Database Research Summaries
2018 Glyphosate-resistant horseweed (marestail) management in soybean

calendar_today Year of Research: 2018
update Posted On: 12/04/2019
group Christy Sprague (Principal Investigator, Michigan State University)
bookmark Michigan Soybean Promotion Committee

Research Focus

The focus of this project is to conduct several trials that will expand and strengthen current horseweed management recommendations.


  • Evaluate the effect of the fall planted cover crops, cereal rye and winter wheat, at two seeding rates on the suppression of glyphosate-resistant horseweed in no-till soybean.
  • Compare the integrated approaches of the combination of cover crops with different herbicide strategies with the herbicide programs alone on horseweed management.
  • Evaluate the effectiveness of various herbicide programs in LibertyLink soybean.
  • Evaluate the effectiveness of various herbicide programs using dicamba (XtendiMax) in Roundup Ready 2 Xtend soybean for management of glyphosate-resistant horseweed.

Provide this new and additional information on the management of herbicide-resistant horseweed to Michigan soybean producers.


  1. There was a difference in the baseline seed number and distribution between in the two years. Higher amounts of waterhemp seed were counted in 2017 compared with 2018 and more seed was found in the upper 2-inches in 2017.
  2. Higher seed numbers were found in the 2-7 inch samples in the moldboard plowed treatments (33-35% more) in the prior to planting soil samples. These numbers ended up being 11 and 65% less seed in the spring tillage and no-till treatments that than moldboard plow treatments by the at harvest sampling period.
  3. The soil-applied (PRE) herbicide treatment of Fierce at 3 oz/A in the standard and high management treatments provided good to excellent waterhemp control for six weeks.
  4. In conclusion, moldboard plowing reduced the number of seeds in the upper 2” of the soil at planting and waterhemp emergence was earlier and more uniform.
  5. There was significant variation in the initial control and the length of residual activity for the different soil-applied herbicides.
  6. Overall from two years of this research the LibertyLink and Roundup Ready 2 Xtend systems were more effective than the Roundup Ready systems.


  • This research will be important to provide effective information to soybean growers to help manage this troublesome economically significant weed problem.
  • This research will provide additional control strategies and herbicide options to aid in the management of a weed that has the ability to develop resistance to multiple-herbicide sites of action.

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

Funded in part by the soybean checkoff.