First report of the establishment of the biocontrol agent Trichilogaster acaciaelongifoliae for control of invasive Acacia longifolia in Portugal H. Marchante 1,2 , F. A. L  opez-N u ~ nez 1 , H. Freitas 1 , J. H. Hoffmann 3 , F. Impson 3 and E. Marchante 1 1 Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calc ßada Martim de Freitas, 3000-456 Coimbra (Portugal); e-mail: hmarchante@gmail.com 2 Escola Superior Agr  aria, Instituto Polit ecnico de Coimbra, Bencanta, 3045-601 Coimbra (Portugal) 3 Department of Biological Sciences, University of Cape Town, Rondebosch 7700 (South Africa) Acacia longifolia is one of the most widespread invasive plants in coastal areas of Portugal, where it disrupts the composition and function of natural plant and insect communities as well as microorganisms in the soil. The Australian bud-galling wasp, Trichilogaster acaciaelongifoliae, induces a reduction in seed production of A. longifolia and has been suc- cessfully used as a biological control agent in South Africa for more than 30 years. After a long period of host specificity testing and risk assessment, release permits were issued by national and European Union authorities and, in late 2015, T. acaciaelongifoliae was released into eight selected sites along the Portuguese coast. During April–July 2016, post- release monitoring detected 56 galls at four of the release sites. At two of the sites second- generation galls were noted in January 2017, but it is still too soon to measure their abun- dance. Despite the inherent difficulties associated with transferring the insects between hemispheres, T. acaciaelongifoliae successfully completed its life cycle in Portugal in the wild, and is seemingly starting to proliferate. Further releases were made in late 2016 and monitoring of the insects will continue. Introduction Acacia longifolia (Andrews) Willd. (Fabaceae) is one of the most widespread invasive plants in Portugal. This Aus- tralian woody plant was introduced between the late 19th and early 20th centuries to curb sand erosion, but it has since spread widely, mainly in association with fire events. Nowadays, it invades extensive areas of coastal ecosystems where it is transforming plant communities that were natu- rally dominated by herbs and small shrubs into woody com- munities dominated by A. longifolia (Marchante et al., 2015; Fig. 1). It further changes soil chemistry and func- tioning (Marchante et al., 2008), and ecological networks of plant galls and associated communities (Lopez-Nu~nez et al., 2017). Some of these impacts persist even after removal of A. longifolia and make restoration of invaded areas increasingly difficult and complex (Marchante et al., 2009, 2011a). In addition, it reduces forest productivity, mainly in littoral pine plantations, and increases fire hazard, with consequent negative economic impacts. The produc- tion of numerous long-lived seeds contributes significantly to the invasive and dispersal ability of this species (March- ante et al., 2010). Although biological control is frequently considered to be a sustainable and environmentally compatible method of pest control (for insect pests and weeds) and has been used extensively around the world for over a century, the inten- tional introduction of natural enemies to control invasive plants has only recently been considered for use in Euro- pean Union Member States (Shaw et al., 2016). The Aus- tralian bud-galling wasp Trichilogaster acaciaelongifoliae (Hymenoptera: Pteromalidae) reduces seed production and curbs growth of A. longifolia and has been successfully used as a biological control agent in South Africa for more than 30 years (Wilson et al., 2011). The wasp is highly host-speci- fic, affecting A. longifolia almost exclusively (Prinsloo & Neser, 2007). The adults are small (3 mm) and short lived (2–3 days). They are univoltine (one generation per year) and most of the annual life cycle is spent as eggs, larvae and pupae within the developing galls. After emergence, females search for flower buds and later vegetative buds into which they lay their eggs (Fig. 2). Although some male wasps emerge from the galls, they are always much scarcer than females (usually less than 10% of all adults that emerge) and the females are predominantly, if not exclusively, partheno- genic (i.e. they produce viable eggs without mating). In the short term there is a decrease in annual seed production, which in turn means fewer seeds for dispersal and in the long term should result in a reduction of germination after control operations, fire or other disturbances (Dennill, 1990). Trichilogaster acaciaelongifoliae was considered as a candidate for control of A. longifolia in Portugal, and ª 2017 The Authors. Journal compilation ª 2017 OEPP/EPPO, EPPO Bulletin 0, 1–5 1 Bulletin OEPP/EPPO Bulletin (2017) 0 (0), 1–5 ISSN 0250-8052. DOI: 10.1111/epp.12373