Xylella Fastidiosa Could Be Contained With Better Monitoring

New data from the Sbarro Health Research Organization suggest that even 100-percent compliance to the present uprooting containment strategy would only partially stop the spread of Xyella fastidiosa in Italy.

Workers cut down an olive tree infected with Xylella fastidiosa near Brindisi, southern Italy. Photograph: Gaetano Lo Porto/AP
Aug. 19, 2019
By Julie Al-Zoubi
Workers cut down an olive tree infected with Xylella fastidiosa near Brindisi, southern Italy. Photograph: Gaetano Lo Porto/AP

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A new study by Enrico Bucci from the Sbarro Health Research Organization (SHRO) sug­gests that the cur­rent strat­egy for mon­i­tor­ing Xylella fas­tidiosa fails to iden­tify all the infected plants and enables pro­gres­sion of the epi­demic via unde­tected infec­tion hotspots.

The data revealed in Bucci’s report on the effec­tive­ness of cur­rent mea­sures could prove vital for the fine-tun­ing of an effec­tive con­tain­ment strat­egy; which due to the lack of a cure for Xylella offers the best chance of stop­ping the dis­ease in its tracks and pre­serv­ing both the tra­di­tional land­scapes of the impacted Mediterranean coun­tries and their economies.

Bucci told Olive Oil Times that data shows there is a fail­ure in the cur­rent dis­ease mon­i­tor­ing strat­egy. He believes the weak­ness can be attrib­uted to the way in which trees are sam­pled. Whilst the cur­rent focus is on trees dis­play­ing symp­toms; most newly infected plants are usu­ally symp­tom-free and there­fore escape detec­tion.

Having unde­tected infected plants means the infec­tion could be present with­out peo­ple being aware of this and if this occurred in a zone with­out manda­tory con­tain­ment mea­sures in place the infec­tion would spread.- Enrico Bucci, Sbarro Health Research Organization

To effec­tively con­tain the dis­ease the iden­ti­fi­ca­tion of infected trees in pre­vi­ously unin­fected regions must be fol­lowed up with appro­pri­ate con­tain­ment mea­sures such as uproot­ing infected plants and fight­ing the insects respon­si­ble for spread­ing the bac­te­r­ial infec­tion.

Having unde­tected infected plants means the infec­tion could be present with­out peo­ple being aware of this and if this occurred in a zone with­out manda­tory con­tain­ment mea­sures in place, the infec­tion would spread,” Bucci said.

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Bucci’s report states that 98 per­cent of infected olive trees clus­ter in spots within a 100-meter (109-yard) radius; which ratio­nal­izes the cur­rent strat­egy of uproot­ing and destroy­ing all trees located in a 100-meter radius of newly detected infected plants.

See Also: Xylella fas­tidiosa News

However, the sci­en­tist believes that cur­rent mon­i­tor­ing misses many infec­tion hotspots and in order to effec­tively con­tain the epi­demic the iden­ti­fi­ca­tion of infected plants in pre­vi­ously unaf­fected regions is nec­es­sary. Bucci said that even 100 per­cent com­pli­ance with the present uproot­ing con­tain­ment strat­egy would only par­tially stop the spread of the dis­ease.

Containing the epi­demic requires infec­tion hotspots to be iden­ti­fied, as this is the only way to both mea­sure the effi­ciency of our poli­cies and to apply uproot­ing [which is nec­es­sary to lessen the inocu­lum pres­sure in the newly col­o­nized area],” he said.

Bucci spoke of the need for greater invest­ment in mon­i­tor­ing to pre­vent dire con­se­quences adding, if infected plants escape detec­tion, they can­not be uprooted, and the infec­tion can­not be con­tained.”

However, he abstained from lay­ing blame for the spread of the dis­ease on any­one.

Phytosanitary offi­cers are fight­ing a vast epi­demic with scarce resources, and the mon­i­tor­ing pro­to­col is a com­pro­mise between avail­able money and staff from one side and the neces­sity to sam­ple as many plants as pos­si­ble from the other side,” he said.

Bucci believes that in any mon­i­tor­ing strat­egy, some infected trees will not be detected due to unavoid­able errors cou­pled with infec­tion hotspot trees that escape uproot­ing due to delays in apply­ing the law as a result of bureau­cracy and people’s hes­i­tancy among other rea­sons.

