tar spot

noun

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

Word History

Etymology

tar entry 1

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