About 4700 species of Aphididae have been described and one third of these species are present in Europe worldwide. The European aphid fauna currently includes 1,373 species and about 7.4 % of them are invasive species originating from another continent. Most of the alien aphid species in Europe originate from temperate regions of the world and in particular Asia and North America have contributed the largest numbers. Only few alien aphid species in Europe are of African origin and no alien aphids has yet been introduced into Europe from Australasia or South America.
Among the Europe countries, Italy is one of the nations mostly involved in alien aphid spread since at present about 60 invasive species have been described, with a single Italian region, Sicily, that alone has more invasive species than entire nations such as Germany, Portugal and Switzerland.
Aphid invasive species in number: Great Britain (64 invasive species), France (63), Italy (58), Spain (56), Germany (44), Portugal (31), Czech Republic (29).
Most of the alien aphids are recognised as pests, since they are feeding on crops commercially exploited, causing both direct (sap-feeding, deformation of their hosts) and indirect damages (transmission of plant diseases, deposition of honeydew on the leaves).
Among invasive species, the polyphagous species Myzus persicae, Macrosiphum euphorbiae and Aphis gossypii attack a wide range of vegetable crops, both indoors and outdoors. They are vectors of many viral diseases and are probably the aphids with the greatest economic impact in vegetable crops.
The analysis of the invasive insect list shows an overrepresentation of Aphididae in the alien insect fauna of Europe. This result could be due to their economic impact that results in many studies carried out on the distribution, taxonomy and biology of this family. New alien species of Aphididae are therefore more likely to be detected than new members of other taxonomic groups. However, aphid reproductive biology could also their wide presence. Indeed, aphids have the ability to reproduce both parthenogenetically and sexually and several species can reproduce exclusively by parthenogenesis in region with mild winters. Consequently, very few introduction events, and theoretically even the introduction of a single parthenogenetic female, may lead to the development of a population and the establishment of an alien species. Moreover, global warming is also likely to promote the survival of alien tropical and subtropical species, at least locally (e.g. along the Mediterranean coast or in islands such as Sicily) favoring their establishment as an alien species.
