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]

Chinese: da piao

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)
Federated States of Micronesia Kosrae Island	Kosrae Island	introduced cultivated	Lorence, David H./Flynn, Timothy (2010) (p. 6) "Potentially invasive"
French Polynesia Society Islands	Tahiti Island	introduced	Fosberg, F. R. (1997) (p. 10)
French Polynesia Society Islands	Tahiti Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Voucher cited: J. Florence 4621 (PAP) Naturalisée
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 (Belau ) (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 Bougainville Islands	Bougainville Island		Foreman, D. B. (1971) (p. 23)
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)
Philippines Philippine Islands	Philippine Islands		Merrill, Elmer D. (1925) (p. 189) Floating in shallow water of lakes and slow streamsat low altitudes; often abundant.
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)	introduced invasive	Shine, C./Reaser, J. K./Gutierrez, A. T., eds. (2003) (p. 179)

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)
Central America Central America (Pacific rim)	El Salvador (Republic of)		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (pp. 381-384)
Central America Central America (Pacific rim)	Honduras (Republic of)		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (pp. 381-384)
Central America Central America (Pacific rim)	Nicaragua (Republic of)		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (pp. 381-384)
China China	China (People's Republic of)	introduced invasive	Li-ying, Li/Ren, Wang/Waterhouse, D. F. (1997) (p. 174)
China China	Hong Kong	native	Wu, Te-lin (2001) (p. 300) Prefer hot, humid environment, in ponds and ditches.
Indonesia Indonesia	Indonesia (Republic of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 68, 78)
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 193)
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)
Singapore Singapore	Singapore (Republic of)	introduced invasive	Waterhouse, D. F. (1993) (pp. 68, 78)
Singapore Singapore	Singapore (Republic of)	introduced invasive	Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 70) Naturalised
South America (Pacific rim) South America (Pacific rim)	Colombia		Holm, Leroy G./Plucknett, D. L./Pancho, J. V./Herberger, J. P. (1977) (p. 381)
Taiwan Taiwan Island	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)
United States (west coast) United States (west coast states)	USA (California)		U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
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)
Seychelles Seychelles Islands	Seychelles Islands	introduced	Invasive Species Specialist Group (2017)

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
United States (continental except west coast) United States (other states)	United States (other states)		U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
United States (continental except west coast) United States (other states)	USA (Florida)		U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)

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

Planting of this species in the State of Florida (U.S.) is prohibited by Florida Department of Environmental Protection (Hunsberger, 2001).

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".