Humungus Fungus
DB: This is Earth and Sky. The largest animal on Earth is the blue whale. The tallest tree is California’s coastal redwood . . .
JB: But bigger than either of those is the world’s biggest fungus. It was discovered last June in the Blue Mountains of Eastern Oregon and the Malheur National Forest . It’s called Armillaria, and it’s a parasite that infects evergreen trees. Armillaria fungus lives mostly underground. Beneath the soil, it sends out filaments that look like long, black shoestrings. The filaments invade tree roots and suck up water and carbohydrates. That interferes with tree growth, and eventually the tree dies.
DB: Each of its filaments is fairly small, but scientists have located a single Armillaria that’s spread through 2200 acres of forest soil. It measures about five-and-a-half kilometers – or about three and a half miles – across. This organism is thought by some scientists to have a lifespan of a couple of thousand years.
JB: Forest managers want to control this parasite. But even though the Armillaria fungus kills trees, it also benefits the forest ecosystem. Dead, decaying trees provide nesting cavities for woodpeckers and other forest birds. And when trees fall to the forest floor, they return nutrients to the soil. That’s our show for today. We have links to information about Armillaria on our web site. Come to today’s show at earthsky.com. We’re Block and Byrd for Earth and Sky.
Our thanks to the following individual who assisted in the preparation of this script:
Dr. Tina Dreisbach
Botanist
U.S. Forest Service
Forestry Sciences Lab
Pacific Northwest Research Station
Corvallis OR
Dr. Catherine Parks
Plant Pathologist
USDA Forest Serivce
Pacific Northwest Resaerch Station
La Grande Forestry and Range Sciences Lab
La Grande, OR
The following articles and websites were used in preparing this script:
Hudler, George W. Magical Mushrooms, Mischevious Molds. Princeton: Princeton University Press, 1998.
An article from the Richmond Times Dispatch, August 6, 2000 based on a press release by Jeff Barnard of the Associated Press -has pictures of the Armillaria fruiting body.
Discovery.com news item for August 5, 2000
The original Forest Service press release
Author’s notes:
Catherine Parks located the big Armillaria accidentally, when she was reviewing some aerial photos. She noticed that certain conifer stands had many dead trees, and wondered what had killed them. So researchers went out, took root samples from the dead trees, and cultured them in the lab to see what kind of fungus they were. Once the knew all the samples were Armillaria, they decided to do another kind of test to see if they that they were all genetically identical.
In fact there were five different individual specimens of Armillaria in the area with dead trees, but because they knew the exact location of each sample, they could map the extent of the one really large individual. The fungus is calculated to be about 2400 years old, although it could be two to three times older.
Here’s how scientists estimated the fungus’s age: They went into the records and looked at aerial photos of the forest a couple of decades ago. By comparing those photos to RECENT photos, they could tell how far the fungus had spread over a know period of time and establish a growth rate. Using the growth rate and the total size of the individual they could calculate back and see how old it was.
Earlier findings of large fungi include about 37-acres of Armillaria bulbosa discovered in 1992 in a hardwood forest in Michigan and a clone of Armillaria ostoyae infecting ponderosa pine in eastern Washington that is estimated to be 1,500-acres in size. Clonal studies on other species of Armillaria in eastern North America, Europe, and Australia were found to be no more than a few tens of acres in size at the most.
Additional Teacher Resources
USDA Forest Service, Forest Insect & Disease Leaflet: Armillaria Root Disease
Armillaria root disease is found throughout temperate and tropical regions of the world. In the continental United States, the disease has been reported in nearly every State. Hosts include hundreds of species of trees, shrubs, vines and forbs growing in forests, along roadsides, and in cultivated areas. This site explains the role this gigantic living organism plays in the forest ecosystem.
U.S. National Park Service, North Cascade National Park: Snags, Are a Woodpecker’s Best Friend?And Other Woody Debris
Is there life in a dead tree? Whooooo asked that question? Dead trees (snags), partially dead, and dying trees provide some of the richest habitats in the forest. Snags in Northwest forests provide homes and feeding sites for nearly 100 species of birds and mammals. Host of insects, larvae, spiders, fungi, mosses, lichens, and microscopic organisms make the snag a vibrant column of life, an important component of the whole forest.
