Xylella fastidiosa

What is Xylella fastidiosa?

Xylella fastidiosa (Wells et al.) is one of the most dangerous plant bacteria worldwide, causing a variety of diseases, with huge economic impact for agriculture, public gardens and the environment.

Xylella fastidiosa has the potential of causing in the EU, an annual production loss of 5.5 billion euros, affecting 70% of the EU production value of older olive trees (over 30 years old), and 35% value of younger ones; 11% of citrus; 13% of almond and between 1-2% of grape production in a scenario of full spread across the entire EU.

This would put at risk nearly 300 000 jobs across Europe currently involved in that production. In addition to direct impacts on production, pests have significant indirect effects on upstream or downstream economic sectors.

There are four frequently reported subspecies of Xylella fastidiosa worldwide - fastidiosa, pauca, multiplex and sandyi - although other subspecies (e.g. morus) as well as recombinations within the same or different subspecies have been also identified.

The bacterium lives in the plant xylem tissue and it is normally spread by insect vectors feeding from the plant xylem.

Symptoms associated with the presence of Xylella fastidiosa in plants vary broadly from non-expressed infections to plant death within a limited time, depending on the host plant species, the level of bacterial inoculum, the subspecies involved or even the specific recombinations within the same or different subspecies, as well as the climatic conditions.

Based on the scientific literature, the bacterium has been detected in or isolated from more than 500 plant species worldwide, although not all of these plants are susceptible to disease and not all plant species are affected by all Xylella fastidiosa subspecies.

In the Union territory, several cultivated plants of high economic value (e.g. olive trees, stone fruits - plums, almonds, cherries) or wide-spread ornamental plants (e.g. myrtle-leaf milkwort, oleander) have been identified as hosts. Many other widespread plant species remain potential hosts in the Union territory.

Numerous species of xylem sap-sucking insects are known to be vectors of the bacterium. As a consequence, the risk that this pest is spreading further to other parts of the EU is very high unless strict control measures are taken immediately after any new outbreak is detected.

Please check the Latest Developments of Xylella fastidiosa in the EU territory.

EU Legislation

Xylella fastidiosa is regulated in the EU as quarantine pest under Regulation (EU) 2016/2031 ('Plant Health Law') on protective measures against plant pests. Its introduction into and spreading within all Member States is banned. In case of detection, irrespective of the symptoms and subspecies concerned, all necessary measures shall be taken to eradicate it, or in case of approval by Commission Regulation, to inhibit its further spread if eradication is no longer achievable.

On 14 August 2020, following the latest scientific evidences made available by the European Food Safety Authority (EFSA) and experience in the different EU outbreak areas, the Commission adopted new measures against Xylella fastidiosa (Commission Implementing Regulation (EU) 2020/1201) repealing current Decision (EU) 2015/789.

A. Regulated plant species

Two different categories of plant species are regulated under Commission Implementing Regulation (EU) 2020/1201:

Host plants: means plants for planting, other than seeds, found infected worldwide by Xylella fastidiosa in natural conditions and confirmed by at least two different diagnostic methods.
Specified plants: means host plants which have been found infected worldwide by specific subspecies of Xylella fastidiosa (e.g. multiplex, pauca, fastidiosa). Thes list of specified plants is limited to the subspecies detected in the Union territory.

B. Control measures to prevent spread within the Union

Establishment of the demarcated area

As soon as the presence of Xylella fastidiosa is confirmed in the territory of a Member State, the competent authorities shall without delay demarcate the area, consisting of an infected zone and a buffer zone. That demarcated area may be established per specific subspecies of Xylella fastidiosa, if it has been identified.

The infected zone shall have a radius of at least 50 m around the plant found infected by Xylella.

The buffer zone shall be of a width of at least 5 km for outbreaks subject to containment measures, while 2,5 km for outbreaks subject to eradication measures and 1 km for isolated outbreaks where no natural spreading occurred and eradication measures have been immediately taken.

Eradication measures

The eradication measures as laid down under Articles 7 to 11 of Commission Implementing Regulation (EU) 2020/1201 apply to any outbreak of Xylella fastidiosa detected in the Union territory, with the exception of those infected zones where containment measures are authorised (e.g. South of Apulia, Corsica and Baleares).

