Armillaria ostoyae
Encyclopedia
Armillaria solidipes is a species of fungus
in the Physalacriaceae
family. It is the most common variant in the western U.S.
, of the group of species
that all used to share the name Armillaria mellea. Armillaria solidipes is quite common on both hardwood
and conifer wood in forests west of the Cascade
crest. The mycelium
attacks the sapwood and is able to travel great distances under the bark or between trees in the form of black rhizomorphs ("shoestrings").
In most areas of North America, Armillaria solidipes can be separated from other species by its physical features. Its brown colors, fairly prominent scales featured on its cap, and the well-developed ring on its stem sets it apart from any Armillaria. (Herink, 1973)
It is known to be one of the largest living organisms, where scientists have estimated a single specimen found in Malheur National Forest
in Oregon to have been growing for some 2,400 years, covering 3.4 square miles. Armillaria solidipes grows and spreads primarily underground and the bulk of the organism lies in the ground, out of sight. Therefore, the organism is not visible to anyone viewing from the surface. It is only in the autumn when this organism will bloom “honey mushrooms”, visible evidence of the organism lying beneath. Low competition for land and nutrients have allowed this organism to grow so huge and become arguably the largest living organism.
in 1900, long before Henri Romagnesi
had described it in 1970.
s, released into the environment by a mature mushroom. In the specific case of Armillaria solidipes, it has a white spore print
in which all the spores are stored until they are released and dispersed. There are two types of mating types for spores (not male and female but similar in effect). The spores can be dispersed by environment factors such as wind or they can be redeposited by an animal. Once the spores are in a resting state, the single spore must come in contact with a spore of an opposite mating type and of the same species. If the single spore isolates are from different species, the colonies will not fuse together and they will remain separate. When two isolates of the same species but different mating types fuse together, they soon form coalesced colonies which become dark brown and flat. With this particular fungus it will produce mycelial cords also known as rhizomorphs. These rhizomorphs allow the fungus to obtain nutrients from long distances away. These are also the main factors to its pathogenicity. As the fruiting body continues to grow and obtaining nutrients, it forms into a mature mushroom. Armillaria solidipes in particular grows a wide and thin sheet-like plates radiating from the stem which is known as its gills. The gills hold the spores of a mature mushroom. This is stained white when seen as a spore print
. Once spore formation is complete, this signifies a mature mushroom and now is able to spread its spores to start a new generation.
(Pseudotsuga menziesii), true fir
s (Abies spp.) and Western Hemlock
(Tsuga heterophylla). A commonly prescribed treatment is the clear cutting of an infected stand followed by planting with more resistant species such as Western redcedar (Thuja plicata) or deciduous seedlings.
Pathogenicity is seen to differ among trees of varying age and location. Younger conifer trees at age 10 and below are more susceptible to infection leading to mortality, with an increased chance of survival against the fungus where mortality can become rare by age 20. While mortality among older conifers is less likely to occur, this does happen, however, in forests with dryer climates.
The pathogenicity of Armillaria solidipes appears to be more common in interior stands, but its virulence is seen to be greater in coastal conifers. Although conifers along the coastal regions show a lower rate of mortality against the root disease, infections can be much worse. While the differences for how infections occur between these two regions, pathogenicity is attributed to rhizomorph production.
A mushroom of this type in the Malheur National Forest in the Strawberry Mountains of eastern Oregon, U.S. was found to be the largest fungal colony in the world, spanning 8.9 square kilometres (2,200 acres) of area. This organism is estimated to be 2,400 years old. The fungus was written about in the April 2003 issue of the Canadian Journal of Forest Research. While an accurate estimate has not been made, the total mass of the colony may be as much as 605 tons. If this colony is considered a single organism, then it is the largest known organism in the world by area, and rivals the aspen grove "Pando
" as the known organism with the highest living biomass.
In 1992, a relative of the Strawberry Mountains clone was discovered in southwest Washington state. It covers about 6 square kilometres (1,500 acres).
Another "humongous fungus" is a specimen of Armillaria gallica
found at a site near Crystal Falls, Michigan
, which covered 0.15 square kilometres (37 acres).
A. solidipes may be confused with Mottled rot (Pholiota limonella
). It has similar mushrooms, but only if mycelial fans are not present.
Dead and diseased trees usually occur in disease centers, which appear as openings in the canopy. GPS tracking can aid in the monitoring of these areas. However, sometimes distinct centers will be absent and diseased trees are scattered throughout the stand.
or true fir stands with ponderosa pine
, western larch
, western white pine
, lodgepole pine
, western red cedar, alder
, or spruce
. Species susceptibility varies somewhat from location to location. All trees in the disease center as well as uninfected trees within 50 feet should be cut. No tree from a highly susceptible species should be planted within 100 feet of a disease center.
