witches'-broom

[wich-iz-broom, -broom]
noun Plant Pathology.
an abnormal, brushlike growth of small thin branches on woody plants, caused especially by fungi, viruses, and mistletoes.

Origin:
1865–70

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
witches'-broom, witchbroom or witches'-besom (ˈwɪtʃˌbruːm)
 
n
a dense abnormal growth of shoots on a tree or other woody plant, usually caused by parasitic fungi of the genus Taphrina
 
witchbroom, witchbroom or witches'-besom
 
n
 
witches'-besom, witchbroom or witches'-besom
 
n

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Britannica
Encyclopedia

witches'-broom

symptom of plant disease that occurs as an abnormal brushlike cluster of dwarfed, weak shoots arising at or near the same point; twigs and branches of woody plants may die back. There are numerous causes, including rust (Gymnosporangium and Pucciniastrum); Apiosporina, Exobasidium, and Taphrina fungi; mites; insects; viruses; mycoplasmas; bacteria; and mistletoes. Susceptible plants include alder, alfalfa, Amelanchier, birch, California buckeye, Chamaecyparis, cherry, cherry laurel, elm, fir, hackberry, Holodiscus (ocean spray), honey locust, juniper and red-cedar, manzanita, mountain heath, mulberry, oak, potato, rhododendron, rose, sophora, spruce, and strawberry.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Yellow to bronze areas at tips of needles or twisted, distorted foliage or witches'-broom.
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