Exotic scale insects on ornamental plants in Italy: a never-ending story

The introduction of ornamental plants into Italy for commercial and hobby purposes has provided scale insects with many chances of dispersion. Coccoidea often go unnoticed at border controls due to their morphology, biology and behaviour, being mainly concealed on hidden parts of the host plants. Many of the introduced alien species then become acclimatized, surviving outdoors, possibly in connection with urban pollution and global warming.The authors attempt to analyse this phenomenon and report data on the records of new alien species in Italy, starting from the end of the Second World War. In the period 1945-1995 an average of 0.64 new introduced alien scale insects has been reported per year, an average of 0.8/year between 1995 and 2005 and 1.37/year since 2005. More than fifty previously unrecorded species have been recorded so far, of which about 50% are presently acclimatized. The progressive increase in records of alien species is probably related to: the ever easier and faster transport and dispatch of material at a time of globalization of commerce and trade; the free movement of goods within the European Union and the National Plant Protection Organization (NPPO) monitoring ability. Moreover, the effect of global warming may have played an important role, directly affecting the development and survival of the insects and indirectly affecting the trophic relations (host plants and natural enemies). The authors comment on and discuss the more invasive species, namely Ceroplastes japonicus Green, Protopulvinaria pyriformis (Cockerell), Phenacoccus madeirensis Green, Phenacoccus peruvianus Granara de Willink and Phenacoccus defectus Ferris.