Study Predicts the Spread of Xylella Pathogen in Olive Trees

A team of ecologists at the Centre for Ecology and Hydrology (CEH) in the UK have released a study in which they constructed a scientific model which may be able to predict how Xylella fastidiosa will spread.

By Sheherzad Preisler
Jan. 26, 2020 09:43 UTC

Xylella fas­tidiosa is a pathogen spread­ing through Europe that poses a grave threat to its abun­dant olive trees.

The pathogen, which was once exclu­sive to America, was found in Italy in 2013. Since then, it has rav­aged its way through south­ern Italy, destroy­ing almost 60,000 acres of olives. Farmers through­out Southern Italy and the Mediterranean basin are wor­ried Xylella fas­tidiosa could cause seri­ous dam­age to these areas eco­nom­i­cally, as olives and their accom­pa­ny­ing prod­ucts are among their most pop­u­lar agri­cul­tural prod­ucts.

A team of ecol­o­gists at the Centre for Ecology & Hydrology (CEH) in the UK have released a study in which they con­structed a sci­en­tific model which may be able to pre­dict how and where Xylella fas­tidiosa will spread. This could be a game-changer and allow farm­ers to help cre­ate pre­ven­ta­tive buffer zones.

The lead author and a the­o­ret­i­cal ecol­o­gist at CEH, Steven White, said it has been dif­fi­cult to pre­dict how and where Xyllela fas­tidiosa will spread largely due to bio­log­i­cal and envi­ron­men­tal dif­fer­ences between where the strain is invad­ing and where it has orig­i­nated.” Another cause for worry is that there is some­times a large gap in time between when an olive becomes infected and when it starts to present symp­toms, which can cause farm­ers to unin­ten­tion­ally over­look infected plants, thereby caus­ing the dis­ease to spread.

The study focused on mod­els of con­trol zones that are in use in Apulia, Italy. The team found that though widen­ing buffer zones low­ered risk of infec­tion past the con­trol zone, it may not be com­pletely effec­tive in stop­ping the spread of Xylella; this was the case because cer­tain infec­tious insects were able to travel between the dif­fer­ent sites. And while some dis­ease pre­ven­tion mea­sures such as weed removal and the use of insec­ti­cide are fairly sim­ple, stop­ping farm vehi­cles from becom­ing dis­ease vec­tors will pose more of a chal­lenge.

The study also hinted that there may be a vari­ety of plants other than olive trees that can serve as vec­tors, many of which are quite com­mon in Southern Italy and the Mediterranean. These include myr­tle-leaf milk­wort, coastal rose­mary, almond, and ole­an­der.

In fact, the CEH model sug­gested that the risk of infec­tion may sky­rocket up to eight­fold if alter­na­tive host plants are not taken into account and removed from farm plots. Because of this, the team stressed that it is essen­tial to also study and iden­tify other host plants in the areas in ques­tion; this could be done via more exper­i­ments and field work.

The model con­structed by the CEH team seeks to reca­pit­u­late how the dis­ease spreads. The team then used their new model to test out a new buffer zone con­trol pro­gram; their work could help pol­icy-mak­ers within the European Union make wiser and more effec­tive deci­sions regard­ing dis­ease con­trol efforts.

The study showed that the width of pre­ven­ta­tive buffer zones is cru­cially impor­tant” to pre­vent the dis­ease from spread­ing north; pre­vi­ously-made buffer zones were shown to be insuf­fi­ciently wide in rela­tion to dis­per­sal dis­tances.”

Moving for­ward, the team has received addi­tional fund­ing from the European Union. They will be con­tin­u­ing their study and expand­ing their model to deal with con­tain­ment, sur­veil­lance, as well as the elim­i­na­tion of recent Xylella fas­tidiosa out­breaks.

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