black knot

noun

1

: a destructive disease of plum and cherry trees characterized by black excrescences on the branches and caused by a fungus (Dibotryon morbosa)

2

: a destructive disease of the gooseberry characterized by black excrescences on the branches and caused by a fungus (Dibotryon ribesia)

3

: a disease of the filbert and hazel characterized by black warty excrescences on the bark and caused by a fungus (Cryptosporella anomala)

4

: a cane infection of the grape caused by the crown-gall bacterium

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