Taxonomy
Salvinia molesta | Sailvín mhór
Pre 2017
2017 - 2020
Status
Legal status
Regulated invasive species of Union concern under the
European Regulation on the prevention and management of the introduction and
spread of invasive alien species [1143/2014].
Third
Schedule listed species under Regulations 49 & 50 in the European
Communities (Birds and Natural Habitats) Regulations 2011. (Note: Regulation 50
not yet enacted).
Listed as a schedule 9 species under Articles 15 & 15A of the
Wildlife Order (Northern Ireland) 1985 (Article 15A not yet enacted).
First reported in the wild
Non-native
Invasiveness
Invasive species - risk of High Impact
Irish status
Absent
Introduction pathways - 1
Escape from Confinement
Introduction pathways subclass - 1
Landscape/flora/fauna improvement
Introduction pathways - 2
Transport Contaminant
Introduction pathways subclass - 2
Contaminant nursery material
NAPRA Ireland risk assessed
No
Species Biology
Identification
Salvinia molesta is a
species of perennial plant in the family Salviniaceae (floating herbs)
that is associated with freshwater habitats (Encyclopedia
of Life, 2021). This species is a free-floating aquatic plant with short green leaves
arranged in whorls of three (two upper and one lower) (Invasive
Species Ireland, 2021). Salvinia molesta is a mat-forming
species that can be up to 30 cm long, 5 cm wide and over 2.5 cm thick (CABI, 2021). The short, round upper leaves are 0.7-3 cm
long and 1.8 cm wide (CABI, 2021). These leaves are photosynthetic (CABI, 2021). The lower leaves are 1.5-2 cm long and 0.5
cm wide (CABI, 2021). They lie submerged in the water and are
non-photosynthetic (CABI, 2021).
Ecology
Salvinia molesta can act as either a perennial or annual
depending on the climatic conditions of the habitat it is found in (Global
Invasive Species Database, 2021).This species passes through three different
growth stages throughout its lifecycle. The first stage is known as primary
growth and sees the growth of single ramets (plantlets) (Global
Invasive Species Database, 2021). The next stage is known as the secondary
growth stage and sees the growth of a linear chain of ramets (Global
Invasive Species Database, 2021). The final stage is known as the tertiary
stage and sees the formation of a compact cluster of biomass (Global
Invasive Species Database, 2021).
Salvinia molesta will grow best in habitats that provide high light intensities, high nutrient availability and relatively high water temperatures (CABI, 2021). If temperatures drop to as low as -3ºC, the terminal buds of this species can be damaged and the plant may die (CABI, 2021). Salvinia molesta is a freshwater species and has little tolerance for saline conditions (CABI, 2021).
The mono-specific growth dominating an area can also negatively influence invertebrates, fish and waterfowl, which can permanently alter trophic dynamics (the way energy is transferred between trophic levels in an ecosystem) in the system (Chapman et al., 2017).
Ecosystem services - Provisioning services may be negatively affected as decomposition of Salvinia molesta can influence water quality and availability. This could result in stress exertion on fish stocks (Chapman et al., 2017).
Regulating services can be impacted as native biodiversity is outcompeted, aquatic systems are altered and dense mats of vegetation can block engineering structures (Chapman et al., 2017).
The rapid growth rate of Salvinia molesta combined with its slow rate of decomposition may negatively impact nutrient cycling and primary production, adversely affecting supporting services within the system (Chapman et al., 2017).
The dense, mono-specific mats of vegetation produced by this species may limit access to water for recreational activities such as swimming and boating, resulting in a negative influence on cultural services within an area (Chapman et al., 2017). Moreover, the loss of biodiversity and species richness resulting from the mono-specific mats of vegetation can hurt the aesthetics of a natural area (Chapman et al., 2017).
Economic - Salvinia molesta invasion can bring about a multitude of economic impacts such as interference with weirs, floodgates and locks; flooding due to blocked drains; preventing livestock reaching drinking water; and generally degrading water quality (Chapman et al., 2017).
Habitat
Salvinia molesta is associated with slow flowing or stagnant
waters such as lakes, low energy rivers or streams, wetlands, irrigation
channels, ditches, ponds and canals (Chapman et
al., 2017).
Mechanism of impact
Competition
Management approach
Prevention
As Salvinia molesta is
listed as an Invasive Alien Species of Union concern under the EU Regulations
of Invasive Alien Species, it cannot be imported, traded, or released to the
wild. Measures must also be taken to prevent spread of existing populations of
it (European Commission, 2017).
The
public should be urged to use the Check Clean Dry protocol on their equipment
and clothing when moving between water bodies to prevent contamination (Invasive Species Ireland, 2021).
Early
detection of an invasive species within a country will allow for a much greater
chance of successfully controlling its spread before it can become fully
established. Early detection will allow for trained personnel to swiftly
address the issue at hand (van Valkenburg, 2017). The use of Citizen
Science can be a powerful tool to aid in early detection of invasive alien
species as the public can be shown what to look for and have a place that they
can log possible sightings of invasive species. This will decrease the chances
of an invasive species going unnoticed.
