Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


Azolla pinnata
(mosquito fern)



Azolla pinnata (mosquito fern)


  • Last modified
  • 08 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Host Plant
  • Preferred Scientific Name
  • Azolla pinnata
  • Preferred Common Name
  • mosquito fern
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Pteridophyta
  •       Class: Filicopsida
  •         Family: Azollaceae
  • Summary of Invasiveness
  • A. 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 n...

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Azolla pinnata (ferny azolla, mosquito fern); in water feature at Kula Ace Hardware and Nursery, Maui.  September 06, 2007
CaptionAzolla pinnata (ferny azolla, mosquito fern); in water feature at Kula Ace Hardware and Nursery, Maui. September 06, 2007
Copyright©Forest Starr & Kim Starr - CC BY 4.0
Azolla pinnata (ferny azolla, mosquito fern); in water feature at Kula Ace Hardware and Nursery, Maui.  September 06, 2007
HabitAzolla pinnata (ferny azolla, mosquito fern); in water feature at Kula Ace Hardware and Nursery, Maui. September 06, 2007©Forest Starr & Kim Starr - CC BY 4.0
Azolla pinnata (ferny azolla, mosquito fern) Habit in koi pond at Kula Botanical Garden, Maui.  March 07, 2011
CaptionAzolla pinnata (ferny azolla, mosquito fern) Habit in koi pond at Kula Botanical Garden, Maui. March 07, 2011
Copyright©Forest Starr & Kim Starr - CC BY 4.0
Azolla pinnata (ferny azolla, mosquito fern) Habit in koi pond at Kula Botanical Garden, Maui.  March 07, 2011
HabitAzolla pinnata (ferny azolla, mosquito fern) Habit in koi pond at Kula Botanical Garden, Maui. March 07, 2011©Forest Starr & Kim Starr - CC BY 4.0
Close-up of Azolla pinnata (ferny azolla, mosquito fern); in water feature at Kula Ace Hardware and Nursery, Maui.  September 06, 2007
TitleClose-up of shape and form
CaptionClose-up of Azolla pinnata (ferny azolla, mosquito fern); in water feature at Kula Ace Hardware and Nursery, Maui. September 06, 2007
Copyright©Forest Starr & Kim Starr - CC BY 4.0
Close-up of Azolla pinnata (ferny azolla, mosquito fern); in water feature at Kula Ace Hardware and Nursery, Maui.  September 06, 2007
Close-up of shape and formClose-up of Azolla pinnata (ferny azolla, mosquito fern); in water feature at Kula Ace Hardware and Nursery, Maui. September 06, 2007©Forest Starr & Kim Starr - CC BY 4.0


Top of page

Preferred Scientific Name

  • Azolla pinnata R. Br.

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

EPPO code

  • AZOPI (Azolla pinnata)

Summary of Invasiveness

Top of page A. 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).

Taxonomic Tree

Top of page
  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Pteridophyta
  •             Class: Filicopsida
  •                 Family: Azollaceae
  •                     Genus: Azolla
  •                         Species: Azolla pinnata

Notes on Taxonomy and Nomenclature

Top of page The genus Azolla was first classified by Lamarck in 1783; seven species are currently included. Three subspecies of A. pinnata are recognized: subsp. africana (Desv.) R.M.K. Saunders & K. Fowler, subsp. asiatica R.M.K. Saunders & K. Fowler, and subsp. pinnata R. Br.


Top of page A. pinnata is small, 1.5-2.5 cm long, with a +/- straight main axis with pinnately arranged side branches, progressively longer towards the base, thus roughly triangular in shape; the basal branches themselves becoming pinnate and eventually fragmenting as the main axis decomposes to form new plants. Roots have fine lateral rootlets, giving a feathery appearance in the water. Leaves minute, 1-2 mm long, overlapping in two ranks, upper lobe green, brownish green or reddish, lower lobe translucent brown; minute, short, pillae, +/- cylindrical unicellular hairs often present on the upper lobes. When fertile, round sporocarps 1-1.5 mm wide can be seen on the under side at the bases of the side branches. The leaves often have a maroon-red tinge and the water can appear to be covered by red velvet from the distance. For further details see Croft (1986).

