A decade of monitoring surveys for Xylella fastidiosa subsp. pauca in olive groves in Apulia (Italy) reveals a low incidence of the bacterium in the demarcated areas

In October 2013, Xylella fastidiosa subsp. pauca (Xfp) was reported as being associated with a decline of olive groves in Salento (Apulia, Italy) and named as “olive quick decline syndrome” (OQDS). Due to its quarantine status, a series of mandatory actions were established in the Apulia region to impede its further spread in the territory. Upon the demarcation of “containment” and “buffer” zones, monitoring surveys were carried out in these areas for sampling olive trees and other host plants that showed symptoms putatively attributable to OQDS. The eradication of plants that tested positive for Xfp, including also all the asymptomatic ones in a radius of 100 or 50 m, was performed over 10 years. An analysis, based on the official data of such surveillance activities over the period of a decade, was performed. The data show that the Xfp incidence in the “containment” and “buffer” zones is very low, especially during the last three campaigns from 2020–2021 to 2022–2023, when the bacterium was detected in a range of 0.06%–0.70% of the sampled plants. In most of the sampled trees that showed symptoms of OQDS, the bacterium was not detected. Based on these data and according to epidemiological models that verified the negligible role of asymptomatic olive trees in the spreading of OQDS, we propose to eliminate the rule requiring the uprooting of all host plants that surround one Xfp-positive tree in a radius of 50 m. Such an implementation could save many healthy centennial and monumental olive trees and the remarkable landscape that they contribute to.