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Xylella fastidiosa

Xylella fastidiosa is a bacterial disease with many sub species and strains not known to occur in the UK.

In February 2021, Defra introduced legislation which implemented new measures for Xylella following the consultation and Defra's response. The legislation is summarised in this letter with further details provided in an annex.

The list of Xylella hosts is found here

In mainland Europe, most notably France (Corsica and mainland France) and Italy there have been several outbreaks of different sub-species which have led to significant impacts on plants both in the wider environment and those grown commercially for olive production. In 2016 Xylella was detected in Spain for the first time on cherry trees in a nursery on the Balearic Islands. It was found for the first time on mainland Spain in 2017, in almond trees, and in 2019 was confirmed for the first time in Portugal, on lavender. Although EU regulated, there remains some concern about the risk of introduction to the UK via infected host plants imported as plants for planting considered to be the most likely pathway for entry. The disease is spread by insects that feed on the xylem fluid, that is the vessel of the plant which carries water. This includes the widespread and common meadow spittlebug, which is the principle insect spreading the disease in Italy and France.

Eradication measures for Xylella in the event of an outbreak have been set out in emergency EU legislation. When Xylella is detected in an outbreak situation, all hosts within 100 metres must be destroyed and the area treated to control the vectors. There will also be measures placed on businesses trading in host plants within 5 km. The implementation of these measures would lead to environmental and social impacts.

Xylella fastidiosa sub species multiplex

Of the known outbreaks to date, the outbreak of Xylella fastidiosa sub species multiplex detected in Corsica, mainland France, mainland Spain and Portugal, in a small area of southernmost Tuscany, and in nursery stock on the Spanish Balearic Islands is of most concern to the UK.  This subspecies is able to survive in cooler climates and affect a wide range of hosts, including many native broadleaved trees such as oak.

Xylella symptoms on oak

Xylella oak scorch

Photo: John Hartman, University of Kentucky (Bugwood/ Forestry Images images)

Xylella symptoms on Polygala 

Xylella on polygalla2

Photo: Bruno Legendre, Anses Plant Health Laboratory, Angers (FR)

Xylella fastidiosa sub species pauca


An outbreak of Xylella fastidiosa sub species pauca is causing substantial damage to olive production in the south of Italy. The priority is to prevent further spread from that area through robust EU regulation. Although this sub-species is unlikely to be able to thrive in the UK preferring a warmer climate and demonstrating a preference for olive as a host. Further information:

Forestry Commission

Defra pest factsheet

Xylella fastidiosa Contingency Plan

Xylella consumer pest alert - what you need to know and do

Olive trees, risk to trade from Xylella fastidiosa

Xylella fastidiosa Evidence Statement; a summary of the threat to the U.K. and the current preparations

Xylella fastidiosa 2020 PRA and supplementary data