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1 An appraisal of non-native invertebrate plant pest establishments in Great Britain, between 1970 and, 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 humanassisted 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 humanassisted 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.

SUMMARYThe pinewood nematode (PWN), Bursaphelenchus xylophilus , is a major pathogen of conifers, which impacts on forest health, natural ecosystem stability and international trade. As a consequence, it has been listed as a quarantine organism in Europe. A real-time PCR approach based on TaqMan chemistry was developed to detect this organism. Specific probe and primers were designed based on the sequence of the Msp I satellite DNA family previously characterized in the genome of the nematode. The method proved to be specific in tests with target DNA from PWN isolates from worldwide origin. From a practical point of view, detection limit was 1 pg of target DNA or one individual nematode. In addition, PWN genomic DNA or single individuals were positively detected in mixed samples in which B. xylophilius was associated with the closely related non-pathogenic species B. mucronatus , up to the limit of 0.01% or 1% of the mixture, respectively. The real-time PCR assay was also used in conjunction with a simple DNA extraction method to detect PWN directly in artificially infested wood samples. These results demonstrate the potential of this assay to provide rapid, accurate and sensitive molecular identification of the PWN in relation to pest risk assessment in the field and quarantine regulation.

The potato cyst nematodes Globodera pallida and G. rostochiensis are listed in the EU Plant Health Directive 2000/29/EC and are also subject to the new EU Council Directive 2007/33/EC on the control of potato cyst nematodes, requiring unilateral suppression of these pests in Europe. At the same time there is also pressure to increase world trade in potatoes. Such pressure has to be balanced by the risks involved in the associated spread of these pests and subsequent problems in management. Populations of the potato cyst nematodes from outside Europe, in particular South America, which is considered the origin of G. pallida and G. rostochiensis, pose a risk to those European countries where limited genetic variability of these nematode species has been recorded. The development and usage of resistant cultivars under such conditions has formed a pivotal role in integrated management programmes in Europe. Molecular studies have shown that populations of G. pallida and G. rostochiensis from South America have a different genetic composition from those in Europe. The introduction of such populations would pose a threat to the use of resistant cultivars as a major tool in reducing the potential spread and damage caused by these species. At present, an inability to link precisely genetic variability to the virulence characteristics of a specific nematode population, and quickly identify the virulence status of intercepted populations for inspection purposes, strengthens the case for using plant health legislation to prevent their introduction.

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