Pathway analysis: aquatic plants imported in 10 EPPO countries

Pathway analyses are regarded by National Plant Protection Organizations as a very efficient way to address the risks posed by invasive alien species. Data on import of aquatic plants was obtained from 10 EPPO countries (Austria, Czech Republic, Estonia, France, Germany, Hungary, the Netherlands, Latvia, Switzerland and Turkey) and aggregated in order to consider whether invasive or potentially invasive alien plants could be introduced in the EPPO region through this pathway. This study highlights that this pathway mainly consists of the import of tropical plants for use in aquaria, and which do not represent a risk due to their climatic requirements. However, a few species require thorough attention owing to the threats they cause. Of the 247 species recorded as imported, only 10 are currently considered to be a threat, representing 4% of the total number of plants imported. These 10 invasive or potentially invasive species continue to be traded in huge quantities in spite of the fact that Crassula helmsii and Eichhornia crassipes are recommended for regulation by EPPO, Azolla filiculoides, Egeria densa, Elodea nuttalli, Lagarosiphon major, Ludwigia grandiflora and Myriophyllum aquaticum should have their entry and spread prevented by countries and Hydrilla verticillata and Pistia stratiotes are recorded on the EPPO Alert List. Six additional species have been identified as representing a moderate to high potential risk: Alternanthera sessilis, Adiantum raddianum, Gymnocoronis spilanthoides, Hygrophila polysperma, Limnophila sessiliflora and Syngonium podophyllum. These species could be subject to further investigation, possibly a pest risk analysis, to evaluate the risk they may represent.