What is Xylella fastidiosa?
Xylella fastidiosa (Wells et al.) is one of the most dangerous plant bacterium worldwide, causing a variety of diseases, with huge economic impact for agriculture. Since October 2013, a strain of this bacterium is spreading in Apulia (Italy). For the moment the first and only confirmed outbreak in the EU, affecting mainly olive groves.
Xylella fastidiosa is regulated in the EU as quarantine organism under Council Directive 2000/29/EC ('Plant Health Directive') on protective measures against the introduction into the Community of organisms harmful to plants or plant products and against their spread within the Community. As such, the introduction of this organism into, and its spreading within all Member States, shall be banned. The Plant Health Directive provides Member States with the legal obligations to abide by, once the organism is known to be present. Irrespective of the symptoms, all necessary measures to eradicate it, or if that is impossible, to inhibit its further spread, must be taken.
The bacterium lives in the plant xylem tissue and it is normally spread by spittlebugs, cicadas and sharpshooters feeding with the plant xylem. Philaenus spumarius (commonly known as 'meadow froghopper') - a spittlebug very common, polyphagous and abundant on olive trees - is known to be the vector responsible for the transmission of the bacterium in Apulia. Symptoms associated with the presence of Xylella fastidiosa in plants vary broadly and can lead to plant death within a limited number of years, depending on the host plant species, the severity of the infection and the climatic conditions.
Based on scientific literature, approximately 300 plants species are susceptible to the bacterium and associated with the four different subspecies of Xylella fastidiosa; however, not all are susceptible to the disease. The strain identified in Apulia is considered to be a new genetic variant of Xylella fastidiosa, subspecies pauca, for which the range of host plants is still unclear. It has not yet been found on citrus and grapevine, although pathogenicity tests are still ongoing. However, because of the large number of confirmed (e.g. olive trees, plum fruit plants) or potential host plants (e.g. citrus and grapevine) as well as the abundance and widespread distribution of the insect vectors, the risk this pest spreading further to other parts of Italy and to the rest of the EU is very high.
EU emergency measures have been in place since February 2014 to combat this organism. They were refined in July 2014 and further strengthened in May 2015 with the aim of preventing the further spread of the bacterium within the EU.
What measures have been taken by the Commission to prevent further spread into the Union territory?
Due to the high uncertainty of the full range of host plants susceptible to the Apulian strain (11 species and 2 genera currently regulated), EU emergency measures provide strict requirements for the movement within and outside of the affected area for a long list of specified plants, consisting of 160 species and 27 genera of plants for planting, except seeds, including citrus and grapevine.
The entire province of Lecce, declared as an infected zone, is subject to containment measures and surrounded by an extensive buffer zone of 20km that is free from the bacterium. An intensified surveillance zone has to be established around the demarcated area of Lecce to ensure early detection of new outbreaks. A specific demarcated area (i.e. the infected zone plus the buffer zone) is also established around the new outbreak of Oria, in the province of Brindisi, where strict eradication measures apply.
- Outbreaks found outside the province of Lecce (e.g. in the municipality of Oria, in the province of Brindisi) are subject to very strict eradication measures, which include a clear cut of all host plants (11 species and 2 genera), irrespective of their health status, in a radius of 100 m around the infected plants;
- Outbreaks within the province of Lecce are subject to containment measures, where at least the removal of all infected plants (no clear cut) has to be undertaken in an area of 20 km, in the Northern part of the province, adjacent to the neighbouring provinces of Brindisi and Taranto, as well as in proximity of authorised sites of growth (e.g. nurseries, garden centres) and sites with particular cultural, scientific and social value.
- Movement out of the demarcated areas of specified plant species is only authorised if those plants are grown in authorised sites, under protected conditions, properly sampled and tested prior to movement, with notification to the national Competent Authority of destination, including traceability requirements.
These measures will have a significant impact on the province of Lecce and its neighbouring provinces of Brindisi and Taranto due to the economic and cultural importance of the olive production in the affected area. The area subject to EU emergency measures is 570 200 hectares in size. The province of Lecce, 350 000 hectares in size, contains around 12 580 000 olive trees, 2 900 000 of which are older than 100 years. However, as the large majority of these plants are still healthy today, maximum effort is needed to avoid them from being infected.
How will the Commission prevent the further introduction of Xylella fastidiosa from non-EU countries?
Current import rules have been further strengthened. This means that imports from infected non-EU countries of the specified plants (160 species and 27 genera) are only possible if the plants are grown under protected conditions and, prior to their export and on entry into the EU, they are inspected, sampled and tested for the absence of the bacterium. The conditions for these imported plants to move within the EU are strictly applied.
The import from pest free countries or pest free areas is possible only if the Commission has officially been previously notified of the health status of these areas. Imports of Coffea plants for planting from Honduras or Costa Rica are prohibited.
Is there any financial support available for farmers affected by Xylella fastidiosa?
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 will be possible only from 2017 onwards. Additional financial support is currently being discussed in the framework of the EU Common Agricultural Policy.
Also, a specific research call on Xylella fastidiosa is being foreseen under the forthcoming 2016/2017 Work Programme of Horizon 2020, which 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.
Could there be other causes for the decline of olive trees since some scientific papers argue that it is caused by a combination of fungi which weaken the plants before being attacked by Xylella fastidiosa, and specific treatments seem to exist?
The Commission has reviewed all the information available during the revision of the EU emergency measures. All relevant documents were sent to EFSA for scientific assessment. On 17 April 2015, EFSA made a statement that there is currently no scientific evidence to support the suggestion that fungi rather than the bacterium Xylella fastidiosa are the primary cause of the olive decline syndrome observed in Apulia in Southern Italy. In addition, there is no published evidence that the treatment of fungal disease will reduce the establishment, spread and impact of Xylella fastidiosa, although good orchard management is generally beneficial for plant health.
Already in the Scientific Opinion of January 2015, EFSA concluded that olive trees showing symptoms of the bacterium, were generally affected by a multitude of pests and pathogens including Xylella fastidiosa¸ several fungi and Zeuzera pyrina (commonly known as the 'leopard moth'). However, although the specific role of Xylella fastidiosa in the quick "decline syndrome of olive" remains to be fully understood, Xylella fastidiosa has been found in young plants showing signs of the declining syndrome, where no other pathogens where found.
How can Xylella fastidiosa be controlled?
According to the plant health experts of the European Food Safety Authority (EFSA), there is no control method currently available to cure diseased plants in the field. Changes in cropping systems could have some impact on the disease (e.g. pruning, fertilisation and irrigation), but this is not enough to cure plants. In Apulia, severe pruning of infected olive trees resulted in the emission of new sprouts from the base of the tree but so far, this has not been shown to cure the plants and prevent them from dying.
The control strategy has to be focused on the insect vector and on the removal of infected plants that, if left on the field, can act as a reservoirfor 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 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 low infections can escape surveys based solely on visual inspection and even based on laboratory tests because of early infections 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 outbreaks found outside the province of Lecce.
What can I do as citizen to prevent further spread of Xylella fastidiosa in the EU?
National competent authorities should be immediately informed of any suspected case of Xylella fastidiosa so that the necessary measures can be taken
It is important that the movement, within and out of the demarcated areas in Apulia of specified plants originating from that area, is restricted to plants grown in an authorised nursery and accompanied by a plant passport.
Lastly, do not bring any plant when travelling back from third countries unless accompanied by a phytosanitary certificate.
To know more about the outbreak of Xylella fastidiosa, please consult the following webpage, map and timeline: http://ec.europa.eu/food/plant/plant_health_biosecurity/legislation/emergency_measures/xylella-fastidiosa/index_en.htm