Saflufenacil-Resistant Kochia Confirmed in South Dakota

Updated May 02, 2025

Eric Jones

Assistant Professor and SDSU Extension Weed Management Specialist

Additional Authors: Philip Rozeboom

Written collaboratively by Eric Jones, Philip Rozeboom, Jill Alms, and David Vos.

Kochia is a widespread weed in South Dakota and the Northern Great Plains states. Kochia germinates early in the growing season and often needs to be managed before crop planting. In no-till farming, herbicides are relied on to manage kochia before planting. Saflufenacil (Sharpen) is an herbicide that can be applied at a burndown timing before most crops in South Dakota and is very effective on kochia. However, overreliance on saflufenacil has selected for resistant kochia in North Dakota and Saskatchewan (Geddes et al. 2025) (Figure 1). Therefore, herbicide screens were conducted at South Dakota State University to determine if resistant populations of kochia existed in South Dakota.

Regional Herbicide Screens

North Dakota

Multiple black pots with green kochia plants within. Blue text boxes with white words added to the photo to explain the 4, North Dakota locations and a susceptible control.
Figure 1. Saflufenacil sprayed on kochia plants from North Dakota with a 1X (1 fl. oz. per acre) and 2X (2 fl. oz. per acre) rate two weeks after treatment. The susceptible plants (far left) were controlled but none of the tested resistant plants died. (Courtesy: Dr. Brian Jenks, North Dakota State University)

South Dakota

Ten small green pots with brown dirt and green kochia plants within with a black background.
Figure 2. A kochia population from Northeast South Dakota (bottom plants) surviving saflufenacil applied at 1 fl. o.z per acre 28 days after treatment. The susceptible comparison (top plants) kochia population died after treatment. The four plants on the right for each population were treated with saflufenacil. The single plants on the far left for each population are nontreated.

A kochia population from Northeast South Dakota was found to survive the 1X rate of saflufenacil (1 fl. oz. per acre) in the greenhouse (Figure 2). Twenty kochia plants from the Northeast South Dakota population and a susceptible population from Southeast South Dakota collected were treated with saflufenacil applied at 1 fl. oz. per acre. No plants from the Northeast South Dakota population died after treatment, while only four plants from the susceptible population survived (Figure 3). This level of survival in the screen is comparable with the survival levels of saflufenacil-resistant kochia treated with similar rates (Geddes et al. 2025). The results of the saflufenacil screen are that the population from Northeast South Dakota is resistant to saflufenacil. Current efforts are screening more kochia plants collected from across South Dakota to determine the distribution of saflufenacil resistance (Figure 4).

Survival Rates

100% NE 20% susceptible
Figure 3. Survival of kochia plants from two populations treated with saflufenacil (1 fl. oz. per acre) 28 days after treatment. No plants from the Northeast population were killed while 80% of the plants from the susceptible population were killed. Twenty plants from each population were treated.

South Dakota Regional Samples

Multiple, small black pots with dark-brown soil and green kochia plants within. Pink, green, blue and white stakes are within the pots.
Figure 4. Kochia plants collected across South Dakota being screen to determine the distribution of saflufenacil resistance.

Implications

While saflufenacil can be effective on kochia and other weeds, efforts should be made to reduce selection pressure on resistant weeds. Other herbicides should be mixed with saflufenacil to reduce selection pressure on resistant weeds while still providing effective management. Paraquat (Gramoxone, others) is an effective burndown herbicide with flexibility to subsequently plant crops after spraying. Dicamba (Banvel, Clarity, others) can be effective on kochia, but more restrictions are presented for plant back restrictions based on the crop to be planted. Refer to the most-recent South Dakota Pest Management Guides and specific herbicide labels for use and restrictions.

If herbicide failures occur, first manage the surviving weeds, then report the failure to SDSU Extension. Control failures can be retreated with a different and effective herbicide. However, mowing, tillage (if feasible), and hand weeding can be effective tactics to manage surviving weeds to ensure seeds are not produced. If a control failure is realized at the burndown timing, extensive and intensive efforts should be implemented during the growing season to manage kochia plants to ensure seed production is ceased. Cultural, chemical, and mechanical management tactics should be utilized.

References

  • Geddes CM, Law QD, Jenks BM, Howatt KA, Ikley JT, Jaster A, Pittman MM, Biggers K, Meiners I, Porri A (2025). Protoporphyrinogen oxidase (PPO)-inhibitor resistance in kochia (Bassia scoparia). Weed Sci. 73(e26), 1–12. doi: 10.1017/wsc.2025.4

Related Topics

Corn Weeds, Soybean Weeds, Wheat Weeds

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