Advancements in precision agriculture are transforming how we manage weeds in row crops. New real-time, camera-based weed detection technologies such as the BASF–Bosch One Smart Spray, John Deere See & Spray, Greeneye, and Ecorobotix ARA Ultra Precision Sprayer, offer site-specific herbicide applications that detect and spray weeds only where they occur. These systems can operate in “green-on-brown” situations (burndown or preemergence [PRE] applications before crop emergence) and “green-on-green” conditions (postemergence [POST] applications in standing crops).

Targeted herbicide application technologies represent an exciting frontier in precision weed management. Compared to conventional broadcast spraying, these systems can reduce total foliar herbicide use, lower application costs, and reduce the risk of off-target movement. Despite their promise, adoption in U.S. corn and soybean systems still faces practical and financial barriers. Continued research is needed to effectively integrate these technologies into season-long weed management programs amid the increasing complexity driven by herbicide resistance evolution.

A common question we continue to receive from stakeholders is: “What can one do as part of their chemical weed control program to maximize POST foliar herbicide savings and weed control when using targeted herbicide application technologies?”

This summer, Ph.D. student Zaim Ugljic and our WiscWeeds team conducted a series of experiments evaluating how effective PRE herbicide programs influence the success of “green-on-green” targeted herbicide applications.

The research clearly demonstrated that a strong PRE herbicide program, one that includes multiple effective modes of action, is essential for maximizing the benefits of targeted POST applications. In this article, we use results from our 2025 corn trials as a case study to illustrate these findings.

Field plots treated with robust PRE herbicides had lower overall weed pressure and distribution, and smaller weeds at the time of POST spraying. This directly translated into greater foliar herbicide savings at POST (65%) compared to field plots treated with weaker or no PRE programs (15% or less; Figure 1). Field plots with limited or no PRE control experienced widespread weed emergence and larger weeds, forcing the technology to treat a greater percentage of the field at POST, diminishing potential herbicide savings.

Figure 1. Effect of PRE-emergence herbicide program selection on foliar herbicide savings at the time of POST-emergence application [Savings (%), y-axis]. Data represent a summary of 2025 corn research trials conducted at the UW Arlington Agricultural Research Station and the O’Brien Family Farm in Wisconsin using the One Smart Spray small-plot research unit.

Stronger PRE = PRE-emergence program with multiple effective modes of action. Weaker PRE = PRE-emergence program with a single effective mode of action. Research led by WiscWeeds Ph.D. student Zaim Ugljic.

Key Takeaways for Growers and Ag Professionals

• Start Clean, Stay Clean: An effective PRE herbicide program remains the backbone of successful weed management, even with advanced technologies. PREs suppress early-season weed emergence, maintaining cleaner fields until POST application time.
• Use Multiple Effective Modes of Action: Applying preemergence soil residual herbicides with effective modes of action reduces weed pressure and slows the evolution of herbicide resistance.
• Optimize Targeted Sprayer Efficiency: Lower weed density and distribution, and smaller weed size allow green-on-green technologies to selectively treat fewer spots, maximizing foliar herbicide savings.
• Support Long-Term Resistance Management: By reducing reliance on POST control strategies, growers can preserve the efficacy of critical foliar herbicides for future use.

Bottom Line

Targeted herbicide application technologies are reshaping the future of precision weed management. However, their success depends on a solid foundation, using effective PRE-emergence herbicides in tandem with integrated management strategies that limit early-season weed pressure and create favorable conditions for targeted POST-emergence applications.

As these tools continue to evolve, ongoing research at the University of Wisconsin–Madison aims to provide practical, data-driven recommendations to help growers and applicators adopt these technologies successfully and sustainably.

Acknowledgments: We thank Aaron Hunsinger (One Smart Spray), Jeff Laufenberg and Dr. Jose Junior Nunes (Syngenta), and the WiscWeeds team for the technical support. This research was partially sponsored by Syngenta and the National Corn Growers Association.

This article was written by Rodrigo Werle and Zaim Ugljic, UW–Madison Cropping Systems Weed Science Program.