Gridlock over Italy’s olive tree deaths starts to ease

From a small hill in the Puglia region of southern Italy, plant pathologist Donato Boscia gestures towards a landscape of the dullest brown — dead and dying olive trees as far as the eye can see. Six months earlier, he says, that canopy was mostly green, with just a few tell-tale brown spots marking the relentless advance of a vicious pathogen, Xylella fastidiosa, that was previously unknown in Europe. Almost three years ago, Boscia, who heads the Bari unit of the CNR Institute for Sustainable Plant Protection (IPSP), and other colleagues identified a subspecies of the bacterial pathogen, Xylella fastidiosa pauca, as the cause of olive quick decline syndrome (OQDS) in Puglia. They said that it probably arrived with an ornamental plant imported from the Americas, where some Xylella species are endemic. But an alarming political and legal impasse has stopped measures to contain the pathogen, which has invaded nearly 200,000 hectares of olive groves and is killing most olive trees in its wake — including beloved specimens that are more than 1,000 years old. Now the gridlock shows some signs of easing. On 12 May, the European Court of Justice declared that containment measures agreed by the European Union more than a year ago — but that were quickly blocked by dismayed protesters — were indeed appropriate, paving the way for them to now go ahead. These include monitoring the disease’s spread, uprooting infected trees and, in some cases, any apparently healthy trees surrounding them, and killing the insects that carry the bacteria. There is currently no cure for Xylella, and evidence from the Americas indicate that it cannot be eradicated. Still, challenges to fighting the outbreak remain. The infected area has grown over the past year, increasing the chance that the disease will spread to other countries in the Mediterranean basin, which accounts for 95% of the world’s olive production (see ‘Olive geography’). In February last year, Italian authorities began implementing the EU-agreed containment plan. But protesters, with local political support, dismissed the evidence that OQDS was caused by Xylella, and that it cannot be cured or eradicated. They argued that the measures were not warranted and took their case to a local administrative court, which referred it to the European Court of Justice. P L A N T PAT H O G E N S