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Common Name Salvinia Botanical Name Salvinia molesta D.S. Mitchell Status Salvinia is one of only fourteen weeds proclaimed as State Prohibited Weeds in Victoria. This is the highest category to which a noxious weed can be allocated and means that salvinia is to be eradicated if possible from the State. Origin Salvinia is native to south-eastern Brazil. It has been distributed worldwide and probably throughout Australia by use in aquariums. Description A perennial aquatic fern with most leaves floating on the water surface, forming mat-like growths. The plant has different forms depending on its density. The leaf stems, which are rhizomes, and modified leaves which act like roots, are submerged, but they both float and do not “take root” in any substrate. Stems - up to 30 cm long, 1 to 2 mm thick, multiply branched. Stem length decreases with increasing plant density. In dense infestations the stem length between leaves is very short. Leaves - are of two kinds, emergent (floating) and submerged. Emergent leaves have two leaflets growing on opposite sides of the leaf stem. There is significant variation in size and shape of floating leaves depending on the growth stage of the plant. Leaves of isolated plants are oval to heart-shaped, flat and as small as 10 mm by 5 mm. In dense infestations the leaves are crowded together, oblong in shape, deeply keeled, and up to 3 cm by 6 cm wide when opened flat. The floating leaves are green, non-wettable on the upper surface and have complex waxy hairs about 1 mm long. The submerged modified leaves which act like roots are short brown hairy stalks ending in hairy filaments up to 50 cm long which look like wet hair. Roots - absent. Being a fern salvinia does not produce flowers. Ferns generally reproduce by spores but salvinia is a sterile hybrid. It produces spore capsules on submerged stems but any spores produced are incapable of germination. Life Cycle Reproduction of salvinia is vegetative and results from buds shooting at stem nodes and the continual creation of daughter plants. Daughter plants are the invasive form of salvinia. In order to grow they require nutrients and an area of clear water surface amid, or on the edge of the infestation.  Figure 1. Invasive growth form of salvinia  Figure 2. Dense infestation of salvinia. Dispersal As salvinia only reproduces vegetatively by division, dispersal is by invasive growth or physical transfer of parts of the plant. Daughter plants break away from the parent and may be moved with water currents and the wind. Careless disposal of aquarium contents could result in salvinia being deposited in freshwater and must be avoided. Salvinia has also been used as an ornamental in garden ponds. General When conditions are suitable salvinia can spread very rapidly and completely cover water surfaces. Its growth can block waterways including irrigation and drainage systems and smother dam and reservoir surfaces. Masses of salvinia carried by flood waters can destroy fences and other structures. Dense infestations significantly decrease water quality and reduce penetration of sunlight. Masses of decaying salvinia de-oxygenate the waters on which they are growing, resulting in the death of fish and other aquatic fauna. Infestations also increase the rate of water loss, because the plants use water faster than it normally evaporates. Access to water by stock and wildlife can be restricted. Infestations have occurred in rice fields overseas. Distribution in Victoria seems to be limited to aquariums and garden ponds. In other states salvinia has become a major problem in water storages and rivers. Control Salvinia plants found in aquariums should be dried and burned or buried so they cannot enter the storm water system. Tanks which contain the weed should be emptied onto lawns and gardens, not into sinks, drains or waterways. Mechanical removal of large infestations is extremely difficult. Early detection of this weed is therefore very important. Chemical Control Under Victorian legislation there are controls on various aspects of the uses of agricultural chemicals. Some particular uses are prohibited and some require permits. Users of certain agricultural chemicals are required to obtain an Agricultural Chemical User Permit (ACUP) or work under the direct supervision of an ACUP holder. Additional restrictions on the use of some herbicides apply to particular geographic areas known as Chemical Control Areas (CCA). It is the responsibility of chemical users to familiarise themselves with these controls. See Agriculture Note: Agricultural chemical user permits (ACUP) and chemical control areas(CCA) for further information. Contact the Regional Chemical Standards Officer of the Department of Natural Resources and Environment if further advice is required. You should read the product label and follow all label instructions carefully before using any herbicide. Use a product containing the following active constituent that is registered for use in Victoria to control salvinia in the particular situation in which you need to use chemical control. Consult the product label for detailed information.
This list of chemicals is based on information supplied to the Department of Natural Resources and Environment by the National Registration Authority for Agricultural and Veterinary Chemicals (NRA). The State of Victoria through the Department of Natural Resources and Environment has not assessed or checked the accuracy of the information supplied to it from the NRA as that responsibility rests with the NRA. Important Any person who believes they have located an infestation of salvinia, regardless of the area, please notify a Catchment Management Officer at a local office of the Department of Natural Resources and Environment. References
Acknowledgements Prepared by R Williamson, KTRI, 1996. Updated by I. Faithfull, KTRI, January 1998. Active constituents information supplied by Chemical Standards Branch January 1998. This note replaces note number PPA0009 The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. |
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© The State of Victoria, 1996 - 2008.
This document was published on 26/10/2008.