Investigations on alternative substances for control of apple scab - Results from Conidia germinating tests and experiments with plant extracts

Summary in the original language of the document

The intention of this research project, which was supported within the "Bundesprogramm Ökologischer
Landbau", was to find alternatives for the control of Venturia inaequalis for the organic fruitgrower.
Beside the investigations on reducing the ascospore potential on fallen leaves, experiments
were conducted in laboratory, greenhouses and in orchard to test direct control of scab with different
plant extracts, concentrations and methods of extraction. Extracts from Inula viscosa, Quillaja
saponaria-bark, citrus-species (AGROMIL) and Saponaria officinalis revealed a distinct efficacy
against apple scab in greenhouse studies on apple seedlings. ELOT-VIS, CHITOPLANT, COMCAT,
MOOSEXTRAKT, SILIOPLANT und FZB 24 did not show sufficient efficacy with the application schedule
used for control of scab. Mixtures of Quillaja-saponine and sulphur reduced effectively apple scab
incidence. In an experiment concerning rain stability Citrus-extract and Quillaja-saponine showed a
lower efficacy against scab after a simulated rain of 5 mm. The screening of different supplements
to Citrus-extract as surfactants and adhesives revealed GREEMAX and BIOPLUSS as promising additives.
Both combinations showed an efficacy comparable to copperoxychloride corresponding to
400 g elementary copper per ha.