Common Water Hyacinth, Eichhornia Crassipes: An Invasive Plant Species That Has Wrecked Havoc In Lake Victoria

Abstract

Among the 7 species of water hyacinth that belong to the genus Eichhornia, the common hyacinth, E. crassipes, is the most invasive. The common hyacinth has one of the greatest multiplying rates of any known plant and its population can double in as few as 6 days, making it one of the world‟s worst invasive weeds. Although the water hyacinth is native to South America, it has naturalized a lot in the southern part of the USA. The weed is also found in other tropical and subtropical regions of the world except Europe and Antarctica. E. crassipes is believed to have been introduced to Africa over a century ago from the Amazon basin as a pot plant due to its aesthetic beauty. The weed was then introduced later to Congo in the region. The food value of the weed to wildlife has however not been documented. The weed could have entered Lake Victoria from Rwanda via River Kagera. The rapid proliferation of the water hyacinth that has been exacerbated by emission of untreated industrial and domestic effluents into Lake Victoria has resulted in formation of thick mats of the weed especially in sheltered bays and river mouths of the lake. Areas covered by the water hyacinth have suffered ecological and economical impacts. The thick mats have interfered with light penetration into water, smothered native plant species, reduced levels of oxygen that diffuses into water. Boat transport, fishing as well as other water activities have been affected while the presence of the weed has created an ideal environment for vectors of malaria and schistosomiasis as well as snakes. The habitats created by hyacinth mats have however effectively synergized with the decline of the Nile perch to hasten restoration of some fish species that were in the 1990s under threat of local extinction. Control of the common water hyacinth once it has spread extensively in a body of water is an expensive process. Control measures are meant to tame or reduce the level of invasion of the weed since it is not easy to eradicate the plant once it has invaded a body of water. Mechanical methods of control using machinery as well as biological ways using a weevil (Neochetina species) have been used to control the common water hyacinth in L. Victoria with varying degrees of success. Native plants of the lake including the hippo grass have also played a role in controlling the spread of the water hyacinth.