Armillaria

<h2 id="taxonomy">Taxonomy</h2>
The name Armillaria was defined in 1821 by <a href="/facts/Elias_Magnus_Fries/IspFbsTk">Elias Magnus Fries</a>, but at that time most gilled mushrooms were considered to belong to genus Agaricus and Armillaria was only a subgenus (a "tribe"). In 1857, Friedrich Staude established the independent genus.<a class="footnote-ref" id="fnref:1" href="#fn:1">1</a>
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).<a class="footnote-ref" id="fnref:2" href="#fn:2">2</a>
Intersterile species of Armillaria occurring in North America (North American Biological Species = NABS) were listed by Mallett (1992):<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a>

<ul><li>I Armillaria ostoyae (Romagn.) Herink</li>
<li>II Armillaria gemina Bérubé & Dessureault</li>
<li>III Armillaria calvescens Bérubé & Dessureault</li>
<li>V Armillaria sinapina Bérubé & Dessureault</li>
<li>VI Armillaria mellea (Vahl.:Fries) Kummer</li>
<li>VII Armillaria gallica (Marxmüller & Romagn.)</li>
<li>IX Armillaria nabsnona T. J. Volk & Burds. (1996)</li>
<li>X Armillaria altimontana Brazee, B. Ortiz, Banik & D. L. Lindner (2012)</li>
<li>XI taxonomically undescribed</li></ul>
NABS I, V, VII, IX, X, and XI have been found in <a href="/facts/British_Columbia/Ty3e3g1Q">British Columbia</a>; I, III, V have been found in the <a href="/facts/Prairie_Provinces/RLsC6Cn2">Prairie Provinces</a>, with I and V occurring in both the <a href="/facts/Taiga/xjkPQRJs">boreal</a> and <a href="/facts/Montane_ecology/gXbt5Gqn">subalpine regions</a>; I, III, V, and VII have been found in <a href="/facts/Ontario/HUkxk5Rf">Ontario</a>; and I, II, III, V, and VI have been found in <a href="/facts/Quebec/4hhNvb4t">Quebec</a>. Armillaria ostoyae is the species most commonly found in all Canadian provinces surveyed (Mallett 1990).<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a> Armillaria root rot occurs in the <a href="/facts/Northwest_Territories/au0ajf7T">Northwest Territories</a>, and was identified on <a href="/facts/White_spruce/UGT4jv4c">white spruce</a> at <a href="/facts/Pine_Point,_Northwest_Territories/jjIoHUhz">Pine Point</a> on <a href="/facts/Great_Slave_Lake/bvEQlKbr">Great Slave Lake</a> prior to NABS findings.
In 1791 <a href="/facts/Albrecht_Wilhelm_Roth/a1kMGf3h">Albrecht Wilhelm Roth</a> described the species Rhizomorpha fragilis for a collection which consisted entirely of rhizomorphs. The genus Rhizomorpha thus became established and later these <a href="/facts/Mycelial/znB97XNn">mycelial</a> cords were shown to belong to Armillaria mellea. According to the <a href="/facts/International_Code_of_Nomenclature_for_algae,_fungi,_and_plants/EbaUF9P5">code of nomenclature</a> 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. The proposal awaits decisions by the <a href="/facts/Nomenclature_Committee_for_Fungi/48oPw9So">Nomenclature Committee for Fungi</a> and eventually by an <a href="/facts/International_Botanical_Congress/LP3DtgVg">International Botanical Congress</a>.<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a><a class="footnote-ref" id="fnref:6" href="#fn:6">6</a><a class="footnote-ref" id="fnref:7" href="#fn:7">7</a>

