Fire blight
Fire blight / Erwinia amylovora
Flower infection
During the blooming period, under certain conditions (temperature, humidity), flowers grown outdoors may become infected with the fire blight pathogen Erwinia amylovora. Symptoms can be identified a few days later by the presence of oozing droplets on the flower. The company Bio-Protect has developed a flower test that allows preparations to be tested in the laboratory for their efficacy against the pathogen. The flower test simulates flower infection as it occurs in the field, thus providing the best possible approximation of an active ingredient’s potential efficacy under natural conditions.
An apple blossom infected with fire blight, with droplets of mucus.
Test system
Apple blossoms are placed in a sugar solution and inoculated with a fire blight bacterial suspension. One hour later, the blossoms are sprayed with the active ingredient at the desired concentration. The blossoms are then incubated at 20–23°C and 100% relative humidity. After six days, the number of blossoms with bacterial slime is determined, and the treatment’s efficacy is calculated. Efficacy is defined as the reduction in the number of infected blossoms compared to the control group treated with water. The test is conducted four times for each active ingredient.
An in vivo test system for evaluating the efficacy of formulations against the fire blight pathogen E. amylovora.
A: Apple blossoms were placed in a sucrose solution and incubated at 100% humidity.
B: Uninfected blossom after 6 days of incubation.
C: Blossom showing symptoms of fire blight. Bacterial ooze is oozing from the flower stalk (arrow).
Correlation between the efficacy of 34 fire blight control products in a flower test and their efficacy in the field. The orange dot represents Blossom Protect+Buffer Protect, and the red dot represents streptomycin sulfate.
Shake cultures
To assess the direct efficacy of a preparation against the fire blight pathogen, we conduct tests in shaking flasks. In this procedure, medium in Erlenmeyer flasks is inoculated with the pathogen, and the preparation is added at the appropriate concentration. After one day in a shaking water bath, the growth of Erwinia amylovora in the test sample is examined and compared to a positive control that was inoculated but did not receive the preparation. Of course, it is also possible to assess the antagonistic potential of microorganisms against fire blight. The growth factor is determined via photometric measurement or analysis using real-time PCR.