Ornamental Pear: Fire blight
categories: Ornamental Pear Ornamental Pear Diseases Ornamental trees Ornamentals
revision date: 2022-12-05 12:00
Biology
Fire blight is a bacterial infection which typically attacks via wounds or blossoms. Initially, twigs and flowers appear water-soaked. Infected tissues quickly turn brown to black and die back, often bending over in a characteristic “shepherd’s crook.” Blighted tissues remain on the tree, giving it a scorched appearance. Dark, somewhat sunken cankers develop on twigs and branches, sometimes girdling the limb and causing dieback. Brownish bacterial ooze is common at the margins of cankers, especially during humid weather. Fruit may also be infected, showing sunken black spots up to 1″ in diameter and 1/4″ deep. The bacteria overwinter in infected tissues and can be transmitted by rain and pollinating insects. Fire blight is not a proven problem in western Washington. Pseudomonas blossom blast and dieback is caused by a different species of bacteria, but the symptoms may be similar.
Management Options
Use Integrated Pest Management (IPM) for successful plant problem management.
Non-chemical Management
Select non-chemical management options as your first choice!
- Avoid wounding plants.
- Plant resistant varieties when possible. Pyrus calleryana ‘Chanticleer’ (aka ‘Cleveland Select’), P. betulifolia ‘Dancer,’ and P. ussuriensis ‘Prairie Gem’ are reported to have some fire blight resistance.
- Provide proper culture to minimize amount of succulent shoot growth and to reduce injuries including winter injury.
- Prune out and destroy infected tissues when noticed. Make cuts at least 6″ below infected areas and sterilize pruning tools between cuts. To reduce chances of spreading bacteria, do not perform blight removal during regular pruning.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
- Bactericidal sprays applied during the main bloom season are very effective.
- Copper products may cause russetting of fruit.
- 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.