Treatment to Mitigate the Impact of Xylella Fastidiosa Shows Promise in Italy

Researchers found that a recently-patented bio-complex killed bacteria from three strains of Xylella in infected trees, while increasing their resilience to the disease.
Olive trees affected by Xylella fastidiosa in Salento, Italy
Feb. 1, 2021
Paolo DeAndreis

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New evi­dence con­firms that one of the most promis­ing tools to com­bat Xylella fas­tidiosa in Italy is work­ing.

As the new treat­ment, com­posed of zinc, cop­per and cit­ric acid, has shown an abil­ity to mit­i­gate the impacts of the deadly olive tree pathogen, a grow­ing num­ber of farm­ers in the south­ern olive-pro­duc­ing region of Puglia are tak­ing notice.

When reg­u­larly applied to trees, not only did they return to their nor­mal pro­duc­tion, but the dif­fer­ences in the resilience to Xylella of the dif­fer­ent cul­ti­vars tended to min­i­mize.- Marco Scortichini, research direc­tor, CREA Olive, Fruit Trees and Citrus Center

In a study recently pub­lished in the sci­en­tific jour­nal, Pathogens, a team of researchers assessed the effects of the patented bio-com­plex both in the field and in vitro.

The com­pound has proven to be effec­tive against three strains of Xylella, includ­ing the Pauca sub­species (Xfp), which has spread widely in Puglia.

See Also: Xylella Fastidiosa Updates

The bio-com­plex also demon­strated bac­te­ri­ci­dal prop­er­ties in the in vitro exper­i­ments, inhibit­ing biofilm for­ma­tion, which is essen­tial for the devel­op­ment of all three of the tested Xylella strains.

Our paper can be con­sid­ered a fol­low-up of the pre­vi­ous research about the patented com­pound,” said Marco Scortichini, co-author of the study and research direc­tor of the Olive, Fruit Trees and Citrus Center at CREA (Council for Agricultural Research and Agricultural Economy Analysis).

After a few years of con­stant treat­ments, we had to eval­u­ate the results of our pro­to­col of cohab­i­ta­tion with Xylella,” he told Olive Oil Times.

To study the effects of the con­trol strat­egy, two olive groves in the most infected areas – the Salento region of south­ern Puglia – were mon­i­tored for three and four years, respec­tively, with mol­e­c­u­lar diag­nos­tic PCR test­ing as the main tool of eval­u­a­tion.

Researchers assessed the field symp­toms and Xfp DNA con­cen­tra­tions in the trees on which the bio-com­plex was used. The pro­to­col strat­egy did not aim to erad­i­cate the bac­te­ria from the ter­ri­tory, which would not be fea­si­ble due to the abil­ity of Xylella to repli­cate in many dif­fer­ent plants. Instead, it aimed to increase the resilience of the olive trees after being infected by the plant pathogen.

The pro­to­col pro­vides for six treat­ments to be applied in the groves from March to September,” Scortichini said. Protecting the trees with these kinds of inter­ven­tions reminds me of what grape grow­ers reg­u­larly do against the late blight dis­ease.”

The bio-com­plex appli­ca­tion method is also quite sim­ple and requires the trees to be sprayed with the prod­uct, sim­i­lar to what farm­ers cur­rently do with many other agri­cul­tural com­pounds.

The mon­i­tored groves included 41 trees of three dif­fer­ent cul­ti­vars – Leccino, Ogliarola salentina and Cellina di Nardò – all of which are typ­i­cal of Salento.

When reg­u­larly applied to trees, not only did they return to their nor­mal pro­duc­tion, but the dif­fer­ences in the resilience to Xylella of the dif­fer­ent cul­ti­vars tended to min­i­mize,” Scortichini said. The results of the most sen­si­tive to the bac­te­ria, Ogliarola and Cellina, come close to the reac­tion of the most Xfp-resis­tant Leccino.”

The bio-com­plex has shown its con­tain­ment qual­i­ties even when diluted,” he added. It can be diluted 1:100 with­out los­ing its effi­ciency.”

However, not all olive trees can be treated. Researchers pointed out that the Xylella con­tain­ment suc­cess depends on the sys­temic absorp­tion of the bio-com­plex. For those olive trees that have already been severely hit by the infec­tion, it might be too late.

For the cur­rent treat­ment to work, at least 50 or 60 per­cent of the crown must be intact,” Scortichini said.

Still, the treat­men­t’s sys­tem­atic nature makes it of inter­est for future tests that researchers have already planned.

Thanks to a part­ner­ship with the Invaio com­pany, we have pro­grammed new field exper­i­ments start­ing next March or April, if the cur­rent Covid-19 pan­demic will let us oper­ate in the area,” Scortichini said. The idea is to use a spe­cial san­i­tary agri-machine devel­oped by the Swiss-American com­pany to inoc­u­late a spe­cific dose of the bio-com­plex directly under the cor­ti­cal layer.”

The goal is to expand the num­ber of trees that can be treated while con­tain­ing inter­ven­tion costs.

We should be able to work on the infected mon­u­men­tal sec­u­lar plants as well,” Scortichini added.

Another area of appli­ca­tion for the bio-com­plex is in the fight against the brown mar­morated stink bug, the spread of which in north­ern Italy has caused exten­sive dam­age to the local agri­cul­ture in recent years.

The team of pro­fes­sor Alberto Alma at the University of Turin has found that our bio-com­plex can be sprayed on the bugs’ eggs,” Scortichini said. Once done, there is evi­dence that the prod­uct kills the sym­bi­otic bac­te­ria that feed the larva vital pro­teins. Without them, the lar­vae die in 98 per­cent of the cases.”

The results obtained by the first farm­ers to adopt the treat­ment are attract­ing an increas­ing amount of atten­tion from other Apulian grow­ers.

We are see­ing farm­ers join­ing in the provinces of Lecce, Taranto and Brindisi,” Scortichini said. They are expand­ing the treated areas. We are cur­rently at about 700 hectares and we are see­ing large olive com­pa­nies approach­ing [to learn more about the treat­ment].”





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