Azolla pinnata

Preferred Scientific Name

Azolla pinnata

Preferred Common Name

mosquito fern

International Common Names

English: African azolla; feathered mosquito fern; ferny azolla; pinnate mosquito fern; water velvet

Local Common Names

Australia: red azolla; red water fern; water moss

Germany: Afrikanischer Algenfarn; Gefiederter Algenfarn

Japan: aka-ukikusa

Vietnam: beo-dau

Summary of Invasiveness

pinnata can spread very quickly forming dense vegetative masses on areas of still water. This in turn limits the light available to other aquatic plants and oxygen used by other aquatic life. In New Zealand it has had a detrimental impact on the native species A. rubra (Owen, 1997). It is included on the federal noxious weed list for the USA (USDA-NRCS, 2004).


Azolla pinnata is locally distributed in its native range of Africa and Madagascar, India, Southeast Asia, China and Japan, Malaysia and the Philippines, the New Guinea mainland and Australia (Croft, 1986). The native ranges of the three subspecies is given in USDA-ARS (2005) as: tropical Africa, southern Africa and Madagascar for subsp. africana; tropical Asia, China and Japan for subsp. asiatica; and Australia and New Caledonia for subsp. pinnata.

Distribution Table and Maps

The distribution in the summary table and maps below is based on all the information available, as listed in the ISC.
A. pinnata worldkeyA. pinnata asiaA pinnata SE Asia

Country Distribution Origin Invasive References
Bangladesh Restricted distribution Native Shahjahan et al., 1980; EPPO, 2014
Brunei Darussalam Present Waterhouse, 1993
Cambodia Restricted distribution Waterhouse, 1993; EPPO, 2014
China Restricted distribution Native Croft, 1986; EPPO, 2014
-Anhui Present Native USDA-ARS, 2005
-Fujian Present Native USDA-ARS, 2005
-Henan Present Native USDA-ARS, 2005
-Hubei Present Native USDA-ARS, 2005
-Jiangsu Present Native USDA-ARS, 2005
-Jiangxi Present Native USDA-ARS, 2005
-Sichuan Present Native USDA-ARS, 2005
-Zhejiang Present Native USDA-ARS, 2005
India Restricted distribution EPPO, 2014
-Assam Widespread Native Devashish & Kar Barbhuiya, 2001
-Bihar Widespread Native Srivastava & Amarjeet Singh, 1984
-Gujarat Widespread Native Sreenivas & Rana, 1992
-Jammu and Kashmir Widespread Native Dutta et al., 1991
-Kerala Widespread Native Thomas, 1976; Madhusoodanan et al., 1993
-Odisha Present Native Satapathy & Chand, 1984
Indonesia Restricted distribution Waterhouse, 1993; USDA-ARS, 2005; EPPO, 2014
Japan Restricted distribution Native Croft, 1986
Korea, DPR Restricted distribution Dostálek et al., 1989
Laos Present Waterhouse, 1993
Malaysia Restricted distribution Native Waterhouse, 1993; Mansor & Sam, 1992
Myanmar Present Waterhouse, 1993; USDA-ARS, 2005
Pakistan Restricted distribution USDA-ARS, 2005; EPPO, 2014
Philippines Restricted distribution Native Bravo, 1991; Waterhouse, 1993; EPPO, 2014
Sri Lanka Restricted distribution Native Weerakoon & Gunewardena, 1983
Taiwan Present Native USDA-ARS, 2005
Thailand Restricted distribution Native Takara, 1981; Waterhouse, 1993; EPPO, 2014
Vietnam Restricted distribution Native Waterhouse, 1993; Thuoc et al., 1978; Croft, 1986;EPPO, 2014
Angola Restricted distribution Native Dyer et al., 1963; Exell & Wild, 1960
Botswana Restricted distribution Native Dyer et al., 1963; EPPO, 2014
Burundi Restricted distribution Native Dyer et al., 1963
Cameroon Restricted distribution Native Dyer et al., 1963
Central African Republic Restricted distribution Native Dyer et al., 1963
Congo Restricted distribution Native Dyer et al., 1963
Congo Democratic Republic Restricted distribution Native Dyer et al., 1963; Exell & Wild, 1960; EPPO, 2014
Côte d’Ivoire Restricted distribution Native Dyer et al., 1963
Egypt Restricted distribution Native Galal & El-Ghandour, 2000
Gabon Restricted distribution Native Dyer et al., 1963
Guinea Restricted distribution Native Dyer et al., 1963
Guinea-Bissau Restricted distribution Native Dyer et al., 1963
Kenya Restricted distribution Native Dyer et al., 1963; Johns, 1991
Liberia Restricted distribution Native Dyer et al., 1963; Johns, 1991
Madagascar Restricted distribution Native Johns, 1991; EPPO, 2014
Mozambique Restricted distribution Native Johns, 1991
Nigeria Restricted distribution Native Johns, 1991
Rwanda Restricted distribution Native Dyer et al., 1963; Johns, 1991
Senegal Restricted distribution Native Dyer et al., 1963; Johns, 1991
Sierra Leone Restricted distribution Native Dyer et al., 1963
South Africa Restricted distribution Native Dyer et al., 1963; Hill, 1998; Johns, 1991
Tanzania Restricted distribution Native Dyer et al., 1963
Uganda Restricted distribution Native Dyer et al., 1963; Johns, 1991
Zambia Restricted distribution Native Dyer et al., 1963; Johns, 1991
Australia Restricted distribution Native Croft, 1986; EPPO, 2014
-Australian Northern Territory Restricted distribution Native Chapman et al., 1981; USDA-ARS, 2005
-New South Wales Present Native USDA-ARS, 2005
-Queensland Present Native USDA-ARS, 2005
-Victoria Present Native USDA-ARS, 2005
New Caledonia Present Native USDA-ARS, 2005
New Zealand Restricted distribution Introduced Invasive Owen, 1997; EPPO, 2014
Papua New Guinea Restricted distribution Native Croft, 1985; Croft, 1986