Plant Type

Top of page Aquatic
Vegetatively propagated


Top of page A. 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

Top of page

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes


BangladeshRestricted distributionNativeShahjahan et al., 1980; EPPO, 2014
Brunei DarussalamPresentWaterhouse, 1993
CambodiaRestricted distributionWaterhouse, 1993; EPPO, 2014
ChinaRestricted distributionNativeCroft, 1986; EPPO, 2014
-AnhuiPresentNativeUSDA-ARS, 2005
-FujianPresentNativeUSDA-ARS, 2005
-HenanPresentNativeUSDA-ARS, 2005
-HubeiPresentNativeUSDA-ARS, 2005
-JiangsuPresentNativeUSDA-ARS, 2005
-JiangxiPresentNativeUSDA-ARS, 2005
-SichuanPresentNativeUSDA-ARS, 2005
-ZhejiangPresentNativeUSDA-ARS, 2005
IndiaRestricted distributionEPPO, 2014
-AssamWidespreadNativeDevashish and Kar Barbhuiya, 2001
-BiharWidespreadNativeSrivastava and Amarjeet Singh, 1984
-GujaratWidespreadNativeSreenivas and Rana, 1992
-Jammu and KashmirWidespreadNativeDutta et al., 1991
-KeralaWidespreadNativeThomas, 1976; Madhusoodanan et al., 1993
-OdishaPresentNativeSatapathy and Chand, 1984
IndonesiaRestricted distributionWaterhouse, 1993; USDA-ARS, 2005; EPPO, 2014
JapanRestricted distributionNativeCroft, 1986
Korea, DPRRestricted distributionDostálek et al., 1989
LaosPresentWaterhouse, 1993
MalaysiaRestricted distributionNativeMansor and Sam, 1992; Waterhouse, 1993
MyanmarPresentWaterhouse, 1993; USDA-ARS, 2005
PakistanRestricted distributionUSDA-ARS, 2005; EPPO, 2014
PhilippinesRestricted distributionNativeBravo, 1991; Waterhouse, 1993; EPPO, 2014
Sri LankaRestricted distributionNativeWeerakoon and Gunewardena, 1983
TaiwanPresentNativeUSDA-ARS, 2005
ThailandRestricted distributionNativeTakara, 1981; Waterhouse, 1993; EPPO, 2014
VietnamRestricted distributionNativeThuoc et al., 1978; Croft, 1986; Waterhouse, 1993; EPPO, 2014


AngolaRestricted distributionNativeExell and Wild, 1960; Dyer et al., 1963
BotswanaRestricted distributionNativeDyer et al., 1963; EPPO, 2014
BurundiRestricted distributionNativeDyer et al., 1963
CameroonRestricted distributionNativeDyer et al., 1963
Central African RepublicRestricted distributionNativeDyer et al., 1963
CongoRestricted distributionNativeDyer et al., 1963
Congo Democratic RepublicRestricted distributionNativeExell and Wild, 1960; Dyer et al., 1963; EPPO, 2014
Côte d'IvoireRestricted distributionNativeDyer et al., 1963
EgyptRestricted distributionNativeGalal and El-Ghandour, 2000
GabonRestricted distributionNativeDyer et al., 1963
GuineaRestricted distributionNativeDyer et al., 1963
Guinea-BissauRestricted distributionNativeDyer et al., 1963
KenyaRestricted distributionNativeDyer et al., 1963; Johns, 1991
LiberiaRestricted distributionNativeDyer et al., 1963; Johns, 1991
MadagascarRestricted distributionNativeJohns, 1991; EPPO, 2014
MozambiqueRestricted distributionNativeJohns, 1991
NigeriaRestricted distributionNativeJohns, 1991
RwandaRestricted distributionNativeDyer et al., 1963; Johns, 1991
SenegalRestricted distributionNativeDyer et al., 1963; Johns, 1991
Sierra LeoneRestricted distributionNativeDyer et al., 1963
South AfricaRestricted distributionNativeDyer et al., 1963; Johns, 1991; Hill, 1998
TanzaniaRestricted distributionNativeDyer et al., 1963
UgandaRestricted distributionNativeDyer et al., 1963; Johns, 1991
ZambiaRestricted distributionNativeDyer et al., 1963; Johns, 1991


AustraliaRestricted distributionNativeCroft, 1986; EPPO, 2014
-Australian Northern TerritoryRestricted distributionNativeChapman et al., 1981; USDA-ARS, 2005
-New South WalesPresentNativeUSDA-ARS, 2005
-QueenslandPresentNativeUSDA-ARS, 2005
-VictoriaPresentNativeUSDA-ARS, 2005
New CaledoniaPresentNativeUSDA-ARS, 2005
New ZealandRestricted distributionIntroduced Invasive Owen, 1997; EPPO, 2014
Papua New GuineaRestricted distributionNativeCroft, 1985; Croft, 1986

History of Introduction and Spread

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

Risk of Introduction

Top of page 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.


