''Armillaria'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
fungi
A fungus ( : fungi or funguses) is any member of the 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, separately from ...
that includes the ''
A. mellea'' species known as honey fungi that live on trees and woody shrubs. It includes about 10
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
formerly categorized summarily as ''A. mellea''. ''Armillarias'' are long-lived and form the
largest living fungi in the world. The largest known organism (of the species ''
Armillaria ostoyae
''Armillaria ostoyae'' (synonym ''Armillaria solidipes'') is a species of fungus (mushroom), pathogenic to trees, in the family Physalacriaceae. In the western United States, it is the most common variant of the group of species under the nam ...
'') covers more than in
Oregon
Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...
's
Malheur National Forest
The Malheur National Forest is a United States National Forest, National Forest in the U.S. state of Oregon. It contains more than in the Blue Mountains (Pacific Northwest), Blue Mountains of eastern Oregon. The forest consists of Great Basin ...
and is estimated to be 2,500 years old.
Some species of ''Armillaria'' display
bioluminescence
Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some b ...
, resulting in
foxfire
Foxfire, also called fairy fire and chimpanzee fire, is the bioluminescence created by some species of fungi present in decaying wood. The bluish-green glow is attributed to a luciferase, an oxidative enzyme, which emits light as it reacts with ...
.
''Armillaria'' can be a destructive
forest pathogen. It causes
"white rot" root disease (see
Plant pathology
Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungus, fung ...
section) of forests, which distinguishes it from ''
Tricholoma
''Tricholoma'' is a genus of fungus that contains many fairly fleshy white-spored gilled mushrooms which are found worldwide generally growing in woodlands. These are ectomycorrhizal fungi, existing in a symbiotic relationship with various spec ...
'', a
mycorrhiza
A mycorrhiza (from Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role of the fungus in the plant ...
l (non-parasitic) genus. Because ''Armillaria'' is a
facultative saprophyte
Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ( ...
, it also feeds on dead plant material, allowing it to kill its host, unlike
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
s that must moderate their growth to avoid host death.
Description
The basidiocarp (reproductive structure) of the fungus is a
mushroom
A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans.
The standard for the name "mushroom" is t ...
that grows on wood, typically in small dense clumps or tufts. Their
caps
Caps are flat headgear.
Caps or CAPS may also refer to:
Science and technology Computing
* CESG Assisted Products Service, provided by the U.K. Government Communications Headquarters
* Composite Application Platform Suite, by Java Caps, a Java ...
(mushroom tops) are typically yellow-brown, somewhat sticky to touch when moist, and, depending on age, may range in shape from
conical to
convex
Convex or convexity may refer to:
Science and technology
* Convex lens, in optics
Mathematics
* Convex set, containing the whole line segment that joins points
** Convex polygon, a polygon which encloses a convex set of points
** Convex polytope ...
to depressed in the center. The
stipe (stalk) may or may not have a
ring
Ring may refer to:
* Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry
* To make a sound with a bell, and the sound made by a bell
:(hence) to initiate a telephone connection
Arts, entertainment and media Film and ...
. All ''Armillaria'' species have a white
spore print
300px, Making a spore print of the mushroom ''Volvariella volvacea'' shown in composite: (photo lower half) mushroom cap laid on white and dark paper; (photo upper half) cap removed after 24 hours showing pinkish-tan spore print. A 3.5-centimeter ...
and none have a
volva (cup at base) (compare ''
Amanita
The genus ''Amanita'' contains about 600 species of agarics, including some of the most toxic known mushrooms found worldwide, as well as some well-regarded edible species. This genus is responsible for approximately 95% of the fatalities result ...
'').
Similar species include ''
Pholiota
''Pholiota'' is a genus of small to medium-sized, fleshy mushrooms in the family Strophariaceae. They are saprobes that typically live on wood. The genus has a widespread distribution, especially in temperate regions, and contains about 150 spe ...
'' spp. which also grow in cespitose (mat-like) clusters on wood and fruit in the fall. ''Pholiota'' spp. are separated from Armillaria by its yellowish to greenish-yellow tone and a dark brown to grey-brown spore print.
Mushroom hunter
Mushroom hunting, mushrooming, mushroom picking, mushroom foraging, and similar terms describe the activity of gathering mushrooms in the wild, typically for culinary use. This practice is popular throughout most of Europe, Australia, Japan, K ...
s need to be wary of ''
Galerina
''Galerina'' is a genus of small brown-spore saprobic fungi (colloquially often ''mushrooms''), with over 300 species found throughout the world from the far north to remote Macquarie Island in the Southern Ocean. The genus is most noted for some ...
