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Phytophthora spp. literally translates as the ‘Plant destroyer’. But, is there a new plant pathogen out there trying to take this title: Xylella fastidiosa?

In 2018, Xylella fastidiosa hit the headlines as it devastated miles of olive groves in Italy and prompted a significant and concerted effort to deal with the threat of Xylella.

The threat level in the areas surrounding the immediate outbreak is high, as Xylella can spread via insect vectors and human activities through trade and a lack of robust bio-security measures. So, it is understandable why countries such as the United Kingdom (UK), where Xylella fastidiosa is not yet present, are concerned that the disease may impact their economies.

Why does Xylella fastidiosa pose such a problem?

A big issue is that Xylella‘s symptoms; leaf scorch, defoliation, chlorosis, withering and desiccation of branches, and dwarfing, can mirror symptoms created as a result of biotic or abiotic causes. So, complacency i.e. not taking all changes in a plant’s appearance during the growing-cycle seriously, and shrugging them off as nothing to worry about, could turn a small problem into a big problem.

Even the most diligent of growers can fall foul to this bacterial plant pathogen because the pathogen can spread via insect vectors, which left unmanaged could aid the spread of the disease, in all directions, quickly. However, even with a management strategy, Xylella can raise its ugly head!

Horticulture Week reported ‘the damage caused by the spread of Xylella fastidiosa has risen to €1.2 billion’. This is a large amount of money to lose as a result of a plant pathogen that should be monitored very closely.  An example of this significant financial impact: in Italy back in 2016 thousands of olive plants were felled after an outbreak. Destroying commercial trees and plants is a massive concern for any grower, but more so for an olive farmer because the plants take many years to mature – so, the impact is not just immediate, it’s long lasting.

What is being done to tackle Xylella?

It was quoted on GOV.UK in August 2018: ‘Xylella has not ‘yet’ been found in the UK, but it has recently affected olive trees in Italy, and a range of trees and plants in areas of Spain and France. Plants in North and South America are being damaged by the disease.’ This pathogen is slowly moving and is not isolated to one area, and poses a global threat.

Such is the real and significant threat of Xylella fastidiosa, it has prompted the UK to establish a Xylella pathogen consortium which aims to build resilience against the bacterial plant pathogen within the UK.

Xylella fastidiosa is a regulated quarantine organism in the European Union (EU), and there are certain activities taking place to prevent the spread and introduction of the pathogen [from outside the EU]. A summary is below, but full details can be found at https://ec.europa.eu/food/plant/plant_health_biosecurity/legislation/emergency_measures/xylella-fastidiosa_en 

Regulated species:

There are a number of plant species that are susceptible to Xylella fastidiosa and the movements and trade of these plants are monitored closely. There are a few host plants listed below but a full list can be found here: https://gd.eppo.int/taxon/XYLEFA/hosts.

olive trees in an olive grove that are susceptible to Xylella fastidiosa

  • Erysimum (Wallflowers)
  • Juglans regia L. (Walnut)
  • Lavandula dentata L, Lavandula x chaytorae (Lavender)
  • Olea europaea L. (Olive)
  • Prunus avium L. (Sweet Cherry)
  • Prunus dulcis (Almond)
  • Streptocarpus
  • Vitis vinifera (Grape Vine)

As you can see the list of susceptible plants above contains high-value crops!

Containment and eradication measures:

The EU recommends the following for tackling Xylella in the event of detection:

  • The establishment of a demarcated area on the detection of the disease.
  • All host plants or the host plants of the Xylella subspecies concerned located in the 100m radius around the infected plants should be removed, irrespective of their health status.
  • Within the km buffer zone, intensive surveillance should be carried out consisting of visual inspections, sampling and testing of symptomatic plants.
  • Agricultural practices such as removal of weeds, ploughing of the soil, and other practices should be implemented both in the infected zones and in the buffer.
  • Movement of plants in out of the area to be stopped.

More information about Xylella fastidiosa can be found at:

Rapid diagnosis of Xylella fastidiosa

As with the likes of Phytophthora spp., the most famous species being Phytophthora infestans (the causal pathogen that decimated potato crops during the Irish Potato Famine), it looks like Xylella fastidiosa is here to stay for some time and has the potential to affect a number of sectors; particularly the olive industry and therefore the olive industry’s consumers.

Abingdon Health is interested in speaking with organisations that are looking for a Xylella fastidiosa rapid diagnosis solution. If you are a researcher, an expert in this area or you work in plant health inspection, and have access to reagents specific to Xylella fastidiosa and think a tool for the on-site detection would be beneficial for the containment of Xylella, please contact us on +44 (0) 1904 406080 or info@abingdonhealth.com.

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