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Organic Treatment Shows Promise Against Xylella

The implementation of an organic treatment with good agricultural practices during a three-year trial gave encouraging results against Xf.

Aug. 9, 2018
By Ylenia Granitto

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We have been fol­low­ing the devel­op­ments over the years of a study for the con­tain­ment of the Xylella fas­tidiosa (Xf) bac­te­ria led by the research direc­tor of the Olive, Fruit Trees and Cit­rus Cen­tre of the Coun­cil for Agri­cul­tural Research and Agri­cul­tural Eco­nom­ics Analy­sis (CREA) in Roma and Caserta, Marco Scor­ti­chini, in col­lab­o­ra­tion with other Ital­ian research insti­tu­tions includ­ing the Uni­ver­sity of Salento in Lecce, and the US Agri­cul­tural Research Ser­vice Depart­ment of Agri­cul­ture, in Cal­i­for­nia.

The research was con­ducted to eval­u­ate, both in vitro and in the field, the bac­te­ri­ci­dal activ­ity of a patented com­pound con­tain­ing zinc and cop­per with cit­ric-acid hydracids to con­trol the phy­topathogen.

The pre­lim­i­nary find­ings of the research were pre­sented two years ago dur­ing a sem­i­nar orga­nized by the IOC, and the final results have recently been pub­lished in the peer-reviewed jour­nal devoted to plant pathol­ogy, Phy­topatholo­gia Mediter­ranea.

The researchers car­ried out a three-year field trial in an olive grove in Veg­lie, in the province of Lecce, con­tain­ing adult Cel­lina di Nardò and Ogliarola salentina olive trees, which before the trial were offi­cially declared infected by Xylella fas­tidiosa subsp. pauca and showed symp­toms of the olive quick decline syn­drome (OQDS or CoDiRO).

Exper­i­men­tal field tests are the fun­da­men­tal core of the research since they allow us to under­stand how a phe­nom­e­non works, but a very impor­tant phase is the sub­se­quent imple­men­ta­tion of the trial, which in this case gave us encour­ag­ing results,” Scor­ti­chini said. Now, our pro­to­col is cur­rently fol­lowed by some farm­ers in infected areas as a prac­tice to con­tain the dis­ease.”

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The researcher said the grow­ers vol­un­tar­ily asked to fol­low the pro­ce­dure, after attend­ing pre-trial meet­ings, since their olive grove had strong symp­toms of the dis­ease. There­fore, in April 2016 they started to imple­ment the pro­to­col, first remov­ing the por­tions of the olive trees affected by des­ic­ca­tion, then apply­ing the treat­ment.

At the present time, their olive trees are full of olives in excel­lent health,” Scor­ti­chini observed. To give an exam­ple, two weeks ago, we counted in some cases, 16 – 18 olives under devel­op­ment on a 12- to 13-cen­time­ter branch.”

Each year dur­ing the trial, from early April to Octo­ber the com­pound was applied by means of six spray treat­ments on the crowns of the olive trees. The research results showed that the com­pound reduced the sever­ity of symp­toms in both cul­ti­vars. While most untreated trees died by the end of the trial, all treated trees sur­vived with good veg­e­ta­tive sta­tus, accord­ing to NDVI (Nor­mal­ized Dif­fer­ence Veg­e­ta­tion Index), as recorded in early Octo­ber 2017.

Quan­ti­ta­tive real-time PCR (Poly­merase Chain Reac­tion) was per­formed from June 2016 to Sep­tem­ber 2017, fol­low­ing the offi­cial pro­ce­dures estab­lished by the Euro­pean and Mediter­ranean Plant Pro­tec­tion Orga­ni­za­tion (EPPO). The analy­sis revealed a sta­tis­ti­cally sig­nif­i­cant decrease of Xylella fas­tidiosa cell den­si­ties within the leaves of treated trees.

Olive tree in full production in the third year of the field trial

The reduc­tion of the bac­terium is not impos­si­ble — co-exis­tence is some­thing that can be achieved,” Scor­ti­chini told Olive Oil Times reporter, Cain Bur­deau in the third arti­cle of his inves­tiga­tive series on Xylella.

Accord­ing to our researcher, as the bac­terium is present over a huge area, at this moment the only solu­tion is to learn how to live with it. To do that, we devel­oped a method aimed at pro­mot­ing the vital bal­ance of the olive trees and the ter­ri­tory, includ­ing the soil,” he pointed out, adding that they con­sider it fun­da­men­tal to rein­tro­duce sta­bi­liz­ing fac­tors in the envi­ron­men­tal sys­tem, through the devel­op­ment of organic and sus­tain­able prac­tices.

(A fur­ther debate con­cerns the oppo­si­tion to this kind of approach by those who see a solu­tion to Xf in pes­ti­cides.

There­fore, the promis­ing results we achieved sug­gest that an inte­grated man­age­ment which includes reg­u­lar prun­ing of olive trees; soil har­row­ing toward the end of win­ter and the begin­ning of spring, to reduce the pop­u­la­tions of the insect vec­tors which sur­vive on the weeds; and spray treat­ments with this com­pound on the olive trees crowns from spring to the end of autumn, could effec­tively con­trol the dis­ease,” Scor­ti­chini con­cluded.

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  1. Mr. V. says:

    This arti­cle ignore the severe crit­i­cism to the sci­en­tific results of the treat­ment. Lec­tur­ers should be also informed on those (https://www.researchgate.net/profile/Enrico_Bucci/publication/324128524_Scortichini_et_al_2018_a_critical_reappraisal/links/5af00b7b458515f5998462be/Scortichini-et-al-2018-a-critical-reappraisal.pdf?origin=publication_detail), as well as on the evo­lu­tion of the exper­i­men­tal field reported in the pub­li­ca­tion of Scor­ti­chini et al. (some pho­tos cir­cu­lat­ing in the web are not at all reas­sur­ing…).
    This infor­ma­tion is essen­tial for those who have to invest money in this pro­to­col; It is bad and mis­lead­ing to present the crit­i­cism as a sup­port for the use of pes­ti­cides

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