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Agroscope | 2019 Organic substances against Monilia laxa on apricot – in-vitro and on-farm experiments Flore Lebleu2, Jorge Del Cueto1, Patrick Stefani2, Danilo Christen1 1Agroscope 2 , CH-8820 Wädenswil; www.agroscope.ch FiBL, CH-5070 Frick ; www.fibl.org Monilia laxa is an ascomycete causing brown rot in different important cultures, especially in Prunus genus. So far chemical products were used during flowering and harvest time to avoid the propagation of this fungus in flowers and fruits. Recently the tendency of using less and less these products and the high demand of the consumers takes to an organic or integrated production using biological agents to control this disease. In order to find some organic solutions to manage Monilia laxa, some in-vitro and on-farm tests were achieved between 2017 and 2019. On-farm trials On-farm trials were conducted in 3 locations according to GEP standards: - Agroscope-Conthey (Wallis), var. Bergeron, planted in 2013 - Vétroz (Wallis), var. Bergeval, planted in 2008 - Olsberg (Aargau), var. Goldrich and Bergarouge, planted in 2014. Products were applied during the bloom period of apricot (BBCH 53 to 69), before a wet period. Efficacies were assessed with two methods: In-vitro-tests A set of biological fungicide products were used in Petri plates with a special medium (V8-agar) where three inverted mycelial plugs of - V = visual assessment (rating on 10) - A = Agroscope method (Monilia weight / branch section) Monilia laxa were added. Plates were incubated four days at 23°C and 100,0 the growth of the mycelium was measured. Product Active Ingredient % 90,0 80,0 Oregano Oil Oregano Oil 4 Curatio Lime Sulphur Calciumpolysulfides 1.6 Vitisan Potassium bicarbonate 0.3 70,0 Sulphur Stulln Micronized sulphur 0.2 60,0 T-77 Trichoderma atroviride 0.05 Airone WG Cupric Fungicide 280 g/kg Cu 0.2 Amilo-X Bacillus amyloliquefaciens subsp. plantarum 0,16 40,0 F-aa Plant extract 0,18 30,0 Biological fungicides used in the in vitro test. Name of the product, active ingredient and recommended dosage in %. 30,0 0,0 15,0 Bergeval 2018 V Bergeval 2018 A Bergeval 2019 A Bergarouge 2019 A Goldrich 2019 A Average visuel Average Agroscope 20,0 10,0 20,0 Bergeron 2017 A Bergeval 2019 V 50,0 35,0 25,0 Bergeron 2017 V Vitisan + Sulphur Vitisan + Sulphur Stulln + Airone F-aa Vitisan + Amylo-X Vitisan + Oregano Sulphur Sulphur oil Stulln + FStulln + aa Amylo-X Curatio T-77 Efficacies (%) in comparison to untreated plot 10,0 5,0 The two methods of assessment don’t always match and the results are 0,0 fluctuating according to weather conditions and parcels. Oregano oil reached the best efficacy but was only tested one year on one parcel. Globally all others products achieved medium efficacies. M. laxa mycelium growth diameter (in mm) after application in vitro of different fungicides. Recommended concentration. The mix of Vitisan, Sulphur and Amilo-x, Oregano oil and Amylo-X alone were the products that most inhibited the mycelium growth of M. laxa. Inhibiting totally the growth of the fungus. Curatio, the mix of Vitisan, Sulphur and F-aa, T-77, the mix of Vitisan and Sulphur and Faa inhibited more than the half of the mycelium growth respect to the non treated sample. Abstract Natural substances against Monilia laxa were onfarm and in-vitro tested. According to on-farm tests, some products reached interesting efficacies. The fluctuation of the year and parcel pressures, makes it difficult to perform the results.