Efficacy evaluation of copper formulations for the control of lettuce downy mildew (Bremia lactucae)

Summary

A four-year field trial was run to determine the effectiveness of copper fungicides and foliar fertilizers in controlling lettuce downy mildew (Bremia lactucae Regel) in Italy’s Emilia-Romagna Region. The experimental design was randomized blocks with 4 replicates using the highly susceptible Camaro cultivar. Eleven different fungicide formulae and foliar fertilizers with low copper concentration were compared. Tribasic copper sulphate (Cuproxat S.D.I.), copper sulphate (Poltiglia Caffaro 20) and copper oxychloride (Pasta Caffaro Nc) exhibited the best control; the effects of pentahydrate sulphate (Kay Tee) and hydroxyde (Kocide 2000) were less consistent. Hydroxide sulphate (Poltiglia disperses), tribasic sulphate (Cuproxat liquido) and the Special Kopper were less effective. The action of the foliar dressings Kendal TE, Fertileader rame and Labicuper showed the most promising results. The only non-copper-based alternative product, grapefruit seed extract, or DF 100 V, proved to be ineffective. Some of the tested foliar sprays were thus as effective as some copper-based fungicides and released less copper into the environment.