Efficacy of foramsulfuron + thiencarbazone-methyl towards different development stages of weed species in sugar beet cultivation

Abstract

The currently available weed control system in sugar beet cultivation has low flexibility due to the necessity of applications at the cotyledon stage of the weeds. The aim of the present study was to evaluate a new herbicide providing more flexibility in terms of application time. In 2013 and 2014, efficacy of an ALS-inhibiting herbicide (foramsulfuron + thiencarbazone-methyl) was evaluated in six field trials in Germany. Sugar beet varieties not sensitive to ALS-inhibiting herbicides are currently in the breeding process. The herbicide was tested on five weed species in different development stages (later than cotyledon stage). In the trials, only weeds but no sugar beet were sown. The herbicide was applied with three dosages at five development stages of the weeds. Efficacy towards Brassica napusL. and Galium aparineL. was nearly 100%. Efficacy towards Chenopodium albumL., Matricaria chamomillaL. and Polygonum convolvulusL. was reduced due to unfavorable weather conditions and with decreasing dosages and increasing development stages. Efficacy was lowest in case of Chenopodium album being close to 95% at BBCH 14 and 16 with 0.50L/ha and 1.00L/ha, respectively. It was thus concluded that the herbicide can be applied later than at cotyledon stage. This implies more flexibility of application timing than current herbicides. To develop a comprehensive evaluation of the weed control system, further studies regarding selectivity, duration of efficacy and resistance risks are necessary.