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Xylella Marches On: Lethal Olive Disease Discovered in Central Spain

Xylella fastidiosa continues to kill many tens of thousands of olive trees in south Italy's Puglia region and is on track to widen its deadly clasp across the Mediterranean basin.

Olive tree near Oria, felled due to an outbreak of Xylella fastidiosa. (Photo by Cain Burdeau)
Apr. 17, 2018
By Cain Burdeau
Olive tree near Oria, felled due to an outbreak of Xylella fastidiosa. (Photo by Cain Burdeau)

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Xylella fas­tidiosa, a plant bac­terium native to Cen­tral Amer­ica that causes seri­ous, often lethal, plant dis­eases con­tin­ues to kill tens of thou­sands of olive trees in south Italy’s Puglia region and it is also on track to widen its deadly clasp across the Mediter­ranean basin.

New reports this spring from Italy and Spain are grim. Span­ish author­i­ties this month reported that an olive tree on its main­land has been iden­ti­fied with the bac­terium.

Span­ish sci­en­tists pre­vi­ously had iden­ti­fied the Xylella dis­ease in olive trees on the island of Mal­lorca, said Alexan­der Pur­cell, a Xylella expert at the Uni­ver­sity of Cal­i­for­nia at Berke­ley who has been track­ing the dis­ease since the 1970s.
See more: Xylella World Map

Sub­se­quently other strains of Xylella fas­tidiosa were found in all of the other Balearic Islands, indi­cat­ing that the bac­terium must have been inde­pen­dently intro­duced at least sev­eral times,” he said in an email.

The Min­istry of Agri­cul­ture, Fish­eries and Food and Envi­ron­ment told Europa Press, a Span­ish news agency, that Xylella had been iden­ti­fied at an estate out­side Madrid.

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At press time, Span­ish min­istry offi­cials had not responded to a request for details and com­ment from Olive Oil Times.

The trou­bling news isn’t lim­ited to Spain. The bac­teri­um’s progress may be infect­ing olive trees in France, too.

Ear­lier this month, Cor­si­ca’s chap­ter of the Inter­pro­fes­sional Union of Ole­i­cul­tur­ists declared that olive trees on the French island are infected with Xylella.

In 2015, French offi­cials reported find­ing Xylella fas­tidiosa in Cor­sica and also in orna­men­tal plants in the French Riv­iera, but that the bac­terium had not begun to infect olives, Pur­cell said.

Back in the epi­cen­ter of the cri­sis, Italy’s region of Puglia, the num­ber of infected trees con­tin­ues to grow.

On April 4, Italy’s state news agency, ANSA, reported a qua­dru­pling of infected trees in a crit­i­cal con­tain­ment zone north of the flat­land of the Salento where Xylella first made its deadly impact, lay­ing waste to exten­sive tracts of olive groves.

Where the Olive Trees Are Dying: A Front-Line Report on Xylella

CASALINI, Puglia — Deep in Pugli­a’s hills green with olive groves there’s no sign of trou­ble. The trees look healthy and are hung with strands of olives — green and black pearls. This is the Valle d’I­tria, a rus­tic place of dirt roads, mean­der­ing stone walls, and cone-shaped struc­tures called trulli.


Spring­time is a crit­i­cal period to com­bat and mon­i­tor Xylella. These are the months when the bac­terium grows in the main insect vec­tor — the native spit­tle­bug — and devel­ops on weeds, Pur­cell said.

Elim­i­nat­ing weeds or using insec­ti­cides can pre­vent the matur­ing of spit­tle­bugs into adults, the stage at which they fly and carry the bac­terium to other trees.

Puglia, as has become cus­tom­ary, is again the scene of olive tree destruc­tion. Crews are cut­ting down even more olive trees.

The con­tain­ment zone, for now, encom­passes an area known as the Valle d’I­tria, a lush agri­cul­tural region famous for its ancient stone struc­tures, the trulli.

The bac­terium has the poten­tial to spread from the Valle d’I­tria into the Piana degli Olivi Mil­lenari, an exten­sive coastal plain and home to some of the old­est olive trees in Puglia. The con­cern is that its dev­as­tat­ing path will con­tinue to march through Italy and into other olive-pro­duc­ing regions of the Boot and fur­ther afield.

Xylella was intro­duced into Europe via trop­i­cal plants brought from Cen­tral Amer­ica. Inves­ti­ga­tors believe the bac­terium was spread through Hol­land’s flower mar­kets and wound up flour­ish­ing in olives near Gal­lipolli, a port town in the Salento region.

Xylella has been blamed for attack­ing cit­rus and cof­fee in Brazil, grape and Asian pear in Tai­wan and grape, almond, and alfalfa crops in Cal­i­for­nia, Pur­cell said.

The out­break of Xylella con­tributed last year to a world­wide drop in olive oil pro­duc­tion, accord­ing to the Inter­na­tional Olive Coun­cil.





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