Sugarbeet tolerance to acifluorfen (Ultra Blazer) in Michigan.

Abstract

The lack of postemergence herbicide options to control the glyphosate-resistant Amaranthus spp., Palmer amaranth and waterhemp, is a concern for sugarbeet growers. In the past, sugarbeet has shown some tolerance to the Group 14 herbicide, acifluorfen (Ultra Blazer). In soybean, acifluorfen’s strengths include control of Amaranthus spp., eastern black nightshade, and common ragweed. Field research (2018-2022) on sugarbeet tolerance to acifluorfen was conducted to justify and support Section 18 labeling of Ultra Blazer in Michigan sugarbeet. Early studies examined acifluorfen combinations with glyphosate (0.84 kg ae ha^-1) at rates ranging from 0.14 to 0.43 kg ai ha^-1 to sugarbeet at the 2-, 6-, and 12-leaf stages. This research showed that acifluorfen should only be applied after sugarbeet was at the 6-leaf stage. We have continued to examine the effects from multiple applications of acifluorfen to 6- and 12-leaf sugarbeet and combinations with the tank-mixture partners of clopyralid, ethofumesate, s-metolachlor, dimethenamid-P, or acetochlor at 6-leaf sugarbeet. In many cases, the addition of tank-mix partners has increased sugarbeet injury and in the case of acifluorfen combination with ethofumesate sugarbeet yield loss was also observed. When acetochlor was tank-mixed with acifluorfen sugarbeet injury was less. While sugarbeet injury is a concern with acifluorfen, applications to sugarbeet at the 6-leaf stage or greater could be an option for postemergence glyphosate-resistant waterhemp control.