Ethofumesate Applied at Greater than Labeled Rates Postemergence in Sugarbeet

Ethofumesate is a broad spectrum, soil-applied herbicide for control of broadleaf and grass weeds in sugarbeet. Ethofumesate is commonly applied preemergence at rates ranging from 1.25 to 4.2 kg ai ha−1, or applied postemergence, up to 0.38 kg ai ha−1. Generic Crop Science has developed a new Ethofumesate 4SC label that increased ethofumesate postemergence rates up to 4.48 kg ha−1 in sugarbeet with more than two true leaves per plant. Field and greenhouse experiments were conducted in 2018 and 2019 to evaluate sugarbeet tolerance and herbicide efficacy. Field tolerance experiments indicated sugarbeet stature from ethofumesate postemergence at 0.28, 0.56, and 1.12 kg ha−1 was the same as the non-treated control, but ethofumesate at 2.24 kg ha−1 reduced sugarbeet stature; however, did not affect yield components. Ethofumesate postemergence at 4.48 kg ha−1 reduced sugarbeet stature and affected sugarbeet yield components. Ethofumesate alone postemergence provided weed control of up to 85, 76, and 84% on common lambsquarters, redroot pigweed, and waterhemp, respectively, in field efficacy experiments. Mixing ethofumesate at 1.12 kg ha−1 with glyphosate does not provide a second effective herbicide for postemergence control of common lambsquarters and redroot pigweed, but does provide residual control of these weeds when at least one-half inch of penetrating rainfall occurs, following application. In greenhouse experiments, ethofumesate alone or ethofumesate plus glyphosate timed to common lambsquarters, redroot pigweed, or waterhemp less than 2.5-cm provided the best combination of burndown and soil residual control compared with 2.5- to 5-cm tall weeds. Ethofumesate postemergence at 1.12 kg ha−1 plus glyphosate provided the best combination of tolerance and efficacy, especially on waterhemp.