WSU Extension

Hortsense

Common Diseases : Nectria cankers
(revision date: 4/30/2013)


Biology
Nectria canker is a fungal disease affecting the twigs and branches of a wide variety of woody plants, including pear, maple, and apple (where it is called European canker). The fungus infects during rainy weather in the fall, attacking through leaf scars and wounds. Young cankers are sunken, dark, and water-soaked in appearance. Cream-colored fungal fruiting bodies appear in the canker during the spring or fall/winter of the first season following infection. Twigs are often girdled and die back above the infected site. Older cankers are either irregularly elongated and covered with dead bark, or surrounded by roughened, irregular, cracked bark in concentric rings. Small, round, red fruiting bodies are produced on cankers during the second winter and spring. Fruit may also be infected, causing an eye rot at the blossom end or a rot on the side of the fruit which resembles bull's-eye rot.
Management Options

Non-Chemical Management
  • Remove and destroy affected twigs and limbs. Do not leave them on the ground between the rows, but carry them out to a burn pile or rotovate them into the soil so they are completely buried.
  • Prune during dry weather near the end of the dormant period. Make cuts well below infected area and disinfect pruning tools between cuts to avoid spreading infection.
  • Avoid wounds.
  • Avoid leaving pruning stubs. Make a sharp, clean cut which will heal promptly.
  • Maintain tree vigor through proper fertilizing and watering.
Select non-chemical management options as your first choice!

Chemical Management

Fungicide applications may be useful when used in conjunction with canker removal. Applications should be made in the fall during leaf fall to protect the leaf scars from infection. Make certain that the fungicide is registered for the target host.

Images
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Caption: Nectria canker fruiting bodies
Photo by: R.S. Byther
Caption: European canker on apple
Photo by: R.S. byther