Glufosinate (Liberty) management strategies

Herbicide-resistant weeds continue increasing geographically and in frequency with in a field in North Dakota. The top herbicide-resistant weed species in North Dakota are kochia, waterhemp, common ragweed, horseweed (marestail), wild oat, and green foxtail. 

• Kochia has been confirmed resistant to herbicides in Groups 2, 4 (2,4-D, dicamba, and fluroxypyr), 5 (atrazine), 9, and 14.
• Waterhemp has been confirmed resistant to herbicides in Groups 2, 4 (dicamba only), 9, and 14.
• Common ragweed has been confirmed resistant to herbicides in Groups 2, 9, and 14.
• Horseweed has been confirmed resistant to herbicides in Groups 2 and 9.
• Wild oat and green foxtail have been confirmed resistant in some cases to ALL Group 1 and 2 herbicides and some populations to both.

Why does the presence and density of herbicide-resistant weeds continue to increase in North Dakota? A NDSU Ph.D. graduate student, Alicia Harstad, is conducting a survey of farmers, weed management advisers, and Extension personnel to better understand the economic and social factors influencing weed resistance management decisions. Alicia is asking farmers and weed management advisers in North Dakota to complete a 20 to 30 minute survey to help identify related to adopting weed resistance management practices. Please complete Alicia’s survey to help determine how to reduce herbicide-resistant weeds in North Dakota and help Alicia complete her Ph.D. research project. Please complete this survey prior to April 15.

No dicamba products may be applied preemergence or postemergence to Roundup Xtend and Roundup Xtendflex soybeans in 2025. Many farmers have switched to Enlist (E3) soybeans and will apply glufosinate (Liberty) plus Enlist One. Farmers planting Roundup Xtendflex soybeans will be applying glufosinate one or two times this growing season.

Glufosinate is a finicky herbicide for consistently achieving effective weed control. In addition, some kochia populations in North Dakota have plants no longer controlled by glufosinate. Individuals applying glufosinate in 2025 need to adopt all strategies to maximize glufosinate activity, particularly with kochia, but waterhemp as well.

There are many practices applicators need to use in 2025 and beyond to maximize glufosinate activity:

1. Use the best quality glufosinate formulation. Not all glufosinate formulations are created equal!
2. Apply as many sites of action of the most effective preemergence herbicides (sulfentrazone, metribuzin, and pyroxasulfone are the best) at the highest rates possible based upon soil type, organic matter, and pH in each field, particularly dense kochia populations. Consider variable rate applying preemergence herbicides.
3. High humidity and good sunlight are the two most critical environmental factors maximizing glufosinate activity. Please consider using Delta T values to determine when to apply glufosinate. Consult page 133 in the 2025 North Dakota Weed Control Guide to learn more about Delta T.
4. Apply glufosinate to <3-inch kochia or before axillary (branch) growth begins.
5. Apply glufosinate only at 20 gallons per acre spray volume.
6. Always include a minimum of 3.0 pounds per acre of spray grade ammonium sulfate (AMS) to glufosninate. Do not use AMS replacement products alone with glufosinate.
7. Apply glufosinate using medium to coarse spray droplets.
8. Apply the maximum rate of glufosinate in each application.
9. Apply glufosinate at a sprayer travel speed of less than eight miles per hour.
10. Scout fields 5 to 10 days after glufosinate applications to determine if all plants were controlled in the first application. If weeds were not completely controlled, automatically apply a different effective herbicide site of action 14 days after the first application.
11. Dust/soil particles on weed leaves can create a barrier for glufosinate entering into the weed.
12. Do not apply glufosinate at night. Consult glufosinate label for when to apply glufosinate.
13. If a weed plant survives a glufosinate application remove the weed prior to plants flowering.
14. Maintain a properly calibrated sprayer and maintain boom height at all times across the entire boom at 20 to 25 inches above the weed canopy.

Please adopt all 14 of these glufosinate management strategies to reduce the risk of selecting for any more kochia plants not being completely controlled by glufosinate. This is critical to the longevity of glufosinate since there are no new herbicide sites of action coming soon.

Neither NDSU Extension nor the NDSU Agricultural Experiment Station endorse commercial products or companies even though reference may be made to tradenames, trademarks or service names.

Jeff Stachler, Ph. D. 
Jeff.Stachler@ndsu.edu
Extension Cropping Systems Specialist