Of the several species of salvinia that occur naturally in America, Europe and Asia, only one – Salvinia molesta, a native of Brazil – has become established in Australia. Salvinia is mainly spread by people who empty aquariums and ponds into waterways.
Impacts:
Forms thick mats that can completely cover water storage areas in a short time, endangers children and livestock who can become entangled in heavy infestations, creates a haven for mosquitoes, prevents access by stock to drinking water, reduces water flow to irrigation equipment, increasing pumping times and costs, builds up and collects debris during flooding, causing bridges and fences to collapse, causes a fourfold increase in water loss through evaporation, degrades water quality, destroys wildlife habitats, interferes with recreational activities such as boating, fishing and swimming, spoils the natural beauty of open water, such as dams and lakes
Description:
A free-floating aquatic fern, small spongy green leaves are positioned in pairs along a common stem, leaf surfaces are covered with long, stiff, water-repellent hairs, as the plant matures, leaves become thick and fold at the mid-rib, young leaves are oval, about 12 mm across and lie flat on the water, often resembling duckweed, roots trail from each pair of young leaves, as the plant matures, the long roots resemble wet hair
Control:
Treat infestations when small, remove small areas by hand or machine, release biological control agent, Salvinia weevil, apply herbicides strictly in accordance with label directions
Source http://www.dpi.qld.gov.au