The destruction of olive trees infected with a bacterium has caused controversy in Italy.Credit: Fabio Serino/Ropi via Zuma

A vicious bacterium that is devastating southern Italy’s valuable olive groves is still spreading years after it was identified, because of opposition to measures meant to contain the pathogen.

After months of inaction, authorities in the Puglia region have now resumed efforts to track the spread of the bacterium, Xylella fastidiosa, which causes a disease called olive quick decline syndrome (OQDS) that cannot be cured or eradicated.

But scientists say that the delays in implementing disease-containment measures have added to the growing risk that the infection will spread out of the Puglian peninsula, the region contained within the heel of Italy’s ‘boot’, and towards olive groves in Italy’s main landmass.

Italy declared a state of emergency over the crisis in 2015. But quarantine efforts — which can involve uprooting beloved, ancient trees — have been opposed by environmentalists and some farmers, and stopped again most recently in May. In the same month, the European Commission published an update on the situation and moved the certified infection zone 20 kilometres north.

The delays have been a problem, says plant pathologist Maria Saponari of the Institute for Sustainable Plant Protection in Bari, Puglia’s capital. “The later you detect an infection, the later you can start all the containment actions that are needed.”

The budget now allocated by the Puglia’s regional government to track the bacterium — €1.8 million (US$2 million) — still falls short of what is needed to implement the full set of containment measures agreed to by the Italian government and the European Commission four years ago.

Italy could now also face legal consequences for its inaction, after the European Commission in May made good on its longstanding threat to refer the nation to the European Court of Justice for violating its quarantine regulations. If found guilty, Italy could, for example, lose access to important agricultural subsidies.

Quarantine needed

The bacterium had never been seen in Europe until it was identified in 2013 in southern Puglia.

The outbreak was immediately subject to stringent European Union quarantine regulations, which were agreed on with the Italian government.

The original containment plan required infected trees to be uprooted and destroyed, as well as the destruction of apparently healthy trees surrounding them. It also mandated the spraying of insecticides to control spittlebugs, which transfer the bacteria between trees.

But environmentalists and some farmers have objected to these practices, and some have claimed that the containment measures were based on false science, inflaming tensions with researchers trying to understand and track the disease. Politicians have wavered over whom to please, and the activities have often been stopped by protests and court cases. Some trees identified as infected through monitoring activities earlier this year have remained standing.

And in spring this year, mayors of eight communities in Puglia publicly declared that they would not comply with the insecticide requirement.

The area affected by the bacterium has expanded steadily since 2013. The European Commission’s May update designated the whole of south and central Puglia as an infected zone, and a region to its north as a buffer zone that must be also carefully monitored for new cases of the disease (see ‘Olive-tree disease spreads’).

Source: European Commission

Italy’s agriculture minister, Gian Marco Centinaio, promised in July to propose a full containment plan within a few months, but has not done so yet, despite public nudges from EU and Puglian politicians. The agriculture ministry did not respond to Nature’s request for comment.

Last month, an association of olive growers called Coldiretti Puglia sent the government a list of proposals for the containment plan. The group wants special rules to be put in place to stop regional administrative courts from blocking containment measures. It also suggested tapping national disaster funds to support the development of new Xylella-resistant olive trees, and for an expanded monitoring programme.

Next steps debated

The long-running affair and its handling are now being dissected in Italy’s parliament.

In June, some parliamentarians formally deposited documents at the Senate, one of Italy’s two houses of parliament, which﻿ challenged the scientific evidence on which Xylella management plans have been based and called for a Senate inquiry into whether scientists have misled the public. These claims were repudiated the following month, in an independent analysis commissioned by the national science academy, the Accademia dei Lincei. The Senate has not yet acted on the call for an inquiry.

The proposal has fortunately not been carried forward, says Michele Morgante, a plant geneticist at the University of Udine in Italy. Still, he says, it is disturbing that the anti-science activities have received attention at such a high political level.

In a series of hearings launched independently in September by the Chamber of Deputies, Italy’s second house, parliamentarians have interviewed scientists, olive producers and other stakeholders about the Xylella outbreak, and what can be done about it; hearings are scheduled to continue into next month.

Morgante welcomes the hearing — but says it has come too late. “It is good that parliament [Chamber of Deputies] finally wants to listen to scientists, but they should have paid attention much earlier when it would have been easier to control,” he says.