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black knot

noun, Plant Pathology
a disease of plants, especially of plums and cherries, characterized by black knotlike overgrowths on the branches, twigs, etc., caused by a fungus, Dibotryon morbosa.
1835-45, Americanism Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for black knot

black knot

a fungal disease of plums and cherries caused by Dibotryon morbosum, characterized by rough black knotlike swellings on the twigs and branches
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Article for black knot

disease of wild and cultivated plums, cherries, and apricots in North America caused by the fungus Dibotryon morbosum. Infected twigs, branches, and fruit show light brown swellings that turn velvety olive-green in late spring. By autumn, hard, rough, coal-black knots girdle and kill affected parts. Older knots, often riddled by insects, stunt and kill the tree. Black knot can be controlled by pruning infected parts during the winter (knots on large limbs are cut away, and the wound is treated), destroying nearby wild plums and cherries that may be affected, and spraying the opening buds with a fungicide. Japanese plums are less susceptible than most American and European varieties

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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