Salvinia facts
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in the right conditions it can double the surface
area it covers in two days
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it is one of, if not the worst, water weed in
the world
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floats on the water and obtains its nutrients
direct from floating roots in the water
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reproduces asexually, which means the smallest
piece of Salvinia can grow to cover the entire lake in a matter
of months
Why is it there?
Salvinia was originally introduced as a decorative plant for ornamental
ponds and fish tanks. It is now common in the greater Sydney region
with infestations at Duck River, Vineyard Creek, the Hawkesbury
Nepean, Liverpool and Lake Parramatta. Small fragments can be reintroduced
by machinery, local fish ponds or small pieces hidden by other water
plants.
The high level of nutrients coming into the lake from the surrounding
catchment and the large area of still water in the lake provide
a perfect breeding ground for Salvinia. The nutrients stored in
the sediments of the Lake are occasionally released due to chemical
changes related to the temperature in the water. This provides a
massive boost of nutrients which feeds the growth of the Salvinia
and has been a major cause of past outbreaks
How is it being controlled?
A biological control, the Salvinia weevil, was released in the
lake in 1994. This method of control has been successful in controlling
a number of infestations in Australia, however its success has been
variable. The weevil may still provide a long term effective method
for the control of Salvinia in Lake Parramatta, but has not been
effective to date.
In the short term, Parramatta City Council has employed a contractor
to periodically spray the Salvinia with a herbicide licenced for
use on water.
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Harverting Salvinia on Lake Parramatta
In 1994 Salvinia covered the entire 10 hectares of Lake Parramatta
and in places was 30 cms deep
Lake Parramatta free of Salvinia
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