae is a parasitic fungus with long black tentacles that spread out and attack vegetation. Its cordlike structures, called rhizomorphs, seek out and attack trees by sucking out their nutrients. They are fungus is known to infect and kill over 600 types of woody plants, posing a substantial threat to forests and the agriculture industry. (Photo: Debora Lyn Porter)

The rhizomorphs have an outer melanized layer that protects the tendrils from chemicals and mechanical forces. "This outer layer is pretty tough," says Steven Naleway, the university's mechanical engineering assistant professor who led the research.

"It's kind of like a tough plastic," he said. "For the natural world, it is quite strong."

In the 1980s, researchers studied a form of the fungus in Michigan that was nearly the size of the Mall of America in Bloomington, Minnesota.

Once these tendrils penetrate the tree, they cover the bark much like paint, depriving the tree of water and nutrients.

Porter said what is particularly exciting is that this research dove into the mechanics of the fungus and how to potentially combat the nasty invader.

"If we could understand how it is better controlled, it would be a huge, huge help for agricultural industries where they are such a huge blight."

While the fungus could be considered the "circle of life" in forests, it is not viewed that way for agricultural producers.

Nathan Porter digs into the base of a tree damaged by
the Armillaria ostoyae fungus.
Nathan Porter digs into the base of a tree damaged by the Armillaria ostoyae fungus. (Photo: Debora Lyn Porter)

"If you have a vineyard or an orchard, and your plants are not that hardy, they can be completely wiped out," Porter said.

She said it is the hard shell of the tendrils that makes it so difficult to kill, taking on properties envisioned in science fiction movies that cannot be pierced.

But this latest research shows farmers and others may have a much needed weapon in the battle to control the fungus if the proper "biocontrols" are deployed.

Breaking down its chemical properties, such as calcium, is key.

"This has really been exciting to work on," Porter said. "Gosh, this is a really big problem. How do we work on this?"

She said there is a remote cousin of this fungus in Utah, but its impacts are still being explored.

"There is a lot of future work that needs to be looked at," Porter said. "What is the strength of the shield? What is the shield made out of? What chemical protection does it offer?"

A tree shows the Armillaria ostoyae
fungus.
A tree shows the Armillaria ostoyae fungus. (Photo: Debora Lyn Porter)

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