Global and European Status and Response to the Plant Pathogen Xylella fastidiosa and possible biocontrol solutions
- Stanislav M.
- Jun 27
- 6 min read
Xylella fastidiosa (Xf) is a vector-transmitted bacterial pathogen that poses a significant threat to global agriculture and ecosystems. The bacterium colonizes the xylem vessels of plants, which are responsible for water transport. This colonization leads to blockage, causing symptoms such as leaf scorching, desiccation, and ultimately, plant death. It is the causal agent of numerous severe plant diseases, including Pierce’s disease in grapevines, citrus variegated chlorosis in citrus, and Olive Quick Decline Syndrome (OQDS) . The pathogen's spread has resulted in an estimated annual economic impact of €5.5 billion in Europe alone.
Global Distribution and Spread
Historically considered a pathogen confined to the Americas, Xylella fastidiosa has overcome geographical barriers, likely through the global trade of plant materials, and is now established in multiple countries across Europe and Asia.
Americas: The bacterium is widespread throughout North, Central, and South America, where it affects a wide range of crops and native plants.
Asia: In recent years, Xf has been reported in several Asian countries, including Iran, Israel, and Lebanon.
In 2024, first reports emerged from continental China and in 2025 from Iraq and Colombia.
A distinct but related species, Xylella taiwanensis, is known to cause pear leaf scorch in Taiwan, where X. fastidiosa subsp. fastidiosa is also present.
Europe: The pathogen was first detected in the European Union in 2013 in Apulia, Southern Italy. This constituted a major change in its known geographical distribution.
The European Outbreak
The arrival of Xylella fastidiosa in Europe has had a devastating ecological and economic impact, particularly in Southern Italy's olive industry, where OQDS has led to the death and uprooting of millions of olive trees.
Pathogen Subspecies and Vectors
Of the six known subspecies of X. fastidiosa worldwide, four have been recorded in Europe: fastidiosa, multiplex, pauca, and sandyi .
Transmission within Europe is primarily attributed to insects of the Aphrophoridae family (spittlebugs).
While the primary vectors in the Americas are sharpshooter leafhoppers (subfamily Cicadellinae), in Europe the meadow spittlebug, Philaenus spumarius, is the main confirmed vector.
This species is common, widespread, and feeds on a wide variety of plants, making it a highly effective transmitter.
Neophilaenus campestris is also a confirmed vector, and in January 2025, Mesoptyelus impictifrons was identified as a new vector in the EPPO region.
All xylem-sap feeding insects are considered potential vectors, and research is ongoing to identify other species that may contribute to the pathogen's spread.
Regulatory and Research Framework in the European Union
In response to the threat, the EU has classified Xylella fastidiosa as a priority quarantine pest, with strict measures in place to prevent its introduction and spread .
Containment and Eradication Measures
Under Commission Implementing Regulation (EU) 2020/1201, member states must establish demarcated areas upon detecting the pathogen. These consist of an "infected zone" and a surrounding "buffer zone" .
Control strategies focus on containment and prevention, as there is no known cure for infected plants.
Measures include the removal of all infected plants and the control of insect vector populations.
The buffer zone is typically 2.5 km for eradication efforts and was historically 5 km for containment areas where the pest is established .
In July 2024, the European Commission proposed an update to these rules, suggesting a reduction of the mandatory survey area in containment zones from 5 km to 2 km to facilitate replanting. The proposal also aims to expand the list of high-risk host plants under surveillance to include specific species of lavender and rosemary, which have been frequently found infected.
Based on the comprehensive research gathered, I'll now write a separate paragraph on vector control for the Xylella fastidiosa context.
Vector Control Strategies for Xylella fastidiosa Management
Effective vector control represents the cornerstone of Xylella fastidiosa management strategies, given the absence of curative treatments for infected plants.
