Metobromuron is a major preemergence herbicide controlling mainly broadleaf weeds in common bean production in Ontario. Rainstorms at the seedling stage may splash metobromuron on the plants which results in serious injury, reduced plant stand, and low seed yield. This study determined the appropriate rates of metobromuron for identification of germplasm tolerant to the herbicide. Metobromuron of 0, 0.28, and 0.56 kg ai ha−1 in the glasshouse and 0, 0.28, 0.42, and 0.56 kg ha−1 in the field were applied POST at the unifoliolate stage of 30 bean cultivars. A significant linear effect of herbicide rate on plant injury and recovery was detected. Plant growth was reduced significantly on sensitive cultivars. Two cultivars, Taylor Hort’ and ‘UI 51’, and several plant introductions were tolerant to metobromuron. A rate range of 0.42 to 0.56 kg ha−1 of metobromuron would be appropriate to separate tolerant from sensitive bean lines.
