Salvinia molesta

Short description: Species of aquatic plant

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Giant salvinia

The fern Salvinia molesta floating on a pond surface
Scientific classification
Kingdom:  | Plantae
Clade:  | Tracheophytes
Division:  | Polypodiophyta
Class:  | Polypodiopsida
Order:  | Salviniales
Family:  | Salviniaceae
Genus:  | Salvinia
Species:  |

S. molesta

Binomial name
Salvinia molesta

D.Mitch.

Giant salvinia completely cover Lake Wilson in Hawaii.

Salvinia molesta, commonly known as giant salvinia, or as kariba weed after it infested a large portion of Lake Kariba between Zimbabwe and Zambia, is an aquatic fern, native to south-eastern Brazil.[1] It is a free-floating plant that does not attach to the soil, but instead remains buoyant on the surface of a body of water. The fronds are 0.5–4 centimetres (0.20–1.6 in) long and broad, with a bristly, waterproof surface caused by the hair-like strands that join at the end to form eggbeater shapes.[2] The fronds are produced in pairs with a third modified root-like frond that hangs in the water. It has been accidentally introduced or escaped to countless lakes throughout the United States, including Caddo Lake in Texas, where the invasive species has caused eutrophication to occur.[3]

In Europe, Salvinia molesta has been included since 2019 in the European Union's List of invasive alien species of Union concern.[4] Its inclusion means that the species cannot be imported, cultivated, transported, commercialized, planted, or intentionally released into the environment in the European Union.[5]

## Contents

* 1 Description
* 2 Growing conditions
* 3 Distribution
* 3.1 Invasion
* 4 Relation to humans
* 4.1 Salvinia effect
* 4.2 Bioremediation
* 4.3 Cancer research
* 4.4 Control
* 4.4.1 Biological control
* 4.4.2 Mechanical control
* 4.4.3 Chemical control
* 4.4.4 Prevention
* 5 References
* 6 Bibliography
* 7 External links

## Description

This is missing information about specific morphology. Please expand the to include this information. Further details may exist on the talk page. (June 2025)

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Salvinia molesta is a complex of closely related floating ferns and can be difficult to distinguish from each other. This water fern is often grown as an ornamental plant but has escaped and become a noxious pest in many regions worldwide. There are a few different growth forms for S. molesta; the primary growth form is an invading form with small flat leaves, while the tertiary or mat form has large, crowded, folded leaves. Under the best conditions plants can form a two-foot-thick mat. These mats can put a halt to recreational activities on lakes and waterways. S. molesta has been used to extract nutrients and pollutants from the water. When this plant is dried out, it can be used as mulch.[6]

The phenolic compounds 6'-O-(3,4-dihydroxy benzoyl)-beta-D-glucopyranosyl ester, 4-O-beta-d-glucopyranoside-3-hydroxy methyl benzoate, methyl benzoate, hypogallic acid, caffeic acid, paeoniflorin and pikuroside can be isolated from Salvinia molesta.[7]

## Growing conditions

Salvinia molesta prefers to grow in slow-moving waters such as those found in lakes, ponds, oxbow lakes, streams, ditches, marshes, and rivers. It prefers nutrient-rich waters such as those found in eutrophic water or those polluted by wastewater. It does not usually grow in brackish or salty waters, but has been reported in streams with a tidal flow in southeast Texas. It copes well with dewatering, and while it prefers to grow in moderate temperatures, it will tolerate low or very high temperatures. The United States Geological Service believes that it could grow in zones 7a, 8, 9, and 10 of the USDA Plant Hardiness Map.[2]

Environmental conditions can have a strong effect on this plant. S. molesta can survive on a mud bank for a short period of time, but because of the dry conditions, it cannot survive there permanently. It grows best at a pH of 6–7.7 and at a water temperature of 20–30 degrees Celsius (68–86 °F). Growth can be increased in high light intensities. S. molesta cannot grow in high salt concentrations due to the increase in salt causing a decrease in chlorophyll.[8]

## Distribution

This is missing information about information from countries other than the United States. Please expand the to include this information. Further details may exist on the talk page. (June 2025)

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Salvinia molesta is native to Brazil, but is now widely distributed in tropical and subtropical areas. This floating fern is known for its capability to take over large bodies of slow-moving fresh water. S. molesta has been naturalized in Texas[9] and Louisiana, but has now also been found and reported in Alabama, Mississippi, Florida, and Georgia. It can also be found where the lower Colorado River borders Arizona and California. "While S. molesta rapidly colonizes new states, current populations are too small to assess, but have been targeted for eradication". The naturalized regions of Texas have 14 drainage basins that contain infested water bodies; these are used as impoundments on tributaries that flow near federally protected wetlands.[10] In October 2020 Texas Parks and Wildlife detected S. molesta on Lone Star Lake while surveying fish populations.[9]