Top of page A. pinnata is a floating aquatic fern, found on the surface of small, still ponds or backwaters without wave action, at low to middle altitudes. It becomes especially abundant in water with high nutrient levels, such as ponds in cattle paddocks and farm ponds, where it can completely cover the water surface. It has the ability to survive on moist soil in and around rivers, ditches and ponds which may allow the plant to survive low water levels and periods of drought. In New Guinea the altitudinal distribution falls into two disjunct ranges: lowland populations at 3-60 m altitude; and highland populations at 1000-3000 m altitude. However, there is no obvious difference between plants from the highlands and those from the lowlands (Croft, 1986).

Habitat List

Top of page
Terrestrial ‑ Natural / Semi-naturalRiverbanks Present, no further details
Wetlands Present, no further details
Freshwater Present, no further details Harmful (pest or invasive)

Hosts/Species Affected

Top of page A. pinnata is often applied to rice paddies as a nitrogen fertilizer and weed suppressant.

Biology and Ecology

Top of page Genetics

Known chromosome counts for the genus Azolla are centred around n=22, with many variations. This probably indicates that a tetraploid n=22 was the original count, deriving from n=11. A. pinnata has been reported as n=22 (tropical Africa), n=33 (Asia) and n=44 (Australia) (Knouse, 1997).

Physiology and Phenology

Growth occurs all year round in tropical and sub-tropical areas. Reproduction by spores is often triggered by crowding, as is a change to red coloration, although there is no definitive link between sporulation and colour change. Fronds divide vegetatively, with doubling possible every 3 days, leading to very rapid growth rates and colonization of new lakes and ponds. Development of the red coloration of A. pinnata is also promoted by phosphorus starvation (Nirmala Gunapala and Amarasiri, 1983).

The upper surfaces of the leaves are totally water repellent and, if completely submerged, the plants quickly refloat with the right side up (Croft, 1986). Deoxyanthocyanins are present in A. pinnata and act as a feeding deterrent to molluscs (Cohen et al., 2002a).

Reproductive Biology

Vegetative reproduction is by fragmentation of the fronds. Sexual reproduction leads to the formation of spores that are released into the water. Azolla is heterosporous, a clear adaptation to an aquatic environment. Sporangia are borne in sporocarps, usually paired micro- and megasporocarps, borne in the axils of the submerged lobes, basally on the branches, quite enclosed by a thin indusium. The microsporocarp is large, globose, containing several to many globose microsporangia, each containing 32-64 microspores. The megasporocarp is smaller, containing a single megasporangium with a single megaspore. Spores are globose, trilete, smooth to variously pitted or sculptured. Microspores are imbedded in the outer edge of several mucilaginous masses (massulae) in the microsporangium, the massulae bearing several to many, hooked (glochidiate) or non-hooked, septate or non-septate processes on one or all sides. Megaspores have three or nine apical massulae or 'floats'.

Environmental Requirements

Nitrogen levels are relatively unimportant for growth of Azolla, although growth rates are higher in eutrophic conditions. In southeast Asian countries, it is especially common in (wet) rice fields. It is used as a natural fertilizer, which takes advantage of the nitrogen-fixing abilities of the symbiotic blue-green algae (Moore 1969; Lumpkin and Plucknett, 1980).


A feature of the genus is the symbiotic association of the cyanobacterium Anabaena azollae. This alga lives endophytically in the inter-cellular spaces of basal leaves of Azolla. Atmospheric nitrogen is fixed by heterocysts in the algal cell, and transferred as ammonia to Azolla.

Air Temperature

Top of page
Parameter Lower limit Upper limit
Absolute minimum temperature (ºC) 4
Mean annual temperature (ºC) 14 23
Mean maximum temperature of hottest month (ºC) 14 35
Mean minimum temperature of coldest month (ºC) 12 29

Rainfall Regime

Top of page Bimodal

Natural enemies

Top of page
Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Elophila africalis Herbivore Leaves
Paulinia acuminata Herbivore Leaves
Stenopelmus rufinasus Herbivore Leaves

Notes on Natural Enemies

Top of page 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 a 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.