The primary focus centers on managing populations of xylem-feeding insects, particularly spittlebugs of the Aphrophoridae family, with Philaenus spumarius serving as the main confirmed vector in Europe21. Vector control approaches encompass three complementary strategies: biological control, chemical control, and cultural management practices.
Biological control methods have demonstrated significant promise in field applications. The entomopathogenic fungus Metarhizium brunneum has emerged as a particularly effective biocontrol agent, with field trials showing remarkable efficacy rates of 100% for nymph control and 85% for adult spittlebug populations in olive groves.
The fungus can be applied as a soil treatment, where it persists in the environment and colonizes plants endophytically, providing sustained vector control.
Additionally, classical biological control using natural predators shows potential, with the predatory bug Zelus renardii identified as an effective predator of P. spumarius, functioning as a "living insecticide" when deployed in inundation strategies. Laboratory studies indicate that such biocontrol approaches can reduce pathogen incidence below 10%, offering an environmentally sustainable alternative to chemical intervention.
Chemical control remains a critical component of integrated vector management, particularly through targeted insecticide applications timed to coincide with vector activity periods.
Plant-based formulations have shown considerable promise, with hot pepper-infused oil combined with Salvia guaranitica extracts achieving mortality rates of up to 100% in spittlebug adults, rivaling the effectiveness of synthetic insecticides like deltamethrin.
Systemic insecticides applied as preventive treatments to olive trees can provide protection against vector transmission, with the dual benefit of killing vectors upon feeding and reducing overall transmission potential.
Cultural management practices provide the foundation for sustainable vector population suppression.
Ground cover management through tillage operations has proven particularly effective, reducing P. spumarius populations by up to 60% compared to control plots, while frequent mowing achieves only modest reductions of approximately 20% . These practices work by disrupting the vector's life cycle, destroying overwintering eggs and nymphs, and eliminating the herbaceous vegetation required for spittlebug development.
Controlled burning, soil preparation through discing or raking, and strategic grazing management can further reduce vector habitat suitability by altering microclimate conditions and removing protective litter layers.
The integration of these approaches within a comprehensive management framework offers the most promising pathway for sustainable Xylella fastidiosa vector control, balancing efficacy with environmental sustainability and agricultural practicality .
EU-Funded Research
The EU has invested significantly in research to combat the pathogen through framework programs like Horizon 2020 and Horizon Europe.
Major projects such as XF-ACTORS, POnTE, BIOVEXO, and BeXyl aim to deepen the understanding of the bacterium, develop advanced control strategies, and provide tools for risk assessment and policy-making.
These initiatives focus on the pathogen's biology, its interaction with vectors, and the development of sustainable management solutions.
Future Outlook and Global Challenges
The spread of Xylella fastidiosa is influenced by environmental conditions. Climate change models predict that rising global temperatures will increase the risk of the pathogen establishing itself further north in Europe, beyond the Mediterranean basin .
A global temperature increase of 3°C has been identified as a potential tipping point that could dramatically expand the pathogen's viable range.
The continued detection of Xf in new countries underscores the persistent risk posed by the international movement of plants and the need for robust global surveillance and biosecurity protocols.
Key Sources for Scientific Articles on Xylella fastidiosa
Comprehensive overview of Xylella’s biology, global distribution, host range, and economic impact.
Cornara et al. “Vectors of Xylella fastidiosa around the world: an overview”
In‐depth review of insect vectors, transmission biology, and implications for pathogen spread.
Sanna et al. “A biological control model to manage the vector and the infection of Xylella fastidiosa on olive trees” (PLOS ONE)
Peer-reviewed study on use of Metarhizium brunneum and Zelus renardii biocontrol agents in olive groves.
Commission Implementing Regulation (EU) 2020/1201EU legal framework for demarcated infected and buffer zones, eradication and containment measures.
“Xylella fastidiosa in Europe: From the Introduction to the Current Status” (PMC)Scientific review of outbreaks, host range, subspecies in Europe, and current control strategies.
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