Within the infected zone, all infected or symptomatic plants have to be removed. Plants which belong to the same species as that of the infected plant or other species found infected in the demarcated area, irrespective of their health status, shall also be removed. Moreover, other regulated specified plants known to be susceptible to that specific subspecies of Xylella fastidiosa shall also be removed if it has not been immediately sampled and tested for the presence of Xylella.

All other host plants in the 50 m infected zone have to be sampled and tested for the presence of the bacterium.

In order to respect the tradition and history of a particular location, Member States have the possibility to decide that specified plants officially designated as plants of historic value do not need to be removed if they are not found infected, even if they are located within the 50 m radius around the infected plants.

However, in order to prevent their potential infection and spread of Xylella fastidiosa, they should be intensively surveyed and subject to vector control treatments.

Within the 2,5 km buffer zone, intensive surveillance should be carried out consisting of sampling and testing of host plants.

The survey activities carried out in the respective zones shall be performed taking into account the EFSA Guidelines on Risk-Based and Statistically Sound Survey.

Agricultural practices such as removal of weeds, ploughing of the soil, and other practices identified by the Member States should be implemented both in the infected zones and in the buffer zones with the aim to prevent the presence of the bacterium in its herbaceous hosts and to reduce the vector population in the area concerned.

Containment measures

The containment measures as laid down under Articles 12 to 17 of Commission Implementing Regulation (EU) 2020/1201 are applicable to the South of Apulia (Italy), Corsica (France) and Baleares (Spain), as the bacterium is already widely established in those areas and eradication would not be feasible.

Within the infected zone, lighter provisions apply, consisting of intensive surveillance and immediate removal of at least the infected plants. These measures should be implemented, where applicable, at least within the last 5 km strip of the infected zone adjacent to the buffer zone, as well as around sites with high cultural and social value.

Within the 5 km buffer zone, the same provisions as the ones presented in the eradication measures apply. As regards Corsica and Baleares, there are no provisions applied to buffer zones as the infected zones are surrounded by the sea.

Agricultural practices such as removal of weeds, ploughing of the soil, and other practices identified by the Member States should be implemented in that area with the aim to prevent the presence of the bacterium in its herbaceous hosts and to reduce the vector population in the area concerned.

Planting of specified plants in the infected zone

The planting of specified plants in infected zone may be authorised by the Member State concerned in specific cases.

First, those specified plants are grown in insect-proof production sites free from Xylella and its vectors.

Second, those specified plants preferably belong to varieties assessed as being resistant or tolerant to Xylella andare planted in the infected zones subject to containment measures, but outside the 5 km strip adjacent to the buffer zone.

Third, the specified plants belong to the same species of plants which have been tested and found free from Xylella on the basis of the last two years of monitoring campaign and are planted in the infected zones under eradication.

Movement of plants within and out of the demarcated areas

Strict requirements apply for the movement of specified plants out of demarcated areas and from infected zones into buffer zones.

That movement is only permitted if they fulfil certain conditions (e.g. they are grown under protected conditions, sampled and tested prior to movement, with traceability requirements in place).

Specific derogations apply on specified plants which are found not infected in demarcated areas as part of the annual monitoring campaign.

C. Control measures to prevent introduction into the Union

Same conditions as for EU Member States also apply on host plants imported from third countries.

More specifically, import of host plants from infected third countries is only possible if those plants are grown under protected conditions and, prior to their export and on entry into the EU, are inspected, sampled and tested for the absence of the bacterium. Strict conditions apply for these imported plants to move within the EU as well.

The import from pest free countries or pest free areas is possible only if the Commission has officially been informed about the health status of these areas (see list of official declarations submitted by non-EU countries). The Commission is following very closely any interception at import and ensures immediate follow-up where needed.

Survey activities performed in third countries to confirm the status of Xylella fastidiosa shall also be performed taking into account, from 2023 onwards, the EFSA Guidelines on Risk-Based and Statistically Sound Survey.

Surveys activities

Member States must carry out annual surveys for the presence of Xylella fastidiosa in their territory on the entire list of host plants. Any positive finding must be reported to the Commission and other Member States at the latest within 8 working days following the day of confirmation of the presence of Xylella fastidiosa.

In order to ensure the highest possible level of early detection of outbreaks of X. fastidiosa in the Union territory and harmonised survey activities across the Union, those survey activities shall be performed, from 2023 onwards, taking into account the EFSA Guidelines on Risk-Based and Statistically Sound Survey.

