Database Research Summaries
Tracking Herbicide resistant weeds and managing Xtend Soybeans

calendar_today Year of Research: 2017
update Posted On: 05/23/2019
group Bryan Young (Lead Investigator, Purdue University)
bookmark Indiana Soybean Alliance

Research Focus

The widespread weed resistance to multiple herbicides, primarily glyphosate has resulted in challenges in weed management practices. To ensure continued successful soybean production, the scope of herbicide resistance must be determined to successfully deploy more robust weed management strategies, including the introduction of new herbicide-resistance traits in soybean.

PPO-Resistant Waterhemp 30 counties
Glyphosate-Resistant Waterhemp 37 counties

The focus of this project is to track and record the presence of weeds in agricultural fields resistant to herbicides commonly used, while determining adaptability of the Roundup Ready Xtend soybean variety can provide to Indiana soybean growers dealing with weed resistance.


  • Document the distribution of Palmer amaranth, waterhemp, giant ragweed, horseweed and other emerging weeds that are resistant to glyphosate, PPO inhibiting herbicides, and other key herbicides.
  • Identify and demonstrate best management practices for Roundup Ready Xtend soybeans for Indiana.


  1. The weed samples submitted identified waterhemp as the primary weed of concern with suspected resistance to commonly used PPO-inhibiting herbicides, such as Cobra or Flexstar.
  2. Further findings concluded herbicide resistant (both glyphosate and PPO) waterhemp in the southwest, northwest and central regions of Indiana with areas expected to continue expanding.
  3. 1,400 individuals viewed our field demonstration trials on weed management and findings from those trials were incorporated into extension presentations.
  4. Analyzed weather patterns such as wind speeds and temperature inversions for safe, legal applications of dicamba. Related research funding has been leveraged to quantify the off-target movement of dicamba in commercial applications.


  • Information concerning the spread of herbicide resistant weeds is necessary for growers to form sustainable weed management plans.
  • Growers need to diversify management tactics to combat the growing presence of herbicide-resistant weeds.
  • Xtend soybean technology can be a great benefit to growers, but only if off-target movement of dicamba can be limited.

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

Funded in part by the soybean checkoff.