'' spp. which can grow side by side with ''Armillaria'' spp. on wood. ''
Galerina
''Galerina'' is a genus of small brown-spore saprobic fungi (colloquially often ''mushrooms''), with over 300 species found throughout the world from the far north to remote Macquarie Island in the Southern Ocean. The genus is most noted for some ...
'' have a dark brown spore print and are deadly poisonous (
alpha-amanitin) – see:
mushroom poisoning
Mushroom poisoning is poisoning resulting from the ingestion of mushrooms that contain toxic substances. Its symptoms can vary from slight gastrointestinal discomfort to death in about 10 days. Mushroom toxins are secondary metabolites produced by ...
.
Fungus pathology
Honey fungus is a "white rot" fungus, which is a
pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
ic organism that affects trees,
shrub
A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...
s, woody climbers and rarely, woody
herbaceous perennial plants. Honey fungus can grow on living, decaying, and dead plant material.
Honey fungus spreads from living trees, dead and live roots and stumps by means of reddish-brown to black
rhizomorph
Mycelial cords are linear aggregations of parallel-oriented hyphae. The mature cords are composed of wide, empty vessel hyphae surrounded by narrower sheathing hyphae. Cords may look similar to plant roots, and also frequently have similar functio ...
s (root-like structures) at the rate of approximately a year, but infection by root contact is possible. Infection by spores is rare. Rhizomorphs grow close to the
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
surface (in the top ) and invade new roots, or the root collar (where the roots meet the stem) of plants. An infected tree will die once the fungus has
girdled
Girdled identifies various animal species:
{{TOC right
Girdled lizards
Lizards from the genus '' Cordylus''.
* Angolan girdled lizard (''Cordylus angolensis''), also known as the Angolan spiny-tailed lizard
* Black girdled lizard (''Cordylus niger ...
it, or when significant root damage has occurred. This can happen rapidly, or may take several years. Infected plants will deteriorate, although may exhibit prolific flower or fruit production shortly before death.
Initial symptoms of honey fungus infection include
dieback
Dieback may refer to a number of plant problems and diseases including:
* Forest dieback caused by acid rain, heavy metal pollution, or imported pathogens
* The death of regions of a plant or similar organism caused by physical damage, such as from ...
or shortage of leaves in spring.
Rhizomorphs
Mycelial cords are linear aggregations of parallel-oriented hyphae. The mature cords are composed of wide, empty vessel hyphae surrounded by narrower sheathing hyphae. Cords may look similar to plant roots, and also frequently have similar function ...
(also called mycelial cords) appear under the
bark and around the tree, and mushrooms grow in clusters from the infected plant in autumn and die back after the first frost. However these
symptoms and signs
Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...
do not necessarily mean that the pathogenic strains of honey fungus are the cause, so other identification methods are advised before diagnosis. Thin sheets of cream colored
mycelium
Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrate (biology), substrates. A typical single ...
, beneath the bark at the base of the trunk or stem indicated that honey fungus is likely the pathogen. It will give off a strong mushroom scent and the mushrooms sometimes extend upward. On
conifers
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extan ...
honey fungus often exudes a gum or
resin
In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...
from cracks in the bark.
Taxonomy
The name ''Armillaria'' was defined in 1821 by
Fries
French fries (North American English), chips (British English), finger chips (Indian English), french-fried potatoes, or simply fries, are '' batonnet'' or ''allumette''-cut deep-fried potatoes of disputed origin from Belgium and France. The ...
, but at that time most gilled mushrooms were considered to belong to genus ''Agaricus'' and ''Armillaria'' was only a subgenus (a "tribe"). It was only in 1857 that Friedrich Staude created it as a genus in its own right.
[ ]
The linkage of morphological, genetic, and molecular characters of ''Armillaria'' over the past few decades has led to the recognition of intersterile groups designated as "biological species". Data from such studies, especially those using molecular diagnostic tools, have removed much uncertainty for mycologists and forest pathologists. New questions remain unanswered regarding the phylogeny of North American ''Armillaria'' species and their relationships to their European counterparts, particularly within the "''Armillaria mellea'' complex". Some data suggest that North American and European ''A. gallica'' isolates are not monophyletic. Although North American and European isolates of ''A. gallica'' may be interfertile, some North American isolates of ''A. gallica'' are more closely related to the North American taxon ''A. calvescens'' than to European isolates of ''A. gallica''. The increase in genetic divergence has not necessarily barred inter-sterility between isolated populations of ''A. gallica''. Although the relationships among some groups in the genus seem clearer, the investigation of geographically diverse isolates has revealed that the relationship between some North American species is still unclear (Hughes et al. 2003).
