New approaches in biological control of apple scab

Apple scab caused by Venturia inaequalis is a major disease in apple production. In organic farming scab control depends on the use of fungicides based on copper or sulphur. Since the use of copper will be restricted in the European Union and the use of sulphur often leads to insufficient control and phytotoxicity, alternative control measures are needed. The use of microbial antagonists may be an alternative to fungicides for scab control. Scab epidemics during summer are driven by conidia produced only on apple leaves. In this situation, antagonists present in the phyllosphere may interfere with conidia of the pathogen during sporulation or infection. Within the EU-funded project REPCO, more than hundred fungi were isolated from sporulating scab colonies and tested on apple seedlings for their potential to reduce sporulation of the pathogen. Since the aim of the study was to contribute to the development of a biocontrol product, only candidates were selected which fulfilled a range of additional criteria considering major constraints in development of biocontrol products. The best antagonists were applied under orchard conditions during two growing seasons. The antagonist H39 significantly reduced sporulation of V. inaequalis after most applications. However, in a few cases no effect was found.