Emerging targeted herbicide application technologies, such as the ONE SMART SPRAY system (a joint venture of Bosch, Gerlingen, Germany; and BASF Corporation, Research Triangle Park, NC), enable postemergence herbicide application only where weeds are detected. Field studies were conducted in 4 site-years in Seymour, Illinois, and Janesville, Wisconsin, during 2023 and 2024 to compare area treated and waterhemp control between broadcast and targeted herbicide applications to soybean. Early postemergence application of herbicides to soybean at the V2 growth stage at the Seymour location in 2023 resulted in less area treated (26%) than when herbicides were applied at the standard time (76%) but required inclusion of a layered residual herbicide to reach 89% to 93% waterhemp control and biomass reduction ≥94% at 28 d after the standard application time (DASAT). The standard herbicide application time (the V4 growth stage of soybean) at the Seymour location in 2023 provided 87% to 97% waterhemp control and ≥94% biomass reduction at 28 DASAT. In 2 site-years, when waterhemp densities were low (≤5 plants m−2), treatments provided >96% waterhemp control and biomass reduction at 28 DASAT, and targeted applications resulted in 17% to 34% area treated, regardless of application time. In contrast, at Janesville in 2024 (high waterhemp density, >30 plants m−2), waterhemp control and biomass reduction did not exceed 90% at 28 DASAT, but the area treated was ≥97% at postemergence application, indicating that targeted spraying essentially functioned as a broadcast application and would have required additional postemergence applications for effective season-long control. Under high waterhemp densities, frequent nozzle activation reduced potential herbicide savings and diminished differences from broadcast applications, clearly indicating that targeted herbicide application systems are best suited for fields where effective foundational management practices, including robust preemergence herbicide applications and other integrated weed management tactics, reduce weed density during postemergence application season.

Targeted sprayers use artificial intelligence to enable on-the-go weed detection and herbicide application, reducing the need to spray entire fields with foliar herbicides. A targeted sprayer was evaluated for treating weeds in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] cropping systems in the midwestern United States. Using a ONE SMART SPRAY sprayer, our objectives were to (1) evaluate the efficacy of different herbicide application programs: two-passes, spot-spray (SS) only, or simultaneous broadcast residual and SS foliar herbicides; (2) determine whether weed detection thresholds influence weed control; and (3) determine the cost for each herbicide program compared with a traditional broadcast application. Field experiments were conducted in 2022 and 2023 near Manhattan, KS, and in 2023 in Seymour, IL. Both green-on-brown (GOB; burndown applications) and green-on-green (GOG; in-crop applications) were applied. Main plot treatments consisted of four herbicide programs, and the split-plot consisted of four weed detection thresholds: herbicide Efficacy, Balanced, Savings, and a Broadcast application. The percentage of area infested with weeds within each plot was estimated visually 42 d after the GOG application. An “as-applied map” was constructed using raw sprayer data to show when nozzles were turned on or off within a subplot and used to determine herbicide program costs based on the percentage of each plot area sprayed. Results indicated that herbicide programs with simultaneous broadcast and SS components in many cases resulted in a similar area infested with weeds compared with broadcast applications with the same herbicide products. As expected, herbicide costs were lower in SS applications than in broadcast applications. The ONE SMART SPRAY sprayer demonstrated potential to reduce herbicide input costs without compromising weed control.

Field experiments were conducted to compare performance of glyphosate with three different boom arrangements in a winter wheat-fallow rotation near North Platte, NE, in 1994 and 1995. One boom was optically controlled, and the other boom was for broadcast herbicide applications. Spraying with both booms at the same time was called “dual boom.” The sprayers were tested during May, June, and July on two weed density levels established by applying glyphosate at 0.42 kg ae/ha with and without atrazine at 0.84 kg ai/ha in October following wheat harvest. The dual-boom and the broadcast herbicide applications were more efficient in controlling weeds than the optically controlled system. The dual boom reduced weed density 4.5-fold compared with the optically controlled sprayer used alone. Horseweed < 8 cm tall was more difficult to control with the optically controlled sprayer than redroot pigweed and kochia because of its cylindrical-shaped growth patterns. Barnyardgrass and green foxtail seedlings with an erect growth pattern were also difficult for the sensors to detect. Poorer control with the optically controlled sprayer was associated with failure to identify small weeds, chlorotic plants, inconsistency among sensors, and too wide a field of view (FOV), as sensors were spaced farther apart than presently recommended. The number of sensors on a boom needs to be increased to improve the performance of the optically controlled sprayer.

Field studies were conducted from 1993 through 1995 to determine potential reductions in herbicide use and associated cost savings by utilizing a weed-sensing sprayer, named Detectspray, to control weeds throughout the fallow season and to control perennial weeds after crop harvest. The Detectspray system gave comparable weed control to conventional broadcast spraying on 80% of the application dates and reduced glyphosate/dicamba use over the fallow season by 19 to 60%. This reduced herbicide use resulted in cost savings of $6 to $32 ha−1. A fallow treatment that combined two herbicide applications with the Detectsprayer plus one to two wide-blade tillage operations was less costly than conventional tillage at two of 11 sites and at all sites retained more surface crop residues to reduce the risk of erosion. Postharvest glyphosate use on quackgrass with the Detectsprayer was reduced 50 to 78% compared to broadcast applications and resulted in cost savings of $16 to $25 ha−1. Clopyralid use on Canada thistle with the Detectsprayer was reduced 71 to 80%, with cost savings of $44 to $50 ha−1. The Detectspray system is a useful tool to effectively manage weeds in conservation fallow and reduced tillage cropping systems.