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Lagarosiphon major

Nova espécie: 

Dark green submerged aquatic plant, scarcely branched, with small alternated and curved-down leaves, closer joint near the apex. It forms “tufts” at the bottom of the water body, and can grow up to 6 meters tall, forming surficial floating “carpets”.

Scientific name: Lagarosiphon major (Ridley) Moss

Common name: African elodea, African curly leaved waterweed, African oxygen-weed, African waterweed, coarse oxygen weed, curly water thyme, curly waterweed, fine oxygen weed, Lagarosiphon, oxygen weed, oxygen-weed, South African oxygen weed, submerged onocotyledon

Family: Hydrocharitaceae

Status in Portugal: Invasive species (listed in annex II Decree-Law no. 92/2019, 10th July). Included in the list of species of concern in the European Union, by Regulation (EU) no. 1143/2014 of the European Parliament and of the Council of October 22, 2014. Introduced in some points, it is already showing invasive behaviour, although with still relatively limited distribution.

Risk Assessment Score: [In developement]

Synonymy: Lagarosiphon muscoides var. major Ridl. It is often sold under the name Elodea crispa, although this scientific name does not exist.

Last update: 13/06/2020

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Avistamentos actuais da espécie: 
Appearence: 

How to recognise it

Dark green submerged aquatic plant, little branched, with small leaves alternated and curved down and closer together near the apex. It forms “tufts” at the bottom of the water, and can grow up to 6 meters, forming floating “carpets” close to the surface.

Leaves: dark green, pointed and finely toothed, 5-20 mm long and 2-3 mm wide. They are arranged alternately, in a spiral, around the stem and are generally curved downwards towards the stem, (but in alkaline waters, they may appear straight). They usually appear closer together near the apex.

Stem: brittle and sparsely branched, it can grow to over 6 meters in length and curves like a “J” towards the base. It has adventitious roots and rhizomes that fasten the plant to the substrate.

Flowers: the female flowers are very small, with 3 transparent, white or pink petals and are situated above the surface, attached to a thin and long filamentous peduncle.

Outside its native range, only female plants are known, but in South Africa, where it originates, male plants produce flowers that detach from the plant, floating freely to disperse pollen.
 

Similar species

Hydrilla verticillata, Egeria densa, Elodea canadensis

The three species look very similar but the number of leaves that unite at each node is different; see the illustrated key to see how they are distinguished. Or download the PDF [here]                    

 

 

 

Characteristics that aid invasion

Although it does not reproduce sexually in Europe (no male flowers, fruits or seeds are known outside its Native range), it reproduces effectively vegetatively, either by expansion of the rhizomes or by fragmentation. Small fragments can be carried by the current in rivers and be accidentally dispersed by boats, fishing artifacts or other human activities and each fragment can give rise to a new plant.

The fact that herbivorous animals (such as fish, waterfowl, invertebrates, etc.) generally prefer native plants can lead to their progressive elimination in places with the presence of exotic oxygenating species (e.g. Lagarosiphon major, Egeria densa, and Elodea canadensis). For this reason, it is common for only exotic species to remain, forming monospecific communities (with only one species).

Native distribution area

South Africa.

Distribution in Portugal

Beira Litoral (Coimbra) and Algarve (Odeleite).

For more detailed locations of this species, check the online interactive map. This map is still incomplete – we need your help! Contribute by submitting records of the location of the species where you can find it.
 

 

Other places where the species is invasive

Europe (Austria, France, Germany, Italy, Spain, Switzerland and the United Kingdom), Oceania (New Zealand).
 
Introduction reasons

The main reason for its introduction is its use in aquariums as an ornamental and oxygenating plant.

Preferential invasion environments

Lagarosiphon major prefers still or slow-current freshwater habitats, with muddy or sandy substrates. It occurs in both oligotrophic and eutrophic environments and has great tolerance to high pH waters. It prefers temperatures ranging between 20ºC and 23ºC, but tolerates winter and supports maximum temperatures of 25ºC (Kasselmann 1995). It only occurs up to 7 meters deep because it cannot withstand higher pressure, but in deep habitats it can form floating mats. It can colonize ponds, lakes, dams, reservoirs and rivers and slow-current canals.

 

Although already introduced, its dispersion in Portugal is still relatively limited.

Impacts on ecosystems

It can create dense floating 2-to-3-meter thick mats that can cause several negative ecological and economic impacts as they block the light and eliminate native aquatic plants, also negatively affecting aquatic invertebrate and vertebrate populations. Lagarosiphon major can make navigation difficult and limit recreational activities such as swimming or fishing, it can block hydroelectric systems, reduce aesthetic value and adversely affect water quality.

