WSU Extension

Hortsense

Plum, Prune (Fresh) : Black knot
(revision date: 6/5/2018)


Use Integrated Pest Management (IPM) for successful plant problem management.

Biology
Black knot is a fungal disease that infects cherry and plum. Early infections of twigs are elongated olive-green, corky knots. They turn black and hard as they mature. Every year they expand lengthwise. It is possible for the fungus to stunt and kill limbs as it grows around the twig or branch.
Management Options

Non-Chemical Management
  • Remove knots, cutting 3 inches below the knot. Burn or bury infected debris.
Select non-chemical management options as your first choice!

Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides

None recommended.

Images
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Caption: Black knot
Photo by: R. Byther