<h2 id="description">Description</h2>

The basidiocarp (reproductive structure) of the fungus is a <a href="/facts/Mushroom/sRdY6lfe">mushroom</a> that grows on wood, typically in small dense clumps or tufts. Their <a href="/facts/Pileus_(mycology)/6d91unJ1">caps</a> (mushroom tops) are typically yellow-brown, somewhat sticky to touch when moist, and, depending on age, may range in shape from conical to convex to depressed in the center. The <a href="/facts/Stipe_(mycology)/032SVJIw">stipe</a> (stalk) may or may not have a <a href="/facts/Annulus_(mycology)/CJzTJSbU">ring</a>. All Armillaria species have a white <a href="/facts/Spore_print/WFAfnvuK">spore print</a> and none have a <a href="/facts/Volva_(mycology)/Ll5fEySA">volva</a> (cup at base).<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a>
Armillaria species are long-lived and form the <a href="/facts/Largest_organisms/F3HjLlq7">largest living fungi</a> in the world.<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> The largest known organism (of the species <a href="/facts/Armillaria_ostoyae/1kvv4g7J">A. ostoyae</a>) covers more than 3.4 square miles (8.8 km2) in <a href="/facts/Oregon/4Uq446Ko">Oregon</a>'s <a href="/facts/Malheur_National_Forest/lEE6Y3CH">Malheur National Forest</a> and is estimated to be 2,500 years old.<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a><a class="footnote-ref" id="fnref:11" href="#fn:11">11</a> Some species display <a href="/facts/Bioluminescence/IlzgyV4E">bioluminescence</a>, known as <a href="/facts/Foxfire/3A4Rg6j9">foxfire</a>.

<h3>Similar species</h3>
Similar species include <a href="/facts/Pholiota/NFwNdez1">Pholiota</a> 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. <a href="/facts/Mushroom_hunter/vqAw1fWa">Mushroom hunters</a> need to be wary of <a href="/facts/Galerina/rfF6TuFo">Galerina</a> spp. which can grow side by side with Armillaria spp. on wood. <a href="/facts/Galerina/rfF6TuFo">Galerina</a> have a dark brown spore print and are deadly <a href="/facts/Mushroom_poisoning/hJVmEYvx">poisonous</a> (<a href="/facts/Alpha-amanitin/aQMkd2hA">alpha-amanitin</a>).
The white spore print and lack of volva can be compared to <a href="/facts/Amanita/SeajBxmT">Amanita</a>.<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a> As a <a href="/facts/White_rot/UHRCmnQ8">white rot</a>, it is distinguished from <a href="/facts/Tricholoma/kM2EDyev">Tricholoma</a>, a <a href="/facts/Mycorrhiza/bAqxvRwm">mycorrhizal</a> (non-parasitic) genus.

<h2 id="pathology">Pathology</h2>
Main article: <a href="/facts/Armillaria_root_rot/qoR2yfwa">Armillaria root rot</a>
Honey fungus is a white-rot fungus, which is a <a href="/facts/Pathogen/axMXtV1M">pathogenic</a> organism that affects trees, <a href="/facts/Shrub/X1gKVxL5">shrubs</a>, woody climbers and rarely, woody herbaceous <a href="/facts/Perennial/MQ3NvAUW">perennial</a> plants. Honey fungus can grow on living, decaying, and also dead plant material (being a <a href="/facts/Facultative_saprophyte/sJkDfrJW">facultative saprophyte</a>). This means it can kill its host with little consequence, unlike <a href="/facts/Parasite/HWPcgky7">parasites</a> that must moderate their growth to avoid host death.<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a>
Honey fungus spreads from living trees, dead and live roots and stumps by means of reddish-brown to black <a href="/facts/Rhizomorph/wyRdw1TT">rhizomorphs</a> (root-like structures) at the rate of approximately 3.3 feet (1 m) a year, but infection by root contact is possible. Infection by spores is rare. Rhizomorphs grow close to the <a href="/facts/Soil/5Ddpr3QM">soil</a> surface (in the top 7.9 inches (20 cm)) 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 <a href="/facts/Girdling/9l6gdvjd">girdled</a> it, or when significant root damage has occurred. Additionally, Infections can occur through the activity of wood boring beetles. For example, <a href="/facts/Agrilus_biguttatus/T3qwkRo9">Agrilus biguttatus</a> most commonly girdle in <a href="/facts/Oak/1NJJzkzB">oak trees</a>, which allows fungi to grow in the stems of these infected trees. This can happen rapidly, or may take several years. Infected plants will deteriorate, although may exhibit prolific flower or fruit production shortly before death.[why?]