Means of Movement and Dispersal

Top of page Natural Dispersal (Non-Biotic)

Vegetative fragments and spores can spread easily downstream, and be carried with floodwaters to colonize new areas.

Agricultural Practices

It is sometimes introduced and used by farmers as a natural fertilizer for its ability to fix atmospheric nitrogen in rice paddies. It is thought to have been spread in New Guinea with cattle between drinking ponds (Croft, 1986).

Intentional Introduction

It has been introduced as an ornamental pond and aquarium plant.

Plant Trade

Top of page
Plant parts not known to carry the pest in trade/transport
Fruits (inc. pods)
Growing medium accompanying plants
Seedlings/Micropropagated plants
Stems (above ground)/Shoots/Trunks/Branches
True seeds (inc. grain)

Impact Summary

Top of page
Animal/plant collections None
Animal/plant products None
Biodiversity (generally) Negative
Crop production Positive
Environment (generally) Negative
Fisheries / aquaculture Negative
Forestry production Negative
Human health None
Livestock production Positive
Native fauna None
Native flora Negative
Rare/protected species Negative
Tourism Negative
Trade/international relations None
Transport/travel Negative


Top of page 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.

Environmental Impact

Top of page A. pinnata can spread rapidly, and has the ability to survive on moist soil in and around rivers, ditches and ponds. It forms dense surface mats, which degrade water quality by reducing oxygen levels.

Impact: Biodiversity

Top of page In New Zealand it has replaced a native floating fern, A. rubra, over most of northern New Zealand (Owen, 1997).

Risk and Impact Factors

Top of page Invasiveness
  • Invasive in its native range
  • Proved invasive outside its native range
  • Highly adaptable to different environments
  • Highly mobile locally
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
Impact outcomes
  • Damaged ecosystem services
  • Ecosystem change/ habitat alteration
  • Negatively impacts agriculture
  • Negatively impacts tourism
  • Reduced amenity values
  • Reduced native biodiversity
Impact mechanisms
  • Competition - monopolizing resources
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Highly likely to be transported internationally deliberately


Top of page Azolla is useful as a fertilizer in rice crops because it can assimilate atmospheric nitrogen owing to the nitrogen fixation by Anabaena azollae (cyanobacteria) living in cavities located on the lower side of upper (dorsal) lobes of leaf (Kundu and Chaterjee, 1985; Satapathy, 1995; Sevichan and Madhusoodanan, 1996).

Satapathy and Singh (1985) reported suppression of weed quantity by up to 50% in rice crops when A. pinnata was present, in agreement with the results of Kannaiyan et al. (1983) and Janiya and Moody (1984).

It is used as an ornamental pond and aquarium plant.

Broiler chicken diets have been supplemented with up to 5% A. pinnata resulting in improved live weight, production number, protein efficiency and feed conversion ratios (Basak et al., 2002). A. pinnata was assessed as a promising additive to abalone feed by Reyes and Fermin (2003). Dried, powdered A. pinnata has also been used to supplement carp diets (Basudha and Vishwanath, 1997).

A. pinnata has been investigated for use in the decontamination of land in India (Kaur, 2001). Bacterial flocs produced on decaying A. pinnata enhanced degradation of diesel in experimental microcosms by up to 100% (Cohen et al., 2002b).

There is some evidence to suggest that extracts of A. pinnata have inhibitory effects on root-knot nematodes (Thakar et al., 1988; Patel et al., 1994, Malek et al., 1996; Ramakrishnan et al. 1996; Hossain et al. 2002,), on Cucumber green mottle mosaic virus (Tewari et al., 2001) and on the mollusc Biomphalaria alexandrina (Abdel-Hafez, 1997; Zidan et al., 1998).

Uses List

Top of page

Animal feed, fodder, forage

  • Fodder/animal feed

Similarities to Other Species/Conditions

Top of page There are six other species of Azolla, all of which are morphologically similar: A. caroliniana (southeastern USA, scattered through tropical America); A. filiculoides (western hemisphere, tropical and subtropical);
A. mexicana (northern South America to western North America); A. microphylla (tropical and subtropical Americas); A. rubra (Australia and New Zealand); A. nilotica (tropical Africa).

Prevention and Control

Top of page Chemical Control

A. pinnata is susceptible to applications of diquat, glyphosate and terbutryn. A mixture of kerosene and a wetting agent is used for control of A. pinnata in Australia (Wall, 1994).


