tar spot

noun

Definition of tar spot

1 a :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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Origin and Etymology of tar spot


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