Azolla filiculoides Lam., Salviniaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: Pacific azolla, azolla, ferny azolla, large mosquito fern, red azolla, red-water fern, water fern

Habit:  aquatic fern

Description:  "Plants green to yellowish green or dark red, with 2 growth stages; plants fertile only in mature stage, generally in late spring. Stems prostrate when immature, 1--3 cm, internodes elongate to 5 mm, becoming nearly erect to 5 cm or more when mature and crowded. Hairs on upper leaf lobes strictly unicellular. Megaspores warty with raised angular bumps, each with a tangle of filaments" (Flora of North America).

Habitat/ecology:  Taro patches, lakes, ponds, ditches, canals, marshes, and slow-moving streams. Forms dense mats that choke out other species. Azolla lives in symbiosis with blue-green algae (cyanobacteria), taking advantage of their ability to fix nitrogen.  It is sometimes introduced and used by farmers as a natural fertilizer for this reason.  It has also been introduced to assist in mosquito abatement.  In Hawai‘i, "now well established in flooded areas on all the islands"  (Wilson, 1996).

Propagation:  "The fern spreads rapidly by fragmentation of the plant.  Sexual reproduction is common as well, and the spores are extremely resistant to desiccation" (Weber, 2003; p. 64).

Native range:  Western North America (Flora of North America)

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Cook Islands Southern Cook Islands	Mangaia Island	introduced invasive	Space, James C./Flynn, Tim (2002) (p. 13)
Cook Islands Southern Cook Islands	Mangaia Island		Sykes, Bill (year unknown)
Cook Islands Southern Cook Islands	Ma‘uke Island	introduced invasive	Space, James C./Flynn, Tim (2002) (p. 13)
Cook Islands Southern Cook Islands	Ma‘uke Island		Sykes, Bill (year unknown)
Cook Islands Southern Cook Islands	Rarotonga Island	introduced invasive	Space, James C./Flynn, Tim (2002) (p. 13)
Cook Islands Southern Cook Islands	Rarotonga Island		Sykes, Bill (year unknown)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wilson, Kenneth A. (2003) (p. 5) Voucher cited: Imada 99-16 (BISH)
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, W. L./Herbst, D. R./Lorence, D. H. (2013)
State of Hawaii Hawaiian Islands	Kaho‘olawe Island		Wilson, K. A. (1996)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Wagner, W. L./Herbst, D. R./Lorence, D. H. (2013)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive	Wagner, W. L./Herbst, D. R./Lorence, D. H. (2013)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, W. L./Herbst, D. R./Lorence, D. H. (2013)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Wagner, W. L./Herbst, D. R./Lorence, D. H. (2013)
State of Hawaii Hawaiian Islands	Ni‘ihau Island		Wilson, K. A. (1996)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, W. L./Herbst, D. R./Lorence, D. H. (2013)

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)	New South Wales		Australian Biological Resources Study (2013)
Australia Australia (continental)	Queensland		Australian Biological Resources Study (2013)
British Columbia (province of Canada) Province of British Columbia	Canada (British Columbia)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Costa Rica (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Guatemala (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Nicaragua (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
China China	China (People's Republic of)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2013) Naturalized
Indonesia Indonesia	Indonesia (Republic of)		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 41)
South Korea South Korea	South Korea (Republic of)	introduced cultivated	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 36) "Slow moving streams, ponds and lakes".
South America (Pacific rim) South America (Pacific rim)	Chile (Republic of)	native	Belov, Michail (2013)
South America (Pacific rim) South America (Pacific rim)	Colombia	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (west coast) United States (west coast states)	USA (Oregon)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (west coast) United States (west coast states)	USA (California)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

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)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013) Arizona

Comments:  Reportedly introduced to the Cook Islands as a nitrogen supplement in Taro patches (Bill Sykes, pers. com.). In Hawai‘i, "deliberately brought into the Islands as part of a mosquito abatement program in rice fields" (Wilson, 1996).

Control: 

Physical:  "Mechanical control includes removing plants by fine meshed nets.  However, the plant can re-establish from spores, and manual removal may be impractical for large infestations".

Chemical:  "Herbicides used include glyphosate, paraquat, or diquat.  A follow-up program is needed to control new plants germinating from spores"  (Weber, 2003; p. 64).