Database Research Summaries
2018 Investigation of Herbicide Resistance in Waterhemp and Palmer amaranth in Kansas: Survey, Mechanism, and Management

calendar_today Year of Research: 2018
update Posted On: 12/04/2019
group Vipan Kumar (Principal Investigator, Kansas State University), Mithila Jugulam (Co-Invesitagor, Kansas State University), Doug Shoup (Co-Invesitagor, Kansas State University), Phillip Stahlman (Co-Invesitagor, Kansas State University)
bookmark Kansas Soybean Commission

Research Focus

The focus of this project is to better predict and manage 2,4-D resistance in putative waterhemp and Palmer amaranth populations by understanding the level and the mechanism of resistance.


  • Determine the baseline sensitivity of waterhemp and Palmer amaranth populations from Kansas’s fields to glyphosate, 2,4-D, and dicamba.
  • Investigate the mechanism of 2,4-D resistance in Palmer amaranth.
  • Evaluation of integrated herbicide programs for managing herbicide-resistant (HR) waterhemp and Palmer amaranth in Roundup Ready 2 Xtend® soybeans.
  • Develop and deliver education materials for management/containment of HR waterhemp and Palmer amaranth in Kansas soybean production.


  1. Results suggest that resistance to glyphosate is fairly common among Kansas Palmer amaranth populations and there are few populations that showed unacceptable control with 2,4-D herbicide.
  2. Results confirmed the first case of a Palmer amaranth population from Kansas with multiple resistances to RoundUp PowerMax, Glean, Aatrex, Callisto, and Defy herbicides.
  3. Dose-response analysis of visual injury data suggested that KCTR is 13.6-fold and 10.2-fold resistant compared to KSS and MSS respectively. The dry shoot biomass data indicated that KCTR is 14.6-fold and 9.3-fold resistant compared to KSS and MSS respectively.
  4. Preliminary data suggests there is no difference in maximum 14C 2,4-D absorption in these populations. However, MSS showed relatively higher time required achieving maximum absorption compared to KCTR and KSS. Experiments are in progress to assess the 2,4-D translocation and metabolism in KCTR in comparison with MSS and KSS Palmer amaranth. In summary, KCTR is ~ 10-14-fold resistant to 2,4-D compared to MSS and KSS.
  5. The use of two-pass herbicide programs, including PRE herbicides such as Fierce XLT, Panther PRO, Authority Elite, or Zidua PRO followed by a sequential POST application of Roundup PowerMax + Engeniaare recommended for effective and season-longcontrol of GR Palmer amaranth in Roundup Ready 2 Xtend soybean.
  6. Information generated through this research project was communicated to Kansas’s growers through various outlets. The results have also been published in annual field research reports and one refereed journal article.


  • The results from the experiments will provide information for the first time about the potential evolution of 2,4-D resistance in Palmer amaranth in the US and common waterhemp in KS.
  • Understanding the mechanisms of 2,4-D resistance will help to formulate and recommend viable weed management strategies that can delay the evolution of 2,4-D resistance.
  • Also, this research will aid in further work and research efforts aimed at utilizing integrated herbicide programs (PRE and POST) for multiple herbicide-resistant (HR) Palmer amaranth and waterhemp management in Roundup Ready 2 Xtend soybean production systems.

For more information about this research project, please visit the National Soybean Checkoff Research Database.

Funded in part by the soybean checkoff.