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The plant epi­demic that is caus­ing the so-called CoDiRO or Rapid Complex Desiccation of Olive Trees in Salento (Apulia) was, with­out doubt, caused by the Xylella fas­tidiosa bac­terium. This is the con­clu­sion, reached by the European Food Safety Authority (EFSA), on the basis of research con­ducted on its behalf by the National Research Centre (CNR) and by the Basile Caramia Research Center in Locorotondo (Bari).

Researchers exposed vari­eties of major peren­nial crops to the bac­terium through arti­fi­cial inoc­u­la­tion and by expo­sure to infec­tive insect vec­tors in the field. Not only olive trees were tested but also other Mediterranean plants such as grape, cit­rus, almond, peach, cherry and plum, for­est species such as holm oak and orna­men­tal species such as ole­an­der and myr­tle-leaf milk­wort.
See Also: Complete Coverage of the Xylella Fastidiosa Outbreak

“These find­ings con­firm that the CoDiRO strain of Xylella fas­tidiosa causes olive dieback,” said the head of EFSA’s Animal and Plant Health Unit, Giuseppe Stancanelli. ​“This is an impor­tant step for­ward because we can only accu­rately assess the risk of an epi­demic spread­ing from Apulia if we fill knowl­edge gaps on the host range and epi­demi­ol­ogy of the Apulian strain.”

According to EFSA, the olive trees inoc­u­lated with Xylella fas­tidiosa by researchers pre­sented the same severe symp­toms as those in Salento, with des­ic­ca­tion and death, but it was found that not all vari­eties react the same way. The bac­terium seems to take longer to col­o­nize the vari­ety of Coratina, Leccino and Frantoio than the Cellina di Nardò, who is one of the most com­mon vari­eties in the con­t­a­m­i­nated area. However, accord­ing to the researchers, more tests on a larger num­ber of olive cul­ti­vars are nec­es­sary to under­stand the dif­fer­ent phys­i­o­log­i­cal responses to the aggres­sion of the bac­terium.

The field tri­als have also shown that the infec­tive spit­tle­bug (Philaenus spumar­ius), wide­spread in Apulia, can trans­mit the bac­te­ria to olive trees, ole­an­der and myr­tle. While none of the cit­rus, screw or holm plants tested pos­i­tive for Xylella fas­tidiosa upon expo­sure to infec­tive P. spumar­ius or direct inoc­u­la­tions. Further tests are nec­es­sary for stone fruits like peach and plum.

“The results of this study sig­nif­i­cantly reduces the uncer­tain­ties about the risks of Xylella in the European Union. As part of the EU research fund­ing pro­gram Horizon 2020, there will be spe­cific pro­grams for the con­trol of this dis­ease,” Stancanelli con­cluded. All the inoc­u­lated plants will be kept under obser­va­tion for at least one more veg­e­ta­tive sea­son, while field exper­i­ments will be extended for up to 10 years.

Nevertheless, the study is going to raise doubts and protest, first of all for the poten­tial con­flict of inter­est con­cern­ing some of the researchers involved: Vito Savino, Donato Boscia and Maria Saponari are three of the ten peo­ple named in the inves­ti­ga­tion started in December by the Prosecutor of Lecce, Cataldo Motta, for var­i­ous infrac­tions includ­ing spread­ing of a plant dis­ease, will­ful vio­la­tion of the pro­vi­sions on the envi­ron­ment, fake mate­r­ial com­mit­ted by pub­lic offi­cials in pub­lic doc­u­ments, fraud­u­lent mis­rep­re­sen­ta­tion and the destruc­tion or dis­fig­ure­ment of nat­ural beauty.

Moreover, there are those who have expressed con­cerns since EFSA is not a body of the inter­na­tional sci­en­tific com­mu­nity but a gov­ern­ment agency of the European Union that is appointed to assess the state of sci­en­tific research on the Xylella emer­gency, and is fund­ing a study that will be included in its deci­sions.

“Our data are objec­tive. And incon­tro­vert­ible. Nothing changes,” Cataldo told the daily news­pa­per Nuovo Quotidiano di Puglia about the ongo­ing inves­ti­ga­tion: ​“We will acquire the EFSA study and sub­mit it to our experts. It is nec­es­sary to have a com­plete scenery of the most accred­ited stud­ies in order to real­ize a seri­ous con­fronta­tion.”

• ANSA


• Il Fatto Quotidiano