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Salvinia (Salvinia molesta) is an introduced fern from South America that is a declared noxious plant for the whole of Australia. It is a State-declared Category 3 pest plant species, and has a Weeds of National Significance (WONS) status which means the species is already spread over substantial areas of Queensland, but its impact is so serious that it requires active control to avoid further spread onto properties that are still free of the pest (Department of Employment, Economic Development and Innovation, 2011).

It can rapidly double in size within one week under optimal growth conditions and forms mats that completely cover lake systems, affecting water quality, flow, wildlife and recreational activities (i.e. fishing). It is a free-floating aquatic fern with small, spongy, green leaves positioned in pairs along a common stem. The species can be confused with the native Azolla species.

Department of Employment, Economic Development and Innovation 2001, Declared plants of Queensland, The State of Queensland.

Sainty G.R. and. Jacobs S.W.L., 2003. Waterplants in Australia. Sainty and Associates Pty Ltd, Australia.

Department of Primary Industries and Fisheries 2007, Fact sheet invasive plants and animals Salvinia, Biosecurity Queensland, State of Queensland.

City of Gold Coast integrated management program for this pest plant involves mechanical removal, application of registered herbicides and the introduction of biological control agents.


The Salvinia weevil (Cyrtobagous salviniae) was discovered by the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in 1979. The weevil originates from the same native range in Brazil as Salvinia. Extensive host specificity testing was completed to ensure the weevil was not going to affect non-target species. The adult weevils feed on the Salvinia plant. However, most damage is done by the larvae tunnelling into the plant’s stem (rhizome). This causes the plant to turn brown, lose buoyancy and sink.

As part of an integrated approach, the City monitors weevil infestation levels and will implement mechanical removal if Salvinia is growing too fast. Removal of damaged Salvinia is implemented before it decomposes and negatively affects water quality.


For further information regarding management of this species, click on the link below or alternatively, contact us on 1300 GOLD COAST or 07 5582 8211.

Find answers to frequently asked questions about Salvinia below.

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