Europe’s Evolving Fight Against Xylella Fastidiosa

Extreme weather has heav­ily impacted olive grow­ers in south­ern Italy. In the last few days, sud­den and vio­lent hail­storms hit olive groves in Salento, in the Puglia region.

According to the farm­ers orga­ni­za­tion Coldiretti, approx­i­mately 40 per­cent of the olives for the cur­rent sea­son were lost in the area.

In the last decade, olive farms around Salento have been dev­as­tated by Xylella fas­tidiosa. New groves in the area are planted with Leccino and Favolosa, the two olive cul­ti­vars that show sig­nif­i­cant resis­tance to the bac­te­ria.

“New resis­tant olive trees need three or four years to pro­duce olives,” Coldrietti wrote. ​“And now that some olive grow­ers can go back to har­vest­ing the fruits after ten years of epi­demic, there we go with another loss due to extreme events such as hail­storms, tor­na­dos and cloud­bursts.”

The chal­leng­ing sit­u­a­tion in Puglia was among the focal points of the Fourth European Conference on Xylella, orga­nized by the European Food Safety Authority (EFSA).

EFSA plays a cru­cial role in the sci­en­tific coor­di­na­tion of the oper­a­tions against Xylella fas­tidiosa and sup­ports the European Commission and mem­ber states in estab­lish­ing pro­ce­dures, guide­lines and meth­ods.

Ahead of the con­fer­ence, the doc­u­men­tary movie ​“The Era of the Giants” was pre­sented to the del­e­gates. It inves­ti­gates the social, eco­nomic and land­scape impacts of Xyella fatidiosa in a region where the mon­u­men­tal olive trees had thrived for mil­len­nia.

“That is very sig­nif­i­cant, as it allows the European pub­lic to wit­ness the dev­as­tat­ing impact of the pathogen,” Giuseppe Stancanelli, EFSA’s plant health risk assess­ment team leader, told Olive Oil Times.

“Communication to the pub­lic is a key fac­tor to ensure the suc­cess of plant health strate­gies,” Stancanelli added, hint­ing at the comic strip recently pub­lished by EFSA.

“It stresses the impor­tance of sci­ence in devel­op­ing strate­gies to deal with plant health threats, such as Xylella,” he said.

In col­lab­o­ra­tion with the European Commission and mem­ber states, EFSA also launched the #PlantHealth4Life cam­paign.

“The goal is to raise European cit­i­zens’ aware­ness about the impor­tance of plant health and everyone’s respon­si­bil­ity to safe­guard it,” Stancanelli said.

In the E.U., Italy is not the only coun­try affected by Xylella fas­tidiosa. Other strains of the bac­te­ria have been found in the Balearic Islands of Spain, Portugal and France. Insect vec­tors such as spit­tle­bugs carry the pathogen from one plant to the next, infect­ing olive trees, almonds and dozens of other plant species.

Over the years, the Xylella fas­tidiosa out­break, cou­pled with the grow­ing under­stand­ing of the threat rep­re­sented by the epi­demic, spurred an array of E.U.-wide activ­i­ties.

“Xylella is now included in the list of the main quar­an­tine plant pathogens main­tained at the E.U. level, the so-called Priority Pests,” Stancanelli said. ​“That brought all mem­ber coun­tries to develop pre­ven­tive con­tin­gency plans and to inten­sify sur­veil­lance.”

EFSA main­tains the only global data­base of plants infected by the dif­fer­ent Xylella fas­tidiosa strains.

“That sup­ports mem­ber states in case of new out­breaks,” Stancanelli said. ​“It is also use­ful for local insti­tu­tions and farm­ers to decide what to plant in infected areas. It also reports the vari­eties of plants which showed tol­er­ance or resis­tance to Xylella.”

According to the con­fer­ence’s con­clu­sions, cur­rent means to cur­tail the spread of Xylella fas­tidiosa are improv­ing as new tools are devel­oped.

“Xylella is a global phe­nom­e­non, not merely European,” Stancanelli said. ​“Thanks to the advances in sci­en­tific research, new tools that allow the detec­tion over exten­sive areas and advanced pest con­trol strate­gies, we are see­ing sig­nif­i­cant progress.”

“At the con­fer­ence, it emerged how knowl­edge about the biol­ogy and the ecol­ogy related to the vec­tor insects is grow­ing,” Stancanelli said. ​“Not only in the Mediterranean area but also in Northern Europe.”

Current research funded by the E.U. includes work on pre­ven­tion, con­trol, ecol­ogy and soci­ety, such as the BEXYL project, as well as the devel­op­ment of new bio­con­trol solu­tions act­ing either against Xylella fas­tidiosa or its vec­tor, such as the BIOVEXO project.

BEXYL and BIOVEXO co-orga­nized the Xylella con­fer­ence in col­lab­o­ra­tion with EFSA and other E.U. projects.

A large part of the efforts funded by the E.U. goes into fos­ter­ing col­lab­o­ra­tion and coor­di­na­tion among the many national enti­ties involved.

Key to the E.U.’s strate­gies is early detec­tion. ​“With EFSA sci­en­tific sup­port, all European coun­tries are mon­i­tor­ing their whole ter­ri­tory,” Stancanelli said.

Extended mon­i­tor­ing oper­a­tions fol­low EFSA guide­lines and can spot new out­breaks. That allows for a quick inter­ven­tion to con­tain fur­ther spread­ing.

“Significant progress has been made in the sur­vey and mon­i­tor­ing sys­tems and diag­nos­tics, such as those for ana­lyz­ing aer­ial and satel­lite images,” Stancanelli said.

“For exam­ple, if we need to mon­i­tor all of the olive farm­ing areas in the Mediterranean region, we can­not rely on on-field vis­its only,” he added. ​“We need to be able to ana­lyze large por­tions of the ter­ri­to­ries all at once. Now that tech­nol­ogy is avail­able.”

Other cru­cial aspects debated at the con­fer­ence include those olive vari­eties that show tol­er­ance or resis­tance to Xylella fas­tidiosa, such as Leccino.

“There is progress in the research aim­ing to uncover the mech­a­nism of such resis­tance,” Stancanelli said. ​“It is of great inter­est, as unlock­ing these aspects can also allow us to find those mech­a­nisms in other olive cul­ti­vars.”

Since it was first tried in Puglia, the graft­ing meth­ods can pave the way to iden­tify new sources of resis­tance to Xylella.

“In Israel, where Xylella attacked almonds, researchers iden­ti­fied resis­tant almond vari­eties by graft­ing them over infected plants, root­stocks, and observ­ing their responses,” Stancanelli said.

“All over the world, Xylella has become a pri­or­ity plant pathogen,” he con­cluded. ​“Today, sci­en­tific research and inter­na­tional coor­di­na­tion allow us to see hope in the strug­gle against the pathogen.”

• Coldiretti
• EFSA