Barnyard grass (Echinochloa crus-galli) is one of the most yield-limiting weeds in the irrigated rice systems of Sri Lanka. It is better adapted to grow under dry conditions than under wet conditions. Moreover, the paddy fields are direct seeded and frequently not under flooded conditions due to the scarcity of water, thus making conditions conducive for barnyard grass to grow. As a result this weed is expected to cause a greater problem in the future (Im et al., 1993).