Herbicide resistance of Wild Oat (Avena fatua) populations from Rhineland-Palatinate

In Rhineland-Palatinate two seed samples of Wild Oat (Avena fatua) were collected in 2011 and eight samples followed in 2012. They derived from fields with inadequate herbicide performance. In order to harmonise plant development, seeds were treated with gibberellic acid. Herbicide resistance was tested by means of two successive biotests using different ACCase-inhibitors (Ralon Super, Topik 100, Axial 50, Traxos, Focus Ultra) and one ALS-inhibitor (Husar OD). Three samples showed cross-resistance against ACCase-inhibitors, with the exception of Focus Ultra (Cycloxydim). Within two populations resistance was well established. Only single plants expressed resistance in a third sample. Genetic analysis found an I1781L target-site-mutation in two samples. One population showed additional mutations: W1999C, I2041V and C2088N. Further investigations, including different application rates, are necessary to explain the poor performance of the ALS-inhibitor