Managing cool-season weeds in sugarbeet grown for biofuel in the Southeastern U.S.

Authors: Johnson, Wiley - Carroll; Webster, Theodore; GREY, TIMOTHY - University Of Georgia; LUO, XUELIN - University Of Georgia

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2018
Publication Date: 5/21/2018
Citation: Johnson, W.C., Webster, T.M., Grey, T.L., Luo, X. 2018. Managing cool-season weeds in sugarbeet grown for biofuel in the Southeastern U.S.. Weed Technology. 32(4):385-391. https://doi.org/10.1017/wet.2018.5.
DOI: https://doi.org/10.1017/wet.2018.5

Interpretive Summary: Much of the arable land in the southeastern U. S. is fallow during winter months. Sugarbeet, grown for biofuel, is being considered as an alternate cool-season crop in the region, with planting and harvest strategically scheduled between major summer crops in the region. Labels for herbicides registered for use on sugarbeet grown in the traditional sugarbeet production regions do not list any of the cool-season weeds common in the southeastern U. S. Field trials were initiated near Tifton, GA to evaluate all possible combinations of ethofumesate (Nortron®) applied preemergence (PRE), phenmedipham + desmedipham (Betamix®) applied postemergence (POST), clopyralid (Stinger®) POST, and triflusulfuron (UpBeet®) POST for cool-season weed control in sugarbeet. Phenmedipham + desmedipham, alone and in combination with clopyralid and/or triflusulfuron effectively controlled cutleaf eveningprimrose, lesser swinecress, henbit, and corn spurry when applied to seedling weeds. Ethofumesate PRE alone was not as effective in controlling cool-season weeds compared to treatments containing phenmedipham + desmedipham POST. However, ethofumesate PRE applied sequentially with phenmedipham + desmedipham POST improved weed control consistency. Clopyralid and/or triflusulfuron alone did not adequately control cutleaf eveningprimrose. Triflusulfuron alone effectively controlled wild radish. In the 2013/2014 and 2014/2015 seasons, POST herbicides were applied in December and none injured sugarbeet. However, in the 2015/2016 season POST herbicides were applied in late October and the maximum temperature the day of treatment was 25.4 C. This daily maximum temperature exceeded the established upper temperature limit of 22 C for safe application of phenmedipham + desmedipham and sugarbeet were severely injured. In the southeastern U. S., temperatures frequently exceed 22 C in the early autumn and may limit phenmedipham + desmedipham use, which happens to be an effective option to control troublesome cool-season weeds of sugarbeet in the region. Weed control options need to be expanded to compensate for this limitation.

Technical Abstract: Sugarbeet, grown for biofuel, is being considered as an alternate cool-season crop in the southeastern U. S. coastal plain. Typically, the crop would be seeded in the autumn, grow through the winter, and harvested the following spring. Labels for herbicides registered for use on sugarbeet grown in the traditional sugarbeet production regions do not list any of the cool-season weeds common in the southeastern U. S. Field trials were initiated near Tifton, GA to evaluate all possible combinations of ethofumesate applied preemergence (PRE), phenmedipham + desmedipham applied postemergence (POST), clopyralid POST, and triflusulfuron POST for cool-season weed control in sugarbeet. Rates chosen for each were on the low-end of the established rate range due to the Tifton loamy sand soil. Phenmedipham + desmedipham, alone and in combination with clopyralid and/or triflusulfuron effectively controlled cutleaf eveningprimrose, lesser swinecress, henbit, and corn spurry when applied to seedling weeds. Ethofumesate PRE alone was not as effective in controlling cool-season weeds compared to treatments containing phenmedipham + desmedipham POST. However, ethofumesate PRE applied sequentially with phenmedipham + desmedipham POST improved weed control consistency. Clopyralid and/or triflusulfuron alone did not adequately control cutleaf eveningprimrose. Triflusulfuron alone effectively controlled wild radish. In the 2013/2014 and 2014/2015 seasons, POST herbicides were applied in December and none injured sugarbeet. However, in the 2015/2016 season POST herbicides were applied in late October and the maximum temperature the day of treatment was 25.4 C. This daily maximum temperature exceeded the established upper temperature limit of 22 C for safe application of phenmedipham + desmedipham and sugarbeet were severely injured. In the southeastern U. S., temperatures frequently exceed 22 C in the early autumn and may limit phenmedipham + desmedipham use, which happens to be an effective option to control troublesome cool-season weeds of sugarbeet in the region. Weed control options need to be expanded to compensate for this limitation.