Efficacy and residue field trials of different copper rates on soft fruits

In 2009, efficacy and residue field trials using different copper rates and formulations were carried out in Trentino region (North-eastern Italy). In a blackberry and a red currant orchard, the following treatments were applied: three copper rates (99, 62 and 37g/hl of metallic copper) of a commercial product containing copper sulphate, one formulation based on copper oxychloride (76g/hl of metallic copper) and a foliar fertilizer containing copper (15g/hl of metallic copper). Untreated plots were used as control. Copper residues on ripe fruits were analysed. Incidence of downy mildew (Peronospora sparsa) and anthracnose (Drepanopeziza ribis) was evaluated for blackberry and red currant, respectively. Five applications of the different copper treatments were made on red currant during the growing season. Analysis of copper residues on berries showed the overcoming of the MRL for the treatments with the higher copper concentration (99, 76, 62g/hl of metallic copper) while only the treatments with 37g/hl and 15g/hl remained below the limit of 5mg/kg. On blackberry, seven applications were sprayed and the copper residues resulted below the MRL of 5mg/kg in all the treatments. In 2009, both anthracnose and downy mildew showed generally a low rate of incidence, nevertheless all the copper treatments significantly reduced the disease development compared to the untreated plots. No clear differences resulted between treatments with high and low copper rates and even strategies with reduced copper doses were effective to control the target pathogens.