THE GENUS SALVINIA: ITS BIOLOGY, CONTROL AND ECONOMIC UTILIZATION (KARIBA WEED, FERN)

Salvinia is a genus of free-floating aquatic heterosporous ferns often grown as ornamental plants in tropical fish tanks and ponds. Members of the genus are indigenous to the subtropics and tropics. Within recent years some of the formerly innocuous species have become notorious weeds because of their rapid spread over areas of fresh water in regions where they have been introduced. The explosive growth of Salvinia, especially Salvinia molesta poses a potential threat to the management of irrigation projects, man-made lakes and canals in tropical and other areas. Huge economic losses have resulted from the presence of these weeds in areas outside their native environment. This paper examines the problem and offers some solutions. The species causing weed problems are identified, a key presented and their biology studied. The environmental requirements of Salvinia are analyzed to determine what has made it into such a noxious weed. The position of Salvinia in its ecosystem is evaluated. The environmental management of Salvinia is examined along with various chemical, mechanical and biological control methods now available. The most promising methods are described. Utilization of the plant as a method for recovering some of the costs of control and producing benefits as well is examined. Methods for the manufacture of paper from Salvinia, and the production of methane are presented. Salvinia as a source of animal food, fertilizer and leaf protein is discussed. Aquaculture, solid waste management, and water purification systems using the plant are shown