Pear: Pseudomonas blossom blast and dieback
Photo by: R.S. Byther
Biology
Blossom blast and dieback is caused by a bacterial infection. The infection causes buds to turn a papery brown and die. Leaves may be spotted.
Flower petals and stems may also be affected, and fruit cluster bases can turn brown or black. Occasionally, fruiting spurs may be killed. Cankers may develop in twigs and branches.
Symptoms of this disease, especially on flowers, may closely resemble fire blight. However, blast infections seldom extend more than 1″ to 2″ into a spur. Bacterial ooze, which is common with fire blight, is not present with Pseudomonas blast.
Ornamental pears and most Asian pear cultivars are also susceptible. Frost and cold injury promote infection, which is common in cold, wet springs. Warm, dry weather inhibits disease.
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!
- Prevent frost injury when possible. Plant hardy varieties in protected locations.
- Asian pear cultivars ‘Niitaka’, ‘Seigyoku’, ‘Shinseiki’ and ‘Shinsui’ have intermediate resistance.
- Prune out and destroy infected tissues as soon as they are noticed. Make cuts at least 6″ below infected areas and sterilize pruning tools between cuts.
- Provide proper culture to minimize amount of succulent shoot growth and to reduce injuries.
- Avoid wounding plants.
Chemical Management
IMPORTANT: Always read and follow label directions when working with pesticides.
For more information on using pesticides visit :
- Apply before fall rains and again before spring growth starts.
- Excessive amounts may cause fruit russet.
- 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
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.