Survey of efficacy trials for Conviso® One in sugar beet

Abstract

The ALS-inhibitor herbicide Conviso One (foramsulfuron 50 g L^-1 + thiencarbazone-methyl 30 g L^-1, HRAC B) requires a corresponding resistant variety when used in sugar beet cultivation. Experiences with these active ingredients in maize show a high efficacy even at later development stages of weeds, whereas active ingredients applied in current sugar beet cultivation cause highest efficacy at the cotyledonous stage. To acquire insights concerning soil activity, sensitivity of weeds at various development stages and the optimum application timing of Conviso One, numerous field trials were conducted in 2013 and 2014 by the Institute of Sugar Beet Research, Göttingen. Weed plants of the species Chenopodium album, Brassica napus, Galium aparine, Matricaria chamomilla and Polygonum convolvulus were sown to test soil activity (application prior to sowing of weeds) and efficacy after spraying at various development stages of weeds. Additional field trials on naturally infested sites built the basis to investigate efficacy of Conviso One compared to standard herbicides and compared to combinations of Conviso One and standard herbicides in spraying sequence or tank mixture. The results indicate decreasing efficacy when development of weeds increases, especially for C. album. Compared to current herbicide strategies, which require application at the cotyledonous stage of weeds, effective application of Conviso One can take place until BBCH 14 of C. album. Conviso One caused higher efficacy against difficult to control weeds as Mercurialis annua and volunteer-potato (Solanum tuberosum) than the standard herbicide treatment and the number of applications decreased. Soil activity lasted 15-20 days on average of the field trials.