Stratiotes aloides L.

Common Name: Water soldiers

Synonyms and Other Names:

Water Pineapple, Saw Tooth, Water Aloe



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Identification: General: Stratiotes aloides is a loosely rooted aquatic species with emergent and submerged growth forms (Cook and Urmi-König 1983; Erixon 1979).
Roots: Roots can be up to 180 cm long but are usually less.
Stem: Depressed conical stems with a complex but regular branching system that can resemble the household spider plant (Campbell 2009). Stem length: 10-18mm long (Cook and Urmi-König 1983)
Leaves: Serrated leaf edges distinguish it from similar looking aquatic plants in the Great Lakes (MNRF 2014). Submerged leaves can grow up to 60 cm (or rarely 110 cm long) and up to 1 cm wide with somewhat weak spines. Submerged leaves are thin, brittle and droop at an angle. Emergent leaves are thick, rigid, brittle, and dark green and are usually less than 40 cm long and 1-4 cm wide, with well-developed spines along leaf margins.
Flower/Fruit: Emergent form develops rosettes at the surface of the water (Cook and Urmi-König 1983).


Size: Stem length: 10-18mm long, Leaf length: 40-60 cm long, 1-4 cm wide (Cook and Urmi-K├Ânig 1983).


Native Range: Stratiotes aloides is native to the United Kingdom, Spain, Italy, Bulgaria, and Siberia (UK Natural History Museum 2013).


This species is not currently in the Great Lakes region but may be elsewhere in the US. See the point map for details.

Table 1. States/provinces with nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Stratiotes aloides are found here.

State/ProvinceFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
ONT20092022*

Table last updated 6/22/2024

† Populations may not be currently present.

* HUCs are not listed for areas where the observation(s) cannot be approximated to a HUC (e.g. state centroids or Canadian provinces).


Ecology: Stratiotes aloides is found mainly in sheltered bays of larger lakes, backwater ponds, ditches and canals (UK Natural History Museum 2013). S. aloides ranges as far north as Kittila, Finland (Kittila is located at 67°N), where the coldest temperatures in Finland occur. The species is limited to freshwater and can grow in depths of up to 6.5m (Tarkowska-Kukuryk 2006). S. aloides usually inhabits shallow stagnant waters, mainly eutrophic and mesotrophic, with substratum of mud and organic deposits (Strzalek and Koperski 2009).

The Lepidopteran larvae species Paraponyx stratiotata and Nymphula nymphaeata feed on fresh S. aloides tissue (Linhart, 1999). Veen et al. (2013) found that a variety of  vertebrate aquatic herbivores graze on S. aloides, reducing the biomass by 60%.

This species displays vegetative reproduction. Vegetative propagules are formed as axillary buds. When the bottom leaves of the rosette decay, these buds are released. On average 4.7 (±0.28 SE) buds are formed per mature rosette (n = 83) (Sarneel 2013). Buds have high capacity to disperse over long distances via water (84% of propagules re-sprouted, and 92% were still floating after 187 days) (Sarneel 2013).


Great Lakes Means of Introduction: The introduction of Stratiotes aloides was most likely due to escape from recreational culture with spread due to dispersal along the waterway.


Great Lakes Status: Overwintering and reproducing with a self-sustaining population. Spread within the Great Lakes currently restricted to the Bay of Quinte.


Great Lakes Impacts:
Summary of species impacts derived from literature review. Click on an icon to find out more...

EnvironmentalSocioeconomicBeneficial



Stratiotes aloides has a moderate environmental impact  in the Great Lakes.
Stratiotes aloides forms "dense, almost monospecific stands" in native habitat (Strzalek and Koperski 2009) and has the potential to crowd out native vegetation (Ontario Ministry of Natural Resources 2009).

Stratiotes aloides has the potential to alter surrounding water chemistry, which may harm phytoplankton and other aquatic organisms (Ontario Ministry of Natural Resources 2009).  The exact mechanism has not been elucidated, but the likely cause is allelopathy (Mulderij et al. 2006). This species can also reduce phytoplankton and zooplankton biomass (Kurbatova and Yershov, 2018 and Kurbatova et al., 2019).

Stratiotes aloides has a moderate socio-economic impact in the Great Lakes.

Stratiotes aloides’s sharp leaves can cut skin (CommunityPress.ca 2009). Dense floating mats can hinder recreational activities, such as boating, angling, and swimming.

Stratiotes aloides has a moderate benefit to the Great Lakes.

