Has Xylella fastidiosa “chosen” olive trees to establish in the Mediterranean basin?

Severe decline of olive trees was observed in the Lecce province, Apulia (Italy), and received the name ‘complesso del disseccamento rapido dell’olivo’ (olive rapid decline complex). Affected plants showed leaf scorch symptoms and dieback of twigs, branches and even of the whole plant. Similar symptoms, unusual for the area, have also been observed in other Apulian localities (Cerignola, Foggia, Canosa di Puglia, and Andria). Three fungal species were associated with the symptoms: Phaeoacremonium aleophilum, Neofusicoccum parvum, and Pleurostomophora richardsiae. The latter is the first report of this fungal species infecting olives. In the Lecce province, the bacterium Xylella fastidiosa also was detected from affected olive trees. Xylella fastidiosa is a quarantine agent in Europe that had been previously reported in the Mediterranean region, but did not spread probably because of the lack of a vector. Present findings suggest that this fundamental condition has now been met.