Study Finds Treatments Reduce Symptoms But Do Not Eliminate Xf in Olive Trees

The European Food Safety Authority (EFSA) has concluded that treatments used on olive trees in Apulia (Puglia) affected by the bacteria have resulted in a reduction in symptoms, but are not successful in eliminating the disease.

The effect of Xf on grape leaves
May. 4, 2016
By Isabel Putinja
The effect of Xf on grape leaves

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An eval­u­a­tion by the European Food Safety Authority (EFSA) has con­cluded that treat­ments being used on olive trees in Apulia (Puglia) affected by the bac­te­ria Xylella fas­tidiosa have resulted in a reduc­tion in symp­toms, but are not suc­cess­ful in elim­i­nat­ing the dis­ease.

A press release pub­lished by EFSA revealed details of a state­ment adopted by EFSA’s expert Panel on Plant Health out­lin­ing its opin­ion on treat­ment solu­tions for plants infected by Xf. The eval­u­a­tion was con­ducted in response to a request by the European Commission for sci­en­tific advice in response to ques­tions about its con­trol strat­egy against Xf in the Apulia region.

EFSA’s panel eval­u­ated two dif­fer­ent exper­i­men­tal treat­ment meth­ods cur­rently being car­ried out in Apulia by two sep­a­rate groups of researchers. The first group from the University of Foggia has been treat­ing olive trees infected with Xf with bioac­tive com­pounds which are applied after exten­sive prun­ing of the trees. Five months after the treat­ment, the trees quickly grew new branches with new leaves free of symp­toms, and pro­duced good crops.

The other treat­ment method is being car­ried out by researchers from CREA (Consiglio per la ricerca in agri­coltura e l’analisi dell’economia agraria) and involves using a com­mer­cial prod­uct of zinc, cop­per and cit­ric acid to treat infected olive trees. Positive results were also seen here, with the trees sur­viv­ing the sum­mer of 2015 and the fol­low­ing win­ter.

These exper­i­men­tal treat­ments were tested for their effec­tive­ness in sup­press­ing dis­ease symp­toms only, and accord­ing to the researchers, the pos­i­tive results can be con­sid­ered to be only pre­lim­i­nary, and that fur­ther treat­ments would need to be tested over the course of another grow­ing sea­son.


EFSA’s expert panel agrees that the long-term effec­tive­ness of these treat­ments has not been estab­lished, and fur­ther stud­ies of treat­ments spread over sev­eral grow­ing sea­sons would be required to arrive at a con­clu­sion about their sus­tain­abil­ity. But the panel does acknowl­edge in its state­ment the pos­i­tive effects of such treat­ments in poten­tially pro­long­ing the life of olive trees, espe­cially in the infected zone in Apulia which is cur­rently under con­tain­ment.

EFSA’s panel also exam­ined treat­ments used in other parts of the world to con­trol bac­te­r­ial infec­tions in olive trees as well as grapevines, and cit­rus, apple and pear trees. It found that results seen in Apulia are con­sis­tent with expe­ri­ence from other parts of the world and con­firmed that though there are treat­ments that can reduce its symp­toms, there is no treat­ment to elim­i­nate Xylella fas­tidiosa.

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