Introduction of Diabrotica virgifera virgifera into the Old World and its consequences: a recently acquired invasive alien pest species on Zea mays from North America.

Diabrotica v. virgifera LeConte (Coleoptera: Chrysomelidae), (in short D.v.v.), with common name western corn rootworm, is endemic to the New World. Originating in the regions from South America to Mexico where it was in biological equilibrium with its natural enemies, predators and pathogens, it moved north with its food plants. Probably due to human agricultural farm practices with preference for monoculture of maize, the insect found open niches for expanding to the midwestern US where LeConte first described the species in Nebraska in 1867. Cyclodiene insecticide resistance, discovered in 1961, accelerated its spread and movement across the Great Plaines to the Atlantic Coast where it arrived around 1980. D.v.v. is a costly adversary to maize, to cucurbit, and, because of recent hostshifts, a threat to soybean production. Booming air travel and shipments of goods by air provided opportunities for D.v.v., without its natural enemies, to invade Europe where the insect was first described by F. Baca in 1993 near Belgrade airport (Baca 1993, Camprag & Baca 1995). From this focal point, D.v.v. expanded its range in all directions. Ten years later, in 2002, most of southeastern Europe has D.v.v. populations, some of them reaching economic damage levels such as those in Serbia, Croatia, and Hungary. New spot infestations in Northern Italy (Veneto, Lombardy, Piemonte) and in the Ticino region of Southern Switzerland, but also in Austria, Slovakia, Czechia, the Ukraine, even France, signal the final arrival of D.v.v. in Central Europe. The Alps, formerlyconsidered a natural barrier, might be circumvented or trespassed via air and road traffic. Model calculations by Baufeld and Enzian (2003) show that climatic and survival conditions are favorable for D.v.v. in all of Central Europe. Yet, in spite of well known annual losses of one billion dollars in the US, an effective and sustainable European strategy for keeping D.v.v. in check is still missing.