Initial symptoms of honey fungus infection include <a href="/facts/Forest_dieback/dKzn8b2B">dieback</a> or shortage of leaves in spring. Rhizomorphs (also called mycelial cords) appear under the <a href="/facts/Bark_(botany)/vdL49ec1">bark</a> and around the tree, and mushrooms grow in clusters from the infected plant in autumn and die back after the first frost. However these <a href="/facts/Symptom/BzP6MrTN">symptoms and signs</a> 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, 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 <a href="/facts/Conifers/vDUgqxCx">conifers</a> honey fungus often exudes a gum or <a href="/facts/Resin/r1uVThQ8">resin</a> from cracks in the bark.

<h3>Hosts</h3>
Potential <a href="/facts/Host_(biology)/L6mop0kh">hosts</a> include <a href="/facts/Pinophyta/vDUgqxCx">conifers</a> and various <a href="/facts/Monocotyledon/mXCuuCYo">monocotyledonous</a> and <a href="/facts/Dicotyledon/yat51Ncq">dicotyledonous</a> trees, <a href="/facts/Shrub/X1gKVxL5">shrubs</a>, and herbaceous species, ranging from asparagus and strawberry to large forest trees (Patton and Vasquez Bravo 1967).<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a> Armillaria root rot enters hosts through the roots. In Alberta, 75% of trap logs (Mallett and Hiratsuka 1985)<a class="footnote-ref" id="fnref:15" href="#fn:15">15</a> 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).<a class="footnote-ref" id="fnref:16" href="#fn:16">16</a> Reviews of the biology, diversity, pathology, and control of Armillaria in Fox (2000)<a class="footnote-ref" id="fnref:17" href="#fn:17">17</a> are useful.

<h2 id="edibility">Edibility</h2>
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 <a href="/facts/Morel/4AccCGdR">morels</a> and <a href="/facts/Chanterelle/AgSqfjoe">chanterelles</a> and only the <a href="/facts/Boletus_edulis/emubJeq5">cep/porcini</a> 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 that 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 Norwegian health ministry is moving away from the <a href="/facts/Parboiling/e6sntqCj">parboiling</a> practice.<a class="footnote-ref" id="fnref:18" href="#fn:18">18</a><a class="footnote-ref" id="fnref:19" href="#fn:19">19</a>

<h2 id="see-also">See also</h2>
<ul>
<li>Fungi portal</li></ul>
<ul><li><a href="/facts/List_of_Armillaria_species/SgrphIA0">List of Armillaria species</a></li></ul>

