Exploring a sustainable solution to control Xylella fastidiosa subsp. pauca on olive in the Salento Peninsula, Southern Italy

The effectiveness of NuovOlivo®, a natural detergent made from plants oils and extracts of multi botanical species plus sodium and calcium hydroxide, and sulphur, activated with sodium bicarbonate (patent n. 102017000109094 Ministero dello Sviluppo Economico, Italy) was tested in the control of Olive Quick Decline Syndrome associated with Xylella fastidiosa subsp. pauca. Tests were conducted in two naturally infected olive groves located in the province of Lecce, Apulia, Italy). The first experiment included 70 to 75-year-old olive trees cv Cellina di Nardo, in Montesano Salentino. Here the percentage of McKinney's disease index was reduced to 2.5% and plants produced drupe fruits after seven treatments. Olive trees were sprayed twice per year (in March and October) and pruned in winter. The second experiment included 60 to 65-year-old olive trees cv Ogliarola salentina growing in Sternatia which initially showed a disease index of 90.88%. This figure was reduced to 4.0% after two years of three spray treatments. In both olive cultivars, qRT-PCR resulted in lower levels of X. fastidiosa DNA in the treated trees. The leaves of treated plants showed a low total phenolic content and no cell membrane damage associated to lipid peroxidation and electrolyte leakage. NuovOlivo® works as a curative product limiting and/or stopping the destructive epidemic caused by this bacterium.