Pacific Island Ecosystems at Risk (PIER)

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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: azolla, ferny azolla, large mosquito fern, Pacific azolla, 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)
Canada (British Colombia)
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 (Republic of) 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).


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This page was created on 25 FEB 2003 and was last updated on 16 JAN 2011.