Xylella fastidiosa
Xylella fastidiosa is a bacterial pathogen that causes severe diseases in a wide range of plants, such as Pierce’s disease in grapevines, which is a major problem for wine producers in the United States and South America.
X. fastidiosa was detected on olive trees in Italy’s southern Puglia region in October 2013, the first time the bacterium was reported in the European Union (EU). The bacterium was since detected in France, Spain and Portugal.
X. fastidiosa has a wide range of host plants such as olive trees, citrus plants, grapevines and various ornamental plants.
Insects such as sharpshooters and spittlebugs that feed on the xylem sap of plants are vectors, transmitting the bacterium to other plants.
The bacterium causes deficiencies in water and mineral Element inorganiku li jseħħ b’mod naturali (eż. kalċju, ħadid) li huwa meħtieġ fid-dieta għat-tkabbir, l-iżvilupp u s-saħħa normali. uptake in plants by blocking the xylem, the transporting tissue.
The EU has a series of control measures in place to prevent the bacterium from spreading.
Milestones
2023
December
EFSA publishes the latest update of its database of plants that act as hosts of Xylella fastidiosa. Seven additional plant species were identified as hosts of the pathogen, taking the total number of species in the database to 696 plant species from 88 botanical families.
August
EFSA organises the 4th European Conference on Xylella Fastidiosa. The two-day event held in Toulouse, France, gathered more than 200 plant health experts from around the world to discuss the state of the art in research to control this bacterium.
2021
April
EFSA organises the third European conference on Xylella fastidiosa. The online event was attended by scientists, academics and interested stakeholders from more than 60 countries. The conference was preceded by the final meeting of the EU-funded XF-Actors research project.
2020
June
EFSA publishes guidelines for carrying out surveys of Xylella fastidiosa. The document guides plant pest surveyors through the design of statistically sound, risk-based surveys of the pathogen, integrating the key information gathered in the pest survey card for X. fastidiosa published in 2019.
2019
October
EFSA co-organises the second scientific conference on Xylella fastidiosa. Around 350 plant health specialists from around the world gathered in Ajaccio, Corsica, for two days of intensive discussions on how science can help find solutions to the plant pest that is causing environmental and economic damage across Europe.
June
EFSA publishes a pest survey card on X. fastidiosa. The card is designed to help Member States plan their survey activities using a statistically sound and risk-based approach, in line with international guidelines on surveillance.
May
EFSA updates its risk assessment of the risks posed by X. fastidiosa to plants and crops in the European Union. EFSA’s Plant Health Panel used computer modelling to simulate how X. fastidiosa spreads across short and long distances under different conditions.
2018
September
EFSA publishes the latest update of its database of plants that act as hosts for Xylella fastidiosa. The updated list includes 563 plant species identified through a new literature search and from notifications to the EU’s plant health interception service EUROPHYT. The list can be accessed as raw data on Knowledge Junction, EFSA’s open repository of evidence and supporting materials used in food safety risk assessments, or as a series of interactive reports.
July
EFSA updates its pest categorisation of X. fastidiosa, previously included as part of the pest risk assessment published in 2015. EFSA’s Panel on Plant Health concluded that X. fastidiosa meets the criteria for consideration as an EU quarantine pest.
2017
November
EFSA co-hosts a conference on the latest scientific developments surrounding X. fastidiosa. More than 250 plant health experts from around the world attended the event in Palma de Mallorca, Spain.
April
EFSA produces a report on the susceptibility of olive varieties to the Apulian strain of Xylella fastidiosa (subsp. pauca strain CoDiRO, ST53). The report noted that evidence from experimental infectivity studies and from surveys in olive orchards indicate tolerance of the Leccino variety to ST53. Tolerance or resistance traits have also been found in other olive varieties, such as FS-17®.
2016
August
EFSA’s experts conclude that there was no scientific evidence to indicate the presence of multiple types of X. fastidiosa in Apulia. They also reviewed new evidence regarding the categorisation of Vitis (grapevine), Citrus, Quercus ilex (holm oak) and Phoenix roebelenii (ornamental dwarf palm) as host plants of X. fastidiosa.
April
EFSA concludes that research being carried out in Apulia showed that certain treatments reduce the symptoms of disease caused by X. fastidiosa but do not eliminate the pathogen from infected plants.