[Hughes, M. B.; Weir, A.; Rogers, S. O. (2003). "Phylogenetic reconstruction of North American ''Armillaria'' species and related European taxa based on nuclear ribosomal DNA internal transcribed spacers". p. 32 in Laflamme, G.; Bérubé, J. A.; Bussières, G. (eds.), ''Root and Butt Rots of Forest Trees. Proceedings of the 10th International Conference of Root and Butt Rots'', IUFRO Working Party 7.02.01, Quebec, September 2001. Natural Resources Canada, Canadian Forest Service, Information Report LAU-X-126. 450 p.]
Intersterile species of ''Armillaria'' occurring in North America (North American Biological Species = NABS) were listed by Mallett (1992):
[Mallett, K. I. (1992). "''Armillaria'' root rot in the Canadian Prairie Provinces". Forestry Canada, Northwest Region, Northern Forestry Centre, Edmonton, Alberta, Information Report NOR-X-329. 22 p.]
* I ''Armillaria ostoyae'' (Romagn.) Herink
* II ''Armillaria gemina'' Bérubé & Dessureault
* III ''Armillaria calvescens'' Bérubé & Dessureault
* V ''Armillaria sinapina'' Bérubé & Dessureault
* VI ''Armillaria mellea'' (Vahl.:Fries) Kummer
* VII ''Armillaria gallica'' (Marxmüller & Romagn.)
* IX ''Armillaria nabsnona'' T. J. Volk & Burds. (1996)
* X ''Armillaria altimontana'' Brazee, B. Ortiz, Banik & D. L. Lindner (2012)
* XI taxonomically undescribed
NABS I, V, VII, IX, X, and XI have been found in
British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...
; I, III, V have been found in the
Prairie Provinces
The Canadian Prairies (usually referred to as simply the Prairies in Canada) is a region in Western Canada. It includes the Canadian portion of the Great Plains and the Prairie Provinces, namely Alberta, Saskatchewan, and Manitoba. These provin ...
, with I and V occurring in both the
boreal
Boreal may refer to:
Climatology and geography
*Boreal (age), the first climatic phase of the Blytt-Sernander sequence of northern Europe, during the Holocene epoch
*Boreal climate, a climate characterized by long winters and short, cool to mild ...
and
subalpine regions; I, III, V, and VII have been found in
Ontario
Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...
; and I, II, III, V, and VI have been found in
Quebec
Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirtee ...
. ''Armillaria ostoyae'' is the species most commonly found in all Canadian provinces surveyed (Mallett 1990).
[Mallett, K. I. (1990). "''Armillaria'' ]root rot
Root rot is a condition in which anoxic conditions in the soil or potting media around the roots of a plant cause them to rot. This occurs due to excessive standing water around the roots. It is found in both indoor and outdoor plants, although ...
pathogens of the Canadian prairie provinces". ''Canadian Journal of Forest Research'' 20:1859–1863. ''Armillaria'' root rot occurs in the
Northwest Territories
The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...
, and was identified on
white spruce White spruce is a common name for several species of spruce (''Picea'') and may refer to:
* ''Picea glauca'', native to most of Canada and Alaska with limited populations in the northeastern United States
* ''Picea engelmannii'', native to the Ro ...
at
Pine Point on
Great Slave Lake
Great Slave Lake (french: Grand lac des Esclaves), known traditionally as Tıdeè in Tłı̨chǫ Yatıì (Dogrib), Tinde’e in Wıìlıìdeh Yatii / Tetsǫ́t’ıné Yatıé (Dogrib / Chipewyan), Tu Nedhé in Dëne Sųłıné Yatıé (Chi ...
prior to NABS findings.
In 1791
Albrecht Wilhelm Roth
Albrecht Wilhelm Roth (6 January 1757 – 16 October 1834) was a physician and botanist born in Dötlingen, Germany.
He studied medicine at the Universities of Halle and Erlangen, where he received his doctorate in 1778.
After graduation, he pra ...
described the species ''Rhizomorpha fragilis'' for a collection which consisted entirely of rhizomorphs. The genus ''
Rhizomorpha
''Rhizomorpha'' is a genus of fungi that was created for species known only by their mycelial cords ("rhizomorphs") and so impossible to classify within the normal taxonomic system, which is based on reproductive structures.
Origin and naming ...
