Water hyacinth has been given the dubious honour by the UN of the world’s most troublesome weed. Since its introduction as an ornamental it has attained a pan- African distribution. It prevents transport, fishing, commerce, the generation of hydroelectricity and increases incidences of malaria, bilharzia, filariasis and encephalitis. We are studying the potential of using a fungal pathogen as an environmentally friendly method of control. Field surveys and laboratory tests have identified those fungi that are indigenous to Africa, with distribution across the continent and specific to water hyacinth. Of these Alternaria eichhorniae exhibits the greatest virulence. However, control of weed populations by this pathogen varies greatest virulence. However, control of weed populations by this pathogen varies greatly across the different aquatic environments found in Africa. One factor that varies across environments is the nutrient status of the water. We report on studies to determine the influence of varied nutrient status of the water. We report on studies to determine the influence of varied nutrient status on the growth of water hyacinth and how this influence of varied nutrient status on the growth of water hyacinth and how this influences the efficacy of control by A. eichhorniae.In addition, we report on formulations used in mycoherbicides to overcome environmental factors that limit infection. Finally, because this fungal pathogen is foliar, its mode of action can be crudely seen as causing plant defoliation. We report on mechanical defoliation studies of plants to demonstrate whether the rapid regenerative potential of water hyacinth enables plants to overcome leaf losses.

Plant Diseases

Alternaria Eichhorniae; Hyacinthus