NATURAL PRODUCTS ALONE OR WITH COPPER VS. GRAPE DOWNY MILDEW: EFFICACY, COSTS, CU IMPACT

Summary

In organic farming copper is one of the few fungicides that can be used and the only effective against downy mildew.
Due to the problems of environmental impact associated with the use of this heavy metal, the European Union decided to restrict its use (Annex II Regulation EC n. 889/2008). In order to assess the possibility of replacing the copper or reduce the quantities used, we tested natural products and low rate copper formulations in field trials.
The anti-downy mildew activity of these formulations has been studied in an organic vineyard. During the two years of activity we also estimated the economic cost of use of the products to assess their possible use in agricultural practice.
The examined products were:
 homeopathic products (Biplantol), tested either alone or in combination with a cupric formulation;
 potassium bicarbonate (Armicarb);
 copper hydroxide at low copper rate (Glutex).
The anti-downy mildew activity of the products tested was compared with an untreated control thesis, in order to follow the corse of infection and a Standard farm reference thesis, where the treatments were carried out according to the usual farm procedures.
The results showed that under conditions of high risk of infection, only the cupric formulations provided a reasonable anti-downy mildew protection. However at medium epidemic pressure conditions even the substances of natural origin explicated a satisfactory anti-downy mildew defence, comparable with the one obtained by the use of copper formulations.
During the first year of activity the lowest economic cost at the end of the agricultural cycle was obtained with Glutex formulation treatments.
At the end of the second year of activity, cupric formulations used on the Standard thesis ensured the lower cost; little more expensive Armicarb and Biplantol theses.
Regarding the cost-effectiveness ratio in the two years of activity the cupric formulations used on the Standard thesis shown the best result. In the second year of testing, also the other formulations tested showed a good cost-effectiveness ratio.
Moreover we have carried out analytical determinations to evaluate the impacts caused by applied copper on soil, grapes and leaves. On the plant surface, persistence of copper contained in some different formulations has been studied, too.