Xylella research yields practical tools to protect olive groves

Research on Xylella fastidiosa has reached a more advanced stage, with new findings on olive resistance, biological control, insect vector management and surveillance now offering practical guidance for policymakers and growers, according to the European Food Safety Authority at the close of its fifth European conference on the pathogen in Mola di Bari, Italy.

The three-day meeting ended Thursday after bringing together about 400 researchers, policymakers and industry stakeholders from Europe and other regions. EFSA organized the event with the Horizon Europe project BeXyl, the research network EUPHRESCO III, CIHEAM Bari, the Italian National Research Council’s Institute for Sustainable Plant Protection and the plant health service of Italy’s Puglia region.

The conference reviewed more than a decade of research since Xylella fastidiosa subsp. pauca was identified as the cause of olive quick decline syndrome in Apulia, where it severely damaged ancient olive groves. Sessions focused on olive host resistance, biological and integrated control methods, vector biology and management, epidemiological modeling, surveillance, Pierce’s disease in grapevines, and the social and economic effects of the epidemic on farming communities.

EFSA said one of the main milestones this year was the first conference session dedicated specifically to olive resistance. Research presented there examined the genomic and molecular basis of resistance in olive cultivars, long-term field studies on how cultivars respond to infection, and newer approaches including genome editing and microbiome analysis. The agency said those lines of work point to a pipeline of tools that could support the recovery of olive growing in affected areas.

Giuseppe Stancanelli, team leader for plant health risk assessment at EFSA, said the conference showed both the scale of scientific work on Xylella fastidiosa and its growing practical value for preventing, detecting and managing outbreaks while supporting sustainable agriculture. Blanca Landa of the Spanish Institute of Sustainable Agriculture, who served as scientific co-chair, said progress in understanding the bacterium has advanced significantly but still depends on continued cross-border and cross-disciplinary cooperation.

Alongside the scientific sessions, plant health services from Italy, Spain, France and Portugal held a roundtable on more than a decade of European Union policy implementation under the bloc’s Xylella rules. Participants also visited affected areas in Apulia to review eradication, containment and olive sector recovery efforts on the ground.

EFSA said it will open a public consultation in the coming weeks on the latency and incubation period of Xylella fastidiosa. It will also issue a call for data on pest occurrence to support climate suitability assessments. The agency plans to publish an updated EU pest risk assessment by the end of 2026, revising its 2019 scientific opinion with evidence gathered in recent years.

Xylella fastidiosa is spread by sap-feeding insects and can infect hundreds of plant species. In Europe, EFSA said X. fastidiosa subsp. pauca has caused major losses in olive production in southern Italy, while other subspecies threaten grapevines, almonds, ornamental plants and forest species. The bacterium is classified as a priority quarantine pest under EU plant health law.

That makes the new scientific review relevant beyond olive farming. Because one form of the pathogen causes Pierce’s disease in grapevines, any changes in surveillance standards, climate suitability assessments or EU risk evaluations could affect how wine regions monitor vineyard health and prepare for future outbreaks.