Integrated control of water hyacinth in Africa1

Abstract

Water hyacinth, Eichhornia crassipes was first recorded in Africa (Egypt and South Africa) in the late 1800s. Since this time it has invaded streams, rivers, natural lakes and impoundments throughout the continent. Large mats of water hyacinth severely degrade aquatic ecosystems and limit all aspects of water resource utilization, threatening food security and economic development in a number of countries. The severity of these infestations is invariably exacerbated by eutrophication. Control options include manual removal, mechanical control, application of herbicides and biological control. Biological control offers a long‐term solution and excellent results have been achieved in a number of tropical large freshwater bodies, most notably Lake Victoria. However, in the more temperate regions of the continent and where extensive eutrophication exists, biological control is integrated with other control options. The successful control of water hyacinth relies on establishing an acceptable threshold population level for the weed, adopting a management philosophy that includes a top‐down approach within the infested catchment, intelligent use of herbicide, mechanical and biological control and a commitment to the reduction in nitrate and phosphate inputs into the aquatic ecosystem.