Development and Evaluation of a Warning Model for the Optimal Use of Copper in Organic Viticulture

Downy mildew caused by Plasmopara viticola is one of the most serious diseases affecting grapevine worldwide, and can significantly affect crop quality and quantity. In organic viticulture, downy mildew control is mainly based on copper compounds, which are toxic to organisms in the soil. For this reason, restrictions concerning the maximum amount of copper that organic growers can apply per hectare have been enacted in several countries. We have developed a warning model and a decision-making procedure to help organic grapevine growers optimize their use of copper against downy mildew. This system is based on treating vines with a variable rate of copper when there is an immediate risk of infection and the vegetation is not sufficiently protected by previous treatments. In 2007, the warning model and the decision-making procedure were tested in two vineyards in northern Italy and compared with the local common practice and an untreated control. The treatment timings and copper application rates recommended by the system resulted in control of downy mildew equivalent to that associated with the common practice, but with a considerable reduction in the total amount of copper applied. RI Pertot, Ilaria/B-9521-2011