CORRUPT IMAGE Biological control of water hyacinth: close up of a plant with leaves damaged by weevils. The weevils are essential for biological control of water hyacinth. They are released into the infested bodies of water, where they eat the leaves and also lay eggs in the stems of the plants. The water hyacinth is an extremely invasive weed and controlling it with biological methods takes between five and six years. - - General: General. CORRUPT IMAGE The water hyacinth is native to South America. Experts suspect it was brought to Africa in the 1980s by botanists and gardeners as an ornamental plant. However, it is now classed as a water-weed.

Water-weeds cause a lot of damage to the environment. They make waterways unnavigable, reduce the generating capacity of hydro-electric stations and block irrigation canals. By clogging sewage and drainage systems, they can cause flooding, contaminate drinking water and create breeding grounds for harmful insects and bacteria.

Water-weeds also contribute to water shortages. They absorb water and then release it through transpiration. As a result, water losses can be more than three times higher in weed-infested water bodies.

in 1995, FAO became one of the major technical executing agencies in a five-year project to control water hyacinth on lake Victoria using biological methods. This project has succeeded in reducing the weed in the lake by more than 60 percent.