By Ben Werling and Joshua Miranda
Michigan State University Extension conducted an herbicide trial in 2025 to identify a safe rate and timing for sulfentrazone in Michigan turnips. Growers currently rely on Dual Magnum for residual weed control, which is helpful for grasses and broadleaves including pigweeds and nightshades. However, its activity is limited for some challenging weeds including common lambsquarters and smartweeds.
One of our industry partners discovered several sulfentrazone formulations that are labeled for turnips. This active ingredient has a weed control spectrum that compliments Dual Magnum. While it is currently labeled for postemergence (POST) use in turnips, our partner expressed interest in exploring preemergence applications (PRE) at sowing time. We investigated PRE and POST applications to identify rates that provide adequate weed control with acceptable levels of crop injury.
Study overview
In 2025, we worked with our industry cooperator to conduct a trial on a cooperating farm on mineral soil in Ottawa County, Michigan. Dual Magnum at 1 pint per acre (pt/a) was applied at sowing time for all treatments except the control. Treatments included six rates and two timings of sulfentrazone, plus a nontreated control. The three PRE treatments included 1, 2 or 4 ounces per acre (oz/a) of a 4F formulation of sulfentrazone tank-mixed with Dual Magnum and applied over the rows immediately after sowing. The POST treatments included Dual Magnum at planting plus 1, 2 or 4 oz/a of the sulfentrazone 4F formulation applied 12 days later. The study evaluated weed control, weed density, crop injury and yield.
Weed control results
Annual grasses and common lambsquarters were the dominant weeds at this location. Sulfentrazone plus Dual Magnum provided strong overall control of both grasses and broadleaves, with 80–100% control across rates and timings (Table 1, Figures 1–2). Weed control was similar whether sulfentrazone was applied PRE or POST.
Source : msu.edu