Host plant relationships of insect potential vectors of Xylella fastidiosa

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Xylella fastidiosa is regarded as one of the most devastating plant diseases, causing high yield losses and death in major crops, ornamentals and forest trees, including olive, grapevine, cherry, rosemary and lavender.Although not yet recorded in the UK, Xylella is a serious threat to horticulture due to the high volume of imports of these plants from areas where the disease is prevalent. X. fastidiosa is a xylem-limited bacterium that is transmitted by xylem-feeding bugs, notably froghoppers (spittlebugs) and certain larger leafhoppers. The common and widespread 'Meadow spittlebug', Philaenus spumarius, is considered to be the primary vector in Europe; it is also one of the most polyphagous insects known, with a host plant list in excess of 500 species.The student will study the fundamental ecology, behaviour and physiology of P. spumarius feeding on lavender and grapevine (both high-risk hosts for UK incursion), combining field surveys, laboratory and semi-field choice experiments and laboratory examination of vector feeding behaviour and physiology. Our preliminary 2019 data from Downderry Nursery indicates that P. spumarius differentially selects between certain lavender species and varieties; similar preferences might be expected between grapevine cultivars but hitherto have not been investigated. The student will address the following questions:What preferences does spumarius show for different lavender species/varieties and grapevine cultivars?How does this affect insect performance and fitness?How does spumarius feeding behaviour and physiology differ according to plant genotype and is this related to performance?Are the above differences in behaviour and physiology likely to affect Xylella transmission?Improved understanding of feeding in P. spumarius and other xylem-feeding insects will enhance UK capacity to respond to any future incursion of Xylella. It will also inform trade policy in terms of which plant species/varieties should be subject to greater import controls.