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

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.

• European Food Safety Authority


• European Food Safety Authority