Post-emergent Herbicides for Pigweed Control

Before the introduction of Roundup Ready^® soybeans, many remember heading out to the middle of a field in the hot summer heat to walk beans, cutting and pulling stubborn weeds by hand. No one wants to go back to those days, yet hand rogueing is making a comeback as an effective way to deal with resilient late-season weeds.

It’s a compelling reason to stay ahead of weeds emerging between your post-emergence application and canopy closure. Research shows that weeds left uncontrolled after the V2 to V3 growth stage can reduce soybean yield by up to 1% per day.¹ And yield loss isn’t the only concern. If left unchecked, escaped weeds can cause harvestability issues and contribute to the weed seed bank, creating problems for years to come. While there are many benefits that came with the advent of herbicide-tolerant soybean trait systems, you’ve also dealt with the challenges of managing resistant weed species that adapted to these new systems. Waterhemp and Palmer amaranth are particularly aggressive and can be damaging to soybean yields throughout the season.

“We recently surveyed farmers across the Midwest and South on how they’re dealing with waterhemp and Palmer amaranth and their experiences were pretty clear: “Difficult. Frustrating. Relentless. A nightmare,”² said Eric Eade, BASF product manager. “Because pigweeds emerge throughout the season, one of the best tools we have is layering residual herbicides with both pre- and post-emergence herbicide applications. Including a residual herbicide like Zidua^® SC herbicide or Outlook^® herbicide with your post-emergent Liberty^® herbicide or Engenia^® herbicide application can extend control.” 

Waterhemp requires more than twice as many growing degree days to reach 50% emergence as giant foxtail or velvetleaf, for example, resulting in a greater percent of the population emerging after mid-June.⁴ While late-emerging weeds are less competitive than weeds that emerge with the crop, that doesn’t mean you can ignore the threat they pose. At high densities waterhemp can impact yields and, regardless of density, can produce significant quantities of weed seed. Left uncontrolled, waterhemp can reduce soybean yield by up to 44%.⁵

“Yield results from a layered approach speak for themselves. Research shows a 10-bushel average difference between a layered residual approach versus a single pre-emergence herbicide application,”⁶ Eade said. 

The coverage you get by including Outlook herbicide or Zidua SC herbicide with your post-emergence Liberty or Engenia application can reduce late season weed pressure as well as mitigate future resistance issues. The additional modes of action and extended window of control help minimize escapes, which means reduced deposits to the soil seed bank and a step ahead next season. Zidua SC herbicide has up to two weeks longer residual control. And Outlook herbicide is up to 2.5 times more likely to activate than competitive products like metolachor and acetochlor,⁷ and requires as little as a quarter inch of moisture.³

There are many reasons to strive for a weed-free field, not the least of which is the personal satisfaction of a clean soybean field at harvest. Whether your primary goal is preventing yield loss or resistance management, get ahead by including a residual like Zidua SC herbicide or Outlook herbicide with your post-emergent Liberty herbicide or Engenia herbicide application. While we can’t guarantee you won’t ever have to walk your beans to remove weeds by hand, we can help protect your investment and give you the best chance for future success. 

^{1 Hartzler, R. Is your weed management program reducing your economic return? Iowa State University. 2003. http://extension.agron.iastate.edu/weeds/mgmt/2003/economics.shtml}

^{2 Kynetec research survey on weed resistance for BASF. October 2021.}

^{3 Internal BASF trials.}

^{4 Hartzler, R., Anderson M. Achieving full-season waterhemp control in soybeans. 2019. https://crops.extension.iastate.edu/cropnews/2019/02/achieving-full-season-waterhemp-control-soybean}

^{5 Waterhemp management in soybeans. United Soybean Board. February 2022. https://iwilltakeaction.com/weed/common-waterhemp.}

^{6 Managing waterhemp with layered residual herbicides. University of Minnesota Extension. 2021. https://extension.umn.edu/herbicide-resistance-management/managing-waterhemp-layered-residual-herbicides.}

^{7 Comparisons available on ReliableActivation.com.}

Always read and follow label directions. Engenia Herbicide is a U.S. EPA Restricted Use Pesticide. A pH buffering adjuvant, like AEGOS™ or Sentris™ Buffering Technology, is required in every application of Engenia herbicide. Engenia^®, Liberty^®, Outlook^® and Zidua^® are registered trademarks of BASF. Roundup Ready^® is a trademark of Bayer Group. © 2022 BASF Corporation. All rights reserved.