ABSTRACT
Effective management of various weeds competing with agricultural crops greatly enhances the crop yield. Interference of troublesome weeds with crops is an age-old problem occurring from the advent of agriculture. Alhough crops and weeds have coevolved, recently various anthropogenic factors have made weeds more aggressive and problematic. A huge amount of money is spent worldwide to control weeds. In the United States alone weeds cause about 12 percent loss in crop yield, and it costs nearly US$35 billion to control them (Piementel et al., 2001). The costs are even more in developing countries. In underdeveloped countries, unmechanized traditional agricultural practices further increase the loss of yield due to weeds.
