Current Status of Aquatic Weeds and Their Management in India

Aquatic weeds pose several problems in India. The canals of Chambal commanded area in Rajasthan and Madhya Pradesh and Bhakra-Nagal in Himachal Pradesh and Punjab have been greatly slowed by the aquatic weeds. Several irrigation and hydroelectric projects in the country like Tungabhadra project in Karnataka, Nagarjuna Sagar project in Andhra Pradesh and Kakki and Idikki reservoirs in Kerala are suffering with massive growth of aquatic weeds. Vast areas of lowland paddy fields in Kerala, Goa and north-east region of India are badly infested with aquatic weeds like Eichhornia crasipes, Salvinia molesta, Chara spp., Nitella spp. and algal scum. Out of about 140 aquatic weeds, Eichhornia crassipes, Ipomoea aquatica, Typha angustata, Ceratophyllum demersum, Salvinia molesta, Nelumbo nucifera, Alternanthera philoxeroides, Hydrilla verticillata, Vallisneria spiralis,, Chara spp., Nitelia spp., Potamogeton spp. are of primary concern in India. Aquatic weeds can be controlled by several methods like mechanical, biological, chemical and through utilization. Successful attempts have been made to control water hyacinth and water fern by use of exotic weevil Neochetina spp. and Cyrtobagaus salvinae in different parts of the country. But for several other aquatic weeds, suitable bioagents are not available. Some species of herbivorous fishes (Tilapia spp. and Ctenopharyndon idelle) have been utilised to control some submerged weed especially Hydrilla spp. with varying degree of success. Although, no label claim is given for any herbicide use in water bodies in India, some workers recommend the use of 2,4-D, glyphosate, metsulfuron methyl, paraquat etc., for control of floating weeds. Present and future herbicides must be compatible with all the actual and potential uses of water. Aquatic weeds have great potential for biomass production. There is immense scope for utilizing them for compost making, biogas production etc. This paper deals with current aquatic weed problems and their management in India.