'' thus became established and later these mycelial cords were shown to belong to ''Armillaria mellea''. According to the
code of nomenclature that means that the two genus names are synonyms and since genus ''Armillaria'' was not defined until 1857, the name ''Rhizomorpha'' takes precedence and should replace the name ''Armillaria''. To avoid this a 2021 paper by Stalpers et al. proposes that the name ''Armillaria'' should be protected. However the proposal awaits decisions by the
Nomenclature Committee for Fungi
International Botanical Congress (IBC) is an international meeting of botanists in all scientific fields, authorized by the International Association of Botanical and Mycological Societies (IABMS) and held every six years, with the location rotati ...
and eventually by an
International Botanical Congress
International Botanical Congress (IBC) is an international meeting of botanists in all scientific fields, authorized by the International Association of Botanical and Mycological Societies (IABMS) and held every six years, with the location rotat ...
.
[ ]
Edibility
Honey fungus are regarded in Ukraine, Russia, Poland, Germany and other European countries as one of the best wild mushrooms. They are commonly ranked above
morel
''Morchella'', the true morels, is a genus of edible sac fungi closely related to anatomically simpler cup fungi in the order Pezizales (division Ascomycota). These distinctive fungi have a honeycomb appearance due to the network of ridges with ...
s and
chanterelle
Chanterelle is the common name of several species of fungi in the genera '' Cantharellus'', '' Craterellus'', '' Gomphus'', and ''Polyozellus''. They are among the most popular of wild edible mushrooms. They are orange, yellow or white, meaty a ...
s and only the
cep/porcini is more highly prized. However, honey fungus must be thoroughly cooked as they are mildly poisonous raw. Honey mushrooms are one of four UK species can cause sickness when ingested with alcohol. For those unfamiliar with the species, it is advisable not to drink alcohol for 12 hours before and 24 hours after eating this mushroom to avoid any possible nausea and vomiting. However, if these rules are followed this variety of mushroom is a delicacy with a distinctive mushroomy and nutty flavour. Reference texts for identification are ''Collins Complete British Mushrooms and Toadstools'' for the variety of field pictures in it, and Roger Philips' ''Mushrooms'' for the quality of his out of field pictures and descriptions.
In Norway, some mycologists have started to regard honey fungus as poisonous, as the Norway health department is moving away from the
parboiling
Parboiling (or leaching) is the partial or semi boiling of food as the first step in cooking. The word is from the Old French 'parboillir' (to boil thoroughly) but by mistaken association with 'part' it has acquired its current meaning.
The wo ...
practice.
Hosts
Potential
hosts
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
*Host, Pennsylvania, a village in Berks County
People
*Jim Host (born 1937), American businessman
*Michel Host ( ...
include
conifers
Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All extan ...
and various
monocotyledon
Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute one of ...
ous and
dicotyledon
The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...
ous trees,
shrub
A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...
s, and herbaceous species, ranging from asparagus and strawberry to large forest trees (Patton and Vasquez Bravo 1967).
[Patton, R. F.; Vasquez Bravo, R. 1967. "Armillaria root rot ''Armillaria mellea'' (Vahl ex Fr.) Kummer". p. 37–38 in Davidson, A. G.; Prentice, R. M. (compilers and eds.). ''Important forest insects and diseases of mutual concern to Canada, the United States, and Mexico''. Canadian Department for Rural Development, Ottawa, Ontario, Pub. 1180.] ''Armillaria'' root rot enters hosts through the roots. In Alberta, 75% of trap logs (Mallett and Hiratsuka 1985)
inserted into the soil between planted spruce became infected with the distinctive white mycelium of ''Armillaria'' within one year. Of the infestations, 12% were ''A. ostoyae'', and 88% were ''A. sinapina'' (Blenis et al. 1995).
[Blenis, P.; Titus, S.; Mallet, K. 1995. "Impact of Armillaria root rot in intensively managed white spruce/asspen stands". Natural Resources Canada/Alberta Land and Forest Service, Edmonton, Alberta, Canada/Alberta Forest Resource Development Agreement (FRDA), Project A5023-129 Rep. 5 p.] Reviews of the biology, diversity, pathology, and control of ''Armillaria'' in Fox (2000)
[Fox, R. T. V. (2000). "''Armillaria'' Root Rot: Biology and Control of Honey Fungus". ''Intercept'', Andover, Hants., England. 222 p.] are useful.
See also
*
Bioluminescence
Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some b ...
*
Foxfire
Foxfire, also called fairy fire and chimpanzee fire, is the bioluminescence created by some species of fungi present in decaying wood. The bluish-green glow is attributed to a luciferase, an oxidative enzyme, which emits light as it reacts with ...
*
List of ''Armillaria'' species
References
External links
*
Images of ''Armillaria'' species{{taxonbar , from=Q952036
Fungal tree pathogens and diseases
Agaricales genera
Bioluminescent fungi