### Invasion

The plant originated in southeast Brazil and was exported as part of the pet industry to be used in aquaria and garden ponds. From there, it escaped or was deliberately released into the wild. It may also have been brought in with fresh, iced fish. Once in a waterway, it can be spread by infested boats, which not only spread it to new areas, but also break up the plant, allowing it to propagate. It also is spread by waterfowl.[2] S. molesta has been spread by contaminated aquatic plant stocks, boats, and other watercraft. The movement of water spreads S. molesta, and the sale and exchange of S. molesta materials increases chances of release to the environment.[6]

The rapid growth rate of Salvinia molesta has resulted in its classification as an invasive weed in some parts of the world such as Australia, United Kingdom, New Zealand, and parts of the United States. Surfaces of ponds, reservoirs, and lakes are covered by a floating mat 10–20 centimetres (3.9–7.9 in) (in some rare cases up to 60 centimetres (24 in)) thick. The plant's growth clogs waterways and blocks sunlight needed by other aquatic plants and especially algae to carry out photosynthesis, thereby deoxygenating the water. As it dies and decays, decomposers use up the oxygen in the water. It also prevents the natural exchange of gases between the air and the body of water the plant has invaded, causing the waterway to stagnate. This can kill any plants, insects, or fish trapped underneath its growth.

Its ability to grow and cover a vast area makes it a threat to biodiversity. Large infestations covering a wide area may also pose a problem to migratory birds, as they may not be able to recognise an infested waterway when flying overhead, and not stop at it. S. molesta provides ideal conditions for the breeding of mosquitoes that carry disease. The growth habit of Salvinia is problematic to human activities including flood mitigation, conservation of endangered species and threatened environments, boating, and irrigation.[11]

## Relation to humans

### Salvinia effect

Main article: Physics:Salvinia effect

The salvinia effect describes the stabilization of an air layer upon a submerged hydrophobic (water repellent) surface by hydrophilic (water-loving) pins. This physico-chemical phenomenon was discovered on the floating fern Salvinia molesta by the botanist Wilhelm Barthlott (Universität Bonn) while working on the lotus effect and was described in cooperation with the physicist Thomas Schimmel (Karlsruher Institut für Technologie), fluid mechanist Alfred Leder (Universität Rostock) and their colleagues in 2010.

### Bioremediation

See also: Earth:Bioremediation

Research done in the Philippines suggested the effectiveness of S. molesta for the treatment of blackwater effluent for an eco-friendly sewage system that uses a constructed wetland to clean the water. The result of the study showed that it can remove 30.77% of total suspended solids, 74.70% dissolved oxygen and 48.95% fecal coliform from the water.[12]

### Cancer research

Researchers at Stephen F. Austin State University in Nacogdoches, Texas, discovered that extracts of giant salvinia have shown promising signs of inhibiting growth of human cancer cells without destroying nearby healthy ones.[13]

### Control

Satellite images are used to identify S. molesta in reservoirs in Texas.[14]

#### Biological control

The weevil species Cyrtobagous salviniae, found in the native distribution of S. molesta, is being studied as a biocontrol. C. salvinae was first used as a biological control in Australia at Lake Moondarra, a recreational lake in Mount Isa, Queensland in 1980. By mid-1981, the weevil had reduced the population to a few small patches. It ate the leaves of the weed, but preferred the buds. Its larvae ate the roots, rhizomes, and the buds. As the plant died, it turned brown and sank to the bottom of the waterway and decomposed. This weevil was used with success in other parts of the world (13 tropical countries) such as the Sepik River in Papua, Sri Lanka, Lake Ossa in Cameroon as part of an AMMCO project to restore African manatee;[15] Wappa Dam in Queensland, and lagoons (e.g. Kakadu National Park) in the Northern Territory, Australia.[11] In Australia, the moth Samea multiplicalis was also released in the hopes that it would reduce the size of the weed population. While this moth did become established in Australia and spread, it was not effective as a biological control. A third species, the grasshopper Paulinia acuminata, was considered, but not released in Australia. However, this grasshopper has been deliberately released for control of Salvinia molesta in parts of Africa, Sri Lanka and India, and accidentally in Puerto Rico.[16] The giant gourami has long been known to prefer S. molesta and feed on it voraciously. It has been successfully used to control S. molesta in reservoirs of Sri Lanka.[17]

#### Mechanical control

Plants are removed by machine or harvesting equipment and by hand; the latter is suitable only for small infestations. Harvesting equipment also can encounter difficulties, as it cannot remove all of the infestation, it cannot access shallow areas, and equipment can be inhibited by large masses of the plant. Once removed, the plant must be dried, burnt, or disposed of in a manner that ensures it will not re-enter the waterway. Other methods to control the aquatic weed are dredging and chaining.

