Non-target-site Mechanisms of Herbicide Resistance – Changes for Weed Management

Weed scientists generally have done an excellent job of documenting herbicideresistant weeds. Over 400 unique cases of herbicide resistance, involving over 200 weed species in 65 countries, have been reported (Heap 2014). Oftentimes, evolved resistance in weeds is due to a mutation in a gene encoding the herbicide target site, and weed scientists also have done a good job of identifying these mutations. For example, 132 unique cases of mutations in the acetolactate synthase (ALS) gene are catalogued (Tranel et al. 2014).