Susceptibility of local grape cultivars to Plasmopara viticola and response to copper compounds with low cupric salt concentration in Latium (Central Italy)

The EU restrictions to the use of copper salts in organic viticulture has suggested to study the possibilities to control the fungal pathogen Plasmopara viticola with rameic compounds characterized by low cupric salts concentration and to evaluate varietal response. The trial was carried out in Latium region (Central Italy) on two local cultivars: ‘Rossetto’ or ‘Trebbiano giallo’, ‘Romanesco’ and on ‘Trebbiano toscano’ or ‘Procanico’. Three copper compounds with low cupric concentration (sulphate peptidate 5%, sulphate penthahydrate 5.5%, hydroxide peptidate 7%) were compared with copper sulphate 13%. Untreated plants of ‘Romanesco’ and ‘Rossetto’ revealed a lower susceptibility to Plasmopara viticola than ‘Procanico’. ‘Romanesco’ and ‘Procanico’ showed a better response than ‘Rossetto’ to the applied sprays. Low copper compounds efficiently protected leaves and clusters in all cultivars and prevented early leaf fall and senescence with respect to untreated plants, without phytotoxic effects. Yield and grape quality were not negatively affected by the compared treatments.