Water hyacinth (Pontederia crassipes Mart.) is a notorious weed that affects the biodiversity and socio-economic services of freshwater bodies across the world, including Ethiopia. Different management techniques have been applied as long-term and short-term strategies to curb the impact of this weed on aquatic ecosystems. Using water hyacinth weevils as a classical biological control agent is a principal method in the management of water hyacinth. Thus, the main purpose of this research work was to assess the Neochetina bruchi and N. eichhorniae host ranges and their potential for feeding and oviposition on water hyacinth under different nutrient levels. The host-range test results showed that neither of the two weevils could complete their life cycles on the non-target plants. Feeding scars and oviposition potential of both weevils were directly proportional to the nutrient concentration levels that the water hyacinth plants received. Generally, the weevils are safe for non-target plants and could be released for the management of the water hyacinth. The fecundity of the weevils can be maximized by increasing the nutrient concentration provided to the water hyacinth in mass-rearing conditions. As a result, the feeding damage to the water hyacinth could be increased with the supply of additional weevils.

Keywords: Biological control, Feeding scar, Host plant, Oviposition, Weed