Organic viticulture: efficacy evaluation of different fungicides against Plasmopara viticola

The restriction on the use of copper salt fixed by the European Community (Reg. EC n. 473/2002) owing to the environment problems due to the copper accumulation in the soil, has stimulated the research to evaluate the possibility to reduce the copper use. This field experiment was carried out to estimate, in an organic vineyard, the effectiveness, against Plasmopara viticola (Berk. et Curt) Berl. et De Toni, of copper compounds at a low rate or alternative copper products. Guideline EPPO/OEPP PP 1/3 (2) has been used. Plots of 18 plants each, repeated 4 times in a randomized design, have been arranged. The obtained results, even if related to circumscribed and extremely favorable field for the development of the grapevine downy mildew, evidenced the impossibility to practice a defense to fixed cadence, succeeding, at the same time, to respect the limits of European Community for copper metal. The reference product, that has guaranteed the best results, determined a total contribution of copper metal of 25.7 Kg/ha that leaves very little possibilities of copper use in the following years, like previewed from the Reg. EC n. 473/2002; therefore a strategy of defense of this type turns out as not usable. The two cupric products characterized by the low metallic content were not completely satisfactory in our operating conditions with high pressure of grapevine downy mildew, but they determined a contribution of copper metal under the limits established by the European Community. Therefore new experiments, using differentiated strategies, should be carried out to improve the effectiveness of these fungicides. About biofungicide, it gave total absence of biological activity against P. viticola. The limits of the used formulations regarding the operating protocol applied, are evidenced, for some of them, by epidemiological results, for the others by the high amount of distributed copper, that causes an accumulation of residual in soil and leaves. Through the examination of the results and considering the particular climatic condition that characterized 2002, we can conclude that the trial must be considerate valid for the stressful situations that affected the vineyard.