Weed-competitive cultivars and the critical period for weed control (CPWC) are two strategies within integrated weed management (IWM). The objectives of this study were to test an early screening method for selecting competitive germplasm within a barley breeding program and to define a CPWC in barley. Trials were conducted in 2006 and 2007. The results showed that barley cultivars can be ranked for their competitive ability against weeds. Cultivars also differed in their response to low light quality treatments. Biomass allocation, leaf area, and leaf length were correlated with competitiveness. Length of Leaf 2 was correlated strongly with competitive ability (R=0.92). A CPWC could not be defined for barley. However, a study in 2007 defined the critical time for weed removal in barley. The results of this study showed weeds can cause up to 24% yield loss, or $4.35 ha-1day -1, if not controlled before the 3-leaf (i.e., Zadoks 13) stage of crop development.