Leptoglossus occidentalis: an invasive alien species spreading in Europe
Leptoglossus occidentalis (Heteroptera: Coreidae – common names: western conifer seed bug or leaf-footed conifer seed bug) was first described in 1910 in California (US) and is considered as native to the western areas of North America, from Mexico in the south through California and Utah to British Columbia, Alberta, and Saskatchewan in the north. Since the end of the last century the range of this bug has been expanding, more particularly eastwards beyond the Rocky Mountains. In the 1950s and 1960s it reached Indiana, Iowa, Montana, Nebraska and Kansas. By the 1970s it was established in Wisconsin and Illinois, and by the mid 1980s it was found in Minnesota, Michigan, Ontario (Canada), and Connecticut. In the 1990s, it was reported from New York, Massachusetts, Rhode Island, New Hampshire, Maine, Pennsylvania and New Brunswick (Canada).
In Europe, L. occidentalis was observed for the first time in 1999 in Northern Italy, and within a very short time its presence was reported from more than 15 European countries (see below), thus clearly demonstrating an invasive behaviour. It is hypothetized that its current distribution in Europe probably results from several introductions which were then followed by natural spread. It is hypothetized that this insect may have been introduced through trade of timber. Interestingly, L. occidentalis was discovered for the first time in Asia in 2008; few specimens were observed in Tokyo, Japan.
In North America, the main host plants of L. occidentalis are Pinus species and Pseudotsuga menziesii, but the insect has also been found on Abies, Calocedrus decurens, Cedrus, Juniperus, Tsuga canadensis and Picea spp. Adults feed on flowers and seeds of conifer species in spring. Females lay eggs on needles and young larvae feed primarily on developing cones and occasionally on needles. They insert their long proboscises into the cones to suck juices from the seeds (bugs remaining on the outside of the cone). There are five larval instars and adults appear during summer. In USA and Canada, the species is monovoltine, but in Mexico it is polyvoltine. Adults are the overwintering stage, and in autumn they look for shelter and may enter buildings, sometimes becoming a nuisance to humans. In USA, L. occidentalis is considered to be a pest of conifer cones, as its feeding activity can affect the seed production of conifer stands.
Many pictures of L. occidentalis can be found on the Internet, for example: http://www.inhs.uiuc.edu/~sjtaylor/coreidae/coreidae.html
http://www.forestryimages.org/browse/subthumb.cfm?sub=459&start=1
In Europe, no severe damage was reported in forests or conifer seed production, so far. However, it must be acknowledged that many records have been made by both amateur and professional entomologists in cities, essentially in buildings or near parks and gardens. In many cases, it was not possible to associate pest records with observations on potential host plants. Therefore it seems desirable that studies on the distribution of L. occidentalis and the possible impacts of this invasive species on coniferous forest ecosystems or in urban environments should be conducted.
Spread of Leptoglossus occidentalis in Europe
- 1999: first record from Italy
In Europe, L. occidentalis was first observed in Italy near Vicenza (Veneto region) in 1999 (see EPPO RS 2006/160). This first record was followed by a rapid spread in Italy, and L. occidentalis has been found in Lombardia, Veneto, Abruzzo, Friuli-Venezia Giulia, Emilia-Romagna, Trentino-Alto Adige, and Sicilia. In Sicilia, the first specimens were caught in September 2002, and the insect rapidly spread accross the island. It was collected on cones and plants of Pinus halepensis, P. laricio, P. pinea, P. nigra and Pseudotsuga menziesii, as well as inside or near buidlings. In 2009, the regional Plant Protection Organization of the Valle d’Aosta region reported the presence of this insect in the municipalities of Aosta, Châtillon, Introd, and Morgex.
- 2002
Switzerland: L. occidentalis was first recorded in Ticino in 2002. In 2007, it was found in the north, in the cantons of Uri and Vaud (see RS 2008/199).
- 2003
Slovenia: It was first found in 2003 at Brje (near Komen) and in 2004 near Ljubljana (see EPPO RS 2006/160).
Spain: The first specimen was captured in Cataluña in 2003, in woodlands located near Barcelona (Vallbona d’Anoia). In 2007 and 2008, the insect was observed in several sites in the provinces of Barcelona and Girona. In 2008, new records were made in Jaén (Andalucía), and in the cities of Murcia and Madrid.
