Identification of walnut husk (Juglans regia L.) volatiles and the behavioural response of the invasiveWalnut Husk Fly, Rhagoletis completa Cresson

BACKGROUND Several European countries are important walnut (Juglans regia L.) producers. However, these countries must contend with the recent introduction of the Walnut Husk Fly, Rhagoletis completa Cresson (Diptera, Tephritidae), which is causing severe economic losses, especially in organic production. Because most Tephritid fruit flies use kairomones in their search for host plants, we hypothesize that this highly specialist species orients toward the volatile blend released by walnut husks. RESULTS We collected, identified, and quantified the volatile organic chemicals (VOCs) released by walnut husks from the most commonly cultivated variety in France (Franquette). Then, the behavioral response of R. completa toward synthetic odor blends was recorded in dual choice assays conducted in net cages. A total of 26 VOCs were identified, with α-pinene, β-pinene, trans-linalool, eugenol, and tetradecane representing the major constituents. In the dual choice assay, males and females R. completa were strongly attracted to synthetic blend that included most of the identified husk VOCs. CONCLUSION When searching for a host plant, R. completa use host fruit kairomones. The potential of these semiochemicals in monitoring and management of this quarantine pest is discussed.