Family: Pontederiaceae
Common names: Water Hyacinth, Jacinto de Agua, Lirio Acuatico, Jacinthe D'Eau
It is a free-floating aquatic with rosettes of leaves supported by petioles, which may be short and inflated or long and slender up to 50 or even 100 cm long. It spreads rapidly by stolons, which develop from the base of the rosette. The stolons grow up to 30 cm long before developing a daughter rosette. Rate of spread by this means can result in a doubling of the area infested every 6 to 15 days. Flowering stems from the centre of the rosette produce a colourful inflorescence of blue/purple flowers, which develop into fruiting capsules, each with up to 400-minute seeds.
It is an aquatic-floating weed. It does not tolerate brackish water and salinity can limit or modify its distribution. For example, water hyacinth, which accumulates in the coastal lagoons of West Africa during the wet season, is reduced in those areas, which become saline during the dry season.
Growth by water hyacinth is favoured by nutrient rich water, in particular by nitrogen, phosphorus and potassium.
Water hyacinth reproduces vegetatively by means of stolons which, together with solitary plants or drifting mats, are readily distributed by water currents, wind, boats and rafts.
The plant also produces vast quantities of long-lived seed and persistence and spread by this means can be very significant.
Physical removal may be by hand pulling, dragline or specially designed harvesting machine.Permanent drainage to dry-out a pond or lake will control water hyacinth.
The biological control agents, which have been most successful, are 2 weevils Neochetina bruchi Hustache and N. eichhorniae Warner, and a moth Sameodes albiguttalis (Warren). However, optimal control has not been achieved in all situations and additional agents are being evaluated.
Herbicidal control of large infestations of water hyacinth growing under favourable conditions has been attempted only rarely and even when enormous resources have been invested, as in Sudan, has had little effect. However, this method has been successful for controlling small infestations accessible by land or boat and eradicating small infestations in regions, which are climatically unfavourable to growth of this plant. The herbicides most commonly used have been 2,4-D and glyphosate, the first of these being by far the most widely used, as it is relatively inexpensive.
Largely two factors; nutrient supply and the absence of natural enemies of the weeds determine the proliferation of water hyacinth in its exotic range. To be fully effective, control strategies must address both watershed management and direct weed control.
The effects, which the management of watersheds can have on the nutrient level of rivers, lakes and other wetlands, have already been referred to. Watersheds must be managed to control water hyacinth and other floating aquatic weeds, provide a sustainable, acceptable life-style for the human population living in the watershed, and conserve the ecology and biodiversity.
This is a plant affecting water bodies in general. The centre of origin of water hyacinth appears to be Amazon, Brazil with natural spread to other areas of the South American continent. It is also a serious weed in various water bodies of Mexico, Guatemala, Cuba, Bolivia and Ecuador. Extensive infestations developed in the southern U.S.A. (especially Louisiana and Florida). At present the plant is already spread in several countries of Africa (especially the Nile and Congo River systems), South and SouthEast Africa.
Countries: Benin, China, Côte d'Ivoire, Egypt, Ecuador, Ghana, Guyana, Mexico, Nepal, Niger, Nigeria, Panama, Syria, Thailand, Cuba, Dominican Republic, Ethiopia, Fiji, Gambia, Indonesia, Malaysia, Mali, Nicaragua, Senegal, Uganda, Venezuela,
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