Diabrotica virgifera has probably been introduced several times into Europe from North America
In Europe, Diabrotica virgifera (EPPO A2 list) was first detected in 1992 near Belgrade (Serbia), and then spread naturally to many countries in Central Europe. Other distant outbreaks were also discovered in Western Europe, in particular in north-east Italy and southern Switzerland, in Belgium, in United Kingdom, in the Netherlands and in France. So far, it had generally been assumed that outbreaks in Western Europe originated from Central Europe. But this idea was largely contradicted by recent genetic studies on the variation of European and American populations using 8 microsatellites as genetic markers. The analysis was done on European populations collected from 5 outbreak sites: 2 near Paris (outbreaks first detected in 2002 and 2004), 1 in Alsace (2003), 1 near Venezia (2000), and 1 in north-east Italy (2003). Comparisons were made with populations from USA (Illinois, Ohio, Iowa). Results showed that only the outbreak in north-east Italy originated from Central Europe. Outbreaks near Paris (2002) and Venezia (2000) resulted from independent introductions from North America. The outbreak found near Paris in 2004 most probably originated also from North America. The outbreak in Alsace originated from the other French one detected in 2002 near Paris. In summary, this showed that there had been at least 3 independent introductions from North America into Europe, suggesting that incursions from North America are chronic. However, conditions allowing these repeated introductions remain unknown and need to be further investigated to try to prevent them.
Sources
Guillemaud T, Miller N, Estoup A, Derridj S, Lapchin L, Reynaud P, Bourguet D (2005) Diabrotica débarqua trois fois (au moins!). La génétique des populations de la chrysomèle des racines du maïs en Europe révèle de multiples introductions provenant d’Amérique du Nord. Phytoma-La Défense des Végétaux, no. 588, 41-42.
Miller N, Estoup A, Toepfer S, Bourguet D, Lapchin L, Derridj S, Kim KS, Reynaud P, Furlan L, Guillemaud T (2005) Multiple transatlantic introductions of the Western corn rootworm. Science, 310, 992.