Fire blight has become increasingly common in Germany in recent years. The disease shows typical symptoms on medlar. Some measures prevent infection.
Fire blight can be recognized by black spots on the leaves
pathogens and symptoms
Fire blight is caused by the bacterium Erwinia amylovora. It spreads to rose plants that develop pome fruit. Dried flowers and leaves as well as black shoots and branches indicate a disease with the bacterium. When it gets into the plant organism, it clogs the pathways. As a result, leaves, flowers and branches get neither water nor nutrients, which leads to the death of the tissue.
infection
The bacterium spreads in rain and wind. It can be transmitted from flower to flower by insects. The flowers, open areas on the branches and wounds on the fruit serve as entry points for the pathogen. Another possibility of infection is via the respiratory openings on the underside of the leaf, which lead into the ducts. The risk of infection depends on the age and health of the medlar. Young bushes are very vulnerable.
The pathogen survives in the bark of diseased and weakened trees. From spring to autumn there is a risk of infection for other rose plants. Temperatures of over 18 degrees Celsius and humidity of more than 70 percent favor the living conditions of the bacterium.
treatment
The disease ends fatally in most cases, since there are currently no treatment methods. At the first sign of illness, the affected areas should be removed immediately. Once the main stems are infested, the entire plant must be uprooted. Small amounts of leaves and branches are disposed of with the residual waste. If larger branches or plants need to be burned, you need a permit. The responsible office will explain exactly how to proceed in this case.
You can do this preventively:
- do not plant fireblight host species
- avoid over-fertilizing with nitrogen
- find the optimal location for the photinia
obligation to report
Fire blight is a reportable quarantine disease. As soon as there is a suspicion of infection, you must report to your state office or to the state institute for agriculture. Samples are collected from the infested plants and examined in the laboratory. If the bacterium has been detected, the office decides on further measures. They warn surrounding fruit farms of the increased risk of infection.