black knot

noun Plant Pathology.

1. 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.

noun

1. a fungal disease of plums and cherries caused by Dibotryon morbosum, characterized by rough black knotlike swellings on the twigs and branches