Use of Pulse-Width Modulation Sprayers to Optimize Enlist Duo® Applications.

Pesticide input costs have increased in the U.S. by $5.35 billion over the past decade with weed management comprising the largest portion of these applications as greater than 92% of corn, soybean, and cotton hectares were treated for weeds in 2015. More precise and efficient pesticide applications are necessary to reduce pesticide drift and input costs, while increasing weed control. The objective of our research was to evaluate the effect of spray droplet size using a pulse‑width modulation (PWM) sprayer on glyphosate plus 2,4-D choline (Enlist Duo®) pre‑mix efficacy.

A field trial was conducted across three site‑years [Mississippi (2016), Nebraska (2017), and North Dakota (2016)] in a fallow environment. The trial consisted of six Enlist Duo® droplet size treatments (150, 300, 450, 600, 750, and 900 µm) determined from the D_v0.5. The D_v0.5 parameter represents the droplet size such that 50% of the spray volume is contained in droplets of equal or lesser values. Nozzle and application pressure required to create each droplet size treatment were determined through measurements made using a Sympatec HELOS-VARIO/KR laser diffraction system at the Pesticide Application Technology Laboratory in North Platte, NE. One nontreated control was used which provided a total of seven treatments. Treatments were applied using a PinPoint® PWM sprayer.

Results indicated the optimum droplet size for weed control across locations was 620 – 720 µm, or an Extremely Coarse spray classification. Losses in weed control were observed when Enlist Duo® was applied at droplet sizes less than 450 µm (Very Coarse) or greater than 750 µm (Extremely Coarse). Therefore, a critical droplet size was reached with a systemic herbicide, indicating some sprays generated by current nozzle technologies are too coarse to remain efficacious. This research provides a novel, site‑specific approach to weed control using Enlist Duo® and PWM sprayers.