Preliminary observations on a sustainable solution to reduce the impact of Xylella fastidiosa subsp. pauca on olive in the Salento Peninsula

The xylem-limited bacterium Xylella fastidiosa subsp. pauca is the etiological agent of “Olive Quick Decline Syndrome” (OQDS) in the Salento Peninsula on Olea europaea. NuovOlivo®, a natural bioactive detergent made from plants oils and extracts of multi botanical species (patent n. 102,017,000,109,094) was tested in the control of OQDS. The applied protocol associates spray treatments and pruning. Naturally infected 70 to 75-year-old olive trees of cvs Cellina di Nardò and Ogliarola salentina (≡ Ogliarola di Lecce) located in the province of Lecce were used. McKinney’s disease index (MKDI) was calculated using a 0 to 5 rating scale of disease severity. At the beginning of the experiments, all plants showed a MKDI of 85–95%. Treated olive trees (27 of Cellina di Nardò and 35 of Ogliarola salentina) were pruned in winter and sprayed twice per year in March and October. As untreated control plants were selected 14 and 18 trees of ‘Cellina di Nardò’ and ‘Ogliarola salentina’ respectively. After three-years, untreated plants developed leaf scorch and desiccation extending to the whole canopy, MKDI reached 98.85%. On treated plants, MKDI was 2.5% and plants produced new vegetation, flowers, and drupes. After further two years, treated plants were completely recovered. The leaves of treated plants showed a low total phenolic content and no cell membrane damage associated to lipid peroxidation. In the treated trees of both olive cultivars, qRT-PCR resulted in a 99.2% reduction of X. fastidiosa DNA level. At present, this work represents a basis for further data collection.