Pistia stratiotes L., Araceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  Reject, score: 18 (Go to the risk assessment)

Common name(s): [more details]

English: Nile cabbage, tropical duckweed, water cabbage, water lettuce, water lily

French: laitue d'eau, pistie

Spanish: flor de tetumo, lechuga de agua, lechuguilla, lechuguita de agua, repollito de agua, repollo de sapo, verdolago de agua

Habit:  aquatic herb

Description:  "Aquatic, floating, rosette-forming stemless stoloniferous herbs, with sessile, obovate or obcuneate glaucous (water-shedding) leaves.  Spathe small, the limb ovate, enclosing one gynoecium; anthers 4, sessile, connate, in a spathe.  Fruits membranous, few-seeded, the seeds obovoid-oblong" (Stone, 1970). "[A] free-floating but soon stoloniferous, small, aquatic, perennial plant, with a tuft of long, very fibrous roots beneath, primary roots 2 to 7 mm in diameter and 1 m long, very fine, plumosely spreading root hairs; leaves obovate-cuneat, erect, few to many, 2.5 to 15 cm long, the basal part somewhat velvety-hairy, becoming thickened by the production of very porous tissue except when stranded on banks; flowers bisexual; bracts (spathes) subtending flowers; spathes white, densely dotted when dry, finely hairy (pilose) outside, smooth inside, 7 to 12 mm long, 5 mm wide, short-penduncled in the center of the rosette of leaves; spadix bearing the individual flowers is shorter than the spathe, flowering parts minute; fruit berrylike (baccate), rupturing irregularly, seeds usually numerous, oblong, tapering toward the base, the apex appearing as if cut off at the end, about 2 mm long.  The light yellow-green leaves in the form of a rosette (cabbage-like) which are velvety-hairy and prominently veined below are characteristic of this species" (Holm et al., 1977; p. 379).

Habitat/ecology:  "The free-floating plants are found in reservoirs, ponds, and marshes along the edges of large tropical lakes where they are able to thrive amidst the offshore vegetation and debris; in slow-moving or stagnant waters; and in old wells" (Holm et al., 1977; p. 379).  "It is a common floating plant in dams, lagoons, lakes and also grows in wetland rice. It is also found floating on stagnant water and sometimes rooting on muddy banks.  Like Water hyacinth this plant also blocks irrigation canals and provides a breeding ground for mosquitoes and choking fishery waters" (Ecoport).  In Hawai‘i, "occurs in open ditches, ponds, and other watercourses, generally at low elevations"  (Wagner et al., 1999; p. 1359). In New Caledonia, "pante aquatique cultivée dans des bassins artificiels et parfois spontanée" (MacKee, 1994; p. 18).

Propagation:  "This aquatic plant usually propagates by means of stolons which break easily from the plant accounts. Reproduction also takes place by seeds" (Ecoport).

Native range:  Unknown, now pan-tropical. A common aquatic weed in hot climatic countries.

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Rota Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 93)
Cook Islands Southern Cook Islands	Rarotonga Island	introduced	Sykes, Bill (year unknown)
French Polynesia Society Islands	Tahiti Island	introduced	Fosberg, F. R. (1997) (p. 10)
French Polynesia Society Islands	Tahiti Island		Bishop Museum (Honolulu) (1983) (voucher ID: BISH 554434) Taxon name on voucher: Pistia stratiotes L.
Guam Guam Island	Guam Island	introduced invasive	Stone, Benjamin C. (1970) (pp. 123-124) Voucher cited: Stone & Cushing-Falanruw 8234 (GUAM)
Guam Guam Island	Guam Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 93)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1359)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1359)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1359)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1359)
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced invasive cultivated	MacKee, H. S. (1994) (p. 18) Vouchers cited: MacKee 40825, Suprin in MacKee 45680, Jérémie & Tirel 1654
Palau Palau (main island group)	Babeldaob Island	introduced cultivated	Space, James C./Lorence, David H./LaRosa, Anne Marie (2009) (p. 5) Seen in cultivation, source unknown.
Papua New Guinea Papua New Guinea (eastern New Guinea Island)	Papua New Guinea (eastern New Guinea Island)		Waterhouse, D. F. (1997) (p. 64)
Philippines Philippine Islands	Philippine Islands	introduced invasive	Waterhouse, D. F. (1993) (pp. 68, 78)
Solomon Islands Solomon Islands	Solomon Islands		Swarbrick, John T. (1997) (p. 95)
Solomon Islands Solomon Islands	Solomon Islands	native	Hancock, I. R./Henderson, C. P. (1988) (p. 100)
Vanuatu New Hebrides Islands	Vanuatu (Republic of)		Swarbrick, John T. (1997) (p. 95)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	Northern Territory		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (p. 381)
Australia Australia (continental)	Queensland		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (p. 381)
Cambodia Cambodia	Cambodia (Kingdom of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 68, 78)
China China	China (People's Republic of)	introduced invasive	Li-ying, Li/Ren, Wang/Waterhouse, D. F. (1997) (p. 174)
Colombia Colombia	Colombia (Republic of)		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (p. 381)
El Salvador El Salvador	El Salvador (Republic of)		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (pp. 381-384)
Honduras Honduras	Honduras (Republic of)		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (pp. 381-384)
Indonesia Indonesia	Indonesia (Republic of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 68, 78)
Malaysia Malaysia	Malaysia (country of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 68, 78)
Negara Brunei Darussalam Brunei	Brunei (Negara Brunei Darussalam)	introduced invasive	Waterhouse, D. F. (1993) (pp. 68, 78)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (pp. 379-384)
Nicaragua Nicaragua	Nicaragua (Republic of)		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (pp. 381-384)
Singapore Singapore	Singapore (Republic of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 68, 78)
Taiwan Taiwan	Taiwan Island	introduced invasive	Li-ying, Li/Ren, Wang/Waterhouse, D. F. (1997) (p. 174)
Thailand Thailand	Thailand (Kingdom of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 68, 78)
Vietnam Vietnam	Vietnam (Socialist Republic of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 68, 78)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive cultivated	Lavergne, Christophe (2006) "Cultivé/±envahissant"
Seychelles Seychelles Islands	Seychelles Islands	introduced	Weber, Ewald (2003) (p. 332)

Comments:  A Class A (eradicate) noxious weed in New Zealand.