The use of another fungus, Hypholoma fasciculare
has been shown in early experiments to competitively exclude Armillaria solidipes in both field and laboratory conditions, but further experimentation is required to establish the efficacy of this treatment.
Another more expensive alternative to changing species is to remove diseased stumps and trees from the site by pushing them out with a bulldozer. The air will dry and kill the fungus. And any small roots left underground will decay before they can reinfect the new seedlings, so it is not necessary to burn the stumps. After stump removal, any species may be planted. The removal of stumps (stumping) has been used to prevent contact between infected stumps and newer growth resulting in lower infection rates. However, it is unknown if the lower infection rates will persist as roots of young trees extend closer to the original inoculate from the preceding stand.
The most important control measure after planting is to manage for reduced tree stress. This includes regulating species composition, maintaining biological diversity, and reducing the chances for insect pest buildup. Mixed-species forests are more resistant to insect defoliation, and also slow the spread of species-specific pests such as dwarf mistletoe, which are both predisposing agents for Armillaria.
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
in the Physalacriaceae
Physalacriaceae
Physalacriaceae are a family of fungi in the order Agaricales. Species in the genus have a widespread distribution, but most are found in the tropics, particularly in South-East Asia and Australasia. Molecular studies suggested that Physalacria, formerly the sole genus in this family, is related to...
family. It is the most common variant in the western U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, of the group of species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
that all used to share the name Armillaria mellea. Armillaria solidipes is quite common on both hardwood
Hardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
and conifer wood in forests west of the Cascade
Cascade Range
The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...
crest. The mycelium
Mycelium
thumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or within many other...
attacks the sapwood and is able to travel great distances under the bark or between trees in the form of black rhizomorphs ("shoestrings").
In most areas of North America, Armillaria solidipes can be separated from other species by its physical features. Its brown colors, fairly prominent scales featured on its cap, and the well-developed ring on its stem sets it apart from any Armillaria. (Herink, 1973)
It is known to be one of the largest living organisms, where scientists have estimated a single specimen found in Malheur National Forest
Malheur National Forest
The Malheur National Forest is a National Forest in the U.S. state of Oregon. It contains 1.7 million acres in the Blue Mountains of eastern Oregon. The forest include high desert grasslands, sage, juniper, pine, fir, and other tree species. Elevations vary from about 4000 feet to the 9038...
in Oregon to have been growing for some 2,400 years, covering 3.4 square miles. Armillaria solidipes grows and spreads primarily underground and the bulk of the organism lies in the ground, out of sight. Therefore, the organism is not visible to anyone viewing from the surface. It is only in the autumn when this organism will bloom “honey mushrooms”, visible evidence of the organism lying beneath. Low competition for land and nutrients have allowed this organism to grow so huge and become arguably the largest living organism.
Taxonomy
The species was formerly known as Armillaria ostoyae Romagn., until a 2008 publication revealed that the species had been described under the name Armillaria solidipes by Charles Horton PeckCharles Horton Peck
Charles Horton Peck, born March 30, 1833 in Sand Lake, New York, died 1917 in Albany, New York, was an American mycologist of the 19th and early 20th centuries...
in 1900, long before Henri Romagnesi
Henri Romagnesi
Henri Charles Louis Romagnesi was a French mycologist who was notable for a thorough review and monograph of the agaric genus Entoloma , as well as extensive work on the large genus Russula, of which he described several new species.-References:...
had described it in 1970.
Life cycle
This fungus, like most parasitic fungi, reproduces sexually. The fungi begin their life as sporeSpore
In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...
s, released into the environment by a mature mushroom. In the specific case of Armillaria solidipes, it has a white spore print
Spore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...
in which all the spores are stored until they are released and dispersed. There are two types of mating types for spores (not male and female but similar in effect). The spores can be dispersed by environment factors such as wind or they can be redeposited by an animal. Once the spores are in a resting state, the single spore must come in contact with a spore of an opposite mating type and of the same species. If the single spore isolates are from different species, the colonies will not fuse together and they will remain separate. When two isolates of the same species but different mating types fuse together, they soon form coalesced colonies which become dark brown and flat. With this particular fungus it will produce mycelial cords also known as rhizomorphs. These rhizomorphs allow the fungus to obtain nutrients from long distances away. These are also the main factors to its pathogenicity. As the fruiting body continues to grow and obtaining nutrients, it forms into a mature mushroom. Armillaria solidipes in particular grows a wide and thin sheet-like plates radiating from the stem which is known as its gills. The gills hold the spores of a mature mushroom. This is stained white when seen as a spore print
Spore print
thumb|300px|right|Making a spore print of the mushroom Volvariella volvacea shown in composite: mushroom cap laid on white and dark paper; cap removed after 24 hours showing pinkish-tan spore print...
