Xylella fastidiosa ( Wells et al., 1987) is the xylem-limited bacterium causing Pierce's disease of grapevine and other plant diseases. The same may be true for tropical-subtropical Asia and Africa. fastidiosa may have the potential to invade agro-ecosystems in Mediterranean regions wherever suitable vectors (overwintering in the adult stage and thus able to inoculate vines during spring) are endemic or become established. fastidiosa are likely to be transmitted by endemic vector species even without the introduction of non-native vectors ( Almeida et al., 2005). Further studies are needed to confirm transmission in E. fastidiosa in the phloem feeder Euscelis lineolatus in Italy, suggesting that potential vectors may include phloem feeding insects. The European Food Safety Authority suggests that all xylem sap feeder insects should be regarded as potential vectors of X. Among potential insect vectors, only Homalodisca vitripennis, Xyphon fulgida, Draeculacephala minerva and Graphocephala atropunctata are also listed in the EPPO A1 list. fastidiosa is included in the EPPO A1 list of pests recommended for regulation as quarantine pests. The consequences are considered to be major because yield losses and other damage would be high and require costly control measures. According to the EFSA Panel on Plant Health ( European Food Safety Authority, 2015), establishment and spread of X.
These non-symptomatic hosts and hosts which are slow to develop symptoms can limit the effectiveness of quarantine procedures and may provide a reservoir for maintenance of the pathogen in the wider environment. fastidiosa does not always equate to disease development and an endophytic life stage has been suggested ( Chatterjee et al., 2008). It was also detected in numerous other host plants (mainly ornamentals).
In 2013 the bacterium was reported causing serious damage to olive trees in Puglia, Italy. fastidiosa represents a very serious threat for the EPPO region. Intersubspecific homologous recombination of strains is implicated in the potential for invasion of new host plants ( Nunney et al., 2014). fastidiosa have the potential to spread over a few years to cause increasing damage. The spread of phony disease of peach within the south-eastern USA from the 1890s until about 1930 and of citrus variegated chlorosis disease of orange throughout Brazil in the 1990s indicates that new strains of X. Xylella fastidiosa has a wide plant host range and spectrum of insect species capable of serving as vectors which should increase the bacterium's invasiveness and make it difficult to prevent introduction via live plants from the tropical or subtropical Americas.
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