Salvinia

• The plant is a free-floating aquatic fern.
• Small green leaves are positioned in pairs along a common stem.
• Leaf surfaces are covered with long, stiff water-repellent hairs that are joined at the tip to form eggbeater-like shapes.
• As the plant matures, leaves become thick and fold at the midrib.
• Young leaves are oval, are about 12mm across and lie flat on water. They often resemble duckweed.
• Roots trail from each pair of young leaves.

3D model

• View the 3D model to help you identify this plant. You can magnify the image and manipulate the view to inspect the plant from every angle.

• Prefers slow-moving streams or still-water ponds with high nutrient levels and water temperatures of 20–30˚C.

• Visit the Weeds Australia website and click on the distribution tab to view the distribution map.

• Believed to be a sterile hybrid.
• Does not produce flowers; reproduces by vegetative means.
• Produces little growth in winter.
• Under optimal conditions, can double in volume every 2–3 days.

Environmental

• Forms thick mats that can quickly cover water storage areas.
• Degrades water quality.
• Destroys wildlife habitats.

Economic

• Builds up and collects debris during flooding, causing bridges and fences to collapse.
• Reduces water flow to irrigation equipment, increasing pumping times and costs.
• Prevents access by stock to drinking water.

Social

• Endangers children and livestock, who can become entangled in heavy infestations.
• Creates mosquito-breeding habitat.
• Interferes with recreational activities such as boating, fishing and swimming.
• Spoils natural beauty of open water bodies such as dams and lakes.

• Mainly spread by people emptying aquariums and ponds into waterways.
• Also spread by water currents and fouling of fishing equipment and boat trailers.

• Find out how farmers can prevent weed spread.
• Find out how gardeners and outdoor enthusiasts can prevent weed spread.

Mechanical control

• Removal by hand or machine is a practical control method often used for small areas or when weed numbers are low.
• Mechanical control can be used after flooding or water flushing deposits salvinia in dams, lagoons and calm waters of rivers and creeks. When using this method, remove salvinia before rapid growth commences.
• Salvinia can survive for long periods out of water when it is deposited on moist banks. To help prevent its reintroduction into a watercourse, move it away from the water's edge and, preferably, burn it.

Herbicide control

• Herbicides are effective.

See the salvinia fact sheet for herbicide control and application rates.

Biological control

• The salvinia weevil Cyrtobagous salviniae has been extensively released. In Queensland, it can give good biological control.
• The weevils are 2–3mm long and dark brown to black. They are most effective when air temperatures are 27–35˚C and salvinia nitrogen levels are high.
• The weevil larvae feed on new growth buds and tunnel into the rhizome. Tunnelling weakens the salvinia, reducing its ability to grow and compensate for bud loss. Adult weevils also affect plant growth by feeding on buds.
• In the initial stages of weevil damage, some salvinia leaves will turn brown. As the weevils continue their control efforts, the whole mat will turn brown, sink and decompose.
• Although the weevils are effective in tropical areas, they have not established as intensely in cooler southern areas of Queensland and may take longer to control infestations there.
• Depending on infestation size and environmental conditions, the time taken for weevils to control salvinia varies from 13 years. They may take more than 5 years to establish in cooler areas.
• To ensure maximum build-up, release weevil-infested salvinia in spring. Choose warm, sunny positions where a drop in water level will not leave the salvinia stranded.
• To establish an effective breeding population of weevils, place infested plants in an area where salvinia is concentrated.

• Salvinia is a category 3 restricted invasive plant under the Biosecurity Act 2014. You must not:
  • give it away
  • sell it
  • release it into the environment.

If you do any of these, penalties may apply.

• You must take all reasonable and practical measures that are under your control to minimise the biosecurity risks associated with dealing with salvinia. This is part of your general biosecurity obligation.
• All other Salvinia species are prohibited invasive plants. You must report any sightings of these species immediately using 1 of these methods:
  • Report online.
  • Phone Biosecurity Queensland on 13 25 23.
  • Phone the Exotic Plant Pest Hotline on 1800 084 881.
• Each local government must have a biosecurity plan that covers invasive plants in its area. This plan may include actions to be taken on salvinia. Some of these actions may be required under local laws. Contact your local government for more information.