The idea of “catching up” with weed control later in the season may sound appealing, especially when weather or planting windows compress the timing of management decisions. But with aggressive pigweeds such as Palmer amaranth and waterhemp, delayed action often leads to lost yield and escalating control costs.
These weeds emerge early, grow rapidly and compete aggressively, even at low population densities. A single plant can produce hundreds of thousands of seeds, replenishing the seedbank and compounding pressure year after year. Herbicide-resistant pigweed varieties have only intensified the challenge.¹
Season-long pigweed control requires a proactive strategy begun at planting. A layered pigweed herbicide program designed to prevent early establishment, rather than react to visible escapes, is essential for protecting yield and preserving herbicide performance over time.
Pre-emergence herbicides are the foundation for pigweed control
Pigweeds are most vulnerable at the seedling stage, but that window closes quickly. That is why pre-emergence herbicides carry so much weight in a season-long program. Effective pigweed control begins at planting.
A pre-emergence herbicide forms a barrier over your soil that stops any emerging weeds as they germinate, before they ever break the soil surface. By suppressing the first flush, a strong pre-emergence program protects yield during the crop’s most vulnerable early growth stages.
This approach also buys you time. When applied correctly, pre-emergence herbicides can keep fields clean for three to four weeks, allowing growers to plan and make a timely post-emergence application. Skipping that first step creates a management gap. Once pigweeds emerge and begin growing rapidly, control becomes more difficult and more expensive.²
Starting clean and staying clean is operationally easier than reactively trying to control emerged pigweed.
Layering pigweed residual herbicide to close the gap
Pigweed emerges in multiple flushes throughout the season, which means one pass rarely provides full-season control. To stay ahead, growers need to layer residual herbicides and avoid leaving bare soil exposed.
The second application can often be as important as the first. While a pre-emergence spray gives you protection from emerging weeds, a follow-up post-emergence application with a long-lasting residual herbicide will help to kill weeds that might have escaped or slipped through.³
A clean soil bed before your post-emergence herbicide overlaps the residuals and ensures new pigweed flushes never see the light of day. When searching for the best residual herbicides for pigweed, consider products such as Zidua®, Surtain® and Outlook®, which can be used to build and reinforce residual control as part of a layered strategy.
By overlapping residuals, growers reduce the risk of late-season escapes, protect yield potential and slow the development of additional resistance.
Optimizing performance: moisture, timing and field conditions
Pigweed control is impacted by the condition of your soil and cultural practices.
Pre-emergence herbicides need to have 0.5 to 1.0 inches of soil moisture within the first week of spraying.⁴
That moisture moves the pigweed herbicide into the soil zone where pigweed seeds germinate. Without activation, control may be delayed or uneven.
Good soil contact and uniform coverage improve performance of your pigweed herbicides. If rainfall is delayed and small weeds begin to emerge, mechanical tools such as a rotary hoe can disrupt seedlings and help maintain a clean field until the herbicide is activated.⁵
Additional cultural practices further strengthen a layered residual program. Narrower row spacing and faster canopy closure suppress late-season pigweed emergence. Crop rotation allows growers to diversify herbicide sites of action. Most importantly, preventing escapes reduces additions to the weed seedbank, lowering pressure for next season.
When these practices are combined with a disciplined, layered residual approach, growers create a system that works together to extend control and protect yield.
Experts are available to help you make informed herbicide decisions. Reach out to your seed retailer, a nearby extension office agent or a seed company professional like your regional BASF representative.
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Endnotes
- BASF Agricultural Solutions. “Benefits of Zidua PRO Powered by Kixor Herbicide.” BASF Agricultural Solutions, 2022, https://agriculture.basf.us/crop-protection/Campaigns/pre-season-playbook/benefits-of-zidua-pro-powered-by-kixor-herbicide.html
- Smith, Ken, and Bob Scott. A Guide to Pigweed Management for Soybean/Cotton. University of Arkansas System Division of Agriculture Cooperative Extension Service, 2009, https://uaex.uada.edu/farm-ranch/crops-commercial-horticulture/cotton/guide-pigweed-management-aspb.pdf
- Behnken, Lisa, et al. Managing Waterhemp with Layered Residual Herbicides. University of Minnesota Extension, 2021, https://extension.umn.edu/herbicide-resistance-management/managing-waterhemp-layered-residual-herbicides
- Everman, Wesley, and Meaghan Anderson. Herbicides and Variable Weather. Iowa State University Integrated Crop Management, 14 May 2025, https://crops.extension.iastate.edu/post/herbicides-and-variable-weather
- Johnson, Bill, and Marcelo Zimmer. Soil Applied Herbicides and Rainfall for Activation. Pest&Crop Newsletter, Purdue University Extension, 28 Apr. 2023, https://extension.entm.purdue.edu/newsletters/pestandcrop/article/soil-applied-herbicides-and-rainfall-for-activation-4/
