- Widespread. Asia, Africa, North, South and Central America, Europe, Oceania. In Australia, Fiji, French Polynesia, New Caledonia, New Zealand, PNG, Vanuatu.
- Invasive weed of lakes, rivers, streams, rice paddies, thriving in slow-moving, nutrient-rich, warm freshwater, doubling in under 10 days, forming dense, floating mats, reducing water-flow, lowering light and oxygen levels. Impacts biodiversity (plants and fish), transport, clogs irrigation and power-generating systems, harbours mosquitoes.
- Free-floating, aquatic fern, with horizontal stems just below water. Leaves, from buds along stem. Different forms: at first, leaves, small, flat, green or yellowish-green, 2-6 cm long, with hairs aiding buoyancy; later, larger slightly folded and closer together along stems; eventually, very folded and compact. Sterile, hairy, spore sacs hang from feathery roots (modified frond), beneath water surface.
- Spread: by wind and water; floods; fur of animals; clothing; mud on vehicles, boats; garden waste; use as aquatic ornamental.
- Biosecurity: high risk of introduction via aquarium trade. In Australia, 'restricted invasive plant': do not release into environment, give away or sell. Among 100 of World's Worst Invasive Alien Species (IUCN, 2020). Available on internet.
- Biocontrol: success with weevil, Cyrtobagous salviniae, in Australia, PNG, parts of Africa.
- Cultural control: check nutrient levels (important); floating booms; manual removal or mechanical harvesting; vehicle hygiene.
- Chemical control: in Australia: glyphosate; carfentrazone-ethyl; orange oil. In Fiji, MCPA.
Pacific Pests, Pathogens, Weeds & Pesticides
Salvinia. CABI prefers the name kariba weed.
Salvinia molesta. It was previously confused with Salvinia auriculata. It is one of four closely related species; the other species being Salvia herzogii and Salvina biloba. As identification is complicated, because of the similarity of the species, it should be done by specialists. It is a member of the Salviniaceae.
AUTHORS Grahame Jackson & Aradhana Deesh
Adapted from Salvinia (Salvina molesta) (2018) Weeds of SE Qld and Northern NSW. Lucidcentral. (https://www.lucidcentral.org/editors-pick-animal-and-plant-identification-keys/key-to-weeds-of-se-qld-and-northern-nsw); and additional information from CABI (2019) Salvinia molesta (kariba weed). Invasive Species Compendium. (https://www.cabi.org/isc/datasheet/48447); and Waterhouse DF, Norris KR (1987) Salvinia molesta mitchell. Biological Control Pacific Prospects. Inkata Press, Melbourne; and Weeds of national significance (2006) Management and control options for salvinia (Salvinia molesta) in Australia. NSW Department of Primary Industries. Published by The State of New South Wales.(https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0008/425807/Salvinia-biological-control-field-guide.pdf); and from Ensbey R (2010) Salvinia. Primefact. Department of Primary Industries, NSW Government. (http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0006/81789/Salvinia.pdf). Photo 1 Scott Robinson, Georgia Department of Natural Resources, Bugwood.org. Photo 2 Leslie J. Mehrhoff, University of Connecticut, Bugwood.org. Photo 3 Troy Evans, Great Smoky Mountains National Park, Bugwood.org. Photo 4 Barry Rice, sarracenia.com, Bugwood.org. Photo 5 Scott Bauer, USDA Agricultural Research Service, Bugwood.org.
Produced with support from the Australian Centre for International Agricultural Research under project HORT/2016/185: Responding to emerging pest and disease threats to horticulture in the Pacific islands, implemented by the University of Queensland, in association with the Pacific Community and Koronivia Research Station, Ministry of Agriculture, Fiji.