Description
ORIGIN AND SPREAD. X. fastidiosa is native to the Americas, and has been reported in Iran where it has infested vine and almond trees, in Israel on almond trees and in Taiwan on pear leaves. In Europe, it has spread to France, Spain, Portugal and Italy.
HOST PLANTS The number of potential host plants is much higher and includes almost 150 plant species. In addition to the olive tree (Olea europea), the bacterium has also been found in other host plants:
- Oleander(Nerium oleander);
- Almond tree(Prunus dulcis);
- Cherry tree(Prunus avium);
- Mimosa(Acacia saligna);
- Vinca rosea (Vinca rosea);
- Rosemary(Rosmarinus officinalis);
- Westringia (Westringia fruticosa);
- Polygala myrtifolia (Polygala myrtifolia);
- Alaternus (Rhamnus alaternus);
- Vitis L.
BIOLOGY. Vector insect adults developed from hatching eggs (green insects) acquire Xylella fastidiosa by feeding on infected host plants. Infected vector insects can transmit the bacterium to healthy host plants, which consequently become infected. Transmission of the bacterium does not occur through the vector's eggs. Nymphs, on the other hand, can act as vectors for the bacterium, but lose infectivity during moulting.
ROUTES OF SPREAD. Transmission is by widespread vector insects (Cicadellidae and Cercopidae in particular), capable of visiting numerous wild and cultivated plants. Vectors acquire the bacterium by sucking sap from infected plants and transmit it to healthy plants. In Italy, the main vectors are insects belonging to the genus Philaenus and in particular P. spumarius (vulgarly known as sputacchina). Over long distances, the spread of X. Fastidiosa can occur through trade in plants originating from countries where the bacterium is present and with infected propagation material.
SYMPTOMATOLOGY. Typically, an initial desiccation of the apices and leaf edges, which appear burnt, is observed, followed by a desiccation of parts of branches and finally of the entire crown of the tree as well as browning of the wood.
However, Xylella fastidiosa infections are characterised by the diversity of symptomatological manifestations they cause on host species. Despite being one of the most fearsome phytopathogens, it is emphasised that in most host species infections do not give rise to major symptomatological changes, remaining in the form of latent infections in many species. On the other hand, infections in some perennial species and, in particular, in some species of agricultural interest such as vine, citrus, stone fruit and olive trees can be so serious as to compromise not only the productivity of the plants but also the survival of the infected plants themselves.
REPORTING. To provide reports and receive information contact the Provincial Plant Protection Service (tel. 0461/495660; e-mail: serv.agricoltura@provincia.tn.it; pec: serv.agricoltura@pec.provincia.tn.it)
REFERENCE LEGISLATION. Regulation (EU) 2016/ 2031; Implementing Regulation (EU) 2019/2072; Legislative Decree no. 19/2021; Commission Implementing Regulation (EU) 2020/1201 of 14 August 2020 on measures to prevent the introduction into and spread within the Union of Xylella fastidiosa (Wells et al.) as amended and supplemented; Ordinance No. 3 of 26 May 2023 'Definition of areas free from the harmful organism Xylella fastidiosa in the territory of the Italian Republic'; Decree of 24 January 2022 'Adoption of the National Contingency Plan for the control of Xylella fastidiosa (Wells et al.)'.