Impact of Applying Neochetina bruchi (Hustache), (Coleoptera: Curculionidae) on Flowering and Water Loss through Plant Leaves for Biological Control of Water Hyacinth

Two days after releasing 15 Neochetina bruchi (Hustache) adults over 10 water hyacinth plants grown in a plastic bucket filled with 15 lit. of water in 10 replicates, 28.1% reduction in inflorescence was recorded. The rate of reduction increased through successive weeks to reach a maximum of 86.8% after 9 weeks from weevils release compared to non infested plants. The inhibition of inflorescence rate was proportional to the rate of damage caused by Neochetina feeding, stages to water hyacinth. Elimination of flowering by the action of Neochetina reflects, undoubtedly, in reducing seeds' production. N. bruchi reduced, also, water loss caused as a result of evapotranspiration through plant leaves. Nine weeks after weevils' release, only 4.2 lit. of water was lost, opposed to 7.7 lit. from the same amount of water occupied with uninfested water hyacinth, saving 44% of water. This percentage reached 77% after 14 weeks of release to confirm the important role of Neochetina weevil in reducing water loss through evapotranspiration by adults' feeding that reduce plant leaves exposed area.