By Angie Peltier
University of Minnesota Extension crops educator, Joe Ikley, NDSU Extension weed specialist, and Greg Dahl, director of adjuvant education, CPDA
March 18, 2026’s Strategic Farming: Let’s Talk Crops session discussed how spray water quality impacts herbicide efficacy. This webinar series runs through the end of March and registrations are still being accepted: https://extension.umn.edu/courses-and-events/strategic-farming. To watch this episode visit: http://z.umn.edu/StrategicFarmingRecordings.
Why do we need adjuvants?
Weed control can be impacted by environmental conditions at the time of application, with temperature, relative humidity, rainfall and wind all capable of impacting efficacy. Similarly, the quality of the water used for spraying herbicides such as water temperature, pH, water hardness, and sediment load can impact herbicide efficacy. Specific adjuvants have been developed to overcome these water quality issues. Adjuvants can also combat foaming, reduce tank mix compatibility issues, work as surfactants or deposition agents or reduce drift.
Before he retired in 2023, Greg Dahl was asked to obtain adjuvant-related weed control research from land grant universities including University of Minnesota, North Dakota State University and Iowa State University, to determine the value of adjuvants to weed management. Herbicides alone were compared to herbicides with the recommended adjuvant and to herbicides with comparison adjuvants. When compared to the weed control observed when using a required adjuvant, weed control declines by between 30 and 90% when the same herbicide was applied without the adjuvant. Using the correct type of adjuvant is important to improve weed control and limit crop injury; the survey found that using the wrong type of adjuvant (ex. using crop oil instead of a surfactant) can reduce weed control between 5 and 50% compared to using the correct adjuvant. Adjuvant efficacy can vary considerably, with the survey finding that using a ‘premium’ product can improve weed control by 5 to 25% compared to using a product considered simply ‘good enough’.
Source : umn.edu