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Black Knot Disease on Prunus (Plum/Cherry): Hard Black Galls on Branches—Prune or Remove Tree

Tree with black knot galls on branches

Identification

Hard, black, irregular swellings on branches = Black Knot (fungus Dibotryon morbosum). Affects Prunus (plum, cherry, ornamental). Galls look like insect pods but are fungal.

Management

Few galls: Prune 4–6 inches below each gall in winter (dormant). Destroy debris.
Many galls / main trunk infected: Remove and destroy tree, especially if other Prunus nearby.
Disease is contagious; spores spread in spring.

Confirmation

Search "Black Knot" images—match your photo. Prune in winter for best results.

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