Oregon forest has an ancient unseen killer: ‘Humongous Fungus’

By Jacob Jones
Atop a low ridge in the heart of Oregon’s Blue Mountains, Michael McWilliams pushes through brittle branches and scrambles over toppled logs and decay. Bare trunks tower overhead, but the U.S. Forest Service pathologist focuses low. He’s searching for something that lurks underfoot, hidden despite its immense size.

A sickly fir tree is where he finally stops and kneels. He begins raking at its roots with the curved adz blade of his wood-handled Pulaski. The tool clinks and scrapes, revealing a cream-colored film beneath the bark. It’s an inches-long glimpse of what is likely to be the world’s largest single living organism, a fungus thousands of years old yet still capable of strangling an entire forest.

“Yeah, baby,” McWilliams says, scraping away. “This is a tree killer.”

Dubbed the “Humongous Fungus,” the honey mushroom officially classified as Armillaria ostoyae spreads underground through trees’ root systems. It fruits an edible honey-brown cap just a few weeks each year, typically after the first fall rains. The rest of the year it’s elusive, its presence subterranean.

But what a presence that is: Researchers estimate that the colony here covers 3.7 square miles and may weigh a collective 35,000 tons.

“If you can expand your perception of what a mushroom is,” McWilliams says, “you can see it everywhere.”

Another Forest Service scientist first noticed the widespread die-off of local tree stands in 1988. Greg Whipple linked the problem to armillaria, then worked with others to map samples across hundreds of acres. The teams eventually confirmed that many shared the same DNA.

Whipple, now retired, remembers how his early attempts to limit the damage by clearing out infected areas drew death threats. Timber wars were raging between loggers and environmentalists, upending federal forest management in the Pacific Northwest.

“It was my lesson into politics,” he says.

Decades later, the killer fungus carries on, growing 1 to 3 feet a year. In satellite images of the Malheur National Forest in Eastern Oregon, rusty streaks of dead canopy and the pale, crisscrossed skeletons of downed trees now litter the infestation areas.

Researchers believe part of the colony could date to 6600 B.C. “It’s one of those things that makes you realize mankind is pretty insignificant,” Whipple says. “You realize just how small of a blip we are on the landscape.”

Root disease kills more trees in this region than bugs or beetles, but it moves slowly, picking winners and losers over generations. The fungus remakes the forest as it expands, choking off fir or pine while sparing more tolerant larch. Stunted saplings turn orange as the fungus takes hold. Trees often keel over to reveal roots completely eaten away.

Source: Oregon forest has an ancient unseen killer: ‘Humongous Fungus’ – The Bulletin, 2019-09-01

Invasive disease could nearly wipe out the UK’s ash trees this century

By Chrissy Sexton
Professor Matthew Evans from the University of Hong Kong created a computer model to estimate how ash dieback disease may affect the UK’s 125 million ash trees.

Human-induced changes to the environment are increasing the rate at which pests and diseases are introduced, which is severely threatening to native species. Long-lived species that reproduce slowly, such as forest trees, are particularly susceptible to new pathogens.

It is estimated that in 2015, 100 million hectares of forest were affected by pests and diseases around the globe. However, the subsequent impacts to any given forest ecosystem cannot be detected for years, so experts use computer models to predict future outcomes.

In a recent study, Professor Matthew Evans from the University of Hong Kong created a computer model to estimate how ash dieback (ADB) disease may affect the UK’s 125 million ash trees.

ADB disease, which is caused by a fungus native to East Asia, was introduced to the UK seven years ago. This incurable infection leaves diamond-shaped scars on the bark and causes the leaves to fall off of the trees.

About one in every 100 ash trees is able to resist the fungus and avoid infection. This is likely due to a genetic advantage which allows the trees to shed their leaves earlier to prevent the fungus from establishing itself.

Professor Evans found that at the current level of resistance, 95 percent of the UK’s ash trees could be wiped out by the end of the century. He determined that breeding more ash trees with resistance will prevent millions of deaths.

