ASSBT Biennial Meeting – Feb. 24 – Feb 27, 2025 in Long Beach, CA
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Dicamba and glufosinate integrated with soil residual and POST herbicides improves control of GR weeds in sugarbeet.


Glyphosate resistant (GR) common ragweed (Ambrosia artimisiifolia), kochia (Bassia scoparia), and waterhemp (Amaranthus tuberculatus) are weed control challenges in sugarbeet. Sugarbeet producers control GR common ragweed with clopyralid at rates ranging from 53 to 105 g ha-1 and GR waterhemp using soil residual herbicides applied after planting or between 2-lf and 8-lf sugarbeet stage. Timely rainfall to incorporate soil residual herbicides was absent in 2021 and 2022, complicating waterhemp control. GR kochia control in sugarbeet is best when effective herbicides are used in the crop sequence preceding sugarbeet. Ethofumesate is the most reliable sugarbeet herbicide for kochia control but is dependent on rainfall for incorporation. Dicamba and glufosinate integrated into the weed control program with Truvera® sugarbeet will benefit sugarbeet producers. Field experiments were conducted in Minnesota and North Dakota in 2021 and 2022 to evaluate sugarbeet tolerance and to redefine a weed control program to control GR weeds. In tolerance experiments, dicamba at 0.56 kg ha-1 plus a volatility reduction adjuvant and a drift reduction agent at 1.46 L ha-1 and 0.5% v/v, respectively, at 2- to 4-lf sugarbeet caused stature reduction injury 1 to 7 and 8 to 14 days after application as compared with the glyphosate control in 2021. However, sugarbeet injury was negligible from dicamba 15 or more days after application or from glufosinate at 0.62 kg ha-1 across application timing. Root yield from dicamba applied at the 10- to 12-lf stage was less than root yield from the glyphosate control or from dicamba PRE, dicamba at the 2- to 4-lf or the 6- to 8-lf stage and from glufosinate at the 2- to 4-, 6- to 8 or 10- to 12-lf stage. Dicamba or glufosinate did not affect percent sucrose compared with the glyphosate control. Dicamba alone or dicamba mixed with ethofumesate PRE controlled early emerging waterhemp better than and dicamba and glufosinate with glyphosate, and chloroacetamide herbicide(s) provided season long waterhemp control better than our best currently commercialized waterhemp control programs in 2021 and 2022. Treatments combining repeat clopyralid applications at 79 g ha-1 with glufosinate or glyphosate or dicamba PRE followed by repeat applications of clopyralid at 79 g ha-1 with glufosinate or glyphosate provided burndown control of up to 5-cm weeds and provided greater than 95% season-long common ragweed control or greater common ragweed control than repeat glyphosate and clopyralid applications at 1.05 kg ha-1 and 79 g ha-1 with NIS and AMS in 2022. Repeat glyphosate applications with dicamba or glufosinate at the 4 to 6-lf or 8- to 10- lf sugarbeet stage, respectively, provided greater than 95% kochia control of up to 10-cm kochia as compared with kochia control from repeat glyphosate applications alone or repeat glyphosate and ethofumesate applications following ethofumesate PRE.