The effect of copper reduction on the control of downy mildew in Mediterranean grapevines

Abstract The application of copper-based fungicides has led to the problematic accumulation of copper in the soil of many European vineyards. In this work, we tested the effectiveness of downy mildew control strategies that considerably reduce the amount of copper, through the application of other non-toxic compounds. The study took place in three different regions of Catalonia, by combining smaller and larger-scale trials for two growing seasons. Although variations among experiments were detected, the treatments used here may reduce the applied copper content by up to 77 percent. The cooper reduction-strategies, which alternated standard copper application of copper oxychloride with applications of products based on Equisetum arvense L., or with applications of products with heptagluconic acid (an alternative formulation with a very low-rate of copper), provided the most consistent protection against downy mildew. Moreover, these treatments reduced copper inputs by 63 and 47 percent as compared to conventional treatments based on repeated applications of copper oxychloride. This work underlines the possibility of reducing the amount of copper applied to control downy mildew in Mediterranean vineyards, through the use of newly-developed formulations.