MORE RESULTS OF TESTING CONTROL AGENTS FOR FIRE BLIGHT IN THE FIELD WITH A NEW EXPERIMENTAL DESIGN

In Germany, streptomycin has been allowed under strict regulations for control of fire blight since 1994. However, the registration of streptomycin in future is uncertain and alternatives are urgently needed.
To be able to give recommendations to the growers, which are based on experimental data, the plant protection service performs field trials.
A new experimental design was developed with which reproducible results were obtained under almost natural conditions over six years.
One tree in each plot was artificially spray-inoculated with a suspension of Erwinia amylovora (10⁸ cfu/ml) during full bloom.
The trees left non-inoculated were exposed to secondary infection by natural means like wind, rain or blossom visiting insects from the directly infected trees.
At a second location the trial was performed with trees planted not in soil, but in pots.
Similar results were obtained over two years.
Secondary infection of non-inoculated trees was in the range of 7 to 27% infected blossom clusters and resembled the incidence of infection under natural conditions.
The efficacy of the reference product streptomycin was 68 to 92%. The compounds tested were several biological control agents, systemic acquired resistance inducers and bactericides.
As yet only a yeast product had an efficacy that was almost as high as that of streptomycin.
Further experiments will be necessary before commercial use.

X International Workshop on Fire Blight

E. Moltmann, A. Fried, A. Seibold, E. Lange

Erwinia amylovora, apple, biological control, systemic acquired resistance inducers, bactericides

https://doi.org/10.17660/ActaHortic.2006.704.35