Balearic Islands Tighten Restrictions as Xylella Spreads in Mallorca

The strain of Xylella fastidiosa responsible for Olive Quick Decline Syndrome was identified in other plants in Mallorca.

Ibiza, Spain
By Paolo DeAndreis
Feb. 20, 2024 15:45 UTC
Ibiza, Spain

The recent dis­cov­ery of another Xylella fas­tidiosa strain in Mallorca has put the deadly olive tree pathogen back in the spot­light.

Local author­i­ties on the Spanish island announced a new action plan against the bac­te­ria, which causes Olive Quick Decline Syndrome and affects dozens of other plant species.

Eradicating the pathogen is impos­si­ble, and the future involves learn­ing to live with Xylella fas­tidiosa.- Andreu Juan Serra, head of agri­cul­tural ser­vices, Balearic gov­ern­ment

Although Xylella fas­tidiosa was first iden­ti­fied on the Balearic Islands in 2016, this is the first time that Mallorcan author­i­ties have iden­ti­fied strain 53, belong­ing to pauca sub­species.

Xylella fas­tidiosa pauca is the same strain that has spread in south­ern Puglia since 2008, killing mil­lions of olive trees.

See Also:Europe’s Evolving Fight Against Xylella Fastidiosa

The bac­te­ria were iden­ti­fied in ole­an­der and a few wild olive trees in Sencelles, a munic­i­pal­ity in cen­tral Mallorca, the largest island of the vol­canic arch­i­pel­ago.

The plants were destroyed as required by the Xylella fas­tidiosa con­tain­ment pro­to­cols of the local admin­is­tra­tion, which com­ply with cur­rent European Union reg­u­la­tions.

Although the dis­cov­ery is con­cern­ing, it did not sur­prise the local author­i­ties, con­sid­er­ing the impact of the bac­te­ria on the archipelago’s veg­e­ta­tion over the past eight years.

Different strains of Xylella fas­tidiosa are found in the Balearic Islands, affect­ing dif­fer­ent host plants,” Andreu Juan Serra, the head of agri­cul­tural ser­vices at the Balearic government’s gen­eral direc­torate of agri­cul­ture, live­stock and rural devel­op­ment, told Olive Oil Times.

As of January 16th, a total of 1,566 pos­i­tive sam­ples for the Xylella fas­tidiosa bac­terium have been iden­ti­fied in the Balearic Islands,” Juan Serra said.

Thirty-eight host species for Xylella fas­tidiosa were found in the infected areas of the Balearic Islands,” he added, list­ing species includ­ing wild cher­ries, figs, rose­mary, vines and olives.

To date, con­tin­u­ous mon­i­tor­ing by local insti­tu­tions has iden­ti­fied 225 olive trees affected by strains of Xylella fas­tidiosa on the Spanish arch­i­pel­ago.

One hun­dred fifty-nine of these were found in Ibiza, 14 in Menorca, and 52 in Mallorca, where olives have grown for thou­sands of years.

The bac­te­ria was also iden­ti­fied in 596 wild olive trees and 365 almond trees, mostly in Mallorca.

Juan Serra explained that strain 81 affects sev­eral plant species in Mallorca, and to date, only strain 80 has been found in Ibiza. In Menorca, only the sub­species mul­ti­plex strain 81 has been detected, affect­ing var­i­ous plants,” he added.

The phy­tosan­i­tary mea­sures do not dif­fer­en­ti­ate between sub­species, except for the newly iden­ti­fied sub­species strain 53 in Mallorca, which has a spe­cific plan to deter­mine its scope,” Juan Serra said.

The strain 53 con­tain­ment plan fur­ther increases con­trol mea­sures by inten­si­fy­ing sam­pling in the areas where the strain was detected. The goal is to have the bac­te­ria quickly elim­i­nated.


It also requires offi­cials to iden­tify any sub­species found in sam­ples within a 50-meter radius of the infected plant.

The insect vec­tors are also tar­geted. Treatment against the vec­tor in all its life stages in these areas close to the detec­tions is also estab­lished,” Juan Serra said.

Similar pro­ce­dures have been pre­vi­ously taken in Puglia and have sig­nif­i­cantly slowed the spread of Xylella fas­tidiosa.

Balearic Islands author­i­ties are also tak­ing steps to con­tain the fur­ther spread­ing of the bac­te­ria.

As indi­cated by the action plan, estab­lished mea­sures include sur­vey­ing, ana­lyz­ing and remov­ing all veg­e­ta­tion where the Xylella fas­tidiosa infec­tion is detected,” Juan Serra said. Additionally, the move­ment of host plant mate­r­ial between islands and trans­fer­ring plant mate­r­ial off the islands is pro­hib­ited.”

Eradicating the pathogen is impos­si­ble, and the future involves learn­ing to live with Xylella fas­tidiosa,” he added.

