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Thousands of hectares of dying olive trees in the Salento Peninsula in Italy

Desiccated olive trees. Photo: Ivana Ilijaš

Desiccated olive trees. Photo: Ivana Ilijaš

Numerous hectares of olive trees in the Salento Peninsula in Italy are dying out. This is very concerning since the region is the center of olive production in Italy, Europe, and the world. Despite control efforts, the disease is spreading north, threatening olive groves throughout Italy and ringing alarms across Europe.

The culprit is Xylella fastidiosa, a bacterium widespread in the Americas. Some sub species have havocked citrus groves in South American and Northern American’s vineyards. This microbe kills plants by multiplying inside vascular tissue, thereby slowly clogging their water transport system, and many sap-sucking insects transmit it. In Italy, the disease was recorded in 2013 and by October 2014 some estimated 23 000 hectares were infected. The bacterium has probably come to Italy with coffee and oleander ornamental plants exported from Costa Rica.

In Italy, the primary vector of the bacterium is the spittlebug Philaenus spumarius, common species in European olive groves. Up to 80% of these insects are carrying the bacterium Xylella fastidiosa. However, potential vectors of this bacterium could also be insects from the families Cicadidae, Aphrophoridae, Cercopidae and Cicadellidae, while its hosting plants could be species from the families Catharanthus, Nerium, Olea, Prunus, Vinca, Malva, Portulaca, Quercus and Sorghum.

To prevent Xylella fastidiosa from spreading north, Italy has spent 7.6 million € and the regional government has allocated another 5.9 million €. In the southern part of Salento Peninsula authorities imposed phytosanitary measures and established demarcated area – 3 km wide zone spanning the peninsula. In infected area sick trees are being mechanically removed while host plants like oleander are sprayed with insecticides to kill adult spittlebugs. Elsewhere, farmers have plowed thousands of hectares of orchards to kill juvenile spittlebugs. However, all these control methods are not completely effective and infected trees were discovered about 30 kilometers north of the infected zone.

Such olive trees disease poses significant threat to olive groves alongside Adriatic coast in Croatia. Commission implementing decision of 23 July 2014 (2014/497/EU) as regards measures to prevent the introduction into and the spread within the Union of Xylella fastidiosa should stop spreading and ensure the earliest possible action against the potential presence of the Xylella fastidiosa across Europe.