Engineers discover what makes a tree-killing fungus so hard to put down


Date:
December 7, 2021
Source:
University of Utah
Summary:
Armillaria ostoyae is a gnarly parasitic fungus with long black
tentacles that spread out and attack vegetation. Not much was known
about what makes fungus so hard to kill -- until now. A team of
researchers has been studying the defense mechanism of the tree
fungus to better understand what makes it so hearty.



FULL STORY ==========================================================================
It's called Armillaria ostoyae,and it's a gnarly parasitic fungus with
long black tentacles that spread out and attack vegetation with the
ferocity of a movie monster.


==========================================================================
Its cordlike structures called rhizomorphs seek out and attack trees by
sucking out their nutrients. They are known to infect and kill over 600
types of woody plants, posing a substantial threat to forests and the agriculture industry.

From 2000 to 2002, the fungus alone was responsible for causing $1.5
million damage to Georgia's peach trees.

Not much was known about what makes the Armillaria ostoyae so hard to
kill - - until now. A team of researchers led by University of Utah
mechanical engineering assistant professor Steven Naleway has been
studying the defense mechanism of the tree fungus to better understand
what makes it so hearty.

Their findings were published in the newest edition of the Journal of the Mechanical Behavior of Biomedical Materials. Their paper can be read here.

The fungus, which sprouts golden "honey mushrooms" above the surface in
the fall, is known to grow just about anywhere. But U researchers pulled samples of it from what may be the largest specimen known, an enormous
growth in the Malheur National Forest in eastern Oregon that is 3.5
square miles in size and weighs 35,000 tons. The specimen, known as the "Humongous Fungus," is possibly the largest living organism on Earth,
according to scientists.

The black rhizomorphs use enzymes and pressure to penetrate the root
surfaces and under the bark of the trees, said U mechanical engineering doctoral student Debora Lyn Porter, who is the lead author on the
paper. 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.

"Once it gets started, it's very hard to root it out," Porter
says. Farmers, she adds, can keep hacking away at the growing tentacles,
but they just keep growing back.

Much of the previous and current research into the species has been
focused on its biology and ecology, its lifecycle, its interactions with
the environment, and methods of control -- which have not worked well in
the past. But Naleway's team wanted to concentrate on the biomechanical structure of the tendrils, or rhizomorphs.

The rhizomorphs have an outer melanized layer that protects the tendrils
from chemicals and mechanical forces. "This outer layer is pretty tough,"
says Naleway. "It's kind of like a tough plastic. For the natural world,
it is quite strong." They learned that the outer layer of the rhizomorphs
is less porous near the surface yet more porous in the inner layer so
they can still soak in water and nutrients. Researchers also learned
they contain calcium, which can protect itself from the acidic attacks
of insects and chemical compounds.

Naleway hopes that farmers, forestry officials and pest control developers armed with this new knowledge can come up with a more effective method
for containing this resilient fungus.

"If you're going to have some kind of human biocontrol, you need to
combat this calcium and better penetrate this outer surface," he says.

Co-authors of the paper include U mechanical engineering graduate student
Ryan H. Nielsen, Natural History Museum of Utah researcher Alexander
J. Bradshaw, U mechanical engineering assistant professor Pania Newell
and Natural History Museum of Utah Mycology Curator Bryn T.M. Dentinger.

========================================================================== Story Source: Materials provided by University_of_Utah. Original written
by Vince Horiuchi.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Debora Lyn Porter, Alexander J. Bradshaw, Ryan H. Nielsen,
Pania Newell,
Bryn T.M. Dentinger, Steven E. Naleway. The melanized layer
of Armillaria ostoyae rhizomorphs: Its protective role and
functions. Journal of the Mechanical Behavior of Biomedical
Materials, 2022; 125: 104934 DOI: 10.1016/j.jmbbm.2021.104934 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211207092446.htm

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