Many activ­i­ties are under­way to cope with the pathogen. Resources are being allo­cated to research how to com­bat the bac­terium, iden­tify the best prac­tices to pre­vent the vec­tor from trans­mit­ting the bac­terium, study and pro­mote vari­eties of olive, almond and grapevine known to show some resis­tance and study how the plan­t’s micro­biome affects the bac­terium,” Juan Serra said.

This sci­en­tific knowl­edge will help farm­ers and nat­ural resource man­agers estab­lish guide­lines and mea­sures focused on min­i­miz­ing the dam­age caused by the plant path­o­genic bac­terium,” he added.

Juan Serra said farm­ers are on the front line of stop­ping the spread of Xylella fas­tidiosa on the Balearic Islands.

Farmers should pro­tect their crops by prac­tic­ing good agri­cul­tural prac­tices, con­trol­ling the pres­ence or absence of poten­tial insect vec­tors of the bac­terium, apply­ing treat­ments against the insect vec­tors and keep­ing the ground cover free of veg­e­ta­tion dur­ing the breed­ing sea­son of the vec­tor,” he said.

In other words, they should apply a series of good agri­cul­tural prac­tices that are rec­om­mended depend­ing on the time of year,” Juan Serra added. Farmers should buy plant mate­r­ial from autho­rized estab­lish­ments, with plants that have a phy­tosan­i­tary pass­port as a guar­an­tee that they are free of pests and dis­eases.”

According to Miguel Miralles, owner of award-win­ning pro­ducer Treurer on Mallorca, strain 53 is the most sig­nif­i­cant medium-term dan­ger to the island’s olive groves.

However, since the first cases of Xylella fas­tidiosa appeared, farm­ers and pub­lic admin­is­tra­tions, as well as cit­i­zens in gen­eral, have shown a high level of aware­ness about the impor­tance of the prob­lem,” he told Olive Oil Times.

Xylella fas­tidiosa

Xylella fas­tidiosa is a species of Gram-neg­a­tive bac­te­ria that is notable for caus­ing a vari­ety of plant dis­eases. It is trans­mit­ted to plants via xylem fluid-feed­ing sap insects, such as leafhop­pers and spit­tle­bugs. The bac­te­ria col­o­nize the xylem tis­sue of a plant, which is respon­si­ble for the trans­port of water and nutri­ents from the roots to the rest of the plant, and can cause block­ages that dis­rupt water flow, lead­ing to symp­toms such as leaf scorch, wilt, dieback, and even­tu­ally death in sus­cep­ti­ble plant species.

Xylella fas­tidiosa is a sig­nif­i­cant agri­cul­tural pathogen as it affects a wide range of host plants, includ­ing impor­tant crops like grapevines (caus­ing Pierce’s dis­ease), cit­rus trees, cof­fee plants, almonds, and olives. The impact of this bac­terium is a mat­ter of seri­ous con­cern because it can lead to sub­stan­tial eco­nomic losses in agri­cul­ture and hor­ti­cul­ture, as well as to the nat­ural envi­ron­ment when native plants are affected.

Managing and con­trol­ling the spread of Xylella fas­tidiosa is chal­leng­ing due to its wide host range and the diver­sity of insect vec­tors that can trans­mit the pathogen. Measures include con­trol­ling the insect vec­tors, remov­ing and destroy­ing infected plants, and imple­ment­ing plant quar­an­tine pro­to­cols to pre­vent the spread of the bac­te­ria to new areas.

With the emer­gence of strain 53, con­trols have been increased, and we hope that its expan­sion can be halted,” he added.

Miralles high­lighted how tar­geted action on dif­fer­ent lev­els is crit­i­cal to cope with the pathogen.

Adopting pre­ven­tive mea­sures is essen­tial, as it is cur­rently the best mech­a­nism to halt its spread,” he said. Among these mea­sures, it is cru­cial to develop good prac­tices in soil man­age­ment, fer­til­iza­tion, prun­ing and irri­ga­tion. Measures to fight against vec­tors also must be imple­mented.”

All these mea­sures must be gen­er­al­ized, and the best way to do this is through prop­erly train­ing farm­ers,” Miralles added.” In turn, pub­lic admin­is­tra­tions must invest more resources to dis­cover new and bet­ter ways to fight the bac­te­ria.”

Besides farm­ers, local author­i­ties are also try­ing to raise aware­ness among res­i­dents, mostly about behav­iors that could trig­ger fur­ther out­breaks.

Training and infor­ma­tion dis­sem­i­na­tion are pro­vided to raise aware­ness about the risks of bring­ing in plants from dif­fer­ent places, as they can be car­ri­ers of pests and dis­eases,” Juan Serra said.

Signage in mul­ti­ple lan­guages is dis­played at air­ports and ports to alert both the pop­u­la­tion and tourists,” he added.

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