Source: Invasive disease could nearly wipe out the UK’s ash trees this century – Earth.com, 2019-08-29

Aggressive local effort curbed sudden oak death’s spread

 In 2001, forest pathologists in Oregon discovered what was killing trees in Curry County in southwest Oregon – a devastating disease known as sudden oak death. Almost 20 years later, sudden oak death hasn’t spread beyond the county’s borders.

Although the initial goal was eradication, limiting sudden oak death’s spread proved to be a success, said Everett Hansen, a now-retired Oregon State University professor who helped spearhead the effort to contain the spread of the disease.

“From day one, we invoked legal machinery to mandate the destruction of diseased trees,” Hansen said. “Every time we found a diseased tree we cut it down as fast as we could. We were going full bore. So, we went through all these years without any published data to suggest what we were doing was working.”

Until now.

In a new study published in the journal Forest Pathology, Hansen and colleagues at the Oregon Department of Forestry and U.S. Forest Service highlight the successes of the two-decade effort to manage and reduce the spread of sudden oak death in Oregon.

In 2001, federal, state and local agencies marshaled their resources to manage the outbreak. They quarantined areas where the trees had been infected and cut down and burned sick trees.

“We focused on local treatments instead of landscapes, sometimes by design but sometimes out of necessity,” said Hansen, lead author on the study. “If it was one tree and we cut it down and all the surrounding trees for a mile we might well have eradicated it. But we never had that chance. We didn’t have enough chainsaws.”

However, the researchers found that these treatments did demonstrably reduce the infestation. They concluded that eradication of sudden oak death is difficult — the pathogen that causes the disease may survive in soil for several years – but not impossible.

Source: Aggressive local effort curbed sudden oak death’s spread – KTVZ, 2019-08-19

Rapid ʻŌhiʻa Death

The ʻŌhiʻa tree, with its companion lehua blossom, is found only in Hawaiʻi, and is the most common of our Islands’ native trees. It is the keystone of the Hawaiʻi forest, critical to the ecology of our watersheds and sacred in Hawaiian culture. And now it is under attack, with new species of fungi killing trees on two islands.

Source: Rapid ʻŌhiʻa Death | Insights on PBS Hawaiʻ‘i, 2019-04-04

Sacred Hawaiian tree is under threat as tourists are asked to help save it

By Lucy Sherriff
The native ʻōhiʻa is sacred to Hawaiians as a cultural touchstone and ecological underpinning for the state’s lush forests and abundant wildlife.

HONOLULU — A deadly fungus threatens one of Hawaii’s most beloved and important species, the ʻōhiʻa tree, and those believed responsible for introducing the threat to the tree in the first place are now being asked to help save it — tourists.

The native ʻōhiʻa is sacred to Hawaiians as a cultural touchstone and ecological underpinning for the state’s lush forests and abundant wildlife. The flowering evergreens that can tower to 85 feet comprise 80 percent of the state’s canopy, covering 1 million acres, and its nectar sustains birds and insects found nowhere else on Earth.

Now, public agencies and private citizens are trying to avoid biological and economic catastrophe by proclaiming war against a deadly fungal disease coined “rapid ʻōhiʻa death,” or ROD, that is swiftly destroying the trees. What’s more, invasive species like the miconia tree, native to North and South America and called the “green cancer” of Hawaii’s forests, are choking out the ʻōhiʻa.

The federal government has attempted to stop the fungus and tackle invasive species by imposing a quarantine on Hawaii Island and carrying out extensive tests to learn how the fungus spreads, but it has yet to find a solution. Hawaiian organizations, communities and scientists are now stepping in.

Gunstock Ranch, a horse riding stable and tourist destination on Oahu, is replanting native trees, although not the ʻōhi‘a yet. After conducting a survey on 80 acres of its land in 2016, and finding just two native species, owner Greg Smith established a Hawaiian “legacy forest,” where visitors can plant trees and monitor their growth online.

“Our hope is that as our guests plant and dedicate a tree they will form a new connection to the land and Hawaii and leave knowing that they made a difference,” Smith said.

Source: Sacred Hawaiian tree is under threat as tourists are asked to help save it – NBC News, 2019-06-30

Trees talk to each other and scientists have mapped the network

By Robert Dalheim
Scientists discovered that trees talk to each other through the Wood Wide Web. And now, they’ve mapped it.

