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{{distinguish|text=[[Mistletoe]]s, which are not the host plant's own tissue, but parasitic plants growing on the host}}
{{Short description|Type of deformity in a woody plant}}
{{distinguish|text=[[Mistletoe]]s, which are not the host plant's own tissue, but parasitic plants growing on the host}}
{{For|a broom associated with witches|Besom}}
{{About||a broom associated with witches|Besom|the nebula|Witch's Broom Nebula}}
{{For|the nebula|Witch's Broom Nebula}}


[[Image:Betula pubescens Taphrina.jpg|thumb|300px|Witch's brooms on [[downy birch]], caused by the fungus ''[[Taphrina]] betulina'']]
[[Image:Betula pubescens Taphrina.jpg|thumb|300px|Witch's brooms on [[downy birch]], caused by the fungus ''[[Taphrina betulina]]'']]
[[Image:Witch's_broom_pinus_strobus.jpg|thumb|300px|Witch's broom on a white pine.]]
[[Image:Witch's_broom_pinus_strobus.jpg|thumb|300px|Witch's broom on a white pine.]]
[[Image:WitchsBroomYamaska20200207.jpg|thumb|300px|Witch's broom in Yamaska National Park, QC]]


'''Witch's broom''' or '''witches' broom''' is a deformity in a [[woody plant]], typically a [[tree]], where the natural structure of the plant is changed. A dense mass of [[shoot]]s grows from a single point, with the resulting structure resembling a [[Broom (tool)|broom]] or a bird's [[nest]]. It is sometimes caused by pathogens.
'''Witch's broom''' or '''witches' broom''' is a deformity in a [[woody plant]], typically a [[tree]], where the natural structure of the plant is changed. A dense mass of [[Shoot (botany)|shoot]]s grows from a single point, with the resulting structure resembling a [[Broom (tool)|broom]] or a bird's [[nest]]. It is sometimes caused by pathogens.


'''Witch-broom disease''' caused by [[phytoplasma]]s is economically important in a number of crop plants, including the cocoa tree ''[[Theobroma cacao]]'',<ref>{{cite journal|author1=Purdy, L.H. |author2=Schmidt, R.A. |year=1996|title=Status Of Cacao Witches' Broom: Biology, Epidemiology, and Management|journal=Annual Review of Phytopathology|volume=34|issue=1|pages=573–594|doi=10.1146/annurev.phyto.34.1.573|pmid=15012557 }}</ref>
Diseases with symptoms of witches' broom, caused by [[phytoplasma]]s or basidiomycetes, are economically important in a number of crop plants, including the cocoa tree ''[[Theobroma cacao]]'',<ref>{{cite journal|author1=Purdy, L.H. |author2=Schmidt, R.A. |year=1996|title=Status Of Cacao Witches' Broom: Biology, Epidemiology, and Management|journal=Annual Review of Phytopathology|volume=34|issue=1|pages=573–594|doi=10.1146/annurev.phyto.34.1.573|pmid=15012557 }}</ref> [[jujube]] (''Ziziphus jujuba'')<ref>{{cite journal |url=http://en.cnki.com.cn/Article_en/CJFDTOTAL-GSKK200102012.htm |title=Advances in Tissue Culture and Eliminating of the Pathogeny of Witch Broom Disease(MLO) of Chinese Jujube |year=2001 |author1=Li Yun |author2=Wang Yu |author3=Tian Yanting |author4=Sun Haoyuan |name-list-style=amp |access-date=2013-08-08 |archive-date=2021-04-26 |archive-url=https://web.archive.org/web/20210426212804/http://en.cnki.com.cn/Article_en/CJFDTOTAL-GSKK200102012.htm |url-status=dead }}</ref> and the timber tree ''[[Melia azedarach]]''.<ref>{{cite journal|author1=Gomez, G.G. |author2=Conci, L.R. |author3=Ducasse, D.A. |author4=Nome, S.F. |year=1996|title=Purification of the Phytoplasma Associated with China-tree (''Melia azedarach'' L.) Decline and the Production of a Polyclonal Antiserum for its Detection|journal=Journal of Phytopathology|volume=144|issue=9–10|pages=473–477|doi=10.1111/j.1439-0434.1996.tb00327.x}}</ref>
[[jujube]] (''Ziziphus jujuba'')<ref>{{cite journal|url=http://en.cnki.com.cn/Article_en/CJFDTOTAL-GSKK200102012.htm|title=Advances in Tissue Culture and Eliminating of the Pathogeny of Witch Broom Disease(MLO) of Chinese Jujube|year=2001|author1=Li Yun |author2=Wang Yu |author3=Tian Yanting |author4=Sun Haoyuan |last-author-amp=yes }}</ref> and the timber tree ''[[Melia azedarach]]''.<ref>{{cite journal|author1=Gomez, G.G. |author2=Conci, L.R. |author3=Ducasse, D.A. |author4=Nome, S.F. |year=1996|title=Purification of the Phytoplasma Associated with China-tree (''Melia azedarach'' L.) Decline and the Production of a Polyclonal Antiserum for its Detection|journal=Journal of Phytopathology|volume=144|issue=9–10|pages=473–477|doi=10.1111/j.1439-0434.1996.tb00327.x}}</ref>


