Neochetina weevils released from 1995 cut Lake Victoria's 20,000-hectare water hyacinth mat to about 500 hectares by 2000, freeing Uganda's Owen Falls dam intake and boosting fish catches — though nutrient-driven regrowth returned in 2006, showing biocontrol's limits.
~20,000 hectares
Water hyacinth coverage (peak) (1998)
~500 hectares
Water hyacinth coverage (2000)
Details
Promoter
Uganda National Agricultural Research Organisation (NARO); Lake Victoria Environmental Management Project (LVEMP)
Period
1995-2006
Keywords
invasive species control, biological control, hydropower, fisheries, water quality
Context
Water hyacinth was first recorded on Lake Victoria in 1989 and by 1998 covered an estimated 20,000 hectares, densest in Uganda's Napoleon Gulf in front of the Owen Falls hydropower dam at Jinja.
Activities
From 1995-1996, Uganda's National Agricultural Research Organisation released two weevil species as biological control agents alongside the World Bank-funded Lake Victoria Environmental Management Project and mechanical removal crews on the Kenyan and Tanzanian shores.
Results
Coverage fell from its 1998 peak of roughly 20,000 hectares to about 500 hectares by 2000, restoring hydropower generation at Owen Falls and reopening fishing grounds.
Conclusions
Heavy rains in late 2006 washed nutrient-rich runoff into the lake and triggered a fresh outbreak, showing weevil biocontrol reduces biomass but cannot substitute for catchment-level nutrient management long-term.
Implementation
Indicative cost
Medium (€50k–€500k)
Time to results
Long (> 3 years)
Staffing & skills
NARO entomologists, Mechanical removal crews (Kenya, Tanzania shores)