Top of page

Abdel-Hafez AM; Zidan ZH; Abdel-Megeed MI; El-Emam MA; Ragab FM; El-Deeb FA, 1997. Effect of the plant Azolla pinnata on survival, growth rate, fecundity and hatchability of egg-masses of Biomphalaria alexandrina snails. Journal of the Egyptian Society of Parasitology, 27(3):825-841.

Basak B; Pramanik AH; Rahman MS, 2002. Azolla (Azolla pinnata) as a feed ingredient in broiler ration. International Journal of Poultry Science 1:29-34.

Basudha C; Vishwanath W, 1997. Formulated feed based on aquatic weed Azolla and fish meal for rearing medium carp Osteobrama belangeri (Valenciennes). Journal of Aquaculture in the Tropics, 12(3):155-164; 21 ref.

Bravo MVA, 1991. Aquatic weeds in the Philippines: a general assessment of scenario. BIOTROP Special Publication, No. 40:47-49; [A symposium on aquatic weed management held in Bogor, Indonesia, 15-17 May 1990].

Calilung VJ; Lit IL Jr, 1986. Studies on the insect fauna and other invertebrates associated with Azolla spp. Philippine Agriculturist, 69(4):513-520

Chapman AL; Shaw W; Renaud S, 1981. Effect of temperature on the growth and acetylene reduction activity of Azolla pinnata from the Darwin region of northern Australia. Journal of the Australian Institute of Agricultural Science, 47(4):223-225.

Cohen MF; Meziane T; Tsuchiya M; Yamasaki H, 2002. Feeding deterrence of Azolla in relation to deoxyanthocyanin and fatty acid composition. Aquatic Botany, 74(2):181-187.

Cohen MF; Williams J; Yamasaki H, 2002. Biodegradation of diesel fuel by an Azolla-derived bacterial consortium. Journal of Environmental Science and Health. Part A, Toxic/Hazardous Substances & Environmental Engineering, 37(9):1593-1606.

Croft JR, 1985. Ferns and Fern Allies. In: Leach GJ, Osborne PL, eds. Freshwater Plants of Papua New Guinea. University of Papua New Guinea, 33-74.

Croft JR, 1986. The aquatic Pteridophytes of New Guinea. Australian National Herbarium, Centre for Plant Biodiversity Research.

Dath AP; Singh DP, 1998. Effect of rice Rhizoctonia solani Kuhn infection on the biomass of different Azolla species. Oryza, 35(2):186-187; 2 ref.

Devashish Kar; Barbhuiya MH, 2001. Ecology of aquatic macrophytes of Chatla Haor, a floodplain wetland in Cachar district of Assam. Environment and Ecology, 19(1):231-233.

Dostálek J; Kolbek J; Jarolímek I, 1989. A few taxa new to the flora of North Korea. Preslia, 61(4):323-327; 12 ref.

Dutta SPS; Kumar S; Kumari V, 1991. Ecology of macrophytic vegetation in Kunjwani Pond, Jammu. Journal of Nature Conservation, 3(2):133-139.

Dyer RA; Codd LE; Rycroft HB, 1963. Flora of Southern Africa-Volume 26. Myrsinaceae, Primulaceae, Plumbaginaceae, Sapotaceae, Ebenaceae, Oleaceae, Salvadoraceae, Loganiaceae, Gentianaceae, and Apocynaceae. 1963. pp. vii + 307. Many refs. Price Rands 4.60. Government Printer, Pretoria.

EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization.

Exell AW; Wild H, 1960. Flora Zambesiaca, Vol. 1. London, UK: Crown Agents for Oversea Governments and Administrations.

Fannah SJ, 1987. Elophila sp.? africalis Hampson (Lepidoptera: Pyralidae): a new pest of azolla in Sierra Leone. International Rice Research Newsletter, 12(3):30

Galal YGM; El-Ghandour IA, 2000. Biological nitrogen fixation, mycorrhizal infection and Azolla symbiosis in two rice cultivars in Egypt. Egyptian Journal of Microbiology, 35(4):445-461; 27 ref.

Gopal GV, 2000. Azolla pinnata Pteridophyte; Salviniales (Azollaceae) in the management of lake agro ecosystem. In: Ramachandra TV, Rajasekara Murthy C, Nhalya, N, eds. Proceedings of Lake 2000. International Symposium on Restoration of Lakes and Wetlands, 27th to 29th November 2000, Indian Institute of Science, Bangalore. India.

