ISHS Acta Horticulturae 273: V International Workshop on Fireblight
CONTROL OF FIRE BLIGHT BY ERWINIA HERBICOLA EH252 IN AN EXPERIMENTAL ORCHARD IN DAX (SOUTHWEST OF FRANCE). |
| Authors: | J.L. Vanneste, J. Yu |
| Abstract:
Experiments conducted in an experimental orchard in Geneva (Upstate New York) showed that some strains of E. herbicola were highly effective in reducing fire blight incidence on apple blossoms (S. V. Beer, J. L. Norelli, J. R. Rundle, J. L. Vanneste, R. S. Wodzinski and C. H. Zumoff). The outcome of such experiments depends of the balance between pathogenic and saprophytic bacteria. Climatic conditions influencing this balance could determine the success of the biological control. To evaluate the role of climatic conditions in the control of fire blight by E. herbicola, we conducted in Dax (Southwest of France) a similar experiment to what has been done in Geneva (N. Y.). Usually blooming period in Dax (1st to 15th of April) is earlier than the one in Upstate New York (1st to 15th of May). Early spring in Dax is warm and humid while in Upstate New York blooming period is usually cooler and drier thus, less condusive to the growth of E. amylovora. To compare the results of this experiment with the one obtained previously in Geneva, we used the strains Ea273 of E. amylovora and Eh252 of E. herbicola that were used in the experiments done in New York. Bacterial strains were grown separately at room temperature for 48 h in Roux bottle containing King's B medium and diluted before application with RO water. Ea273 was diluted to ca. of 1.2 X108 cfu/ml and Eh252 was diluted to ca. of 3 X 108 cfu/ml. Bacterial suspensions were sprayed to run off onto 100 blossom clusters per tree. Each treatment was applied to 6 trees arranged in a randomized complete block design. The first application of E. herbicola was made when about 60% of the blossoms had opened; water and Plantomycin (streptomycin, 100 ppm), were used as negative and positive control respectively. The following day, the same blossom clusters were inoculated with Ea273. A second application of Eh252, streptomycin and water was done the third day. Four weeks after inoculation, the numbers of healthy and diseased clusters were recorded. Results are shown in Table 1. | |
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