History of Introduction and Spread

Introductions to new countries are assumed to have been through horticultural or ornamental trade with the aquarium industry.

Risk of Introduction

There is a low risk of spread to non-tropical and sub-tropical areas, and spread between waterbodies within natural areas appears to be regulated by deliberate introduction by man for agricultural purposes. Once in a waterbody, vegetative fragments and spores can spread easily downstream, and be carried with floodwaters to colonize new areas.

Notes on Natural Enemies

Calilung and Lit (1986) reported studies on a broad range of insect fauna associated with Azolla in the Philippines, with several species causing frond damage to several Azolla species. It was suggested that herbivory prevented Azolla species from becoming weeds in rice paddies.

Dath and Singh (1998) reported that A. pinnata was very susceptible to the fungus Rhizoctonia solani [Thanatephorus cucumeris], and Shahjahan et al. (1980) reported inhibition of growth of A. pinnata by Sclerotium rolfsii [Corticium rolfsii] and Rhizoctonia sp. These fungal pathogens are opportunists and also attack a range of crop plants. Fannah (1987) reported a completed life cycle of Elophila africalis on A. pinnata in Sierra Leone which was followed up by Roberts et al. (1998).

Sands and Kassulke (1986) reported oviposition by females of Paulinia acuminata after feeding on A. pinnata. However, P. acuminata was introduced into Africa, India and Fiji for the control of Salvinia molesta but is not host specific and did not contribute significantly to control (Julien and Griffiths, 1998). Therefore, it is unlikely that it is an important constraint on A. pinnata.

The frond-feeding weevil Stenopelmus rufinasus was imported into quarantine for testing as a potential natural enemy for the A. filiculoides in South Africa (Hill, 1998). Both the adults and larvae severely reduced A. filiculoides in the laboratory.

Of 31 plant species in 19 families tested, adult feeding, oviposition and larval development were only recorded on the Azolla species (A. filiculoides, A. pinnata subsp. poss. asiatica, A. pinnata subsp. africana and A. nilotica). A. filiculoides was the most suitable host for the weevil. Low adult emergence from A. nilotica and A. pinnata subsp. africana would probably prevent the weevil from establishing on them in the field. A. pinnata subsp. poss. asiatica supported greater development. Impact

The presence of A. pinnata on the US federal Noxious Weeds List implies there is a risk of significant economic impact from this species. There are no data on actual costs to activities restricted by the presence of this species, although it will interfere with navigation, boating, irrigation, recreation, angling and bathing, and there will be costs associated with control.


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