<h2 id="external-links">External links</h2>
<ul><li><a href="https://bie.ala.org.au/species/urn:lsid:indexfungorum.org:names:17098">"Armillaria (Fr.) Staude"</a>. Atlas of Living Australia.</li>
<li><a href="https://www.bioimages.org.uk/html/Armillaria.htm">Images of Armillaria species</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">"the Armillaria page". Species Fungorum. Royal Botanic Gardens Kew. Retrieved 2020-09-05. <a href="http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=17098" target="_blank">http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=17098</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">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. <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">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. <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Mallett, K. I. (1990). "Armillaria root rot pathogens of the Canadian prairie provinces". Canadian Journal of Forest Research 20:1859–1863. <a href="/wiki/Root_rot" target="_blank">/wiki/Root_rot</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">"the Rhizomorpha page". Species Fungorum. Royal Botanic Gardens Kew. Retrieved 2020-09-05. <a href="http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=18461" target="_blank">http://www.indexfungorum.org/names/NamesRecord.asp?RecordID=18461</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Koch RA, Lodge DJ, Sourell S, Nakasone K, McCoy AG, Aime MC (2018). "Tying up loose threads: revised taxonomy and phylogeny of an avian-dispersed Neotropical rhizomorph-forming fungus". Mycological Progress. 17 (9): 989–998. Bibcode:2018MycPr..17..989K. doi:10.1007/s11557-018-1411-8. <a href="https://www.researchgate.net/publication/325653310" target="_blank">https://www.researchgate.net/publication/325653310</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Stalpers JA, Redhead SA, May TW, et al. (2021). "Competing sexual-asexual generic names in Agaricomycotina (Basidiomycota) with recommendations for use". IMA Fungus. 12 (22): 3. doi:10.1186/s43008-021-00061-3. PMC 8359032. PMID 34380577. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8359032" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8359032</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Pegler DN (2000). "Taxonomy, nomenclature and description of Armillaria". In Fox RTV (ed.). Armillaria Root Rot: Biology and Control of Honey Fungus. Intercept. pp. 81–93. ISBN 1-898298-64-5. <a href="1-898298-64-5" target="_blank">1-898298-64-5</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Smith, Myron L.; Bruhn, Johann N.; Anderson, James B. (April 1992). "The fungus Armillaria bulbosa is among the largest and oldest living organisms". Nature. 356 (6368): 428–431. doi:10.1038/356428a0. ISSN 1476-4687. <a href="https://www.nature.com/articles/356428a0" target="_blank">https://www.nature.com/articles/356428a0</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">John L. Ingraham (15 February 2010). March of the Microbes: Sighting the Unseen. Harvard University Press. p. 201. ISBN 978-0-674-03582-9. <a href="978-0-674-03582-9" target="_blank">978-0-674-03582-9</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Daley, Jason (15 October 2018). "This Humongous Fungus Is as Massive as Three Blue Whales". Smithsonian.com. Smithsonian Institution. Retrieved 21 October 2018. <a href="https://www.smithsonianmag.com/smart-news/mushroom-massive-three-blue-whales-180970549/" target="_blank">https://www.smithsonianmag.com/smart-news/mushroom-massive-three-blue-whales-180970549/</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">Pegler DN (2000). "Taxonomy, nomenclature and description of Armillaria". In Fox RTV (ed.). Armillaria Root Rot: Biology and Control of Honey Fungus. Intercept. pp. 81–93. ISBN 1-898298-64-5. <a href="1-898298-64-5" target="_blank">1-898298-64-5</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">Daley, Jason (15 October 2018). "This Humongous Fungus Is as Massive as Three Blue Whales". Smithsonian.com. Smithsonian Institution. Retrieved 21 October 2018. <a href="https://www.smithsonianmag.com/smart-news/mushroom-massive-three-blue-whales-180970549/" target="_blank">https://www.smithsonianmag.com/smart-news/mushroom-massive-three-blue-whales-180970549/</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
<li id="fn:14">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. <a href="#fnref:14" class="footnote-back-ref">↩</a></li>
<li id="fn:15">Mallett, K. I.; Hiratsuka, Y. (1985). "The 'trap-log' method to survey the distribution of Armillaria mellea in forest soils". Canadian Journal of Forest Research. 15 (6): 1191–1193. doi:10.1139/x85-195. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></li>
<li id="fn:16">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. <a href="#fnref:16" class="footnote-back-ref">↩</a></li>
<li id="fn:17">Fox, R. T. V. (2000). "Armillaria Root Rot: Biology and Control of Honey Fungus". Intercept, Andover, Hants., England. 222 p. <a href="#fnref:17" class="footnote-back-ref">↩</a></li>
<li id="fn:18">"Giftige sopper" (PDF) (in Norwegian). p. 10. Retrieved 31 October 2018. <a href="https://www.fhi.no/globalassets/dokumenterfiler/trykksaker/giftige-sopper---norsk-bokmal-2015.pdf" target="_blank">https://www.fhi.no/globalassets/dokumenterfiler/trykksaker/giftige-sopper---norsk-bokmal-2015.pdf</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></li>
<li id="fn:19">Risberg, Tor (28 October 2014). "– Ikke bruk gamle soppbøker! - NRK Livsstil - Tips, råd og innsikt" (in Norwegian). NRK. Retrieved 4 July 2015. <a href="http://www.nrk.no/livsstil/_-ikke-bruk-gamle-soppboker_-1.11966546" target="_blank">http://www.nrk.no/livsstil/_-ikke-bruk-gamle-soppboker_-1.11966546</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></li>
</ol>

Armillaria open-in-new

Armillaria