ORIGINAL ARTICLE Evaluation of copper alternative products to control grape downy mildew in organic farming Anna La Torre 1 & Lorenzo Righi 1 & Valeria Iovino 1 & Valerio Battaglia 1 Received: 4 January 2019 /Accepted: 20 May 2019 # Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2019 Abstract The aim of this work was to investigate the efficacy of copper alternative products of natural origin against Plasmopara viticola to reduce or replace the use of copper in organic farming. The identification of new active and sustainable substances is in fact of priority importance because of the environmental impact of copper. The activity of the products was investigated in laboratory and greenhouse conditions. The laboratory tests included the evaluation of the effect of products on mycelial growth, using artificially inoculated leaf disks, and on sporangial germination. The greenhouse experiments were carried out on grape seedlings cv. Malvasia di Candia treated with products and inoculated, after 24 h, with sporangial suspension of P. viticola. The results both of laboratory and greenhouse tests showed inhibitory activity performed by several botanicals (licorice leaf extract, Yucca schidigera extract), by ALD1901 product, a derivative from Saccharomyces cerevisiae yeast, by Vacciplant formulation con- taining laminarin and by inorganic products as potassium hydrogen carbonate and MenoRame formulation based on micro-doses of copper and zeolites. The identification of sustainable approaches to manage grape downy mildew is very important to enhance the quality of organic production. Keywords Plant protection products . Natural products . Cu . Vitis vinifera L. . Plasmopara viticola Introduction Plant health in organic farming is based on measures that prevent pests, diseases and weeds. Plant protection prod- ucts are only permitted if their use is essential to control a harmful organism or a disease (Council Regulation EC No 834/ 2007). Plant protection products authorized for or- ganic production are included in a restricted list (Annex II of Commission Regulation EC No 889/ 2008). Copper is the most effective substance allowed to control phytopath- ogenic oomycetes, fungi and bacteria in organic farming, but considering its environmental impact due to its ten- dency to accumulate in the soil (Flores-Vélez et al. 1996; Leonardi et al. 2002; Komarek et al. 2010) and the harm- ful effects on human or animal health (Dorsey et al. 2004; Gorell et al. 2004; Santić et al. 2005; Oruc et al. 2009; Komárek et al. 2010; Klein 2011; Lencioni et al. 2016; Tóth et al. 2016; La Torre et al. 2018), the use of this heavy metal should be minimized or alternative options, compatible with the objectives and principles of organic production, should be identified. Consequently, the condi- tions for using copper in organic farming have been re- stricted by the European Commission since 2002 by fix- ing a ceiling on use expressed in term of kilograms of copper per hectare and year (Commission Regulation (EC) 473/ 2002 ). Subsequently, the European Commission further reduced the maximum copper amount allowed for plant protection to 28 kg ha -1 over a period of 7 years (i.e. on average 4 kg ha -1 year -1 ) (Commission Implementing Regulation (EU) 2018/1981). Copper is mainly used in viticulture to control Plasmopara viticola (Berk. & M.A. Curtis) Berl. & De Toni, one of the most destructive diseases of the grapevine responsible for sig- nificant economic losses. Our research thus aimed to eval- uate the efficacy of natural products to reduce the copper dependence of organic winegrowers. * Anna La Torre anna.latorre@crea.gov.it 1 CREA - Council for Agricultural Research and Economics - Research Centre for Plant Protection and Certification, Via C.G. Bertero 22, 00156 Rome, Italy Journal of Plant Pathology https://doi.org/10.1007/s42161-019-00330-6