EFSA has updated its assessment of the risks posed by Xylella fastidiosa to plants and crops in the European Union. The new assessment provides new insights and conclusions on controlling existing outbreaks of this pest and preventing further spread in the EU.
Controlling the threat
EFSA’s Plant Health Panel (PLH) used computer modelling to simulate how X. fastidiosa spreads across short and long distances under different conditions. The modelling showed the importance of implementing control measures, such as those specified by the European Commission, to prevent further spread and even eradicate outbreaks. It illustrated the relative effectiveness of using different-sized buffer zones to control an infected area.
The simulations also demonstrated the importance of controlling the insects that are known to transmit the pathogen in Europe – such as the spittlebug Philaenus spumarius – and minimising the delay between detection and implementation of control measures such as removing infected plants and establishing demarcated areas.
Is there a cure?
The assessment confirms that there is still no known way of eliminating the bacterium from a diseased plant in field conditions. The effectiveness of chemical and biological control measures has been assessed in recent experiments. The results show that they may temporarily reduce disease severity in some situations, but there is no evidence that they could eliminate X. fastidiosa in field conditions over a long period of time.
Stephen Parnell, Chair of the PLH Panel’s X. fastidiosa working group, said: “This was a complex scientific challenge with many areas of uncertainty, but we have distilled some important conclusions that will assist risk managers, risk assessors and researchers.
“Computer simulations are at the core of this scientific opinion. The models we have developed are robust and, importantly, flexible so they can be adapted to explore a wide range of different scenarios and support emergency planning.”
Dr Parnell added: “A wealth of new information has become available since our last opinion was published in 2015, much of it generated by EU-funded projects such as POnTE and XF-ACTORS. Our understanding of this dangerous plant pest is advancing all the time thanks to these initiatives, although much uncertainty remains, particularly at subspecies and sequence type level.
“It is vital that we continue to invest in research that can help us to not only control outbreaks but anticipate them.”