Gesellschaft für Phytopathologie mbH Konstanz

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Fire bligth / Erwinia amylovora

Disease lexicon


Blossom infection

During the flowering season, the fire blight pathogen Erwinia amylovora can infect blossoms outdoors under specific conditions (temperature, humidity). The symptoms can be recognised by ooze drops emerging on the blossom a few days later. The company Bio-Protect has developed a blossom test that makes it possible to analyze preparations for their efficiency against the pathogen in the laboratory. The blossom test simulates a blossom infection just like it occurs outdoors and so results in the best possible approximation of the potential efficiency of an agent under natural conditions.

Fire blight infected apple blossom with ooze drop.

Test system

Apple blossoms are placed in sugar solution and inoculated with a fire blight bacteria suspension. One hour later, the blossoms are sprayed with the agent in the desired concentration. The blossoms are then incubated at 20-23°C and a relative humidity of 100%. After six days, the number of blossoms with bacterial ooze is determined and the efficiency of the treatment is calculated. The effect is described by the reduction in infected blossoms compared to the variant treated with water. The test is carried out four times for each agent.

In vivo test system for investigating the efficiency of microorganisms on the fire blight pathogen E. amylovora.

A: Apple blossoms were placed in sucrose solution and incubated at 100% humidity.
B: Non-infected blossoms after 6d incubation.
C: Blossom with symptoms of fire blight. Bacterial ooze is leaking from the peduncle (arrow).

Shake culture

In order to test the direct efficiency of a preparation against the fire blight pathogen, we perform tests in shaking flasks. In doing so, the medium in the Erlenmeyer flask is inoculated with the pathogen and the preparation added in the desired concentration. After one day in the shaking water bath, the growth of Erwinia amyovora in the test batch is compared to a positive control that has simply been inoculated. Naturally, it is also possible to check the antagonistic effect of microorganisms against fire blight. Determination of the growth factor is carried out by means of a photometric measurement or an analysis using real time PCR.