- 2004
Croatia: It was first reported in 2004 on the Island of Cres on Pinus nigra. In 2007 it was also found on other islands: Rab, Hvar and Brač, showing that this insect has spread rapidly along the Adriatic coast. However, population densities appeared to be low (only few specimens caught).
Hungary: The first specimen was recorded in October 2004 at Keszthely (county of Zala) in the west part of Hungary. Other specimens were later observed in Budapest and Litér (county of Veszprém) in 2005, and in the north-east in Mátrafüred (Gyöngyös, county of Heves) in 2006.
- 2005
Austria: L. occidentalis was first found in Vienna, Kärnten (Carinthia) and Tyrol in autumn 2005. In 2006, it was also observed in Salzburg.
- 2006
Slovakia: It was first observed in May 2006 in a park in the city of Nitra.
France: L. occidentalis was first found in France in September 2006 (the first specimen was observed, drowned in a swimming pool in the Mediterranean part of France). It was later reported from several departments (mainly in the south-east of France, with the exception of Paris): Ain, Alpes-de-Haute-Provence, Alpes-Maritimes, Ardèche, Bouches-du-Rhône, Hautes-Alpes, Haute-Corse, Drôme, Gard, Hérault, Isère, Lot-et-Garonne, Lozère, Paris, Rhône, Tarn, Tarn-et-Garonne, Var, Vaucluse. Interestingly, it is reported that L. occidentalis was intercepted in May 2006 in Le Havre on a consignment from the USA containing sawn wood of Quercus. It is suspected that L. occidentalis may have been introduced via seaports (possibly with trade of wood or wood products), as the insect has been found near major harbours like Venezia (Italy), Barcelona (Spain), Le Havre (intercepted only, France), Weymouth (United Kingdom) and Ostende (Belgium). In an English translation of the original paper from Dusoulier et al. (2008) later published in Het News (no.12 Autumn 2008), a small note has been added and indicated that L. occidentalis has now spread across Northern France, the bug being found in many locations in Normandie and the Centre region. Finally, a recent paper indicates that the bug now occurs in Alsace.
Germany: It was first found in October 2006 in Berlin. Other specimens were observed in Köln (Nordrhein-Westfalen) in 2007, in several urban sites in Baden-Württemberg in 2008 (Mannheim, Freiburg, Villingen), and in Merzig (Saarland) in 2009.
Czech Republic: It was first found on 2006-10-08 on a window of the State Phytosanitary Administration in Brno. Another specimen was found in 2007-07-23 under a Pinus nigra tree in a botanical garden in Brno. Later in 2007, 7 adults and 5 larvae were found in the botanical garden in Brno. Other findings were then made in autumn 2007 in Olomouc and Brno-Lesná.
Serbia: L. occidentalis was observed for the first time in Novi Sad in October 2006. The insect had flown into the apartment of a biologist who was able to take a picture of it! The first specimen which could be firmly identified was caught a year later in September 2007 on the balcony of an entomologist in Belgrade (Stari Košutnjak). Two more specimens were caught in 2008 in Novi Sad.
- 2007
Belgium: L. occidentalis was observed for the first time near Ostende in 2007.
United Kingdom: L. occidentalis was collected for the first time at Weymouth College (Dorset) in England in January 2007. No further specimens were found until 2008 when numerous adults were observed in light traps along the south coast of England, clearly indicating a large migration across the English Channel. Subsequently, it was found at several locations in England (at least 35 records in 2008) mainly along the south coast of England but as far north as Kendal (Cumbria). In addition, a single specimen was intercepted in a timber shipment from the USA.
Poland: In October 2007, two populations of L. occidentalis were recorded in the southern part of Poland: in Wrocław on a window near a group of Pinus strobus trees; and at Miechów near Cracow on a window sill near P. sylvestris trees.
- 2008
Montenegro: In August 2008, L. occidentalis was collected for the first time (1 male specimen) in Budva, in a park.
Bulgaria: In October 2008, 1 female of L. occidentalis was observed for the first time in Bulgaria, in the building of the national radio in Sofia.
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INTERNET (last retrieved in 2010-01)
Delattinia website (fauna and flora of Saarland, Germany). Wanzen. Aktuelle Neufunde. http://www.delattinia.de/Sektion_Wanzen.htm