Hall JW, 1969. Studies on fossil Azolla. American Journal of Botany, 56:1173-1180.

Hill MP, 1998. Life history and laboratory host range of Stenopelmus rufinasus, a natural enemy for Azolla filiculoides in South Africa. BioControl, 43(2):215-224; 25 ref.

Hossain M; Ahmad MU; Ahmed N; Hossain MA; Alim MA, 2002. A study on control of root knot nematode (Meloidogyne javanica) of wheat. Indian Agriculturist, 46:121-128.

Janiya JD; Moody K, 1984. Use of azolla to suppress weeds in transplanted rice. Tropical Pest Management, 30(1):1-6

Johns RJ, 1991. Pteridophytes of Tropical East Africa. Kew, UK: Royal Botanic Gardens.

Julien MH; Griffiths MW, 1998. Biological Control of Weeds: a World Catalogue of Agents and their Target Weeds. Fourth Edition. Wallingford, UK: CAB International.

Kannaiyan S; Thangaraju M; Oblisami G, 1983. Effect of azolla inoculation on weed growth in wetland rice. International Rice Research Newsletter, 8(4):21

Kaur H, 2001. Biomass production of Azolla pinnata R. BR. in contaminated soils of Punjab (India). 5th International Biomass Conference of the Americas, Florida 2001.

Knouse JA, 1997. Genus Azolla: the mosquito ferns.

Konar RN; Kapoor RK, 1974. Anatomical studies on Azolla pinnata. Phytomorphology, 22:211-223.

Konar RN; Kapoor RK, 1975. Embryology of Azolla pinnata. Phytomorphology, 24:228-261.

Kundu AL; Chatterjee BN, 1985. Azolla as a substitute of nitrogen fertiliser for rice. Oryza, 22(2):119k-119m

Loyal DS, 1974. Chromosome size and structure in some heterosporous ferns with a bearing on evolutionary problems. In: Kachroo P, ed. Advancing Frontiers in Cytogenetics, 293-298.

Loyal DS; Gollen AK; Ratra R, 1982. Morphological and cytotaxonomic observations on Azolla pinnata. Fern Gazette, 12:230-232.

Lumpkin TA; Plucknett DL, 1980. Azolla: botany, physiology, and use as a green manure. Economic Botany, 34(2):111-153.

Madhusoodanan PV; Leena KR; Santhosh Nampy, 1993. Taxonomy and ecology of the aquatic pteridophytes of Kerala, south India. Journal of Economic and Taxonomic Botany, 17(3):635-643.

Malek MA; Ahmed MU; Ansari TH, 1996. Effect of soil amendment with azolla (Azolla pinnata) on control of root-knot of brinjal. Bangladesh Journal of Plant Pathology, 12(1/2):59-60; 18 ref.

Mansor M; Sam SK, 1992. The competition between three species of small-leaf floating plants which are frequently found in rice growing areas of northern Peninsula Malaysia. Proceedings of the 3rd international conference on plant protection in the tropics, Genting Highlands, Malaysia, 20-23 March 1990., Vol. 6:242-246.

Moore AW, 1969. Azolla: biology and agronomic significance. Botanical Review, 35:17-35.

Nirmala Gunapala; Amarasiri SL, 1983. Effect of addition of phosphorus on the growth of Azolla.. Tropical Agriculturist, 139:85-95.

Owen SJ, 1997. Ecological weeds on conservation land in New Zealand: a database. Wellington, New Zealand: Department of Conservation.

Patel HR; Patel DJ; Patel CC; Thakar NA, 1994. Effectivity of Clerodendron inerme L., Catharanthus roseus (L.) G. Don. and Azolla pinnata R. Br. for management of root-knot nematodes in okra. Pakistan Journal of Nematology, 12(1):95-98; 9 ref.

Ramakrishnan S; Gunasekaran CR; Vadivelu S, 1996. Effect of bio-fertilizers Azolla and Azospirillum on root-knot nematode, Meloidogyne incognita and plant growth of okra. Indian Journal of Nematology, 26(2):127-130; 9 ref.

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Reyes OS; Fermin AC, 2003. Terrestrial leaf meals or freshwater aquatic fern as potential feed ingredients for farmed abalone Haliotis asinina (Linnaeus 1758). Aquaculture Research, 34(8):593-599.

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