Abstract
Ethofumesate use in sugarbeet in Minnesota and North Dakota has increased with the advent of glyphosate resistant weeds, especially glyphosate resistant waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer]. Hectares treated with ethofumesate soil applied or postemergence increased from 28,045 to 163,047 or 480% between 2020 and 2023 at American Crystal Sugar Cooperative. Similar changes in grower practices have occurred at Southern Minnesota Beet Sugar Cooperative and Minn-Dak Farmers Cooperative. Multiple ethofumesate brands are used by producers including Nortron®, Maxtron 4SC®, Ethotron®, and Ethofumesate 4SC®. Three experiments were conducted at multiple locations in 2024 to evaluate: a) fall vs. spring ethofumesate application; b) waterhemp control with different brands; and c) incorporation (PPI) versus preemergent (PRE) ethofumesate application across rates and resultant length of redroot pigweed (Amaranthus retroflexus L.) control. Experiments were conducted near Beaver Creek, MN, Horace, ND and Moorhead, MN in 2024. Herbicides were applied using a bicycle wheel plot sprayer with a shielded boom to reduce particle drift and calibrated to deliver 159 L ha−1 through 8002XR nozzles (XR TeeJet® Flat Fan Spray Tips, TeeJet® Technologies, Glendale Heights, IL) spaced 51 cm apart and pressurized with CO2 at 207 kPa. Evaluations were a visible assessment of control by comparing the treated area in the plot to the bordering non-treated area. Waterhemp control following fall or spring ethofumesate application was the same 37 DAT (days after treatment) but control was better following at planting application, 47 DAT. Waterhemp control was the same across brands at Moorhead but Nortron, Maxtron and Ethotron controlled waterhemp better at Beaver Creek than Ethofumesate 4SC. Ethofumesate application PRE provided significantly better redroot pigweed control than PPI application. We attribute this to rainfall; site received 3 cm rainfall the evening of application. Ethofumesate PPI or PRE controlled pigweed better at 3.4-4.2 kg ha-1 than ethofumesate at 2.2 kg ha-1 24-44 days after application.