Xylella fastidiosa is a vector-transmitted bacterial plant pathogen associated with serious diseases in a wide range of plants. It causes Pierce’s disease in grapevine, which is a major problem for wine producers in the United States and South America. X. fastidiosa was detected on olive trees in Puglia, southern Italy, in October 2013, the first time the bacterium has been reported in the European Union. Since then it has also been reported as present in France, Spain and Portugal. Controls are in place to prevent the bacterium from spreading.
Numerous species of xylem sap-sucking insects are known to be vectors of the bacterium. X. fastidiosa also has a broad range of host plants, including many common cultivated and wild plants.
In June 2020, EFSA published 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.
In April, EFSA published the latest update of its database of plants that act as hosts of Xylella fastidiosa. Thirty-seven additional species were identified as hosts of the pathogen, taking the total number of species in the database to 595.
In October 2019, EFSA co-organised 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.
In June, EFSA published 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.
In May, EFSA updated 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.
In September 2018, EFSA published 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.
In July 2018, EFSA updated 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.
In April 2017, EFSA produced 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®.
In November 2017, EFSA co-hosted 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. The programme included around 50 presentations looking at issues such as current knowledge of the pathogen, how it is transmitted, resistance in plants and control measures.
In February 2016 EFSA’s database of host plants was 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).
The following month EFSA published a report by the Italian National Research Council on the host range of X. fastidiosa CoDiRO, which confirmed that CoDiRO causes olive dieback.
In April, EFSA concluded 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.
EFSA’s experts concluded in August that there was no scientific evidence to indicate the presence of multiple types of X. fastidiosa in Apulia. They then 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.
In January 2015 EFSA published a full pest risk assessment and evaluation of risk reduction options for X. fastidiosa in the EU. The scientific opinion included a list of host plants and European vectors of the bacterium. In March 2015, EFSA published a report categorising plants for planting, excluding seeds, according to the risk of introduction of X. fastidiosa.
In April EFSA responded to a claim by an Italian non-governmental organisation that a series of fungi – rather than X. fastidiosa – are the main causal agents of olive decline in Apulia. EFSA concluded that there was no scientific evidence that tracheomycotic fungi are the primary cause of olive die-back in Apulia.
A Scientific Opinion published by EFSA in September indicated 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.
In November 2015, more than 100 scientists from around the world attended a workshop hosted by EFSA to identify the main knowledge gaps and discuss research priorities for X. fastidiosa. In the same month, EFSA evaluated 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.
Following publication of EFSA’s advice, in February 2014 the European Commission put in place emergency measures to combat the spread and further introduction of the organism into the EU. These measures were further strengthened in May and October 2015.
In October 2013 Xylella fastidiosa was detected in olive trees in Lecce province in Apulia, Italy. It was the first outbreak of X. fastidiosa under field conditions to be reported in the European Union. In November of the same year EFSA provided the European Commission with urgent scientific advice and technical assistance on X. fastidiosa.