Mountain Ash: Fire blight
Photo by: R. Maleike
Biology
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
See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.
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: Always read and follow label directions when working with pesticides.
For more information on using pesticides visit :
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Apply during prebloom and bloom period.
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Homeowners should not make foliar applications to trees over 10 ft tall.
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Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.
Approved Pesticides
If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.