Selectivity of foramsulfuron plus thiencarbazone-methyl and classic herbicides in sensitive and non-sensitive sugar beet genotypes

A new herbicide for sugar beet cultivation using the ALS-inhibiting active ingredients foramsulfuron and thiencarbazone-methyl is under approval in the EU member states. Sugar beet genotypes that are non-sensitive to this herbicide are currently under development. Selectivity of the ALS-inhibiting herbicide and yield response of the non-sensitive genotypes might be relevant to meet the requirements for variety registration. To evaluate these issues, six field trials were conducted in Germany in 2013 and 2014. Classic herbicides and the ALS-inhibitor herbicide were applied in dosages of up to fourfold the authorised (or applied for) application rates. The ALS-inhibitor herbicide did not cause any significant phytotoxicity and had no effect on leaf area index at a single, double or fourfold dosage. By contrast, classic herbicides had significant negative effects at the single dosage. At fourfold dosage, they caused 41% phytotoxicity and reduced leaf area index by 35%. The relative yield difference between ALS-inhibitor and classic herbicide treatments was 8.6% and 17.4% of white sugar yield at double and fourfold dosage respectively. The ALS-inhibitor herbicide thus showed higher selectivity than the classic herbicides. In the registration process, the resulting yield advantage could balance a possible yield penalty of non-sensitive genotypes. The introduction of a new system for weed control could improve application flexibility and control of troublesome weeds in sugar beet.