Threat of water hyacinth resurgence after a successful biological control program

The aquatic weed, water hyacinth, Eichhornia crassipes, has caused serious socio-economic, industrial and domestic problems in Uganda and indeed the entire East Africa region. Control measures included the use of herbicides (in trials only), mechanical removal and biological control. Five years after the introduction of the weevils, Neochetina bruchi and Neochetina eichhorniae, the weed biomass was reduced to an insignificant level. There have been recent reports of a resurgence in the growth of the weed on Lakes Victoria, Albert and Kyoga. The significance of the successful control and apparent resurgence is discussed.