Do trees actually talk to each other? And if so, how do they do it?

Just over 20 years ago, ecologist Suzanne Simard discovered that trees do communicate with each other, and it’s through a fungal network scientists have nicknamed the Wood Wide Web.

And now, an international team of scientists has created the first global map of the vast underground network. They did this by creating a computer algorithm to analyze a database from the Global Forest Inititiave, which includes 1.2 million trees in more than 70 countries.

The algorithm takes into account the different fungal species that associate with each tree species. It also takes into account local climate factors – which the scientists say has the biggest role to play.

“It’s the first time that we’ve been able to understand the world beneath our feet, but at a global scale,” Thomas Crowther, an author of the study from ETH Zurich, told the BBC. “Just like an MRI scan of the brain helps us to understand how the brain works, this global map of the fungi beneath the soil helps us to understand how global ecosystems work.

“What we find is that certain types of microorganisms live in certain parts of the world, and by understanding that we can figure out how to restore different types of ecosystems and also how the climate is changing,” he said.

Source: Trees talk to each other and scientists have mapped the network – Woodworking News, 2019-05-16

Researchers map symbiotic relationships between trees and microbes worldwide

by Taylor Kubota, Stanford University
In and around the tangled roots of the forest floor, fungi and bacteria grow with trees, exchanging nutrients for carbon in a vast, global marketplace. A new effort to map the most abundant of these symbiotic relationships—involving more than 1.1 million forest sites and 28,000 tree species—has revealed factors that determine where different types of symbionts will flourish. The work could help scientists understand how symbiotic partnerships structure the world’s forests and how they could be affected by a warming climate.

In and around the tangled roots of the forest floor, fungi and bacteria grow with trees, exchanging nutrients for carbon in a vast, global marketplace. A new effort to map the most abundant of these symbiotic relationships—involving more than 1.1 million forest sites and 28,000 tree species—has revealed factors that determine where different types of symbionts will flourish. The work could help scientists understand how symbiotic partnerships structure the world’s forests and how they could be affected by a warming climate.

Source: Researchers map symbiotic relationships between trees and microbes worldwide – Phys.org, 2019-05-15

Tree disease leaving ‘zombie forest’ in its wake, expert warns

A forester from Bancroft, Ont., says the province could be doing much more to deal with an insidious disease that’s killing beech trees across Ontario.

Svetlana Zeran called in to CBC’s Ontario Today Monday to say beech bark disease is a major concern on the nearly 400,000 hectares of forest her company manages.

“We have been dealing with beech bark disease for about a decade,” Zeran said. “Now that it is here on the [Canadian] Shield, it is moving very rapidly and we are seeing the disease come in and infect the trees and they are dead within two to five years.”

The disease begins when an insect bores holes in the bark, allowing a red fungus to invade the tree and slowly weaken it from the inside out.

Source: Tree disease leaving ‘zombie forest’ in its wake, expert warns – CBC News, 2018-11-14

Termite gut holds a secret to breaking down plant biomass

In the Microbial Sciences Building at the University of Wisconsin-Madison, the incredibly efficient eating habits of a fungus-cultivating termite are surprising even to those well acquainted with the insect’s natural gift for turning wood to dust.

According to a study published today (April 17, 2017) in the journal Proceedings of the National Academy of Sciences, when poplar wood undergoes a short, 3.5-hour transit through the gut of the termite, the emerging feces is almost devoid of lignin, the hard and abundant polymer that gives plant cells walls their sturdiness. As lignin is notorious for being difficult to degrade, and remains a costly obstacle for wood processing industries such as biofuels and paper, the termite is the keeper of a highly sought after secret: a natural system for fully breaking down biomass.

“The speed and efficiency with which the termite is breaking down the lignin polymer is totally unexpected,” says John Ralph, a UW-Madison professor of biochemistry, researcher at the Great Lakes Bioenergy Research Center (GLBRC) and lignin expert. “The tantalizing implication is that this gut system holds keys to breaking down lignin using processes that are completely unknown.”

Source: Termite gut holds a secret to breaking down plant biomass – EurekAlert! Science News, 2017-04-17