. Once spore formation is complete, this signifies a mature mushroom and now is able to spread its spores to start a new generation.
Pathogenicity
The disease is of particular interest to forest managers, as the species is highly pathogenic to a number of commercial softwoods, notably Douglas-firDouglas-fir
Douglas-fir is one of the English common names for evergreen coniferous trees of the genus Pseudotsuga in the family Pinaceae. Other common names include Douglas tree, and Oregon pine. There are five species, two in western North America, one in Mexico, and two in eastern Asia...
(Pseudotsuga menziesii), true fir
Fir
Firs are a genus of 48–55 species of evergreen conifers in the family Pinaceae. They are found through much of North and Central America, Europe, Asia, and North Africa, occurring in mountains over most of the range...
s (Abies spp.) and Western Hemlock
Western Hemlock
Tsuga heterophylla. the Western Hemlock, is a species of hemlock native to the west coast of North America, with its northwestern limit on the Kenai Peninsula, Alaska, and its southeastern limit in northern Sonoma County, California.-Habitat:...
(Tsuga heterophylla). A commonly prescribed treatment is the clear cutting of an infected stand followed by planting with more resistant species such as Western redcedar (Thuja plicata) or deciduous seedlings.
Pathogenicity is seen to differ among trees of varying age and location. Younger conifer trees at age 10 and below are more susceptible to infection leading to mortality, with an increased chance of survival against the fungus where mortality can become rare by age 20. While mortality among older conifers is less likely to occur, this does happen, however, in forests with dryer climates.
The pathogenicity of Armillaria solidipes appears to be more common in interior stands, but its virulence is seen to be greater in coastal conifers. Although conifers along the coastal regions show a lower rate of mortality against the root disease, infections can be much worse. While the differences for how infections occur between these two regions, pathogenicity is attributed to rhizomorph production.
Geography
Armillaria solidipes is mostly common in the cooler regions of the northern hemisphere. In North America, this fungus can be found on host coniferous trees located in the northwestern forests of the continent in British Columbia and the Pacific Northwest. While Armillaria solidipes is distributed throughout the different biogeoclimatic zones of British Columbia, the root disease causes the greatest amount of problem in the interior parts of the region in the Interior Cedar Hemlock (ICH) biogeoclimatic zone. It is both present in the interior where it is more common as well as along the coastal lines.A mushroom of this type in the Malheur National Forest in the Strawberry Mountains of eastern Oregon, U.S. was found to be the largest fungal colony in the world, spanning 8.9 square kilometres (2,200 acres) of area. This organism is estimated to be 2,400 years old. The fungus was written about in the April 2003 issue of the Canadian Journal of Forest Research. While an accurate estimate has not been made, the total mass of the colony may be as much as 605 tons. If this colony is considered a single organism, then it is the largest known organism in the world by area, and rivals the aspen grove "Pando
Pando (tree)
Pando is a clonal colony of a single male Quaking Aspen located in the U.S. state of Utah, all determined to be part of a single living organism by identical genetic markers and one massive underground root system, although whether it is a single tree is disputed...
" as the known organism with the highest living biomass.
In 1992, a relative of the Strawberry Mountains clone was discovered in southwest Washington state. It covers about 6 square kilometres (1,500 acres).
Another "humongous fungus" is a specimen of Armillaria gallica
Armillaria gallica
Armillaria gallica is a species of honey mushroom in the Physalacriaceae family of the Agaricales order. The species is a common and ecologically important wood-decay fungus that can live as a saprobe, or as an opportunistic parasite in weakened tree hosts to cause root or butt rot...
found at a site near Crystal Falls, Michigan
Crystal Falls, Michigan
-Demographics:As of the census of 2000, there were 1,791 people, 795 households, and 470 families residing in the city. The population density was 530.6 per square mile . There were 913 housing units at an average density of 270.5 per square mile...
, which covered 0.15 square kilometres (37 acres).
Diagnosis
A tree is diagnosed with this parasitic fungus once the following characteristics are identified:- Resin flow from tree base
- Crown thinning or changing color to yellow or red
- Distress crop of cones
- White mycelial fan under bark
- Black rhizomorphs penetrating root surfaces
- Honey-colored mushrooms near base of tree in fall
- Affected trees often in groups or patches on the east side of the Cascades; usually killed singly on the west side.
