1 3 Appl Entomol Zool DOI 10.1007/s13355-016-0459-7 REVIEW Walnut husk fly, Rhagoletis completa (Diptera: Tephritidae), invades Europe: invasion potential and control strategies François Verheggen 1 · Agnès Verhaeghe 2 · Philippe Giordanengo 3,4 · Xavier Tassus 5 · Abraham Escobar-Gutiérrez 6 Received: 16 February 2016 / Accepted: 20 October 2016 © The Japanese Society of Applied Entomology and Zoology 2016 distributed in Europe, either as isolated wild trees or in orchards, favouring the probability of fly establishment in currently fly-free areas. In addition, the European territo- ries where Juglans species are present share biogeographic similarities. In orchards where R. completa is present and uncontrolled, 100% of walnut trees can be infested, caus- ing losses in walnut yields of up to 80%. The negative effect is low (<10% yield loss) under phytosanitary control, although additional costs must also be considered to sup- port specific monitoring for R. completa. The information presented here underlines a strong need for better walnut husk fly monitoring across European countries, as well as for increasing efforts to develop biological methods to con- trol this emerging pest. Keywords Plant pest risk analysis · Invasive species · Biological invasion · Tephritidae fruit fly Introduction Authorities and policymakers in the agricultural sector are continuously facing the risk of epidemics and pest out- breaks (Peña 2013). At the same time, scientific progress, as well as increasing public concerns for both human and environmental health, continuously prompts legislators and policymakers to create and enforce rules for pest control. In the context of global climate change and global trade, there are increasing concerns about the ecological and economic impacts of non-indigenous invasive species of pathogens and parasites on plants. Tephritidae is a family of the order Diptera comprising a wide group of economically important fruit pests, with the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), being considered one of the world’s most destructive Abstract Rhagoletis completa Cresson (Diptera: Teph- ritidae) is native to North America and invaded Western Europe in the late 1980s, causing important damage to its principal host, walnut (Juglans spp.). In this review, we summarize the important elements of R. completa’s biol- ogy, phytosanitary status and methods used in Europe for its control, and then present the main conclusions associ- ated with a completed risk analysis performed in 2014 to evaluate the dispersion and establishment potential of R. completa in Europe. The walnut husk fly was initially iden- tified in Switzerland (1988) and Italy (1991), from where it spread to at least seven additional countries: France, Spain, Germany, Austria, Croatia, Slovenia and Hungary. R. completa has not reached the limits of its potential dis- tribution. The main dissemination pathways within Europe include: (1) natural adult dissemination; (2) adult hitch- hiker behaviour; and, to a lesser extent, (3) transportation of larvae in fresh fruits. R. completa host plants are widely * François Verheggen fverheggen@ulg.ac.be 1 Laboratoire d’Entomologie fonctionnelle et évolutive, Université de Liège, Gembloux Agro-Bio Tech, 2, Passage des Déportés, 5030 Gembloux, Belgium 2 Centre Technique Interprofessionnel des Fruits et Légumes, 38160 Chatte, France 3 INRA, Université Nice Sophia Antipolis, CNRS, UMR 1355-7254, Institut Sophia Agrobiotech, Sophia Antipolis, France 4 Université de Picardie Jules Verne, 33 Rue St Leu, 80039 Amiens Cedex, France 5 Laboratoire de la santé des végétaux, Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement, et du travail (ANSES), 49044 Angers, France 6 INRA, UR4, 150 route Le Chêne, Lusignan, France