Xylella Spreads Beyond Buffer Zones in Puglia

The spread of Xylella fas­tidiosa in Puglia, the south­ern Italian region, has slowed but not stopped. Signs of the infec­tion have been found in a few olive trees located in an area pre­vi­ously con­sid­ered safe.

The results of the lat­est mon­i­tor­ing oper­a­tions show that the deadly olive tree pathogen has infected 19 olive trees near Polignano a Mare, a coastal town not far from Bari, the regional cap­i­tal.

The newly infected trees are only a few hun­dred meters from one of their so-called buffer zone — the care­fully mon­i­tored radius around the infected plants.

Local author­i­ties mon­i­tor­ing the spread of Xylella fas­tidiosa said they found another infected tree near Castellana Grotte, approx­i­mately 15 kilo­me­ters south of Polignano. The tree still falls within the local buffer zone, but it is only five meters away from its outer bor­der.

The con­stant mon­i­tor­ing of Xylella fas­tidiosa has allowed author­i­ties to track its spread in the last few years, mak­ing it pos­si­ble to allo­cate resources effec­tively to the most vul­ner­a­ble loca­tions.

Tracking also has per­mit­ted author­i­ties to gauge the effi­ciency of the many pro­ce­dures enacted to limit the pop­u­la­tion of the main vec­tor insects, which are mainly respon­si­ble for spread­ing the deadly bac­te­ria.

Along with olive trees, Xylella fas­tidiosa infects about 300 other plant species adding to the com­plex­ity of main­tain­ing effec­tive infec­tion and buffer zones.

Local experts said the dis­cov­ery of the newly-infected trees demon­strates the need for more com­pre­hen­sive and rapid mon­i­tor­ing.

“The early detec­tion of the bac­te­ria and the con­tain­ment mea­sures adopted through­out the region seem to have slowed down the spread,” said Donato Boscia, head of the Apulian Institute for the Sustainable Protection of Plants at the National Research Council (CNR-Ipsp), who was among the first sci­en­tists to focus on Xylella fas­tidiosa in Italy.

“What we need are quick and reli­able tools to diag­nose and inter­vene early as a way to stop the epi­demic for which there is cur­rently no treat­ment capa­ble of bring­ing the infected plants back to a nor­mal state,” he added.

To this end, researchers said they had devel­oped a new detec­tion tech­nol­ogy capa­ble of mak­ing mon­i­tor­ing oper­a­tions faster and more cost-effi­cient.

The researchers from the CNR-Ipsp, the University of Bari’s pho­ton­ics and nan­otech­nol­ogy insti­tute and Agritest have devised what they describe as a ​“bio-sen­sor.”

“It is an elec­tronic device that sits in the palm of your hand and can be con­nected via Bluetooth to a smart device,” Eleonora Macchia, a researcher at the University of Bari and co-author of the study, told Olive Oil Times.

“It is capa­ble of ana­lyz­ing very small quan­ti­ties of olive juice, just above 100 micro­liters,” she added. ​“The analy­sis can tell with 99 per­cent accu­racy if even just one Xylella bac­terium is found in the olive tree fluid sam­ple.”

The pro­to­type takes about 30 min­utes to run the test in the field, far less than the two to three hours that the cur­rent quan­ti­ta­tive poly­merase chain reac­tion (qPCR) method requires in the lab.

Its cre­ators said the new device would con­sid­er­ably cut the costs and time needed to test an olive tree. ​“Costs are sig­nif­i­cantly reduced as the elec­tronic plat­forms are afford­able, and even the con­sump­tion of reagents is reduced to the min­i­mum,” Macchia said.

According to the researchers, who pub­lished their find­ings in Advanced Science, the pro­to­type also can detect Xylella fas­tidiosa infec­tions in asymp­to­matic plants.

“That gives us a con­sid­er­able advan­tage as it moves the diag­no­sis to an ear­lier stage, where pre­ven­tive med­i­cine can be applied,” Macchia said.

Its reli­a­bil­ity and other qual­i­ties might enable author­i­ties to extend their mon­i­tor­ing oper­a­tions. ​“That is one of the first goals, as it could be used to screen large num­bers with a min­i­mally inva­sive method and at a low cost,” she said.

However, Macchia warned that mon­i­tor­ing teams would need some time to adopt the device. ​“We are work­ing on that as fast as we can; we hope this pro­to­type will make a dif­fer­ence in the com­ing years,” she added.

Local author­i­ties are cur­rently try­ing to sup­port strug­gling grow­ers by deploy­ing pub­lic funds to alle­vi­ate the eco­nomic fall­out of Xyella fas­tidiosa’s spread.

In mid-October, Donato Pentassuglia, Puglia’s agri­cul­tural sec­re­tary, con­firmed that new funds would be avail­able for olive grow­ers in the Lecce and Brindisi provinces and sev­eral other munic­i­pal­i­ties in Taranto by the end of the year. Some of the poten­tial recip­i­ents had lamented the slow bureau­cratic process.

The sup­port is par­tial com­pen­sa­tion for the losses accu­mu­lated between 2018 and 2019 and will go to grow­ers whose pro­duc­tion vol­umes have dropped more than 30 per­cent because of the infec­tion.

Approximately 500 com­pa­nies in the olive oil pro­duc­tion chain have received com­pen­sa­tion for only €4 mil­lion against the €51.5 mil­lion cur­rently avail­able.

• Olivo e Olio