The casual agent of fire blight is a bacterium– Erwinia amylovora, which causes a vascular wilt in many varieties of pome trees: apples, pears, and ornamental pears, such as Bradford pears planted in many landscapes.

 Symptoms:

• Water-soaked flowers
• Leaves progressively turning brown and black blotches; curling and eventually shriveling
• Twigs begin to wilt from tip downward, turning black and curl in a classical “Sheperd’s hook”
• Branches develop dark, sunken cankers; as they enlarge and girdle the branches, the branch eventually dies.

Disease Cycle:

• The bacteria over-winters in cankers, bud scars and branches.
• Bacteria forms ooze which attracts insects and the insects then spread the bacteria via the nectarthodes in the flowers.
• The bacteria can also be spread by splashing rain.
• The bacteria can infect leaves and new tender succulent twigs.

 

Control:

• Sanitation pruning during winter dormancy – Cut an infected branch 8 to 12 inches below the visible injury or canker. To avoid spreading bacteria during pruning, sanitize the
• pruning tool before each cut with a 10% solution of bleach (one part bleach to nine parts water). To prevent rust, dry and oil tools after use.
• Reduce excessive succulence.
• Moderate resistant varieties are available.
• A weak (0.5%) Bordeaux mixture or other copper fungicide applied several times as blossoms open can reduce new infections, but will not eliminateall new infections or those already existing in wood.

 

 

Prepared by Sheila McBride¹ and Dr. David Appel²
Diagnostician, Texas Plant Disease Diagnostic Laboratory¹ and Professor of Plant Pathology and Microbiology²
Texas AgriLife Extension Service; The Texas A&M University System
April 10,2010 (Rev. 04112012)

 The information given herein is for educational purposes only. References to commercial products or trade names are made with the understanding that no discrimination is intended and no endorsement by Texas AgriLife Extension Service personnel is implied.

Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national origin.
The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Courts of Texas Cooperating