The sci­en­tific com­mu­nity has gen­er­ally con­cluded that uproot­ing alone would fail to con­tain the epi­demic and as part of the cur­rent con­tain­ment strat­egy weed­ing and insec­ti­cide treat­ments to fight the bac­te­ria are manda­tory.

Bucci told us that unless an effec­tive cure is devel­oped we must focus on con­tain­ment of the infec­tion. He also said that he sup­ports the cur­rent poli­cies of her­bi­cide and insec­ti­cide treat­ments, which cur­rently have no valid alter­na­tive.

The Xylella expert also offered his advice for more effec­tive con­tain­ment of the dis­ease.

First and fore­most is the need to quickly and cor­rectly apply all the manda­tory con­tain­ment mea­sures,” he said.

Secondly, he called for improve­ments to the cur­rent mon­i­tor­ing pro­to­col, in par­tic­u­lar by sam­pling trees fol­low­ing a pre­de­ter­mined sta­tis­ti­cal scheme, instead of rely­ing on arbi­trary selec­tion by staff.”

Finally, he warned peo­ple against the use of sci­en­tif­i­cally unproven reme­dies and rec­om­mended only the use of reme­dies approved by rep­utable sci­en­tific bod­ies, such as the European Food Safety Authority (EFSA).

Ministers are cur­rently on sum­mer hol­i­days, but the bac­terium is not, and new infec­tion hotspots were recently announced.- Enrico Bucci

Bucci said it may be nec­es­sary, to even­tu­ally replace sen­si­tive cul­ti­vars with more tol­er­ant and resis­tant ones, as has been done in the past for other plant dis­eases.”

The sci­en­tist told Olive Oil Times he no longer believes 100 per­cent erad­i­ca­tion of the dis­ease is a pos­si­bil­ity although it could have been achieved if all con­tain­ment mea­sures had been fol­lowed in the early days.

We may think to keep the dis­ease under con­trol, espe­cially after the iden­ti­fi­ca­tion of appro­pri­ate reme­dies such a cure or resis­tant cul­ti­vars; but we know that even most human pathogens were never entirely erad­i­cated any­where, and this is also true for plant pathogens,” he said. As in any Darwinian strug­gle between a host and its par­a­sites, we need to change to resist and sur­vive. We can’t expect Xylella to stop nat­u­rally.”

Bucci stated his opin­ion that the Italian gov­ern­ment had not done enough to either halt the spread of the dis­ease nor help Italian olive grow­ers and added that whilst laws were signed, money allo­cated and solu­tions announced; the crude facts told a dif­fer­ent story.

Ministers are cur­rently on sum­mer hol­i­days, but the bac­terium is not, and new infec­tion hotspots were recently announced,” he said.

Bucci was par­tic­u­larly crit­i­cal of the han­dling of the sit­u­a­tion in Puglia.

Apulian gov­er­nor Emiliano was con­tin­u­ously con­tra­dict­ing him­self, oscil­lat­ing from con­spir­a­to­r­ial posi­tions to vocal activism. In the mean­time, the term estab­lished for manda­tory erad­i­ca­tion by the regional agen­cies in charge of more than infected 300 plants has passed, and for more than 500 oth­ers is approach­ing.”

The sci­en­tist also thought that regional offices were often par­a­lyzed by bureau­cracy and fre­quently deliv­ered con­fus­ing infor­ma­tion to the pub­lic.

Xylella fas­tidiosa first appeared in the olive groves of Puglia in 2013 and went on to destroy 445,000 acres of Italy’s olive groves before spread­ing to the Balearic Islands, Spain, France, Portugal and Israel, spark­ing fears it could reach as far as Africa, Australia and East Asia.

Whilst efforts to keep the epi­demic under con­trol have largely failed and a cure has yet to be found; an organic treat­ment com­bined with good agri­cul­tural prac­tices was believed by some to have shown promise dur­ing a three year trial in Lecce although Bucci did not agree with this.

Italy-based Bucci works as an inde­pen­dent expert for the analy­sis of sci­en­tific data and is an adjunct pro­fes­sor at Philadelphia’s Temple University. He is also affil­i­ated to the Sbarro Health Research Organization.





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