Pest Risk Analysis Xiphinema americanum s.l.
The EU-quarantine nematode Xiphinema americanum s.l. (non-European populations) (IAI) is regularly found in soil attached to or associated with plants during import inspections (PPS, 2008; Annex C). It is likely that not all infested consignments are detected at import because only a sample of soil is taken and not each plant is being sampled (NPPO of the NL). Xiphinema americanum s.l. is a complex group of species and to date 51 species have been described within this group (Lamberti et al., 2000), including X. californicum which is also on the list of EU-quarantine organisms. The phytosanitary risk of non-European populations of X. americanum s.l. is the ability of certain of these populations (or vector species within the X. americanum group) to transmit American nepoviruses (EPPO, 1997a). The nepoviruses are:
- Tomato ringspot nepovirus (ToRSV). Quarantine status in the EU: IAI
- Tobacco ringspot nepovirus (TRSV). EU – IAI
- Cherry rasp leaf nepovirus (CRLV). EU- IAI
- Peach rosette mosaic nepovirus (PRMV). EU – IAI
Within the EU, several species belonging to the Xiphinema americanum – group are present but these are not known as vector species except X. rivesi (Lamberti et al., 2000; Annex G). X. rivesi is present in several EU countries (Lamberti & Ciancio, 1993; Lamberti et al., 2000; EPPO, 2007; CABI, 2007; Sirca et al., 2007). X. rivesi was first described by Dalmasso in 1969 from specimens from eastern France where it may be an introduction from the French Antilles (see also Robbins & Brown, 1991). Lamberti & Cianco (1993) suggested that X. rivesi may have been introduced from North America into Europe. X. rivesi is known as a vector species of nepoviruses in North America (Robbins & Brown, 1991) and the ability to transmit ToRSV and TRSV has recently been demonstrated for a X. rivesi population in Slovenia. (Sirca et al., 2007). Thus, the X. rivesi populations present in Europe may well act as a vector of nepoviruses as non-European populations of X. americanum s.l.. Presently, no measures are taken to prevent spread of X. rivesi populations in the EU, although these populations may pose a threat comparable to those of non-European populations of X. americanum s.l. originating in areas where the viruses are absent. Thus, it is presently unclear which pathways are most important and to which extent non-European populations pose a threat to plant health in the EU as compared to European populations. The present PRA was, therefore, performed to identify and assess or evaluate:
- pathways and risk potential of non-European populations of X. americanum s.l. able to transmit one or more of the four nepoviruses mentioned above;
- pathways (spread within the EU) and risk potential of European X. americanum s.l. populations able to transmit one or more of the four nepoviruses mentioned above;
- pathways and risk potential of X. americanum s.l. infected with one or more of the nepoviruses mentioned above;
- management options to prevent introduction of non-European populations of (vector species of) X. americanum s.l. and further spread of populations of vector species of X. americanum s.l already present in Europe.
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