Recent non-native invertebrate plant pest establishments in Great Britain:: origins, pathways, and trends

1 An appraisal of non-native invertebrate plant pest establishments in Great Britain, between 1970 and 2004, was carried out to improve our understanding of current invasion processes by non-native plant pests, and to assist national strategies in managing the risks they pose. 2 A total of 164 establishments, comprising 50 natural colonists and 114 human-assisted introductions, were recorded across 13 major taxonomic groups. 3 The mean rate of establishment was 22.1 species per 5-year period: 19.1 and 3.0 species outside and inside protected cultivation, respectively. Despite the continuing rapid growth in international trade and a general perception that rates of pest invasions are accelerating, no significant temporal trends in the rate of establishments in Great Britain were detected, either for natural colonists or human-assisted introductions, or for pests of plants grown indoors or outside. 4 The plant trade, particularly in ornamental plants, accounted for nearly 90% of human-assisted introductions; apiculture, biological control, timber imports, transport stowaways and intentional releases each contributed less than 5%. Only eight (4.9%) of the establishments could be considered as having no direct potential economic impact because all other species have been recorded as feeding on cultivated plants. A greater proportion of establishments by both natural colonists and human-assisted introductions occurred on non-native, woody plants. 5 The present study confirms previous work in other European countries that highlight the predominant role of the ornamental plant trade in introducing new plant pests to the European continent, mainly from Asia and North America.