At the present time, with the exception of limited parts in Italy, France, Spain and Portugal, the Union territory is considered free from Xylella fastidiosa based on annual official surveys since 2014.

EU financial support

EU plant health co-financing may be granted for the implementation of surveillance programmes and eradication/containment campaigns under Regulation (EU) No 652/2014. Under the same legal framework, the EU financial contribution for compensation to the owners for the value of the destroyed plants.

Additionally, in the framework of the EU Common Agricultural Policy, as part of the European Agricultural Fund for Rural Development (EAFRD), Regulation (EU) No 1305/2013 supports knowledge transfer activities and the use of advisory services which can help farmers to identify, prevent and combat diseases. Pilot projects testing new ways to combat diseases could also be supported.

The EAFRD also supports investments to prevent diseases as well as to restore the agricultural production potential damaged by diseases. All these forms of support are conditional to the inclusion of the relevant measures in the Rural Development Programme.

EU research programme

There are currently four research projects funded on Xylella fastidiosa within the HORIZON 2020 and HORIZON EUROPE EU Framework:

XF-ACTORS - Xylella Fastidiosa Active Containment Through a multidisciplinary Oriented Research Strategy. The project was funded in November 2016 with an overall budget of around 7 million € for the period 2016-2020. Proposed actions will be complementary to those carried out under the Project POnTE. More specifically, the project aims to promote a comprehensive package of activities to increase the knowledge of the bacterium and develop options for its prevention and control along with tools for risk assessment and plant health policies.
POnTE - Pest Organisms Threatening Europe. The project ran until November 2019 and addressed Xylella fastidiosa amongst other pests. It contributed to increased knowledge of Xylella fastidiosa and its vectors in olive, grapevine, citrus, stone fruit, ornamentals and landscape trees of high socio-economic importance.
BIOVEXO Project: aims to demonstrate a set of novel biopesticides targeting Xylella fastidiosa and its transmitting spittlebug vector. Six innovative bio-based solutions will be tested and at least two best performing solutions will be brought forward closer to the market (TRL 7-8). The project will run from May 2020 to April 2025.
BeXyl Project: Beyond Xylella, Integrated Management Strategies for Mitigating Xylella fastidiosa impact in Europe. The project BeXyl has been conceived to strengthen the two pillars of plant protection: the prevention and the control strategies for the priority quarantine pathogen Xylella fastidiosa (Xf). The project will contribute to promote research and innovation and specifically provide interdisciplinary solutions according to the demand of the stakeholders involved in the project, contributing to deliver specific impacts for each of the expected outcomes as foreseen by the HORIZON-CL6-2021-FARM2FORK-01-04 call. The project will run from September 2022 to August 2026.

Possibilities to cure infected plants

According to the EFSA Plant Health Panel, there is currently no method available to cure diseased plants in the field. Changes in cropping systems (e.g. pruning, fertilisation and irrigation), could have impact on the disease development but this is not enough to cure plants.

The control strategy has to focus on the insect vector and on the removal of infected plants that, if left on the field, can act as a reservoir for the bacterium inoculum. For the control of the vector population, proper phytosanitary treatments are required, such as the removal of weeds needed for the accomplishment of the life cycle of the cicada insect, but also the targeted use of plant protection products, especially prior to the removal of infected plants.

Such treatments have to be jointly implemented, with appropriate agricultural practices.

It is important to note that asymptomatic hosts, asymptomatic infections or infections in early sage can easily escape surveys based solely on visual inspection and even based on laboratory tests because of the low concentration or heterogeneous distribution of the bacterium in the plant.

This is the main reason for the implementation of strict eradication measures (e.g. clear cut of all host plants around infected plants) for any new outbreaks.

Xylella symptoms

A photo gallery of symptoms of diseases caused by Xylella fastidiosa is available on a dedicated webpage of the EPPO Global Database

Role of citizens

National competent authorities should be immediately informed of any suspected case of Xylella fastidiosa so that the necessary measures can be taken.

Detailed information is available about Xylella fastidiosa on the websites of the competent authorities in the Member States. It is important to keep in mind that infected plants may also show no or not evident symptoms especially when the infection is at its early stage.

Therefore, do not bring any plant when travelling back from third countries or from a demarcated area in the EU unless accompanied by a phytosanitary certificate or plant passport as appropriate.