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tar spot

noun
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Definition of tar spot

1a : a leaf-blotch disease of maple, willow, or oak caused by fungi of the genus Rhytisma that produces raised black stromatic cushions on the foliage
b : one of the spots produced
2 : a disease of many grasses caused by a fungus (Phyllacora graminis) and resembling the tar spot of trees

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History and Etymology for tar spot

tar entry 1

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Cite this Entry

“Tar spot.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/tar%20spot. Accessed 19 Jun. 2021.

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