Comparing Soybean Herbicide Trait Fit
Broadleaf weed control of a synthetic auxin herbicide applied to appropriate soybean herbicide trait system.
Weed management in soybeans has become more challenging over the last decade as the broad-spectrum control of glyphosate has become less consistent due to weed resistance. This has increased complexity when developing weed management plans. Recent introductions of soybean herbicide traits have provided new management options but have also increased the knowledge base required to determine the appropriate one. Even with new trait options, fundamental weed management practices are still critical to achieving good weed control:
- Start clean: Tillage or burndown herbicides are essential to control emerged weeds prior to crop emergence.
- Residual control importance: Preemergence herbicides with residual activity help minimize seedbank emergence early in the season, allowing crop canopy to establish quickly and reduce later weed emergence.
- Post-spraying within labeled weed heights: Residual herbicides help delay weed emergence and minimize weed height at the time of post-emergence spray applications. Post-emergence control is greatly improved when herbicides are applied to smaller weeds.
Marestail, ragweed, waterhemp and Palmer amaranth are widely known to be resistant to many of the same herbicide groups in various combinations. Enlist E3® soybeans, Roundup Ready 2 Xtend®, XtendFlex® and LibertyLink® GT27® traits provide additional advantages for managing biotypes of weeds resistant to Groups 2,5,6,7,9,14 and 27 herbicides.
Considerations for Selecting a Soybean Trait Option
- Complimentary herbicide combinations based on individual weed species effectiveness: Each individual field has different combinations of problematic weeds to control. Understanding weed seed banks can help determine the best soybean herbicide trait platform to enable herbicide options that provide the greatest overall weed control. The weed control efficacy chart (Table 1) illustrates the strengths of herbicides labeled for use within specific herbicide trait systems. Depending upon the weed species, an individual or combination of herbicides may have unique advantages.
The ability to apply an approved synthetic auxin (2,4-D and dicamba) or Liberty® herbicides provides unique control advantages with waterhemp, Palmer amaranth and giant ragweed resistant to glyphosate and other herbicides. (Chart reflects glyphosate efficacy on non-resistant weed species.) Post-emergence herbicide plans should take the frequency of glyphosate resistance into consideration and use specific herbicides that have effective sites of action.
- Burndown options: Managing emerged weeds prior to crop emergence in no-till systems is important. Herbicides such as glyphosate, 2,4-D Ester, dicamba, Liberty or Paraquat can provide great options for managing winter annuals and perennial weeds prior to planting. Planting intervals restrict how soon planting can occur after burndown applications when using 2,4-D or dicamba herbicides. Roundup Ready 2 Xtend, XtendFlex and Enlist E3 soybeans trait systems provide additional options to use approved dicamba and 2,4-D herbicides respectively (not interchangeable) when burndown and planting dates need to occur closer together. The extended planting interval restrictions for dicamba herbicides likely limit the usage for burndown unless planting Roundup Ready 2 Xtend or XtendFlex soybeans and using approved formulations.
- Post-tank mix flexibility: Simultaneously controlling emerged grass and broadleaf weeds in a single application is highly advantageous. Glyphosate provides excellent grass control, but due to the number of broadleaves weed species that have become resistant to glyphosate, it is increasingly important to include a second mode of action for effective broad-spectrum control. Repeated use of approved dicamba or 2,4-D herbicides as a single effective mode of action on glyphosate-resistant weeds will only further increase weed resistance selection pressure.
An advantage of Enlist E3 soybean systems is the ability to spray Liberty (or glufosinate) and approved Enlist herbicides in combination, giving 2 effective modes of action against glyphosate-resistant weeds. XtendFlex soybeans also provide tolerance to dicamba and Liberty; however, there are currently no approved dicamba + Liberty tank mix combinations. Spray volume and nozzle requirements needed for Liberty are not generally well suited for dicamba-based herbicide tank mixes. Current dicamba label restrictions limit over-the-top application before June 30th, restricting the opportunity to apply tank mix combinations of any sort during late vegetative and early reproductive stages.
- Application and stewardship requirements: Enlist Duo® applied to Enlist E3 soybeans offers the least restrictive application window (through R2) of all 3 systems. Adding Liberty further limits applications to R1. Over-the-top applications of dicamba-based herbicide to Roundup Ready 2 Xtend or XtendFlex varieties must be applied by June 30th regardless of growth stages. In some cases where planting of Roundup Ready 2 Xtend or XtendFlex soybeans are delayed, there may not be any opportunity to apply dicamba post-emergence or the window for application will be very short, depending on emergence date.
- A key difference between the 2 systems is the 240 and 310-foot downwind sensitive area buffer requirements of Xtend in comparison to the 30-foot downwind requirement for Enlist.
- In addition to distance, it is acceptable to spray Enlist herbicides when wind is blowing toward soybeans without the Enlist trait, although it is not acceptable to spray Xtend herbicides if wind is blowing in the direction of soybeans without the Xtend trait.
Stewardship requirements may be complex and unique to each field and herbicide system being used. To ensure correct application, refer to the product use guides of each trait system and herbicide labels for specific requirements.
Overall Program Effectiveness Summary
Each herbicide trait system offers advantages over glyphosate-only options. However, a holistic comparison of all 3 systems favors Enlist E3 soybeans over the other 2 systems for the following reasons:
- The cumulative “excellent” efficacy ratings across key weed species when applying Enlist One® + Liberty outnumber dicamba + glyphosate herbicides “excellent” ratings.
- The flexibility to tank mix post-applications of Enlist One herbicide with Liberty or glyphosate (premix of Enlist Duo).
- Enlist One + Liberty provides more effective modes of action for glyphosate-resistant weeds in a single application than if using approved dicamba herbicides or Liberty separately.
- Enlist Duo provides a wider window of application than other systems.
- There is less risk of off-site movement with Enlist One than approved dicamba herbicides.
- Enlist herbicides are not restricted use and do not require special applicator certifications whereas approved dicamba herbicides do.
- There are less restrictive stewardship requirements than with Xtend soybean systems.
- There is no planting interval restriction after application of 2,4-D herbicides with Enlist E3 soybeans, whereas LibertyLink GT27 has restrictions.
For additional insights into available soybean traits, contact your local NK Sales Representative.
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©2021 Syngenta. Important: Always read and follow label and bag tag instructions; only those labeled as tolerant to glufosinate may be sprayed with glufosinate ammonium based herbicides.
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Under federal and local laws, only dicamba-containing herbicides registered for use on dicamba-tolerant varieties may be applied. See product labels for details and tank mix partners. Golden Harvest® and NK® Soybean varieties are protected under granted or pending U.S. variety patents and other intellectual property rights, regardless of the trait(s) within the seed. The Roundup Ready 2 Yield® and Roundup Ready 2 Xtend® traits may be protected under numerous United States patents. It is unlawful to save soybeans containing these traits for planting or transfer to others for use as a planting seed. Only dicamba formulations that employ VaporGrip® Technology are approved for use with Roundup Ready 2 Xtend® soybeans. Only 2,4-D choline formulations with Colex-D® Technology are approved for use with Enlist E3® Soybeans. The trademarks or service marks displayed or otherwise used herein are the property of a Syngenta Group Company. All other trademarks are the property of their respective owners. More information about Agrisure Duracade® is available at http://www.biotradestatus.com/