Ludwigia peploides and L. uruguayensis (=L. grandiflora)
Onagraceae - Water primroses

NOTE: a full datasheet is being prepared, in the meantime you can view here the data which was previously available from the EPPO Alert List.

Why: During its studies, the EPPO Panel on Invasive Alien Species decided that Ludwigia peploides and L. uruguayensis should be added to the EPPO Alert List. In particular, their invasiveness has clearly been demonstrated in France during the last 20-30 years.

Description: Perennial aquatic plants which form very dense (almost impenetrable) mats. L. peploides and L. uruguayensis are morphologically very similar and are difficult to differentiate in the absence of flowers. Stems are glabrous to sparsely pubescent. They grow horizontally on water (or mud) and can emerge over the water surface. Leaves are alternate and polymorphic. Early growth consists of rosette-like clusters of rounded leaves on the water surface. At flowering, leaves lengthen to a lanceolate or elliptic shape. Two types of roots are observed: roots which adsorb nutrients and attach the plant to the soil, and adventitious roots located along the stems which ensure oxygen uptake and favour rooting of plant fragments (cuttings). Both species have bright yellow flowers (2-5 cm diameter) with 5 petals, growing from the leaf axils (in France, flowering occurs from June to September). Fruit is a cylindrical capsule of 13-25 mm long and 3-4 mm wide with 5 loculi containing numerous seeds of 1.5 mm. Ludwigia spp. can grow up to 3 m deep in water, and up to 80 cm above water level. These plants have also shown a rather good resistance to frost in Europe.
Pictures can be viewed on Internet:
http://www.corela.org/documents/2004-09jussies.pdf
http://isaisons.free.fr/jussie.htm

Where: L. peploides and L. uruguayensis originate from South America, and they can now be found in North America, Africa, Australia and Europe. Data on their geographical distribution is lacking and complicated by the fact that the genus Ludwigia is under revision. As a consequence, the following distribution is only preliminary.
EPPO region: Belgium (few sites), Italy, France (introduced in the 1820-1830s, they remained for a long time within the southern part of France from Camargue to Aquitaine, but they are now spreading towards the north), Netherlands (few sites), Spain (L. grandiflora is mentioned in Flora Iberica), Switzerland (L. grandiflora was observed for the first time in canton of Geneva in summer 2002), United Kingdom (recorded as present but apparently not as an invasive). Both species of Ludwigia are regulated in Portugal (Ministry of Agriculture).
North America: USA (both species are present in many states, see USDA Plant profiles for more details).
South America and Caribbean: Argentina (L. peploides), Cuba (both species).
Oceania: Australia (L. peploides), Chile (L. peploides).

View a distribution map for L. peploides

View a distribution map for L. uruguayensis

Habitat: Slow-flowing waterways, lakes, ponds, ditches. Ludwigia spp. are also able to colonize river banks and humid pastures (probably due to their high content of saponins and calcium oxalate they are poorly consumed by herbivorous animals).

Damage: The rapid and extensive development of plant populations can block waterways (and thus disturb many human activities such as navigation, hunting, fishing, irrigation and drainage), reduce biodiversity and degrade water quality. Studies done in France have shown that Ludwigia species were able to produce rapidly a high biomass (up to 2 kg of dry matter per m²). Biomass could double in 15 to 20 days in slow-flowing waters, and in 70 days in rivers. As an example, populations of Ludwigia spp. in Marais d’Orx (FR) occupied a few m² in 1993 and reached 130 ha in 1998. In France, these species are considered as dangerous invaders in aquatic or humid environments.

Dispersal: Fragmentation of stems is the main mode of dispersal of Ludwigia spp. The role of seeds remains to be studied further (viable seeds were able to germinate in laboratory conditions but no data has yet been obtained in outdoor conditions). It is suspected that humans and birds are responsible for plant dissemination between waterways. Over long distances, trade for ornamental purposes (aquarium and ponds) can obviously ensure their dissemination.

Pathway: Plants for planting of L. peploides and L. uruguayensis (soil/water containing viable plant fragments or seeds?).

Possible risks: Control is very difficult (mechanical control is possible but care should be taken not to produce more fragments which may disseminate the plants further, herbicides are available but their use in the natural environment is difficult). At least in France, L. peploides and L. uruguayensis have shown a high potential for invasiveness. Further spread of these two species should be avoided.

Source(s)
Cordo, H.A.; DeLoach, C.J. (1982) The flee beetle, Lysathia flavipes, that attacks Ludwigia (water primrose) and Myriophyllum (parrotfeather) in Argentina. Coleopterists Bulletin, 36(2), 298-301 (abst.)
Ramirez, C.; San Martin, J.; San Martin, C.; Contreras, D. (1991) The chemical composition and energetic content of the biomass of weeds in rice fields in central Chile. Turrialba, 41(4), 551-563.
Rostanski, K. (1993) The occurrence of the species of the genus Ludwigia in Cuba. 36th goebotanical seminar on Polish geobotanical investigations abroad, Warsaw, PL, 1991-03-15/16. Wiadomosci Botaniczne, 37, 3-4 (abst.).
Vauthey, M.D.; Jeanmonod, D.; Charlier, P. (2003) La jussie – Ludwigia grandiflora (Michx.) Greuter & Burdet – Une nouvelle espèce pour la Suisse et un nouvel envahisseur. Saussurea, 33, 109-117 (abst.).
INTERNET
Agence Méditerranéenne de l’Environnement – Fiche no. 11. Ludwigia spp. http://www.ame-lr.org/plantesenvahissantes/
Belgian portal site for information exchange in the field of biological diversity. Invasive species. http://www.biodiversity.be/bbpf/forum/invasion/invspecies.html
Cemagref (FR) web site. Les jussies. http://www.cemagref.fr/Informations/Ex-rechr/systemes-aqua/Jussies/Jussies-chapo.htm
Conservatoire et jardin botanique de la ville de Genève (CH). Jussie à grande fleurs. http://www.cjb.unige.ch/conservation/jussie.html
Conservatoire régional des rives de la Loire et de ses affluents – juin 2004-09-08. Fiche technique. Les jussies. http://www.corela.org/documents/2004-09jussies.pdf
Home Page of the Washington State Noxious Weed Control Board (US) – Water primrose. http://www.nwcb.wa.gov/weed_info/primrose.html
International Commission on irrigation and drainage – Aquatic weeds and their management by Lancar & Krake, March 2002. http://www.icid.org/weed_report.pdf
Ministry of Agriculture, PT. Decreto-Lei n.º 565/99. DR 295/99 SÉRIE I-A de 1999-12-21. Ministério do Ambiente Regula a introdução na natureza de espécies não indígenas da flora e da fauna.
http://www.idrha.min-agricultura.pt/ruris/legislacao/dl_565_99.htm
Flora Iberica. http://www.rjb.csic.es/floraiberica/
Rothamsted Research Station (UK) Annual report 2001 of the Centre for Aquatic Plant Management. http://www.rothamsted.bbsrc.ac.uk/pie/JonathanGrp/Annual_Report_2001.pdf
USDA Natural Resources Conservation Service. Plant Profiles. Ludwigia peploides, L. uruguayensis. http://plants.usda.gov

EPPO RS 2004/119

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