Print Email Comment share on Facebook Share on twitter
Print this page
Email link to this page
Send comments about this page
Share on facebook
Share on twitter
Document sans nom

Pathway analysis: aquatic plants imported in 10 EPPO countries (2009)


aquatic plantData on imports of aquatic plants was obtained from 10 EPPO countries (Austria, Czech Republic, Estonia, France, Hungary, Germany, Israel, the Netherlands, Latvia, Switzerland, Turkey) and aggregated in order to determine whether invasive or potentially invasive alien plants could be introduced in the EPPO region through this pathway. The main conclusions of this study were that this pathway was mainly consisting of imports of tropical plants for use in aquaria, and that the vast majority (90%) of these aquatic plant species did not represent a major risk due to their climatic requirements. However, a few species required thorough attention due to their known invasiveness potential.

Among the 247 species included in the study, only 10 are currently considered to be a threat for the EPPO region, representing 4% of the total number of plants imported. These invasive or potentially invasive species continue to be traded in huge quantities despite 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. It should be noted that among the few aquatic species which are planted outdoors, 9 out of 51 (about 17%) are invasive or potentially invasive. Only one plant, Hydrilla verticillata is used for aquarium purposes and is regarded as a potential threat.

Lagarosiphon major
Lagarosiphon major
Rohan Wells, National Institute of Water
& Atmospheric Research,
By combining information on the behaviour of a species where it occurs, its distribution, and its records of invasiveness, it is possible to obtain a subjective indication about its future behaviour in the area where it is introduced. Such rapid assessment has to be taken with care and carries a lot of uncertainties, and only suggests species that could deserve further attention. Six (6) additional species have been identified as representing a moderate to high potential risk: Adiantum raddianum (Pteridaceae), Gymnocoronis spilanthoides (Asteraceae), Hygrophila polysperma (Acanthaceae), Limnophila sessiliflora (Scrophulariaceae) and Syngonium podophyllum (Araceae). These species could be subject to further investigation, possibly a pest risk analysis, to evaluate the risk they may represent.

Hygrophila polysperma
Hygrophila polysperma

Other species should be monitored to verify that they do not threaten managed and unmanaged ecosystems: Alternanthera sessilis (Amaranthaceae), Chlorophytum comosum (Anthericaceae), Cyperus alternifolius (Cyperaceae), Cyperus papyrus (Cyperaceae), Pontederia cordata (Pontederiaceae), Rotala indica (Lythraceae), Sagittaria lancifolia (Alismataceae), further investigation is needed on this species as it might have been underestimated), Hydrocleys nymphoides (Limnocharitaceae), Hygrophila costata (Acanthaceae), Ottelia alismoides (Hydrocharitaceae), Saururus cernuus (Saururaceae).

Because most of these aquatic species originate from tropical areas, it is considered that the Mediterranean Basin and Macaronesia by having the most similar climatic conditions are the most at risk. The species which have been identified based on subjective criteria of rapidly available information, need to be considered with greater scrutiny and will be considered in the next issues of the EPPO Reporting Service.

Ottelia alismoides
Ottelia alismoides
John Wrigley, Australian National
Botanic Gardens,



The full article as well as the excel table with all imported plants are available here.