March
EFSA publishes a report by the Italian National Research Council on the host range of X. fastidiosa CoDiRO, which confirmed that CoDiRO causes olive dieback.
February
EFSA’s database of host plants is updated to include 44 new species. The majority of the new species (70%) were identified in southern Italy (Apulia), Corsica and southern France (Provence-Alpes-Côte d'Azur region).
2015
November
More than 100 scientists from around the world attend a workshop hosted by EFSA to identify the main knowledge gaps and discuss research priorities for X. fastidiosa. In the same month, EFSA evaluates the results of ongoing studies and experiments carried out in Apulia, concluding that grapevine cannot be ruled out as a potential host of X. fastidiosa.
September
EFSA publishes a scientific opinion indicating that hot water treatment – whereby dormant plants and plant parts are submerged for 45 minutes in water heated to 50C – is a reliable method for controlling X. fastidiosa in dormant grapevine planting material.
FAQ
Xylella fastidiosa is a bacterial plant pathogen transmitted by insects that feed on xylem sap. It is associated with serious diseases in a wide range of plants around the world. For example, it causes Pierce’s disease in grapevine, citrus variegated chlorosis, phony peach disease, coffee leaf scorch, olive quick decline syndrome and other diseases that affect common trees such as plum, almond, oak and oleander.
Diseases caused by X. fastidiosa occur in tropical, sub-tropical and temperate areas. The bacterium is widespread in many areas of North, Central and South America and reached Europe in recent years. Official surveys carried out by EU Member States confirm so far that its presence is limited to limited ares in Italy, France, Spain and Portugal.
X. fastidiosa colonises the xylem network within plants. The main function of xylem vessels is to transport water from a plant’s roots to its leaves, so when the bacteria colonise the plant, the xylem vessels become blocked and the plant slowly dies. To reach a new host, X. fastidiosa has to be carried and transmitted by a vector – all xylem sap-feeding insects are potential vectors, until proven otherwise. The most common vectors worldwide are sharpshooter leafhopper (Cicadellinae), spittlebugs (Aphrophoridae) and froghoppers (Cercopidae). The meadow froghopper (Philaenus spumarius) is currently the main insect vector species in Europe.
Symptoms range from leaf browning to plant death. The specific symptoms, sequence and pace of infection vary because of the wide range of potential host plants, the diversity of the pathogen and level of infection, as well as the different climatic conditions in areas where the bacterium is found. Many host plants infected with X. fastidiosa may not express any symptoms; other plants may show severe leaf scorching and wilting up to complete desiccation.
EFSA maintains a database of known hosts, which currently lists 696 plant species – both naturally and experimentally infected hosts – from 88 botanical families. However, not all of the plants listed are susceptible to all “types” (subspecies or strains) of X. fastidiosa and, even when affected, plants will not necessarily become symptomatic. In addition, even plants belonging to the same species can express different levels of susceptibility depending on their variety and growing conditions. The identification of asymptomatic host species is crucial as they can act as symptomless carriers for this bacterium to new zones and more sensitive crops.
Yes. There are five currently recognised sub-species of X. fastidiosa – fastidiosa, morus, multiplex, pauca and sandyi – which in turn have their own variants.
In Europe, the subspecies fastidiosa, multiplex and pauca have been detected.
In addition, another species of Xylella, Xylella taiwanensis, occurs in Taiwan, where it causes pear leaf scorch. X. fastidiosa subspecies fastidiosa is also present in Taiwan.
Xylella fastidiosa is regulated in the EU as a quarantine organism and its introduction into and movement within the Union territory is prohibited. In addition, emergency measures have been in place in the EU since February 2014 to prevent its introduction and further spread within the EU. Stricter rules were introduced in May 2015 on the basis of a full EFSA pest risk assessment, and have been updated regularly as soon as new scientific and technical information has become available.
EFSA has published numerous reports and scientific opinions on X. fastidiosa since the beginning of the outbreak in southern Italy in 2013. Its most up to date risk assessment was published by EFSA in May 2019 providing a comprehensive update on the risk caused by Xylella fastidiosa for the EU territory and the means to prevent its introduction and spread.