Development of a strategy for fire blight control in organic fruit growing

Summary

Effective control strategies are needed in organic fruit growing to prevent blossom infections by the fire blight pathogen Erwinia amylovora. There are many potential control agents under discussion. 18 preparations have been tested for their efficiency against Erwinia amylovora. Twelve of them were highly effective against E. amylovora in vitro. Nevertheless only five of them led to a symptom reduction of more than 50% on de-tached apple blossoms. These results and data on field performance from the literature indicate that Blos-som-Protect is the most effective preparation to prevent blossom infections by fire blight. Therefore further experiments have been performed to develop a strategy for the use of Blossom-Protect in organic fruit grow-ing. The side effect of Blossom-Protect on fruit russeting was tested in two field trials in 2005. No increase of fruit russet was detected in the varieties `Jonagored` and `Golden Delicious` after 2 or 3 applications of Blossom-Protect during bloom.