Research Finds Daytime Herbicide Use Delivers Stronger Weed Control Consistently
New research from South Dakota State University shows that the time of day when herbicides are applied can make a major difference in weed control. While many farmers continue spraying into the evening to complete fieldwork, the study showed that applications made around midday consistently provide better weed control than those made at night.
The research was led by Eric Jones, Assistant Professor and SDSU Extension Weed Management Specialist, with contributions from Philip Rozeboom, Jill Alms, and David Vos. Their 2026 field trial evaluated Enlist One (2,4-D choline) and Liberty (glufosinate), applied individually and as a tank mix. For the third straight year, the results showed that applications made at 12:00 p.m. caused significantly greater weed injury than those made at 9:00 p.m.
The study applied to Enlist One at 32 fluid ounces per acre and Liberty at 43 fluid ounces per acre, together with 3 pounds of ammonium sulfate per acre using a spray volume of 20 gallons per acre. Weed evaluations conducted seven days after treatment on June 26, 2026, again confirmed stronger weed control from daytime applications.
Researchers noted that producers often face challenges such as changing weather, strong winds, rainfall, high temperatures, and equipment breakdowns, making it difficult to complete spraying during the ideal time. These factors often encourage growers to continue spraying later in the evening whenever conditions appear suitable.
However, findings collected over the past three years indicate that nighttime herbicide applications may reduce weed control by as much as 20%. Reduced herbicide performance can allow more weeds to survive, increasing the need for additional treatments, raising production costs, and delaying effective weed management.