Coimbra, Portugal, March 13, 2025 (Lusa) - The director of the plant health laboratory (FitoLab) warns of the ‘powder keg’ that is forming in Portugal with the spread of a bacterium that could affect vineyards, olive groves and other crops with great social and economic potential.

The ‘xylella fastidiosa’ bacterium was first detected in Portugal in 2019, in the Porto Metropolitan Area, and since then there have been another 18 active outbreaks, scattered across various parts of the country, the measure for which in the more than 500 demarcated areas involves eliminating all plants that could potentially host the organism.

"Portugal is the country with the most outbreaks in Europe. It has them in Trás-os-Montes, Porto, the Centre region, Lisbon and Marvão. In terms of areas [affected], it may not be the biggest, but it's the one with the greatest risk, with a likelihood of spreading throughout the whole country," Joana Costa, director of Fitolab, a laboratory located at the Pedro Nunes Institute in Coimbra, which investigates and detects plant pests and diseases, told Lusa.

For the specialist, in addition to the high risk of dissemination, the outbreaks already identified are close to or in areas with high production capacity of various plants that are affected by the bacteria, such as olive, grapevine, cherry or almond trees.

"It's a powder keg," said the director of the laboratory, which has a research project dedicated to xylella.

Joana Costa uses the 2013 outbreak in Puglia, Italy, to illustrate the economic and social impact that this bacterium could have.

In that region of Italy, in the space of ten years, the outbreak led to the death of 21 million olive trees (a third of those in Puglia), affecting a total of 54,000 hectares, according to a scientific article in the journal Nature.

The bacterium, which is transmitted by the foam leafhopper, a common insect in Europe, blocks the xylem and the plants dry out until they die completely, explained Joana Costa.

So far, there is no way of treating the bacterium and the only solution is to create demarcated zones and eliminate all plants susceptible to xylella within a radius of two kilometres.

Beyond this radius, a wider prospecting area is created, in which we try to detect infected plants, which leads the initial outbreaks to expand beyond the initial radius.

"You reach a point where the initial outbreak in Porto is no longer confined to the urban area," she noted.

As well as trying to contain the spread, there is also the need to secure more resistant plants.

In the case of Italy, they have endeavoured to crossbreed and find varieties within their olive trees that are less susceptible to the bacteria, as was done in Brazil in the past when the bacteria attacked orange trees - a job that takes years.

"But for ten years we've seen the slow death of plants in Italy," she said, emphasising that all outbreaks in Europe, even despite tough measures in some cases, have continued to spread.

In the case of Portugal, almost everything remains to be done, said the director of FitoLab, regretting that in 2016 the Portuguese state did not opt for the possibility of creating a quarantine station to test the infection of plants safely, together with Spain.

"The Spanish went ahead and today they have these facilities where they can test the susceptibility of their crops to the bacteria," she said.

In Portugal, at the moment, it's not known which plants are more or less susceptible, which could jeopardise the genetic heritage of Portuguese crops.

"In Puglia, they had millions in funding and started working on genetic improvement from day one, and even so, it took them more than ten years to come up with a solution,"she said.

For Joana Costa, it is essential for the state to invest in the conservation of its crops, with structured and dedicated plans to this end.

She regretted that action will only be taken when the impacts begin to be felt more strongly.

JGA/AYLS // AYLS

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