The first infestation was seen in the Zaire river in 1952 and by 1955 it covered 1,500 kilometres. Using herbicides, several thousand kilometres of the river were cleared by 1957. But after all this effort, it was estimated that 150 tonnes per hour were still passing Kinshasa down near the sea.
The first infestation in the Nile was noted in 1958. The government of Sudan created a Water Hyacinth Section of the Plant Protection Department which took charge of control measures. Previously, the weed was contained above the Jebel Aulia dam near Khartoum. But seedlings have now been found far downstream. It can be commonly seen floating in the Nile in Cairo. As it was found that to eradicate the weed in Sudan is impossible, current activities concentrate on its conversion into animal feed, fertilizer, and for energy production.
Chemical and mechanical means for controlling water hyacinth have proved either ineffective, too expensive, or environmentally hazardous. In the USA, Australia, Sudan and some other countries, substantial reduction in water hyacinth production has resulted from introducing biological control using the weevil [Neochetina eichorniae]. A programme for the mass culture and release of these insects in the Sudan was commenced in 1979, and they are now successfully established and dispersing in the White Nile. More biocontrol agents are being tested.
Infestation of Lake Victoria, the second largest freshwater lake in the world, has been triggered by tree clearance in the water catchments. This has caused excessive soil erosion and accumulation of nutrients in the waters of the lake. Additional nutrients are contributed by agricultural activities, such as sugar cane farms, upstream of the lake. Release of [Neochetina eichorniae] into Lake Victoria was reported to have reduced the population of the weed by 60% in two years.
The main threats to water quality in Africa include eutrophication, pollution and the proliferation of invasive aquatic plants such as the water hyacinth (Eichhornia crassipes) and Salvinia molesta weeds. The water hyacinth has seriously affected most water bodies in the region, including Lake Victoria, the Nile River and Lake Chivero. As no effective means of controlling this weed has yet been found, the water hyacinth will continue to disrupt water transport, water supplies to urban areas, the fishing industry, power generation and the livelihoods of many local communities.