What is Xylella fastidiosa?
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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 spread within all Member States, shall be banned. The plant health directive provides Member States with the legal obligations to take, once the organism is known to be present and irrespective of the symptoms, all necessary measures to eradicate it, or if that is impossible, inhibit its further spread.
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) and the abundance and widespread distribution of the insect vectors, the risk of further spread of this pest to other parts of Italy and 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 to prevent the further spread of the bacterium within the EU.
To know more about the outbreak of Xylella fastidiosa, please consult the folowing map and timeline: