Biological control of water hyacinth – the South African experience1

Abstract

Water hyacinth remains one of the worst aquatic weeds worldwide, and its presence in South Africa since the early twentieth century prompted research into biological control options. The first control agent released in South Africa was the weevil Neochetina eichhorniae in 1974, but the project was terminated three years later, and resumed in 1985. Since then, five arthropod biocontrol agents have been released in South Africa, more than anywhere else in the world, including another weevil, N. bruchi, a moth, Niphograpta albiguttalis, a mite, Orthogalumna terebrantis and a mirid, Eccritotarsus catarinensis. To date, the success of biological control of water hyacinth in South Africa has been variable, and this has been ascribed to, amongst other factors, climatic incompatibility of control agents, and eutrophication of water hyacinth impoundments. Successful control is achieved in warm subtropical sites which are not affected by frost in winter, and in water bodies that are not heavily polluted with nitrates and phosphates. The biocontrol programme is the result of collaborative research with scientists from the USA, Australia and Argentina, and the experience obtained and lessons learned in these regions and South Africa can be used to initiate a biocontrol programme in Europe.