Biological control of strawberry diseases by Aureobasidium pullulansand sugar beet extract under field conditions

Grey mould (caused by Botrytis cinerea) is the most important pathogen underlying high fungicide dependence in strawberry fields. Reliable biocontrol agents (BCAs) with improved efficiency are needed to replace fungicides. The yeast-like beneficial fungus Aureobasidium pullulans(AP-SLU6) has previously exhibited great potential to combat grey mould in greenhouse environments. Here we report results from a two-year full-factorial field trial in a conventional strawberry field, in which we tested two different concentrations of A. pullulans(107CFU/ml and 106CFU/ml) and sugar beet extract (SBE). The results showed that all the field treatments reduced grey mould severity postharvest and increased shelf life of the harvested fruit in both years. The best effect was achieved using the highest conidial concentration of A. pullulans, which also resulted in 53% higher fruit production compared to the control treatment at the end of the season, indicating a plant-growth promoting effect of the BCA. These results reveal that spray applications of these novel BCAs contribute to reliable biocontrol of grey mould, leading to improvement of the shelf life of strawberry sales boxes. These findings suggest that A. pullulansand SBE can contribute to a shift from chemical fungicides to sustainable methods without compromising cropping security.