Examination of efficacy and selectivity of herbicides in ALS-tolerant sugar beets

The development of herbicide-tolerant sugar beet varieties offers the possibility to use only herbicides from the group of the aceto-lactate synthase (ALS) inhibitors. At present, ALS inhibitors are used in many crops of the rotation to a significant extent, in particular in cereals and maize. However, more than 159 weed species with resistance to ALS inhibitors are known. Consequently, this is the mode of action with most cases of herbicide resistances. The advancing spread of ALS-resistant weeds is a major challenge for herbicide management, if herbicide ALS-tolerant crops are used. The present study was concerned with the question of which herbicide strategies ensure the efficacy of the new herbicide CONVISO® with and without presence of ALS-resistant weeds. Furthermore, the selectivity in ALS-tolerant sugar beet was investigated. Without presence of ALS-resistant weeds one treatment with CONVISO® was sufficient for weed control. With a splitting application and use of an additive the CONVISO® efficacy could be improved. The application of CONVISO® herbicide caused no visual symptoms or yield loss in the sugar beet. ALS-resistant weeds were only partly controlled by CONVISO® herbicide. By using tank mixtures with other modes of action efficacy could be improved, but complete control of ALS-resistant weeds was not possible.