2017
Options for glyphosate-resistant horseweed (marestail) management in soybean
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Contributor/Checkoff:
Michigan Soybean Committee
Category:
Sustainable Production
Keywords:
AgricultureCrop protectionHerbicide
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Christy Sprague, Michigan State University
Co-Principal Investigators:
Project Code:
1711
Contributing Organization (Checkoff):
Michigan Soybean Committee
$18,107
Institution Funded:
Michigan State University
$18,107
Brief Project Summary:

Horseweed continues to be a significant problem in many Michigan soybean fields. Resistance to ALS-inhibitors (Group 2), glyphosate (Group 9), and in many cases resistance to both of these classes of herbicides leaves no options for postemergence control of horseweed in Roundup Ready or non-GMO soybean. In addition to multiple herbicide-resistance, prolonged emergence, changes in tillage practices and capabilities of long distance seed dispersal have also contributed to the increased prevalence of horseweed in many of Michigan’s soybean fields. In 2016, we conducted a trial that examined possible fall and spring burndown strategies for horseweed control. One of the things that stood out...

Unique Keywords:
#weed control
Information And Results
Project Deliverables

Information from this research will be used to further develop and demonstrate recommendations for control of glyphosate-resistant horseweed to Michigan soybean growers. We will continue to hold meetings throughout the state to make growers aware of the issues and the options for control of this weed. The awareness from our outreach efforts will continue to be important to identify and manage this troublesome weed.

Final Project Results

Experiment 1: Glyphosate-resistant horseweed control in LibertyLink soybean
• This experiment was evaluated eight times, since planting. At each evaluation from May 19 to September 21 there has been new horseweed emergence. Peak emergence was around July 5. This continued emergence has made this weed extremely difficult to control.
• By 60 DAP, all burndown applications except Roundup and 2,4-D ester + Roundup provided greater than 80% horseweed control. The remainder of these treatments included a residual herbicide with horseweed activity or Shapen.
• After the POST application of Liberty all treatments that provided good burndown resulted in greater than 90% horseweed control by mid-August.
• Combination residuals metribuzin + Valor, metribuzin + Sharpen, or metribuzin + Spartan (Authority MTZ) all provided good residual control.

Experiment 2: Comparison of different burndown herbicide options for glyphosate-resistant horseweed in Roundup Ready 2 Xtend soybean
• The burndown options of XtendiMax at 22 and 44 fl oz/A, 2,4-D ester, Sharpen, and Liberty at 43 fl oz/A all provided greater than 90% control, 21 DAP. Elevore control glyphosate-resistant horseweed 85%.
• However, by 60 DAP only XtendiMax and Sharpen had greater than 90% control of the burndown only treatments. New emergence resulted in horseweed control that ranged from 44 to 86%.
• The addition of metribuzin at 8 oz/A to these treatments significantly improved control of all treatments, with the exception of those that were above 90%, 60 DAP.
• The POST application of XtendiMax + Roundup PowerMax resulted in greater than 95% control of horseweed following all of the burndown treatments, with the exception of the Roundup only burndown treatment (84%).

Experiment 3: Glyphosate-resistant horseweed management in Roundup Ready 2 Xtend soybean
• The residual herbicides of Valor at 2.5 oz/A, Valor + Metribuzin, Spartan at 8 oz/A, Spartan + Metribuzin, Authority MTZ, Trivence, and Zidua PRO included with XtendiMax + Roundup PowerMax provided 90% or greater control of glyphosate-resistant horseweed, 90 DAP (August 16).
• XtendiMax at 22 fl oz/A did provided some residual control, but control became less than 90%, 60 DAP.
• The residual of Metribuzin alone + XtendiMax + Roundup did not provided as long of control than the other residual treatments.
• Interestingly, several of these residual programs with the XtendiMax burndown did not need a followup of XtendiMax POST for horseweed control. This has been an extremely useful trial in demonstrating the importance of early applications of this technology, especially with the increased overall concern of the use of dicamba postemergence in RR2 Xtend soybean.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.