Balearic Islands Tighten Restrictions as Xylella Spreads in Mallorca

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.

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.

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 16^th, 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.

“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.