Weed Control Drops in Changing Weather

By Scout Nelson

Eric Jones, Assistant Professor and SDSU Extension Weed Management Specialist, along with Philip Rozeboom, Jill Alms, and David Vos, highlighted that the 2026 growing season is beginning as temperatures rise across South Dakota. Recent March and April temperatures are above normal in several areas, creating favorable early growing conditions. However, sharp temperature swings during the same day may reduce the performance of burndown herbicide applications.

Warm daytime temperatures can help weeds grow actively, which improves herbicide activity. When temperatures stay between 55 and 75 °F, weeds are usually growing and are better able to absorb herbicides. This makes spring applications more effective.

Problems can develop when temperatures quickly fall to freezing or below freezing levels. Cold stress causes weeds to slow growth, and normal plant functions can stop. When this happens, herbicides may not move through the plant properly, reducing weed control. If leaf tissue freezes, herbicide movement can stop completely.

Because of these conditions, farmers should plan applications carefully during spring weather changes. If major temperature swings are expected, spraying early in the day after temperatures rise above 55 °F can improve results. Later applications may be less effective because weeds face cold stress sooner after spraying.

Tank mixing herbicides can also help improve control. Combining products such as glyphosate and 2,4-D may perform better than using a single herbicide when cooler weather follows an application. Growers should always use the proper adjuvants recommended for each herbicide product.

Spray coverage also remains important. Application output should stay between 15 and 20 gallons per acre, so weeds receive enough spray coverage to absorb the herbicide. Better coverage often leads to stronger control.

Preplant burndown treatments play an important role in reducing early season weed competition. Farmers should choose herbicides based on the weed species present in each field. Matching the product to the target weed helps improve success.

South Dakota producers can also review local pest management guides for more information on herbicide performance and weed control planning. Good timing, correct products, and proper application methods remain key to successful spring burndown programs.

Photo Credit: gettyimages-tlillico