WSU Extension


Crown gall 
European canker (Nectria canker) 
Fire blight 
Pacific Coast pear rust 
Pear trellis rust 
Powdery mildew 
Pseudomonas blossom blast and dieback 
Stony pit 
Virus diseases 
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: European canker
Photo by: R.S. Byther
Pear : European canker (Nectria canker)
(revision date: 4/11/2018)

Nectria or European canker is a fungal disease affecting the twigs and branches of pear and apple. Young cankers occur at leaf nodes on twigs and are sunken, dark, and water-soaked in appearance. Twigs are often girdled and die back above the infected site. Older cankers are either irregularly elongate and covered with dead bark, or are surrounded by roughened, irregular, cracked bark in concentric rings, indicating the infection's yearly advance. In spring or fall of the first season following infection, cankers produce white fungal fruiting bodies. Round, red fruiting bodies are produced on older cankers during subsequent winters and springs. The fungus infects during rainy weather in the fall, attacking through leaf scars and wounds. An eye rot may occur on the flower end of fruit, causing brown, depressed spots with lighter centers on the fruit surface.
Management Options

Non-Chemical Management
  • Prune out and destroy cankered tissues during dry weather in early summer.
Select non-chemical management options as your first choice!

Chemical Management

Apply before fall rains and during early leaf fall. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Copper Fungicide Spray or Dust RTU [Organic]
    Active ingredient: basic copper sulfate  |  EPA reg no: 4-58
  • Bonide Liquid Copper Fungicide Conc/Organic Gardening
    Active ingredient: copper octanoate  |  EPA reg no: 67702-2-4
  • Soap-Shield Flowable Liquid Copper Fungicide [Organic]
    Active ingredient: copper octanoate  |  EPA reg no: 67702-2-56872
  • This list may not include all products registered for this use.

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Caption: European canker
Photo by: R.S. Byther
Caption: European closed canker on pear
Photo by: R.S. Byther
Caption: Nectria canker fruiting bodies
Photo by: R.S. Byther
Caption: Newly-developed European canker
Photo by: R.S. Byther