S. aloides is high in flavonoids including luteolin apigenin, and chrysoeriol derivatives which can provide medicinal benefits (Gawlik-Dziki et al., 2020). This species is able to accumulate Strontium-90 from waterways and it has a higher affinity than other macrophytes (Kalinichenko et al., 2017) Additionally, it provides habitat for planktonic crustaceans, microcrustaceans, and terns (Strzalek and Koperski, 2009, Galowski et al., 2017, and Strzalek and Koperski, 2019).


Management:  

Regulations

It is illegal to import, possess, deposit, release, transport, breed/grow, buy, sell, lease or trade S. aloides in Ontario (Invasive Species Act 2015). Michigan prohibits the introduction, importation, movement, sale, or distribution of S. aloides (NREPA Part 413 as amended, MCL 324.41302(3)(a)). Illinois lists S. aloides as an injurious species as defined by 50 CFR 16.11-15. Therefore, S. aloides cannot be possessed, propagated, bought, sold, bartered or offered to be bought, sold, bartered, transported, traded, transferred or loaned to any other person or institution unless a permit is first obtained from the Department of Natural Resources. Illinois also prohibits the release of any injurious species, including S. aloides (17 ILL. ADM. CODE, Chapter 1, Sec. 805). Wisconsin prohibits the transport, possession, or introduction of S. aloides (Wisconsin Chapter NR 40). It is also prohibited for a person to possess, import, purchase, sell, propagate, transport, or introduce S. aloides in Minnesota (Minnesota Rule 6216.0250). There are no regulations on S. aloides in New York, Pennsylvania, Ohio, Michigan, or Indiana.

Note: Check federal, state, and local regulations for the most up-to-date information.

Control

Biological

Herbivorous birds and fish may be able to limit the establishment and growth of S. aloides in the Great Lakes basin. Veen et al. (2013) found that grazing by a variety of vertebrate aquatic herbivores reduced the biomass growth of S. aloides by 60% and resulted in decreased survival over 16 weeks. S. aloides is also vulnerable to fungi such as Fusarium roseum (Cook and Urmi-Konig 1983), but use of any pathogenic control should be cautiously employed in order to minimize non-target effects.

Physical

Despite being less efficient, removal by hand in the Trent River, Ontario was found to be initially as effective as chemical treatments. However, difficulty in detecting S. aloides in dense macrophyte communities and turbid water reduce the efficacy of hand removal (Anonymous 2014 in Snyder et al. 2016). Shade-cloth enclosures designed to prevent sunlight were utilized on three populations of S. aloides in Ontario. After two months, all water soldiers plants covered by the enclosures were deceased (Ontario’s Invading Species Awareness Program 2016). Other physical control methods, such as mechanical harvesting, have not been conclusively evaluated (Snyder et al. 2016).


Chemical

Several studies investigating the efficacy of diquat revealed that at least 16 hours of 370 ug L-1 was required to achieve a complete collapse of plants without any regeneration over the following six weeks. However, the effectiveness of diquat is limited in deep, fast-flowing, or turbid water (Snyder et al. 2016). In order to minimize non-target impacts, herbicide treatments should be conducted in Fall (September and October) when water soldiers remain actively growing and other native aquatic plants have gone dormant (MNRF 2016).

Intensified agricultural practices and anthropomorphic stressors over the last half century have contributed to the decline of S. aloides in parts of Europe (Smolders et al. 2003; Abeli et al. 2014). Smolders et al. (2003) determined that the decline of S. aloides is mainly due to increased sulphate reduction rates, which can lead to sulphide toxicity, iron deficiencies, and increased internal eutrophication due to mobilization of phosphate. Additionally, increased competition from free-floating plants and increased ammonium concentrations also have contributed to its decline. Sites in Italy where S. aloides had been extirpated were characterized by high inorganic nitrogen concentrations and low CO2 concentrations (Abeli et al. 2014). Therefore, eutrophication events that are seen in areas like Green Bay and the Western Basin of Lake Erie may affect S. aloides if it were to become established in these areas.

Note: Check state and local regulations for the most up-to-date information regarding permits for pesticide/herbicide/piscicide/insecticide use.


References (click for full reference list)


Author: Fusaro, A., A. Davidson, K. Alame, M. Gappy, E. Baker, G. Nunez, J. Larson, W. Conard, P. Alsip and J. Van Zeghbroeck


Contributing Agencies:
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Revision Date: 11/2/2023


Citation for this information:
Fusaro, A., A. Davidson, K. Alame, M. Gappy, E. Baker, G. Nunez, J. Larson, W. Conard, P. Alsip and J. Van Zeghbroeck, 2024, Stratiotes aloides L.: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspx?Species_ID=3159&Potential=Y&Type=2, Revision Date: 11/2/2023, Access Date: 6/22/2024

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.