Europe

Research Confirms Xf to Blame for Desiccation of Salento Trees

A project funded by the European Food Safety Authority EFSA confirmed that the destruction was caused by the Xylella fastidiosa bacterium.

Field trials have shown that the infective spittlebug (Philaenus spumarius), widespread in Apulia, can transmit the bacteria to olive trees.
Apr. 6, 2016
By Ylenia Granitto
Field trials have shown that the infective spittlebug (Philaenus spumarius), widespread in Apulia, can transmit the bacteria to olive trees.

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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 more: 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.

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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.”


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