Joint use of insects and fungal pathogens in the management of waterhyacinth (Eichhornia crassipes): Perspectives for Ethiopia

Waterhyacinth [Eichhornia crassipes (Mart.) Solms] remains one of the worst aquatic weeds worldwide. Its presence in Ethiopia was officially reported in Koka Lake and Awash River about 60 yr ago. Experiences worldwide indicate that the use of bioagents is the most economical and sustainable control measure for waterhyacinth. In Ethiopia, the management of this invasive weed using bioagents is still in an experimental stage. However, the use of bioagents against waterhyacinth at the national level has currently received attention, and researchers have become engaged in surveys and programs to introduce and evaluate native, as well as classical, bioagents. The mottled waterhyacinth weevil (Neochetina eichhomiae Warner) and the chevroned waterhyacinth weevil (Neochetina bruchi Hustache) are the most successful bioagents released worldwide so far. A modeling tool, CLIMEX, has been applied to predict N. eichhomiae and N. bruchi potential distribution and adaptability in Ethiopia. Accordingly, the Ecoclimatic Index and Climate Matching results suggest that these weevils could be a potential bioagent for waterhyacinth in Ethiopia. On the other hand, 25 fungal isolates were collected during the recent survey in addition to the known prevalence of the fungus Cercospora rodmanii Conway. This indicates the opportunity for the joint use of fungal pathogens and the waterhyacinth weevils. In the article, the use of insects and pathogens, their host specificity and their herbivory/ virulence effect, as well as recent advances in the use of those bioagents to manage waterhyacinth are discussed.