Storms can break or loosen floating mat fragments of Lagarosiphon and deposit large masses of decaying vegetation on beaches, reducing their recreational value.

Controlling an invasive species demands a well-planned management, which includes the determination of the invaded area, identifying the causes of invasion, assessing the impacts, defining the intervention priorities, selecting the adequate control methodologies and their application. Afterwards it is fundamental to monitor the efficiency of the methodologies and recuperation of the intervened area as to perform, whenever necessary, the follow-up control. However, all these methods have some substantial drawbacks: cost, ineffectiveness in long-term control and, for some, the issue of adverse environmental effects, both real and perceived. Lagarosiphon major is very difficult to control. 

The control methodologies used (McGregor and Gourlay, 2002) for Lagarosiphon major include:

Physical control

Suction dredging: it can be carried out, but the risk of fragmenting and propagating the plant is great.

Cutting: cutting and removal of plants, ensued by the placement of anti-weed geotextile screens to prevent regeneration from the rhizomes.

Biological control

Some studies were undertaken in order to identify, among the natural enemies of this plant, the possible biological control agents specific to this species. A leaf miner fly (Hydrellia lagarosiphon) is touted as the most promising biocontrol agent and will soon be tested in New Zealand.

Chemical control

Foliar application of herbicide: in New Zealand, the use of the aquatic herbicide Diquat is mentioned as the only one registered in the country for the control of invasive aquatic plants, however it may be ineffective under certain environmental conditions. After the application of herbicides with the active ingredient Triclopyr (and Dichlobenil) only temporary effects on growth were observed.

Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.

 

Baars, J.R., Coetzee, J.A., Martin, G., Hill, M.P. & Caffrey, J.M. 2010. Natural enemies from South Africa for biological control of Lagarosiphon major (Ridl.) Moss ex Wager(Hydrocharitaceae) in Europe. Hydrobiologia 656 656:149–158

CABI (2012) Lagarosiphon major. In: invasive">Invasive species">Species Compendium. CAB International, Wallingford, UK. Disponível:   http://www.cabi.org/isc/datasheet/30548  [Retrieved 13/07/2017].

Center for Aquatic and invasive">Invasive Plants, University of Florida, Institute of Food and Agricultural Sciences, https://plants.ifas.ufl.edu/plant-directory/lagarosiphon-major/  [Retrieved13/07/2017].

Earle, W., Mangan, R., O’Brien, M. & Baars, J-R. 2013. Biology of Polypedilum n. sp. (Diptera: Chironomidae), a promising candidate agent for the biological control of the aquatic weed Lagarosiphon major (Hydrocharitaceae) in Ireland. Biocontrol Science and Technology, 23: 1267-1283.

Global invasive">Invasive species">Species Database (2017) species">Species profile: Lagarosiphon major. Disponível: http://www.iucngisd.org/gisd/species.php?sc=403 on 12-07-2017. [Retrieved 13/07/2017].

Mangan, R., & Baars, J-R. 2012. Use of life table statistics and degree day values to predict the colonisation success of Hydrellia lagarosiphon Deeming (Diptera: Ephydridae), a leaf mining fly of Lagarosiphon major (Ridley) Moss (Hydrocharitaceae), in Ireland and the rest of Europe. Biological Control, 64: 143-151.

McGregor, P. G., Gourlay H., 2002. Assessing the prospects for biological control of lagarosiphon (Lagarosiphon major (hydrocharitaceae)). DOC Science Integral Series 57. Department of Conservation, Wellington. 14p. Disponível: http://www.doc.govt.nz/documents/science-and-technical/DSIS57.pdf  [Retrieved 13/07/2017].

Martin, GD, Coetzee J & Baars J-R (2013). Hydrellia lagarosiphon Deeming (Diptera: Ephydridae) a potential biological control agent for the submerged aquatic weed, Lagarosiphon major (Ridl.) Moss ex Wager (Hydrocharitaceae). African Entomology, 21: 151-160.

Paynter, Q., 2013. Feasibility of biocontrol of Lagarosiphon major in New Zealand.. Landcare Research. Disponível: https://www.landcareresearch.co.nz/__data/assets/pdf_file/0003/100479/Feasibility_biocontrol_Lagarosiphon_major.pdf [Retrieved 13/07/2017].

The Plant List. Lagarosiphon major (Ridl.) Moss. Disponível: http://www.theplantlist.org/tpl1.1/record/kew-308179 [Retrieved 13/07/2017].