- Azolla (mosquito fern, duckweed fern,
fairy moss, water fern) is a genus of seven species of aquatic ferns,
the only genus in the family Azollaceae. They are extremely reduced in
form and specialized, looking nothing like conventional ferns but more
resembling duckweed or some mosses. They float on the surface of water
by means of numerous, small, closely-overlapping scale-like leaves, with
their roots hanging in the water.
- Azolla are also serious weeds in many
parts of the world, covering bodies of water so thickly that no water is
exposed. This is where they derive the name 'mosquito fern', from the
belief that no mosquito can penetrate the coating of fern to lay its
eggs in the water. Azolla is reputed to be able to grow so quickly that
it can double its mass in three days under good conditions.
- Most of the species can produce large
amounts of anthocyanins in bright sunlight, creating an intense red
color and causing the water surface to appear to be covered with a red
carpet.Mosquito ferns are safe to grow in cool temperate areas with
prolonged freezing in winter, as they cannot overwinter in these
conditions. They are often grown as an ornamental plant by water-garden
- Azolla can reproduce asexualy by
breaking off. Each branch that breaks off forms a new plant. Azolla can
also reproduce sexually. Like all ferns, Azolla produce spores. Unlike
most ferns, Azolla produces two kinds of spores. The male sporocarp is
greenish or reddish and looks like the egg mass of an insect or spider.
It is two millimeters in diameter, and inside are numerous male
- Azolla has reportedly been used as a
feed for pigs and ducks in SE Asia; for cattle, fish and poultry in
Vietnam; and for pigs in Singapore and Taiwan. It is described as an
excellent substitute for green forage for cattle in Vietnam and may
replace up to 50% of the rice bran used as feed for pigs in that
country. Although very low in DM, it contains a high level of protein
(24% CP). The amino acid composition of Azolla compared well with
reference protein sources.
- As a supplement for growing pigs,
performance was reduced compared to controls in the growing phase but
the animals compensated and grew faster in the period from 24-89 kg. It
has been used as a sole feed for lactating sows which have a higher
intake to deal with the low DM content.
Ducks (650-1800g LW)
consumed 350g Azolla when given free-choice with sugarcane juice and
soya. It is also used for grazing ducks and geese in paddy fields where
the Azolla is used as a fertilizer.
- Based on year 2000 data, the cost
savings (per user per hectare) resulting from the biological control
program included a reduction of on-site damages caused by the weed to
the value of US$589 per hectare per year.
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