Project No. 2158

Primary Supervisor

Dr Alan J A Stewart – University of Sussex

Co-Supervisor(s)

Dr Michelle Fountain – NIAB EMR

Dr Hayley Jones – RHS (CASE Partner)

Summary

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 1300 species.

The student would 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 would address the following questions:

1. Determine if Philaenus spumarius, nymphs and adults, shows preference for species and/or variety(ies) of lavender and grapevine in the UK.
2. Determine if plant growth form (size and age), and plant availability affect the host plant preference of P. spumarius in lavender farms and vineyards in the UK.
3. Establish a list of other host-plants and non-host plants of P. spumarius in vineyards.
4. Explore host plant functional traits to explain P. spumarius preferences.

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.