S14 - Session O2 - Synthesis of 4 years of evaluation of natural substances in the control of apple scab with a view to reduce copper doses

Authors: Anne Duval-Chaboussou *

Among the bio-aggressors of fruit trees, the fungus Venturia inaequalis (Cooke) Winter, agent of apple scab, is one of the most dreaded. This disease is the main phytosanitary concern of French and European apple growers. Treatments targeting this disease represent nearly 50% of all phytosanitary applications on apple, so between 15 to 20 per year. To date, the organic scab management strategy is based on scab resistance varieties and fungicide treatments, in particular copper. This substance is classified as a "candidate for substitution" at European level and is registered until 2025, so it is urgent to find alternatives. Different types of natural substances (plant extracts, micro-organisms, mineral substances) were evaluated on apple scab, with or without added copper, during 4 years (2018 to 2021). Some substances allow to reduce and/or to replace copper, particularly on low and medium contaminations. Furthermore, there is variability in the effectiveness of some of these substances according to the type of organ (leaf/fruit). The use of the "qPFD" tool helps to identify natural substances with a defence-stimulating action and to improve their positioning in a treatment strategy. Finally, the use of decision support tools is central to create effective strategies without copper.