RESUMO
Few active substances with fungicide activity can be used in organic farming, above all copper and sulphur. The copper is the only substance that can be used against downy mildew; however, since it causes problems of environmental impact, incompatible with organic farming's objective of environmentally friendly farming, the Commission of the European Communities has fixed a ceiling on use expressed in terms of kilograms of copper per hectare per year (Regulation EC n. 473/2002). In order to identify natural products that are able to carry out an anti-downy mildew activity, and to evaluate the effectiveness of low rate copper formulations that can reduce the quantities of copper compound, four-year experimental trials were carried out in organic vineyards. The trials have been carried out according to the Guidelines EPPO/OEPP PP 1/31 (3). Among the low rate copper formulations, copper hydroxide and copper sulphate have been tested. Among the natural substances alternative to copper formulations we have tested: phytostimulant, homeopathic products, acid clay-based products (bentotamnio), resistance promoters (chitosan and lignosulfonate), plant extracts (orange extract, propolis and equisetum) and potassium bicarbonate. All natural substances, with the exception of plant extracts and potassium bicarbonate, were tested in association with low rate copper formulations. In the trials it has been possible to test the effectiveness of different formulations in condition of high, medium and low pressure of Plasmopara viticola (Berk. et Curt.) Berl. et De Toni. Both the copper compounds and the natural products were able to guarantee a satisfactory protection in condition of low and medium pressure of downy mildew. The trial carried out in 2004 was characterized by high pressure of P. viticola; under this condition only the copper formulations produced a satisfactory protection against downy mildew. However, in 2004, we tested only two products alternative to copper compounds. Further studies are needed to verify if the formulations alternative to copper, that gave good results in condition of low and medium pressure of P. viticola, are able to guarantee a satisfactory protection even in condition of high pressure of downy mildew. We would like to highlight that in the four-years of trials the copper formulations tested always guaranteed a metallic copper quantity under 6 kg/ha that is the maximum limit of use/year imposed by Regulation EC n. 473/2002.