13-Biological control of aquatic weeds in reservoirs

Abstract

The free floating weeds (Eichhornia crassipes, Lemna minor, etc.) and submerged aquatic weeds like Hydrilla verticillata, Vallisneria zannichelia, Chara sp., Algae, Potamogeton natans, etc. are problematic aquatic weeds in the water bodies of India. The spread of these aquatic weeds through reservoirs, canals and drains after construction of high dams exemplifies the need for concern. These water systems have slowly been infested with the aquatic vegetation which has caused many problems; they hamper the water flow which results in reduced carrying capacity, increase water loses by evapotranspiration, interfere with water distribution, etc. The control of aquatic weeds due to their high reproduction rate and perennial growth has become a global problem. This paper discusses the management of some aquatic weeds in reservoirs biologically. The studies include the control of Eichhornia crassipes (Water Hyacinth) with the use of two host specific weevils i.e. Neochetina eichhorniea and Neochetina bruchi and submerged weeds with Ctenopharyngoden idella fish (Grass carp). The studies undertaken at Irrigation & Power Research Institute have shown that the Ctenopharyngoden idella readily consumes the aquatic weeds like Chara sp, Hydrilla verticillata, Vallisneria zannichelia, Potamogeton crispes, algae, etc. in its preference order. Biological control by using the host-specific insects and other organism is an alternative method that offers long term potential for control of aquatic weeds in water bodies. It is relatively inexpensive and free from harmful environmental impact.