Mechanical control
It is
possible to manually remove this species from an area through the use of drag
nets, pitch forks etc. but this may only be feasible in the early stages of an
infestation on smaller sites (van Valkenburg, 2017). The chances of
totally controlling the spread of this species on larger sites or in late
stages of infestation are very slim (van Valkenburg, 2017). Where this control
method is implemented, removed biomass should be dried, burnt or buried in order
to prevent its accidental re-establishment (van Valkenburg, 2017). Moreover, ongoing
monitoring should be implemented in order to detect and treat re0infestations
at later dates (van Valkenburg, 2017).
Chemical control
Herbicide
use can be a highly effective method for controlling invasive plant species but
as Salvinia molesta is
aquatic, strict measures need to be implemented in order to avoid unnecessary
damage to the surrounding aquatic environment. Herbicides such as glyphosate
can be used to control this species but they have not resulted in complete
eradication of Salvinia molesta (van Valkenburg, 2017). The high cost associated with ongoing
chemical treatment, combined with the fact that it does not guarantee
eradication of Salvinia molesta, means that chemical control on its own
may not be a feasible approach (van
Valkenburg, 2017).
Integrated control
Integrated control is the concept of
combining two or more control methods in order to control the target species to
a higher degree than any of the individual controls would achieve on their own.
An example would be to use both physical and chemical together by manually
removing as much biomass as possible and then spraying the remaining plant
material (van
Valkenburg, 2017). In theory, this will result in a higher
level of control than just implementing manual or chemical control on their
own. Even with this multi-faceted approach, ongoing monitoring and subsequent
control over the following years may be required to prevent re-establishment.
Species group
Plant
Native region
South America
Distribution
World distribution(GBIF)
In
addition to its native distribution of south-eastern Brazil, Salvinia molesta has spread
through many parts of the world where it is becoming an alien invasive species (Chapman et
al., 2017). This species can be found throughout Africa, Central and South
America, Asia, North America, Europe and Oceania. In many countries where it
has established populations, it has become locally invasive and continues to
spread (Chapman et
al., 2017).
Irish distribution
Not present.
Temporal change
Records submitted to Data Centre in 2025
The following map is interactive. If you would prefer to view it full screen then click here.
How can you help
Report
any sightings of this species to the National Biodiversity Data Centre,
including a photograph, if possible.
Dispose
of unwanted specimens in a responsible manner that does not allow them in to
the natural environment.
Avoid
purchasing this species for ornamental purposes.
Further information
CABI Invasive Species
Compendium: https://www.cabi.org/isc/datasheet/48447
Encyclopaedia Of Life: https://eol.org/pages/52188111
Invasive Species Ireland: http://invasivespeciesireland.com/species-accounts/potential/freshwater/salvinia-moss
Global Invasive Species
Database: http://www.iucngisd.org/gisd/species.php?sc=569#:~:text=GISD&text=Salvinia%20auriculata%20%2C%20Aubl.&text=Salvinia%20molesta%20is%20a%20floating,-rich%2C%20warm%2C%20freshwater.&text=This%20stagnant%20dark%20environment%20negatively,fish%20and%20submerged%20aquatic%20plants.
References
Publications
CABI, 2021. Salvinia molesta (kariba weed). [online]
Available at: <https://www.cabi.org/isc/datasheet/48447#todescription>
[Accessed 14 Jul. 2021].
Chapman, D., Coetzee,
J., Hussner, A., Netherland, M., Newman, J., Pescott, O., Stiers, I., Van
Valkenburg, J. and Tanner, R., 2017. Pest Risk assessment for Salvinia
molesta. [online] Paris. Available at:
<https://circabc.europa.eu/faces/jsp/extension/wai/navigation/container.jsp?FormPrincipal:_idcl=FormPrincipal:_id1&FormPrincipal_SUBMIT=1&id=140f7990-4c3c-4a36-a2d7-216f0e8f9a75&javax.faces.ViewState=t3PgLr9bR%2BLrfDKgjJj3b6dkCpfYhQw3n98NCNzwCi4iJSP6fJLveJ>
[Accessed 14 Jul. 2021].
Encyclopedia of Life, 2021.
Salvinia molesta. [online] Available at:
<https://eol.org/pages/52188111> [Accessed 14 Jul. 2021].
European Commission,
2017. Invasive Alien Species of Union concern. [online] Luxembourg.
Available at: <https://ec.europa.eu/environment/nature/pdf/IAS_brochure_species.pdf>
[Accessed 25 Jun. 2021].
Global Invasive Species
Database, 2021. Salvinia molesta. [online] Available at:
<http://www.iucngisd.org/gisd/species.php?sc=569> [Accessed 14 Jul.
2021].
Invasive Species
Ireland, 2021. Salvinia molesta. [online] Available at:
<http://invasivespeciesireland.com/species-accounts/potential/freshwater/salvinia-moss>
[Accessed 14 Jul. 2021].
van Valkenburg, J.,
2017. Information on measures and related costs in relation to species
considered for inclusion on the Union list. [online] Available at:
<https://circabc.europa.eu/sd/a/a56c8c1c-f2bf-4b13-99d0-cbcd2651be41/TSSR-2016-003
Salvinia molesta.pdf> [Accessed 14 Jul. 2021].