Rapdopholus similis is a quarantine pest in the EU (IIAII) and regulated for 'plants of Araceae, Marantaceae, Musaceae, Persea and Strelitziaceae, rooted or with growing medium attached or associated'. In addition, R. citrophilus is regulated (IIAI) for the same species and for plants of ‘Citrus L., Fortunella Swingle, Poncirus Raf., and their hybrids, other than fruit and seeds’ (EU directive 2000/29/EC). Currently, R. similis and R. citrophilus are considered different races within the same species, R. similis. R. similis has a restricted distribution in some EU countries. The finding of R. similis in roots of the aquatic plant Vallisneria sp. confirms earlier findings (finding in Livistona sp.) that R. similis has a broader host range than for which it is currently regulated in the EU.