WSU Extension

Hortsense

Plum, Prune (Fresh)
 
Disease
Armillaria root rot 
Bacterial canker 
Black knot 
Brown rot 
Crown gall 
Cytospora canker 
Plum pockets 
Russeting 
Shothole (Coryneum blight) 
Silver leaf 
Virus diseases 
Insect
Aphids 
Apple-and-thorn skeletonizer 
Brown marmorated stink bug 
Earwigs 
Fruittree leafroller 
Leafhoppers 
Pacific flatheaded borer 
Peach twig borer 
Peachtree borer 
Pear slug 
Scale insects 
Shothole borer 
Spider mites 
Spotted wing Drosophila (SWD) 



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Caption: Black knot
Photo by: R. Byther
  
Plum, Prune (Fresh) : Black knot
(revision date: 6/5/2018)


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

None recommended.

Images

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Caption: Black knot
Photo by: R. Byther