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. Transmission of the disease in the EU takes place through cicada vector insects that are widespread in the entire Union territory. 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.