Control: 

Biological: "The curculionid weevil Neohydronomous pulchellus [affinis], which was collected in South America substantially reduced growth of Pistia stratiotes in Australia and Zimbabwe. This is the most sustainable method to control this free floating weed" (GPPIS). 

"The host specific South American weevil, Neohydronomus affinis, has been established readily in six countries and, in all, has produced substantial to excellent control.  The moth, Samea multiplicalis, which attacks P. stratiotes and Salvinia spp., has been established in Australia but its impact has not been evaluated.  In Thailand, classical biological control has not been attempted, but mass rearing and release of the native noctuid moth Spodoptera pectinicornis has replaced the use of herbicides.  The prospects are excellent for classical biological control of P. stratiotes in countries where it is still regarded as an important weed." (Waterhouse, 1994; pp. 196-207).

Waterhouse (1994, pp. 199-207) lists natural enemies and summarizes attempts at biological control.

Biological control information from the publication "Biological control of invasive plants in the eastern United States".

Additional information:
Photos and additional information at University of Florida, Center for Aquatic and Invasive Plants.
Photo and additional information at the Environment Bay of Plenty, New Zealand, web site of the Bay of Plenty Regional Council.
Fact sheet from the Bay of Plenty Regional Council, New Zealand.
Photo and additional information at the University of Guam "Plants of Guam" web site.
Fact sheet from the Government of Queensland, Australia (PDF format).
European and Mediterranean Plant Protection Organization mini-datasheet.
Information from the Global Invasive Species Database.
Information from the book "Identification and biology of non-native plants in Florida's natural areas" (PDF format).

Additional online information about Pistia stratiotes is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Pistia stratiotes as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Pistia stratiotes may be available from the Germplasm Resources Information Network (GRIN).

References:

Bishop Museum (Honolulu). 1983. Voucher specimen #BISH 554434 (Florence, J. 4621).

EcoPort Foundation. 2009. EcoPort (on-line resource).

Fosberg, F. R. 1997. Preliminary checklist of the flowering plants and ferns of the Society Islands. Ed. by David R. Stoddart. U. Cal. Berkeley.

Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce. 1987. A geographical checklist of the Micronesian monocotyledonae. Micronesica 20:1-126.

Gerlach, J. 1997. Seychelles wetland invader: Pistia Stratiotes--water lettuce. Aliens 5:12.

Hafliger, E. 1092. Monocot Weeds 3. CIBA-GEIGY Ltd., Basle, Switzerland. 132 pp. plus plates.

Hancock, I. R./Henderson, C. P. 1988. Flora of the Solomon Islands. Research Bulletin No. 7. Ministry of Agriculture and Lands, Honiara. 203 pp.

Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. 1977. The world’s worst weeds: distribution and biology. East-West Center/University Press of Hawaii. 609 pp.

Julien, M. H. (ed.). 1992. Biological control of weeds: A world catalogue of agents and their target weeds (third edition). CAB International, Wallingford, UK. 186 pp.

Langeland, K. A./Burks, K. Craddock. eds. 1998. Identification and biology of non-native plants in Florida's natural areas. Gainesville, FL: University of Florida. 165 pp.

Lavergne, Christophe. 2006. List des especes exotiques envahissantes a La Reunion. Unpublished manuscript (Excel file). .

Li-ying, Li/Ren, Wang/Waterhouse, D. F. 1997. The distribution and importance of arthropod pests and weeds of agriculture and forestry plantations in southern China. ACIAR, Canberra, Australia. 185 pp.

MacKee, H. S. 1994. Catalogue des plantes introduites et cultivées en Nouvelle-Calédonie. Muséum National d'Histoire Naturelle, Paris, 164 p.

Space, James C./Lorence, David H./LaRosa, Anne Marie. 2009. Report to the Republic of Palau: 2008 update on Invasive Plant Species. USDA Forest Service, Hilo, Hawai‘i. 227 pp.

Stone, Benjamin C. 1970. The flora of Guam. Micronesica 6:1-659.

Swarbrick, John T. 1997. Weeds of the Pacific Islands. Technical paper no. 209. South Pacific Commission, Noumea, New Caledonia. 124 pp.

Sykes, Bill. 0. Bill Sykes, pers. com.

U.S. Dept. Agr., Agr. Res. Serv. 2009. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Van Driesche, Roy/Lyon, Suzanne/Blossey, Bernd/Hoddle, Mark/Reardon, Richard. 2002. Biological control of invasive plants in the eastern United States. USDA Forest Service Publication FHTET-2002-04. 413 pp.

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).

Waterhouse, D. F. 1993. The major arthropod pests and weeds of agriculture in Southeast Asia. The Australian Centre for International Agricultural Research, Canberra. 141 pp.

Waterhouse, D. F. 1994. Biological control of weeds: Southeast Asian prospects. Australian Centre for International Agricultural Research, Canberra. 302 pp.

Waterhouse, D. F. 1997. The major invertebrate pests and weeds of agriculture and plantation forestry in the Southern and Western Pacific. The Australian Centre for International Agricultural Research, Canberra. 93 pp.

Weber, Ewald. 2003. Invasive plants of the World. CABI Publishing, CAB International, Wallingford, UK. 548 pp.