Europe’s Evolving Fight Against Xylella Fastidiosa

Early detection across the European Union remains at the forefront of the struggle against the bacterium as officials are hopeful about new research, methods and tools.

Puglia, Italy (AP)
By Paolo DeAndreis
Sep. 6, 2023 12:26 UTC
Puglia, Italy (AP)

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.

Xylella is a global phe­nom­e­non, not merely European. Thanks to the advances in sci­en­tific research… we are see­ing sig­nif­i­cant progress.- Giuseppe Stancanelli, plant health risk asses­sor, EFSA

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.”

See Also:Art Exhibition Reflects on Xylella’s Devastating Impact

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).

Xylella fas­tidiosa

Xylella fas­tidiosa is a gram-neg­a­tive bac­terium that is known for caus­ing a vari­ety of plant dis­eases. It is a pathogen that pri­mar­ily affects the xylem, which is the plant tis­sue respon­si­ble for trans­port­ing water and nutri­ents from the roots to other parts of the plant. Xylella fas­tidiosa is a sig­nif­i­cant con­cern in agri­cul­ture and forestry because it can infect a wide range of plant species, lead­ing to eco­nomic losses and envi­ron­men­tal dam­age.

This bac­terium is trans­mit­ted by insect vec­tors, such as sharp­shoot­ers and spit­tle­bugs, which feed on plant sap. When these insects feed on infected plants, they acquire the bac­terium and can then trans­mit it to healthy plants when they feed on them. Xylella fas­tidiosa can infect both agri­cul­tural crops and orna­men­tal plants, and it has been respon­si­ble for dev­as­tat­ing dis­eases in var­i­ous parts of the world.

Some of the well-known dis­eases caused by Xylella fas­tidiosa include Pierce’s Disease, Citrus Variegated Chlorosis (CVC) and Olive Quick Decline Syndrome (OQDS).

Efforts to con­trol Xylella fas­tidiosa include the use of insec­ti­cides to man­age the insect vec­tors, as well as efforts to quar­an­tine and remove infected plants to pre­vent fur­ther spread. Research is ongo­ing to develop more effec­tive strate­gies for man­ag­ing and pre­vent­ing the spread of this bac­terium and its asso­ci­ated plant dis­eases.

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.


Participants at the Fourth European Conference on Xylella, organized by the European Food Safety Authority

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.”

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