==Causes==
==Causes==
A tree's characteristic shape, or habit, is in part the product of [[auxin]]s, hormones which control the growth of secondary [[Meristem#Apical meristems|apices]]. The growth of an offshoot is limited by the auxin, while that of the parent branch is not. In cases of witch's broom, the normal hierarchy of buds is interrupted, and apices grow indiscriminately. This can be caused by [[cytokinin]], a [[phytohormone]] which interferes with growth regulation. The phenomenon can also be caused by other organisms, including [[fungus|fungi]], [[oomycete]]s, insects, [[mite]]s, [[nematode]]s, [[phytoplasma]]s, and [[virus]]es.<ref name="AA">''Book of the British Countryside''. Pub. London : Drive Publications, (1973). p. 519.</ref> The broom growths may last for many years, typically for the life of the host plant. If twigs of witch's brooms are grafted onto normal rootstocks, freak trees result, showing that the attacking organism has changed the inherited growth pattern of the twigs.<ref name="AA" />
Witch's broom can be caused by [[cytokinin]], a [[phytohormone]], interfering with an auxin-regulated bud. In normal plant function, an [[auxin]] would keep the secondary, tertiary, and so on tips from overgrowing, but cytokinin can sometimes interfere with this control, causing these apices to grow into witch's brooms.


==Ecological role==
Witch's broom may be caused by many different types of organisms, including [[fungus|fungi]], [[oomycete]]s, [[insect]]s, [[mistletoe]], [[dwarf mistletoe]]s, [[mite]]s, [[nematode]]s, [[phytoplasma]]s, or [[virus]]es.<ref name="AA">''Book of the British Countryside''. Pub. London : Drive Publications, (1973). p. 519.</ref> The broom growths may last for many years, typically for the life of the host plant. Human activity is sometimes behind the introduction of these organisms, for example, by failing to observe hygienic practice and thereby infecting the tree with the causative organism, or by pruning a tree improperly, and thereby weakening it.{{citation needed|date=September 2013}}
Witches' brooms provide nesting habitat for birds and mammals, such as the [[northern flying squirrel]], which nests in them.<ref>{{cite web |last1=Mowry |first1=Robert A. |title=Northern Flying Squirrel |url=https://www.adfg.alaska.gov/enwiki/static/education/wns/northern_flying_squirrel.pdf |website=Alaska Department of Fish and Game |access-date=2 June 2020 |date=2008}}</ref><ref>{{cite web |last1=Paragi |first1=Thomas |last2=Rodman |first2=Sue |title=Maintaining wildlife habitat in the boreal forest of Alaska |url=https://www.adfg.alaska.gov/enwiki/static/lands/habitatrestoration/pdfs/maintaining_wildlife_habitat_boreal_forest_alaska.pdf |website=Alaska Department of Fish and Game |access-date=2 June 2020 |pages=18–19 |date=2020}}</ref>

==Uses==
Witches' brooms occasionally result in desirable changes. Some cultivars of trees, such as ''[[Picea orientalis]]'' 'Tom Thumb Gold', were discovered as witch's brooms. If twigs of witches' brooms are grafted onto normal rootstocks, freak trees result, showing that the attacking organism has changed the inherited growth pattern of the twigs.<ref name="AA" />

Witches' brooms are of wide ecological importance. They generally tend to be inhabited by a wide variety of organisms apart from the causative organisms. Some of the invading organisms, such as some species of moths, are specific to particular types of witches' brooms, relying on them for food and shelter for their larvae. Various larger animals nest in them, including the [[northern flying squirrel]].<ref>{{cite web|url=http://www.adfg.state.ak.us/pubs/notebook/furbear/nfsquirl.php |title=Home Page, Alaska Department of Fish and Game |publisher=Adfg.state.ak.us |date=2012-01-01 |accessdate=2012-05-26}}</ref>


