What is Fire Blight?
Fire blight is a serious bacterial disease that affects many members of the rose family, especially fruit trees like apples and pears. It is caused by the bacterium Erwinia amylovora, which infects blossoms, shoots, and branches, giving affected plant parts a scorched or “burned” appearance—hence the name.
Fire blight spreads most easily during warm, wet, or humid spring weather. Commonly affected plants include apple, pear, crabapple, quince, hawthorn, serviceberry, cotoneaster, and pyracantha. Some varieties within these species are more susceptible than others.
Life Cycle
The fire blight bacterium overwinters in cankers—sunken, discolored areas on branches created by previous infections. In early spring, as temperatures rise, the bacteria begin to multiply and produce a sticky, amber-colored ooze. This ooze attracts insects that help spread the bacteria to new blossoms.
The disease first infects blossoms, then moves into shoots and branches. Wind, rain splashes, and pruning tools can all spread the bacteria. Fire blight develops most aggressively when daytime temperatures are between 75–85°F and humidity or rainfall is high.
If cankers remain on the tree after the growing season, they allow the disease to persist and restart the cycle the following spring.
Symptoms
Early Stage
- Water-soaked blossoms that quickly wilt and turn brown or black
- Slight curling or shriveling of new shoots
- A “shepherd’s crook” bend at the tip of young twigs
- Sticky bacterial ooze on infected blossoms or twigs
Middle Stage
- Leaves turning dark brown or black but remaining attached to branches
- Rapid shoot blight—entire young shoots collapse and die
- Spreading discoloration along stems and branches
- Formation of sunken, reddish cankers where infected tissue meets healthy wood
Late Stage
- Large sections of branches die back
- Extensive canker formation that girdles branches or trunks
- Reduced fruit production or fruit shriveling
- Possible death of young trees if the trunk becomes infected
How to Control Disease Progression
Managing fire blight requires quick action and consistent prevention. Because it is a bacterial disease, it can spread rapidly during warm, wet periods.
- Prune out infected branches immediately, cutting 8–12 inches below visible symptoms.
- Disinfect pruning tools between cuts with a 10% bleach solution or 70% alcohol.
- Avoid heavy pruning during warm, wet weather, when bacteria are most active.
- Remove and destroy infected plant material—do not compost it.
- Reduce nitrogen fertilization, which encourages tender new growth that is more susceptible.
- Improve air circulation by removing crossing branches and maintaining proper tree spacing.
Treatment Options
Treating fire blight involves both physical removal of infected tissue and, in some cases, the use of protective sprays.
Organic Treatment Methods
- Pruning out infected branches during dormant season to remove overwintering cankers.
- Applying copper-based sprays in early spring to help reduce bacterial populations.
- Encouraging overall plant health with proper watering, mulching, and soil care.
Chemical Treatment Options
Antibiotic sprays such as those containing streptomycin may be recommended in some regions for high-risk periods during bloom. Copper sprays can also be used but may cause leaf spotting if overapplied. Always follow local guidelines and product labels.
Step-by-Step Treatment Procedure
- Inspect the tree carefully for wilted blossoms, blackened shoots, or cankers.
- Prune out infected wood, making cuts well below the diseased area.
- Disinfect pruning tools between each cut.
- Apply recommended sprays only during bloom, following timing instructions closely.
- Monitor trees weekly during warm, wet spring weather.
Expected Timeline for Recovery
Trees often show improvement within a few weeks after infected tissue is removed, but full recovery may take an entire growing season. Severely infected trees may need multiple years of careful pruning and management, and in some cases may not recover.
Prevention Strategies
- Select fire blight–resistant apple and pear varieties whenever possible.
- Plant trees with adequate spacing to promote airflow.
- Avoid excessive nitrogen fertilization, which produces susceptible new growth.
- Prune during dry winter weather rather than in spring whenever possible.
- Keep tools clean and disinfected, especially when pruning rosaceous plants.
- Remove root suckers and water sprouts, which are highly susceptible to infection.
- Monitor trees regularly during bloom season and act early if symptoms appear.
