Xylella fastidiosa is a bacterial disease not known to occur in the UK. The bacteria colonise the xylem vessels of plants, eventually blocking these, which deprives the plant or tree of water and nutrients. The symptoms vary depending on the host plant species and its degree of susceptibility but can include marginal leaf scorch, wilting of foliage and withering of branches. Severe infections can result in dieback, stunting and death of the plant.
Xylella originated in South America but has now been detected in mainland Europe where outbreaks have had significant impact on commercially grown plants and the wider environment. Although the disease is regulated under law, there is concern about accidental introduction to the UK via imported plants. All Xylella fastidiosa species are of concern due to their wide host range which includes trees such as oak, maple and elm.
The bacteria are spread from plant to plant by infected insects of the infraorder Cicadmorpha whilst feeding on the sap; the bacteria can live in the foregut of the vector. There are a number of these insects native to the UK and the most notable of these is the meadow spittlebug Philaenus spumarius. They can be recognised by the foam nests the nymphs (immature spittlebugs) produce commonly known as ‘cuckoo spit’. Spittlebugs do not cause any damage to plants themselves; they simply carry the bacteria.
In order to prevent the introduction of Xylella to the UK, routine surveillance for the disease is carried out on plants in trade and SASA is also involved in projects with EUPHRESCO, Plant Health Centre of Expertise and BRIGIT project collecting spittlebugs and recording information on what plants they live and feed on across Scotland- see [poster].