The olive oil production chain generates large quantities of waste with a high polyphenolic content that can be valued for protection against fungal diseases in viticulture. In this work, we evaluated the effects of two different experimental extracts (olive mill wastewater and olive leaf decoction) against downy mildew, observing the possible impact on the vine physiology and grape quality at once. The experimental trial was set up in Arezzo (Tuscany, Italy), in a cv Merlot vineyard, where three different pest management strategies were compared for three years (2020-2022). During the vegetative season, downy mildew symptoms on leaves and clusters were monitored. Physiological measurements were carried out on the vines before and after the treatments. At harvest, yields were quantified, and the technological maturities and polyphenol contents of the grapes were assessed. According to the results, the antioxidant properties of the polyphenol extracts added to the phytosanitary treatments with significantly lower amounts of copper limited the infections caused by downy mildew without influencing the physiological and productive capacities of the vines and without altering the grape characteristics.
Zombardo et al. (Wed,) studied this question.