- Apple and pear trees
- Other plants in the Rosaceae family producing a type of fruit known as a pome fruit: serviceberry, flowering quince, hawthorn, loquat, flowering almond, plum and cherry, rose, and spirea.
- The tree’s branches will not only blacken but also droop rapidly as if scorched by fire (hence the name fireblight).
- Additionally, the bark at the base of infected twigs will become water soaked, then dark, sunken and dry, with cracks developing at the edge of the sunken area.
- Other signs include wilted shoots, well-defined areas of burnt-looking, dead foliage or bark, and sticky amber ooze.
- The damage mostly happens during warm, rainy spring weather.
- Fireblight bacteria overwinter between live bark tissue and the tissue killed the previous season.
- Additionally, the bacteria can enter through openings such as flowers and wounds in the spring.
- Then rain, wind, and pruning tools can spread the disease to other plants.
- Finally, in the spring, the bacteria ooze out of the cankers and attract bees and other insects which also spread the disease.
Treatment and Management
- Firstly, do not grow your fruit trees on poorly drained, highly acidic, or over fertilized soils.
- Secondly, if you see infected twigs, cut them off in the early spring at least 8 inches below the damaged area.
- Additionally, if you prune in the summer, disinfect your pruning tools with denatured alcohol or a 10 percent bleach solution between each cut. This will prevent the spread of the disease to other areas.
- Thirdly, plant resistant varieties.
- Some resistant pear varieties include Kieffer, Moonglow, Orient, and Seckel. In fact most other pear varieties are very susceptible to fireblight.
- Resistant apple varieties include Enterprise, Freedom, Liberty, Prima, Priscilla, Adams, Dolgo, Jewelberry, and Liset. Susceptible apple varieties include Idared, Jonagold, Jonathan, Lodi, Crispin (Mutsu), Greening, Paulared, Rome, Sir Prize, Spigold, Twenty Ounce, York and Gala.
- Lastly, if during the flowering and leaf emergence period there is warm, humid, and wet weather, then you can spray preventively with fungicides which contain basic copper sulfate (Kocide) or an antibiotic (Agrimycin).
- At the start of the blooming period, spray the Agrimycin and continue every 3-4 days during the bloom period.
- If you are spraying Kocide, then also begin at bloom and continue every 7 days during bloom. If it rains, then you can spray again.