A. solidipes may be confused with Mottled rot (Pholiota limonella
Pholiota limonella
Pholiota limonella is a mushroom of the genus Pholiota. It is saprobic, growing on coniferous tree stumps and logs....
). It has similar mushrooms, but only if mycelial fans are not present.
Dead and diseased trees usually occur in disease centers, which appear as openings in the canopy. GPS tracking can aid in the monitoring of these areas. However, sometimes distinct centers will be absent and diseased trees are scattered throughout the stand.
Treatment
Armillaria can remain viable in stumps for 50 years. Chemical treatments do not eradicate the fungus entirely, and they are not cost-effective. The most frequent and effective approach to managing root disease problems is to attempt to control them at final harvest by replanting site-suited tree species that are disease tolerant. In eastern Washington that typically means replacing Douglas-firDouglas-fir
Douglas-fir is one of the English common names for evergreen coniferous trees of the genus Pseudotsuga in the family Pinaceae. Other common names include Douglas tree, and Oregon pine. There are five species, two in western North America, one in Mexico, and two in eastern Asia...
or true fir stands with ponderosa pine
Ponderosa Pine
Pinus ponderosa, commonly known as the Ponderosa Pine, Bull Pine, Blackjack Pine, or Western Yellow Pine, is a widespread and variable pine native to western North America. It was first described by David Douglas in 1826, from eastern Washington near present-day Spokane...
, western larch
Western Larch
Western Larch is a species of larch native to the mountains of western North America, in Canada in southeastern British Columbia and southwestern Alberta, and in the United States in eastern Washington, eastern Oregon, northern Idaho and western Montana.It is a large deciduous coniferous tree...
, western white pine
Western White Pine
Western White Pine, Pinus monticola in the family Pinaceae, is a species of pine that occurs in the mountains of the western United States and Canada, specifically the Sierra Nevada, the Cascade Range, the Coast Range, and the northern Rocky Mountains. The tree extends down to sea level in many...
, lodgepole pine
Lodgepole Pine
Lodgepole Pine, Pinus contorta, also known as Shore Pine, is a common tree in western North America. Like all pines, it is evergreen.-Subspecies:...
, western red cedar, alder
Alder
Alder is the common name of a genus of flowering plants belonging to the birch family . The genus comprises about 30 species of monoecious trees and shrubs, few reaching large size, distributed throughout the North Temperate Zone and in the Americas along the Andes southwards to...
, or spruce
Spruce
A spruce is a tree of the genus Picea , a genus of about 35 species of coniferous evergreen trees in the Family Pinaceae, found in the northern temperate and boreal regions of the earth. Spruces are large trees, from tall when mature, and can be distinguished by their whorled branches and conical...
. Species susceptibility varies somewhat from location to location. All trees in the disease center as well as uninfected trees within 50 feet should be cut. No tree from a highly susceptible species should be planted within 100 feet of a disease center.
The use of another fungus, Hypholoma fasciculare
Hypholoma fasciculare
Hypholoma fasciculare, commonly known as the sulphur tuft, sulfur tuft or clustered woodlover, is a common woodland mushroom, often in evidence when hardly any other mushrooms are to be found...
has been shown in early experiments to competitively exclude Armillaria solidipes in both field and laboratory conditions, but further experimentation is required to establish the efficacy of this treatment.
Another more expensive alternative to changing species is to remove diseased stumps and trees from the site by pushing them out with a bulldozer. The air will dry and kill the fungus. And any small roots left underground will decay before they can reinfect the new seedlings, so it is not necessary to burn the stumps. After stump removal, any species may be planted. The removal of stumps (stumping) has been used to prevent contact between infected stumps and newer growth resulting in lower infection rates. However, it is unknown if the lower infection rates will persist as roots of young trees extend closer to the original inoculate from the preceding stand.
The most important control measure after planting is to manage for reduced tree stress. This includes regulating species composition, maintaining biological diversity, and reducing the chances for insect pest buildup. Mixed-species forests are more resistant to insect defoliation, and also slow the spread of species-specific pests such as dwarf mistletoe, which are both predisposing agents for Armillaria.
See also
- Largest organismsLargest organismsThe largest organism found on Earth can be measured using a variety of methods. It could be defined as the largest by volume, mass, height or length. Some organisms group together to form a superorganism, though this cannot truly be classed as one large organism...
- List of Armillaria species