Salvinia molesta

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Common Name(s): Giant salvinia

Non-Native to Florida

This species appears on the following legally prohibited plant lists

Federal Noxious Weed List	Florida Noxious Weed List	Florida Prohibited Aquatic Plants List
Yes	No	Yes

UF-IFAS Assessment of Non-Native Plants in Florida’s Natural Areas

FWC WEED ALERT (PDF)

Salvinia molesta was added to the IUCN List of 100 of the World’s Worse Invasive Alien Species in 2013.

More Info: Plant Management in Florida Waters

Download a recognition card (PDF) from Invasive and Non-native Plants You Should Know1

See Table 1 in Florida’s Established Arthropod Weed Biological Control Agents and Their Targets (2013) for a list of arthropod biological control agents that occur on this species.

For brief control information, see Efficacy of Herbicide Active Ingredients Against Aquatic Weeds (EDIS Pub #SS-AGR-44)

More Resources

Salvinia molesta is native to southeastern Brazil and northern Argentina. It grows year round and has been found in north, central and southwest Florida where it is quickly eradicated when found. Giant salvinia grows rapidly and produces a dense floating canopy on the surface of ponds, lakes, and rivers.

Salvinia molesta is a floating aquatic fern that thrives in slow-moving, nutrient-rich, warm, freshwater. It spreads aggressively by vegetative fragments. It is dispersed long distances within a waterbody (via water currents) and between waterbodies (via animals and contaminated equipment, boats or vehicles). It may be cultivated by aquarium and pond owners and is sometimes released by flooding or intentional dumping.

S. molesta can form dense vegetation mats that reduce water-flow and lower the light and oxygen levels in the water. This stagnant dark environment negatively affects the biodiversity and abundance of freshwater species, including fish and submersed aquatic plants. Salvinia molesta invasions can alter wetland ecosystems and cause wetland habitat loss. Salvinia molesta prefers tropical, sub-tropical or warm temperate areas of the world and grows best in still or slow-moving water bodies including ditches, ponds, lakes, slow rivers and canals. In standing water it forms stable floating mats. Salvinia invasions also pose a severe threat to socio-economic activities dependent on open, flowing and/or high quality waterbodies, including hydro-electricity generation, fishing and boat transport.

Appearance

Free floating fern; stems rootless(although dangling 3rd leaf resembles roots), hairy, about 10 cm long. Exhibits great variation in form and structure depending on habitat conditions such as space and nutrient availability.

Leaves

Borne in threes; appear 2-ranked, but with 3rd leaf finely dissected and dangling, resembling roots; rounded to somewhat broadly elliptical, to 2 cm long, with cordate base,
upper surface with 4-pronged hairs joined at the tips (resembling an egg beater), lower surface hairy.

Spores

In a nutlike sporocarp (a multicellular structure), trailing beneath.

Ecological threat

Spreads rapidly and prolifically into a monoculture which can shade out underwater natives, leaving large bare bottom areas.

Text from Invasive and Non-native Plants You Should Know – Recognition Cards 2

Biological Control

A two millimeter black subaquatic beetle, Cyrtobagous salvinae, has proven to be the best biological control agent for use against giant salvinia. First collected in 1980 by Australian researchers (from the native range in southern Brazil), the beetle adults and larvae feed on the leaf buds and young terminal leaves of the plant, causing leaf darkening, senescence and abscission. The beetle larvae tunnel into the rhizome. C. salvinae has been successful in at least 16 countries.3