DOI: 10.1111/wre.12072 PRIORITY PAPER Ophraella communa, the ragweed leaf beetle, has successfully landed in Europe: fortunate coincidence or threat? HMULLER-SCH€ ARER*,€ S T E LOMMEN*, M ROSSINELLI†, M BONINI‡, M BORIANI§,GBOSIO¶ & U SCHAFFNER** *Departement de Biologie/Ecologie & Evolution, Universite de Fribourg, Fribourg, Switzerland, †Servizio fitosanitario Canton Ticino, Bellinzona, Switzerland, ‡Dipartimento di Prevenzione Medica, ASL MILANO 1, Parabiago, Milano, Italy, §Regione Lombardia, Laboratorio fitopatologico, Servizio fitosanitario regionale, Vertemate con Minoprio, Como, Italy, ¶Regione Piemonte, Settore Fitosanitario, Torino, Italy, and **CABI, Delemont, Switzerland HMuller-Sch€ arer€ and S T E Lommen contributed equally to this work. Received 27 October 2013 Revised version accepted 18 December 2013 Subject Editor: Paul Hatcher, Reading, UK suitability. This oligophagous beetle is a successful bio- Summary logical control agent against A. artemisiifolia in China, We report the occurrence of the North American rag- but despite extensive host specificity tests, the risk of weed leaf beetle Ophraella communa in Europe. During attack and the level of damage of sunflower under field our surveys to monitor populations of the invasive alien conditions remain unclear. The recently launched COST plant Ambrosia artemisiifolia in Europe, we found the Action on ‘Sustainable management of Ambrosia artem- beetle south of the Alps, in more than 130 sites in south- isiifolia in Europe (SMARTER)’ offers an ideal frame- ern Switzerland (Ticino) and northern Italy (Lombardia, work to respond quickly to the recent establishment of Piemonte and Emilia-Romagna). At sites where O. communa in Europe and to collect data that can help O. communa was present, up to 100% of the plants were determine whether this event should be considered a attacked with damage levels high enough to completely troublesome introduction or whether it is likely to defoliate and prevent flowering and seed set of most rag- become the first case of a successful biological control of weed plants. That in its first year of discovery, O. comm- an invasive weed in continental Europe. una was already found over a large area of c. 20 000 km2 Keywords: biological control, leaf feeder, weed manage- and in all habitat types occupied by A. artemisiifolia ment, invasive alien species, Ambrosia artemisiifolia. reflects its great dispersal potential and wide habitat MULLER€ -SCHARER€ H, LOMMEN STE, ROSSINELLI M, BONINI M, BORIANI M, BOSIO G&SCHAFFNER U (2014). Ophra- ella communa, the ragweed leaf beetle, has successfully landed in Europe: fortunate coincidence or threat? Weed Research 54, 109–119. alien plants in Europe (Shine et al., 2010). This plant Introduction originates from North America but has become wide- Ambrosia artemisiifolia L. (Asteraceae; common rag- spread in other continents, including Asia, Australia weed) has uniquely raised the awareness of invasive and Europe (Cunze et al., 2013; GISD, 2013). In Correspondence: Prof. Dr. Heinz Muller-Sch€ arer,€ Departement de Biologie/Ecologie & Evolution, Universite de Fribourg/Perolles, Chemin du Musee 10, CH-1700 Fribourg, Switzerland. Tel: (+41) 26 300 88 35/50; Fax: (+41) 26 300 96 98; E-mail: [email protected] © 2014 European Weed Research Society 54, 109–119 110 HMuller-Sch€ arer€ et al. Europe, it is most abundant in the Pannonian Plains, autumn of 2013. The beetle was discovered and then the Lyon area in France, the Milano area in Italy, Uk- surveyed independently by different teams in different raine and southern Russia (Prank et al., 2013). The regions. During regular surveys of the Swiss cantonal main problem with this plant is its production of phytosanitary service of Ticino, we found for the first highly allergenic pollen, generating huge medical costs time an infestation by a leaf beetle in Switzerland (Bal- and reduced quality of life among the allergic popula- erna, 12 July; Appendix 1). A quick scan of the area tion (Fumanal et al., 2007). Ambrosia artemisiifolia in Ticino and Varese (Lombardia, Italy) within the also has become a major weed in European agricul- next 2 weeks revealed that many other A. artemisiifolia ture, especially in spring-sown crops such as sunflower, sites were infested. Morphological identification of maize, sugar beet and soybean (Komives et al., 2006). specimens collected at three of these sites (1x Ticino, The spread and impact of A. artemisiifolia is likely to 2x Varese, cf. Appendix 1) confirmed that the speci- increase with changing climate, posing a significant risk mens collected were O. communa. This corroborated to society, even in countries presently not yet affected, morphological and molecular analyses of beetles col- as evidenced by both ecological niche models lected in a parallel survey in Lombardia from another (Hyvonen€ et al., 2011; Bullock, 2012; Cunze et al., site in Varese (Castellanza, 30 July) (Appendix 1, Bori- 2013) and process-based (or mechanistic) distribution ani et al., 2013). In hindsight, the beetle had also models (Chapman