#### Chemical control

Chemical control on S. molesta is difficult as it does have some resistance to herbicides. The chemical fluridon has been successfully used, but it requires prolonged contact and is not effective if it is suddenly diluted by rainwater or any other influx of water. Other chemicals, such as hexazinone and diquat and double-chelated copper are used together to kill S. molesta.[2]

#### Prevention

Bans on the spreading, selling, relocation, and transportation of S. molesta may help the prevention of further spreading.[18]

## References

1. ↑ "TNC Global Invasive Species Team page". 9 October 2008. http://tncweeds.ucdavis.edu/alert/alrtsalv.html.
2. ↑ 2.0 2.1 2.2 2.3 "Archived copy". http://www.unce.unr.edu/publications/files/nr/2002/FS0269.pdf.
3. ↑ Hadsell, Martin, "The Relationship Between Salvinia molesta Infestation and the Microbial Ecology of Wetlands at Caddo Lake, TX, USA" (2024). Electronic Theses and Dissertations. 579.
4. ↑ "List of Invasive Alien Species of Union concern – Environment – European Commission". https://ec.europa.eu/environment/nature/invasivealien/list/index_en.htm.
5. ↑ "REGULATION (EU) No 1143/2014 of the European parliament and of the council of 22 October 2014 on the prevention and management of the introduction and spread of invasive alien species". https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32014R1143&from=EN.
6. ↑ 6.0 6.1 "Salvinia molesta". Q-bank.eu. http://www.q-bank.eu/Plants/BioloMICS.aspx?Table=Plants - Species&Rec=74&Fields=All.
7. ↑ Choudhary, M. I.; Naheed, N.; Abbaskhan, A.; Musharraf, S. G.; Siddiqui, H.; Atta-Ur-Rahman (2008). "Phenolic and other constituents of fresh water fern Salvinia molesta". Phytochemistry 69 (4): 1018–1023. doi:10.1016/j.phytochem.2007.10.028. PMID 18177906. Bibcode: 2008PChem..69.1018C.
8. ↑ Upadhyay, R. K.; Panda, S. K. (1 March 2005). "Salt tolerance of two aquatic macrophytes, Pistia stratiotes and Salvinia molesta". Biologia Plantarum 49 (1): 157–159. doi:10.1007/s10535-005-7159-4. Bibcode: 2005BioPl..49..157U.
9. ↑ 9.0 9.1 "Giant Salvinia Detected on Lone Star Lake". 30 October 2020. http://www.einnews.com/pr_news/529650647/giant-salvinia-detected-on-lone-star-lake.
10. ↑ "Status of Salvinia". Fl.biology.usgs.gov. 14 December 2012. http://fl.biology.usgs.gov/posters/Nonindigenous/Status_of_Salvinia/status_of_salvinia.html.
11. ↑ 11.0 11.1 "Biological control of the aquatic weed, Salvinia molesta | CSIRO". Csiro.au. http://www.csiro.au/resources/salvinia-control.html.
12. ↑ "Water fern (Salvinia molesta) shows potentials in removing water pollutants". Pchrd.dost.gov.ph. http://pchrd.dost.gov.ph/index.php/r-d-updates/3217-water-fern-salvinia-molesta-shows-potentials-in-removing-water-pollutants.
13. ↑ – SFA Public Affairs (11 July 2011). "SFA researchers discover cancer-treating potential of invasive plant | News from 2011 | SFASU". Sfasu.edu. http://www.sfasu.edu/5547.asp.
14. ↑ Everitt, J. H.; Fletcher, R. S.; Elder, H. S.; Yang, C. (2008). "Mapping giant salvinia with satellite imagery and image analysis – Springer". Environmental Monitoring and Assessment 139 (1–3): 35–40. doi:10.1007/s10661-007-9807-y. PMID 17516139. https://naldc-legacy.nal.usda.gov/naldc/download.xhtml?id=31992&content=PDF.
15. ↑ Aristide, Takoukam. "Local Residents around Lake Ossa volunteer to help remove S. molesta by hand prior to weevil project". AMMCO. https://www.ammco.org/img/DSC08282.JPG.
16. ↑ Perez-Gelabert, D.E. (2002). "Paulinia acuminata (Orthoptera: Pauliniidae) introduced to Puerto Rico, West Indies", Cocuyo 12: 5.
17. ↑ "Vision Based Automated Biomass Estimation of Fronds of Salvinia molesta". 2018-11-02. https://www.researchgate.net/publication/328701649.
18. ↑ "Salvinia complex". http://www.cdfa.ca.gov/plant/ipc/weedinfo/salvinia.htm.

## Bibliography

* Everitt, J.H.; Lonard, R.L.; Little, C.R. (2007). Weeds in South Texas and Northern Mexico. Lubbock: Texas Tech University Press. ISBN 0-89672-614-2

## External links

* GRIN-Global Web v 1.9.7.1: Taxonomy profile of Salvinia molesta
* USDA Plants Profile for Salvinia molesta (kariba-weed)
* Salvinia molesta information from the Hawaiian Ecosystems at Risk project (HEAR)
* US Geological Survey: Giant Salvinia
* Texas campaign to prevent spread: Hello Giant Salvinia, Goodbye Texas Lakes
* United States National Agricultural Library, National Invasive Species Information Center" Species profile for Giant Salvinia (Salvinia molesta) – general information and control resources.

Wikidata ☰ Q2716094 entry

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