== See also ==
== See also ==
* [[Plant development#Buds and shoots|Plant development: buds and shoots]] – atypical shoot development
* [[Plant development#Buds and shoots|Plant development § buds and shoots]] – atypical shoot development
* [[Epicormic shoot]] – a shoot that develops from buds under the bark
* [[Epicormic shoot]] – a shoot that develops from buds under the bark
* [[Forest pathology]]
* [[Forest pathology]]
* ''[[Longan witches broom-associated virus]]''
* ''[[Melampsora]]'' can cause different kinds of witch's brooms.
* ''[[Melampsora]]'' can cause different kinds of witch's brooms.
* ''[[Moniliophthora perniciosa]]'', cause of witch's broom disease in cacao
* ''[[Moniliophthora perniciosa]]'', cause of witch's broom disease in cacao
*[[Phyllody]], a related plant growth abnormality affecting flowers
* [[Phyllody]], a related plant growth abnormality affecting flowers


== References ==
== References ==
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== External links ==
== External links ==
{{commonscat-inline|Witch's broom}}
{{commons category-inline|Witch's broom}}
* [http://www.bbc.co.uk/dna/h2g2/brunel/A3700261 Witches' Broom] at [[BBC h2g2]].
* [https://www.bbc.co.uk/dna/h2g2/brunel/A3700261 Witches' Broom] at [[BBC h2g2]].
* [http://www.fs.fed.us/r3/resources/health/field-guide/scrp/firbroom.shtml Fir and spruce broom]
* [http://www.fs.fed.us/r3/resources/health/field-guide/scrp/firbroom.shtml Fir and spruce broom]


Latest revision as of 01:29, 14 August 2024

Not to be confused with Mistletoes, which are not the host plant's own tissue, but parasitic plants growing on the host.
For a broom associated with witches, see Besom. For the nebula, see Witch's Broom Nebula.
Witch's brooms on downy birch, caused by the fungus Taphrina betulina
Witch's broom on a white pine.
Witch's broom in Yamaska National Park, QC

Witch's broom or witches' broom is a deformity in a woody plant, typically a tree, where the natural structure of the plant is changed. A dense mass of shoots grows from a single point, with the resulting structure resembling a broom or a bird's nest. It is sometimes caused by pathogens.

Diseases with symptoms of witches' broom, caused by phytoplasmas or basidiomycetes, are economically important in a number of crop plants, including the cocoa tree Theobroma cacao,[1] jujube (Ziziphus jujuba)[2] and the timber tree Melia azedarach.[3]

Causes

[edit]

A tree's characteristic shape, or habit, is in part the product of auxins, hormones which control the growth of secondary apices. The growth of an offshoot is limited by the auxin, while that of the parent branch is not. In cases of witch's broom, the normal hierarchy of buds is interrupted, and apices grow indiscriminately. This can be caused by cytokinin, a phytohormone which interferes with growth regulation. The phenomenon can also be caused by other organisms, including fungi, oomycetes, insects, mites, nematodes, phytoplasmas, and viruses.[4] The broom growths may last for many years, typically for the life of the host plant. If twigs of witch's brooms are grafted onto normal rootstocks, freak trees result, showing that the attacking organism has changed the inherited growth pattern of the twigs.[4]

Ecological role

[edit]

Witches' brooms provide nesting habitat for birds and mammals, such as the northern flying squirrel, which nests in them.[5][6]

See also

[edit]

References

[edit]
  1. ^ Purdy, L.H.; Schmidt, R.A. (1996). "Status Of Cacao Witches' Broom: Biology, Epidemiology, and Management". Annual Review of Phytopathology. 34 (1): 573–594. doi:10.1146/annurev.phyto.34.1.573. PMID 15012557.
  2. ^ Li Yun; Wang Yu; Tian Yanting & Sun Haoyuan (2001). "Advances in Tissue Culture and Eliminating of the Pathogeny of Witch Broom Disease(MLO) of Chinese Jujube". Archived from the original on 2021-04-26. Retrieved 2013-08-08. {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ Gomez, G.G.; Conci, L.R.; Ducasse, D.A.; Nome, S.F. (1996). "Purification of the Phytoplasma Associated with China-tree (Melia azedarach L.) Decline and the Production of a Polyclonal Antiserum for its Detection". Journal of Phytopathology. 144 (9–10): 473–477. doi:10.1111/j.1439-0434.1996.tb00327.x.
  4. ^ a b Book of the British Countryside. Pub. London : Drive Publications, (1973). p. 519.
  5. ^ Mowry, Robert A. (2008). "Northern Flying Squirrel" (PDF). Alaska Department of Fish and Game. Retrieved 2 June 2020.
  6. ^ Paragi, Thomas; Rodman, Sue (2020). "Maintaining wildlife habitat in the boreal forest of Alaska" (PDF). Alaska Department of Fish and Game. pp. 18–19. Retrieved 2 June 2020.
[edit]

Media related to Witch's broom at Wikimedia Commons

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