et al., 2014). Chemical and mechan- already been seen in the Milano area (Lombardia, ical control methods have been developed and partially Italy: Abbiategrasso, 10 July) by the local health ser- implemented to control A. artemisiifolia (Buttenschøn vice authority, but had not been recognised at the et al., 2010), but they are not a solution for all invaded time. In Piemonte, the beetle was first observed by the habitats and often do not result in the eradication of local phytosanitary service (Galliate, 7 Aug.). populations. To mitigate A. artemisiifolia’s further Ophraella communa is presently regarded in China spread and to reduce its abundance in badly infested as the most successful weed biological control agent, areas in Europe, sustainable control strategies need to killing A. artemisiifolia plants over large areas before be based on a combination of methods. seed set (FH Wan and ZS Zhou, personal communica- While classical biological control of A. artemisiifolia tion 2013). This effect could not only be achieved has been successfully implemented in other continents through inundative releases (after mass rearing and (Australia, China: Palmer et al., 2010; Zhou et al., field releases on a given population), but also through 2010), this long-term management tool is not yet imple- migration of the beetles following rapid local popula- mented in Europe. Biological control attempts in China tion build-up (Guo et al., 2011; Chen et al., 2013). The started in the mid-1960s and up to the 1980s, five three larval stages and the adults of the beetle all feed insects species were sequentially introduced (Wan et al., on leaves of A. artemisiifolia (Wan et al., 2009). 2009). Presently, the most efficient and successful spe- Here, we present results on the occurrence of cies are the stem-galling moth Epiblema strenuana O. communa in Europe in 2013 and the phenology of (Walker) (Lepidoptera: Tortricidae; first released in attack at sites in northern Italy and southern Switzer- 1993) and the leaf beetle Ophraella communa LeSage land. We briefly discuss the type of data that need to (Coleoptera: Chrysomelidae; accidental introduction, be collected to allow a thorough assessment of whether discovered in 2001), both with up to six generations per the establishment of O. communa in Europe should be year in southern China (Chen et al., 2013). considered as a fortunate coincidence in the campaign The recently started EU-COST Action ‘Sustainable against the highly invasive A. artemisiifolia, or whether management of Ambrosia artemisiifolia in Europe it should be considered as a threat to closely related (SMARTER)’ aims to develop a sustainable manage- wild or crop species. ment strategy for A. artemisiifolia in Europe, with a focus on biological control (cf. www.ragweed.eu). In Materials and methods this framework, a recent literature survey to explore prospects for biological control in Europe prioritised After discoveries of the beetle in early summer 2013 in six insect herbivores and one rust pathogen from the both Switzerland and Italy, several teams independently native North American range of the plant; the few performed a preliminary survey of O. communa occur- natural enemies that have colonised A. artemisiifolia in rences in adjacent areas. As the different teams had no Europe are polyphagous and cause little damage, ren- prior knowledge of each other’s activities, surveying dering them unsuitable for an augmentative approach methods had not been standardised. As soon as the dif- (Gerber et al., 2011). However, to our surprise, we ferent teams knew of the others’ work, they immedi- found large infestations of a leaf beetle in southern ately decided to homogenise the data as far as possible. Switzerland and northern Italy in the summer and Finally, a handful of beetle occurrences reported by © 2014 European Weed Research Society 54, 109–119 The ragweed leaf beetle has landed in Europe 111 others that we had instructed were included in the data and random way, we only report sites where the beetle set. From mid-July to mid-October 2013, more than was found, and not those where the beetle was absent. 150 A. artemisiifolia sites in Italy (121), Switzerland (30) and France (4) were surveyed. Surveys were gener- Results ally limited to the area where the conducting authority is active (Swiss cantons, Italian regions or provinces, Ophraella communa occurrences French departments) and was sometimes extended somewhat beyond these borders. In the most severely So far, O. communa has only been observed south of the infested areas (Swiss cantons Ticino and Geneva, Ital- Alps (Fig. 2), where we found it in more than 80% of ian province Milano), the surveys were part of the regu- sites surveyed, covering an area of c. 20 000 km2 (112/ lar A. artemisiifolia monitoring by local authorities and 121 sites in Italy, 20/30 in Switzerland, 0/4 in France, previously known A. artemisiifolia sites were visited. In details of occurrences in Appendix 1, including habitat other parts of Lombardia and in Piemonte, where exact types occupied by A.