Xylella Fastidiosa and Olive Quick Decline Syndrome: Integrating a Decade of Research on Pathogen, Vector, Host, Microbiome and Management to Forge Sustainable Strategies

Olive Quick Decline Syndrome (OQDS), first recognized in Apulia, Italy, is associated with the nutritionally fastidious, xylem-limited bacterium Xylella fastidiosa subsp. pauca sequence type 53 (ST53), and has become a major plant-health emergency for Mediterranean perennial agriculture.

This narrative review synthesizes peer-reviewed and regulatory literature published from January 2013 to April 2026, while retaining older foundational studies required to interpret pathogen biology. Searches were conducted in Scopus, Web of Science, PubMed/MEDLINE and Google Scholar, complemented by EFSA, EPPO and EU regulatory documents. Evidence was appraised according to study type, reproducibility, field relevance and translational readiness.

The first decade of research established that OQDS is not a single pathogen-host interaction but a pathosystem involving an introduced xylem-limited bacterium, native xylem-feeding vectors, cultivar-dependent host responses, orchard context and the xylem microbiome. Genomic plasticity, biofilm formation and xylem vessel connectivity contribute to pathogen establishment and systemic movement. Tolerant/resistant cultivars such as Leccino and FS-17 show slower symptom progression and, in several studies, lower bacterial multiplication or more localized colonization through anatomical, physiological, transcriptomic, metabolic and microbiome-associated traits.

Detection has progressed from confirmatory PCR-based assays to integrated surveillance pipelines that combine risk-based sampling, high-throughput molecular tests, remote sensing, volatile organic compound profiling and epidemiological modelling. Management has shifted from emergency eradication in heavily infected zones toward context-specific integrated pest management based on vector suppression, certified plant material, tolerant/resistant germplasm, orchard hygiene, decision support and stakeholder engagement.

Durable OQDS mitigation will require diversified tolerance and resistance sources, transparent surveillance, validation of microbiome- or plant-defense-based interventions, and coordinated policies that balance phytosanitary urgency with social and economic sustainability.