Mountain Ash: Fire blight

categories: Mountain Ash Mountain Ash Diseases Ornamental trees Ornamentals

revision date: 2022-11-25 11:52

Brown and leaves on branches against a horizontal wood plank fence.
Cotoneaster fire blight
Photo by: R. Maleike


Fire blight is a bacterial infection of shoots which enters the plant through blossoms, vigorously growing shoot tips, young leaves, and wounds. Blossom clusters appear blighted. Shoots suddenly wilt, turn black and die back, presenting a “scorched” appearance. Purplish cankers may develop on the shoots. During wet or warm weather, the cankers may ooze brown sticky droplets. Newly infected wood is reddish, while older infections are black. The bacteria are easily spread by rain and pollinating insects. Fire blight also affects pear, pyracantha, apple, and related species. It is not a proven problem in western Washington.

Management Options

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

Non-chemical Management

Select non-chemical management options as your first choice!

  • Immediately prune out and destroy infected tissues. Make pruning cuts at least 6″ below infected tissues. Sterilize tools between cuts. Do not do regular pruning at the same time as blight removal.
  • Avoid wounding plants.
  • Use moderate amounts of nitrogen fertilizer to minimize vigorous growth of susceptible shoots.

Chemical Management

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

  • Apply during prebloom and bloom period.
  • 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.


Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.