Weeds continue to be an important constraint in crop production. Despite the good efforts made in research and extension in the field of weed science, the farmers continue to experience heavy losses in crop yield due to weed interference. The crop loss estimates are many and often confusing and misleading. A conservative estimate of about 10% loss would amount to a loss of about 25 mt of food grains, currently valued at approximately USD 13 billion. Losses of similar magnitude may occur in plantation crops, fruits, vegetables, grass lands, forestry and aquatic environment. The total economic losses will be much higher, if indirect effect of weeds on health, loss of biodiversity, nutrient depletion, grain quality etc is taken into consideration. With considering the above points, should take steps to control weeds proper and on timely to prevent the loss of productivity.