Europe adopts new measures against notorious olive blight Xylella fastidiosa

By Flora Southey contact

- Last updated on GMT

Pic: GettyImages/Mathia Coco
Pic: GettyImages/Mathia Coco

Related tags: Olive oil, Disease, Bacteria

The European Commission is adopting new measures to combat one of the world’s most dangerous plant bacteria: Xylella fastidiosa.

Within the EU, notorious olive blight Xylella fastidiosa has the potential to cause an annual production loss of €5.5b per year.

While best known for its disastrous impact on the olive oil industry, the plant-pathogenic bacteria affects other varieties of fruit trees. In a scenario whereby Xylella fastidiosa spread across the entire EU, it would affect 70% of the EU production value of older olive trees (over 30 years old) and 35% value of younger ones; 11% of citrus, 13% of almond and between 1-2% of grape production.

The presence of the bacterium in trees can be observed in a variety of ways, depending on the host plant species. Some infections are not expressed at all, whereby others lead to plant death within a limited time.

Naturally transmitted by insect vectors which feed on the xylem of host plants, the bacterium can cause symptoms including leaf loss, dieback, and delayed growth. When the bacterium sufficiently obstructs the xylem, and water is unable to flow through to the host, the tree eventually dies.

EU regulation

Under EU law, Xylella fastidiosa is considered a quarantine pest according to Regulation (EU) 2016/2031​. Introducing the bacterium into a Member State and/or spreading it within a specific Member State is prohibited.

When the bacterium is detected, regulation demands that all necessary measures be taken to eradicate it. When this is not possible, measures should be taken to inhibit its further spread.

This month, the Commission adopted new measures​ against Xylella fastidiosa. The new measures follow the latest scientific evidence from the European Food Safety Authority (EFSA) as well as experience in different EU outbreak areas.

Preventing the spread

Control measures designed to prevent the spread of Xylella fastidiosa within the EU include the establishment of a demarcated area, measures to eradicate the bacterium, and containment measures.

As soon as the bacterium is confirmed within a Member State, for example, authorities are required to demarcate the area which should consist of an ‘infected zone’ with a radius of at least 50m around the infected plant and a ‘buffer zone’. The latter may vary from 1km to 5km around the infected zone, depending on whether natural spreading has occurred or eradication measures been taken.

Within the infected zone, all infected or symptomatic plants are to be removed, alongside those which belong to the same species – irrespective of their health status.

In certain areas of Europe, eradication of the bacterium is not deemed feasible. These include the South of Apulia in Italy, Corsica in France, and Baleares in Spain. These regions, therefore, should prioritise containment measures.

“Within the infected zone, lighter provisions apply, consisting of intensive surveillance and immediate removal of at least the infected plants. These measures should be implemented, where applicable, at least within the last 5 km strip of the infected zone adjacent to the buffer zone, as well as around sites with high cultural and social value,” ​noted the Commission.

“Within the 5km buffer zone, the same provisions as the ones presented in the eradication measures apply. As regards Corsica and Baleares, there are no provisions applied to buffer zones as the infected zones are surrounded by the sea.”

Preventing introduction into the EU

The Commission stressed that the same conditions apply for EU Member States as they for host plants imported from third countries.

In an effort to prevent the introduction of Xylella fastidiosa into the bloc, the Commission states that imports of host plants from infected third countries is only possible if those plants are grown under protected conditions. Prior to their export, as well as on entry into the EU, they should be inspected, sampled and tested, to ensure they are not infected.

“Strict conditions apply for these imported plants to move within the EU as well,” ​the Commission noted.

Olive oil industries risk losing ‘billions of euros’

The Commission’s measures come just four months after publication of new research from the University of Wageningen​ in the Netherlands, which estimated that Xylella fastidiosa could cost olive oil producing regions billions of euros over the next 50 years.

According to their findings, Italy, Greece and Spain are expected to be the worst hit.

In a best case scenario, whereby replacing with Xylella fastidiosa-resistant varieties is feasible, Italy could lose between €0.6bn and €1.6bn, the researchers noted. In a worst-case scenario, in which production ceases after orchards die off, the impact could reach €5.2bn.

In Greece, the best-case scenario was estimated at a loss of €0.09bn, and worst-case, €1.94bn. And in Spain, a best-case scenario could see the industry lose €0.39bn. A worst-case scenario, however, could see producers lose up to €16.86bn.

Source:​​ PNAS​​
‘Impact of Xylella fastidiosa​​ subspecies pauca​​ in European olives’
Published 13 April 2020
DOI: https://doi.org/10.1073/pnas.1912206117​​ 
Authors: Kevin Schneider, Wopke van der Werf, Martina Cendoya, Monique Mourits, Juan A. Navas-Cortés, Antonio Vicent, and Alfons Oude Lansink.

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