WSU Extension

Hortsense

Pear
 
Disease
Crown gall 
European canker (Nectria canker) 
Fire blight 
Pacific Coast pear rust 
Pear trellis rust 
Powdery mildew 
Pseudomonas blossom blast and dieback 
Scab 
Stony pit 
Virus diseases 
Insect
Aphids 
Apple-and-thorn skeletonizer 
Brown marmorated stink bug 
Codling moth 
Cutworms and armyworms 
Pear psylla 
Pear slug (pear sawfly) 
Pearleaf blister mite 
San Jose scale 
Spider mites 



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Caption: Crown gall
Photo by: R.S. Byther
  
Pear : Crown gall
(revision date: 5/20/2014)


Biology
Crown gall is caused by a soilborne bacterium. The bacteria infect through wounds on the crown and roots. Young galls are fleshy, white, enlarged masses on the roots or stems. Older galls are hardened and turn dark brown and woody or corky in appearance. They range in size from less than an inch to several inches across. The bacteria can be spread from infected to clean soil by water movement. Damage varies with location and size of galls. Small galls are essentially harmless. Large galls on the crown may weaken or girdle trees. The growths can also be an aesthetic concern.
Management Options


Non-Chemical Management
  • Plant disease-free materials.
  • Remove and destroy declining trees with large crown galls. Also remove roots and surrounding soil where possible.
  • Prune out galls when practical. Sterilize pruning tools between cuts to avoid spreading bacteria to healthy tissue.
  • Avoid injuries to the bark, crown, and roots while planting.
  • Do not replant susceptible species in infected soil.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images

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Caption: Crown gall
Photo by: R.S. Byther