Flores azuis/violetas reunidas numa espiga (Foto: Lísia Lopes)

Eichhornia crassipes

Aquatic herb, floating, with swollen leaves and very flashy blue/violet flowers.

Scientific name: Eichhornia crassipes (Mart.) Solms.

Common names: water hyacinth, common water hyacinth, water orchid

Family: Pontederiaceae

Status in Portugal: invasive species  (listed on the annex I of Decreto-Lei n° 565/99, 21 December)

Risk Assessment score: (in development)

SynonymyPontederia crassipes Mart. & Zucc., Piaropus crassipes (Mart.) Raf., E. speciosa Kunth, Pontederia azurea Hook., Pontederia azurer Roem & Schult, Piaropus crassipes Raf., Piaropus mesomelas Raf., Piaropus tricolor Raf., Heteranthera formosa Miq., E. azureae Miq., Pontederia elongata Balf., E. crassicaulis Schlect., Pontederia crassicaulis Schlect., E. cordifolia Gandoger

Last update: 14/04/2014

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How to recognise it

Rhizomatous aquatic herb, generally floating.

Leaves: aerial, growing in tufts, with a blade from 8 x 9 cm, rhomboid to suborbicular; petioles of variable length, where the shortest are very swollen on the lower half, and all of them have a spongy aerenchyma.

Flowers: blue/violet, 5-7 cm diameter, arranged (8-12 flowers) in spikes with around 15 cm; yellow anthers, variegated with blue.

Fruits: capsules with 3 valves that have numerous small seeds (from 3 to 450).

Flowering: in summer, with a very short flowering period (2 to 3 days).

 

Characteristics that aid invasion

Eichhornia crassipes has an extremely rapid growth: in adequate conditions, the species may double its population in 5 days. The growth rate is higher in springtime, reducing in autumn due the decrease in temperature and formation of frost. It may survive on land if there is a large amount of water available.

It may easily propagate vegetatively, through rhizomes or small fragments from which a new plant may generate. Each fragment may be dragged by the water flow and originate new invasion foci far from the original population.

It also propagates by seed. The seeds can be viable for a long time (up to 20 years) and due to their small size, they are easily swept up by the current. The seeds are also dispersed by aquatic birds.

 

 

Native distribution area

South America, in the Amazon Basin.

 

Distribution in Portugal

Mainland Portugal (Douro Litoral, Beira Litoral, Estremadura, Ribatejo, Alto Alentejo), Azores archipelago (islands of Flores, Faial, Graciosa, Terceira and São Miguel).

Geographic areas where there are records of Eichhornia crassipes

Other places where the species is invasive

Invasive in all continents.

 

Introduction reasons

For ornamental purposes.

 

Preferential invasion environments

Irrigation channels, lagoons, ponds and dam bays.

It doesn’t thrive in brackish water and salinity limits its distribution. It prefers waters rich in nutrients, mainly nitrogen, phosphorus and potassium.  It may endure drastic fluctuations in the water level, acidity and low levels of nutrients.

 

 

It is considered one of the worst aquatic invasive species of the world.

Impacts on ecosystems

It may grow into mats that completely cover the water surface, leading to the aquatic environments’ change. In that case it reduces the water quality, biodiversity (aquatic fauna and flora), light availability and the water flow, besides enhancing eutrophication.

 

Economic impacts

It may clog channels and prevent navigation, diminishing recreational use, fishing or other activities.

Where its colonization becomes effective, elevated costs in the application of control measures and irrigation equipment maintenance are to be expected.

 

Natura 2000 Network habitats more subject to impacts

– Hard oligo-mesotrophic waters with benthic vegetation of Chara spp. (3140);
– Natural euthrophic lakes with Magnopotamion or Hydrocharition-type vegetation (3150);
– Natural dystrophic lakes and ponds (3160).

 

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.

The control methodologies used for Eichhornia crassipes include:

 

Physical control

Manual/mechanical removal (preferred methodology). Manual removal with or without mechanical “sawboats” or “vacuums”. Sometimes, floating barriers are used to contain the species inside a small area. For the success of this method it’s important not to leave large fragments in the water.

Since 2006, this method has been successfully applied in Pateira de Fermentelos using a mechanical sawboat to eliminate water hyacinths.

 

Chemical control

Foliar application of herbicide. Herbicide spray (active substance: glyphosate or 2,4-D in formulas adapted for aquatic environments). It is expensive and provides only a temporary effect. It affects non-target species and its efficiency is very dependent on the age and phenological state of the plants and temperature, so it may result in very low success rates.

 

Biological control

There are several biological control agents (arthropods and fungi) successfully released in several countries to control E. crassipesEccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae), sap-feeding; Neochetina bruchi Hustache and N. eichhorniae Warner (Coleoptera: Curculionidae) that feed in the inside of the stems; Niphograpta albiguttalis Warren (Lepidoptera: Pyralidae), that feed in the petiole; Orthogalumna terebrantis Wallwork (Acari: Scarcoptiformes: Galumnidae) leaf-miner, and the fungus Cercospora rodmanii (Mycosphaerellales: Mycosphaerellaceae).

Tests made in Portugal with Neochetina sp. showed good results. However, the impossibility to use it in our country determines that this type of control is not yet an alternative.

 

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

Agricultural Research Council – Plant Protection Research Institute – Weeds Research (2014) Management of invasive alien plants: A list of biocontrol agents released against invasive alien plants in South Africa. Available: http://www.arc.agric.za/arc-ppri/Documents/WebAgentsreleased.pdf [Retrieved 03/03/2014].

CABI (2012) Eichhornia crassipes. In: Invasive Species Compendium. CAB International, Wallingford, UK. Available: http://www.cabi.org/isc/ [Retrieved 10/11/2012].

Dufour-Dror J-M (2012)  Alien invasive plants in Israel. The Middle East Nature Conservation Promotion Association, Ahva, Jerusalem, 213pp.

Global Invasive Species Database (2012) Eichhornia crassipes. Available: http://www.issg.org/database/species/ecology.asp?si=70&fr=1&sts=sss [Retrieved12/11/2012].

Hill MP, Cilliers CJ (1999) A review of the arthropod natural enemies, and factors that influence their efficacy, in the biological control of water hyacinth, Eichhornia crassipes (Mart.) Solms-Laubach (Pontederiaceae), in South Africa. African Entomology Memoir no 1, pp. 103-112.

Laranjeira C (2008) Eichhornia crassipes control in the largest portuguese frshwater lagoon. In: EPPO/COE whorkshop, Mérida. Available: http://archives.eppo.int/MEETINGS/2008_conferences/eichhornia_files/08_laranjeira/laranjeira1.HTM [Retrieved 12/11/2012].

Marchante E, Freitas H, Marchante H (2008) Guia prático para a identificação de plantas invasoras de Portugal Continental. Imprensa da Universidade de Coimbra, Coimbra, 183pp.

Rebelo MT (2012) Aquatic weed biological control: olfactory attraction of weevils Neochetina bruchi and N. eichhorniae for water hyacinth (Eichhornia crassipes). A case study. In: Monteiro A, Gomes da Silva F, Jorge R (eds) Gestão e conservação da flora e da vegetação de Portugal e da África Lusófona. In Honorium do Prof. Catedrático Emérito Ilídio Rosário dos Santos Moreira. ISA Press, Lisboa, pp. 451-470.

USDA, NRCS. (2012) The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.  Available: http://plants.usda.gov [Retrieved 12/11/2012].

 

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