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Witch's broom

{{Short description|Type of deformity in a woody plant}}

{{About||a broom associated with witches|Besom|the Witch's Broom nebula|Veil Nebula}}

Image:Betula pubescens Taphrina.jpg, caused by the fungus Taphrina betulina]]

Image:Witch's_broom_pinus_strobus.jpg

Image:WitchsBroomYamaska20200207.jpg

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,{{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 }} jujube (Ziziphus jujuba){{cite journal |url=https://caod.oriprobe.com/articles/3375927/Advances_in_Tissue_Culture_and_Eliminating_of_the_.htm |title=Advances in Tissue Culture and Eliminating of the Pathogeny of Witch Broom Disease(MLO) of Chinese Jujube |author1=Li Yun |author2=Wang Yu |author3=Tian Yanting |author4=Sun Haoyuan |journal=Journal of Fruit Science |year=2001 |volume=18 |issue=2 |pages=115–119|name-list-style=amp}} and the timber tree Melia azedarach.{{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}}

Causes

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.Book of the British Countryside. Pub. London : Drive Publications, (1973). p. 519. 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.

Ecological role

Witches' brooms provide nesting habitat for birds and mammals, such as the northern flying squirrel, which nests in them.{{cite web |last1=Mowry |first1=Robert A. |title=Northern Flying Squirrel |url=https://www.adfg.alaska.gov/static/education/wns/northern_flying_squirrel.pdf |website=Alaska Department of Fish and Game |access-date=2 June 2020 |date=2008}}{{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/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}}

See also

References

{{Reflist}}

External links

{{commons category-inline|Witch's broom}}

  • [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]

Category:Plant pathogens and diseases