Agronomy Talk

Controlling Waterhemp with the RR2X System

Keys to Success

Published on Wednesday, November 6, 2019

Why Weed Control So Important

University data has shown that soybean yields can be reduced by up to 35% due to competition with weeds. Problematic weeds such as waterhemp can produce over 800,000 seeds/plant while marestail can produce over 200,000 seeds/plant. Therefore, a handful of escapes can lead to a substantial increase in the seed bank, making future management more difficult.


The Foundation of a Successful Weed Control Program

Start Clean. If heavy weed pressure is present, a burndown should be applied before planting. The burndown is the perfect opportunity to use different sites of action (SOAs) or active ingredients that won’t be used for the rest of the season. Every herbicide group will have strengths and weaknesses when it comes to weed control, so selecting residual products for the specific weeds that you face on your farm is important. Choosing products with multiple SOAs will provide many benefits including; 1) broader weed control 2) the opportunity to use more than one “effective” SOA and 3) longer residual activity.

When evaluating fields 45 days after treatment, Beck’s PFR data shows a 29% increase in waterhemp control when using two SOAs pre-emerge vs. just one SOA. Increasing the pre-emerge treatment from one SOA to three SOA resulted in a 47% increase in control. The best way to control weeds is to never let them emerge in the first place.

Untreated soybean field
Untreated Control

Zidua® Pro 45 DAT

Fierce XLT® 45 DAT

Warrant® Ultra 45 DAT

Power in the Pre™. If tough-to-control weeds are present at the time of planting, consider adding Xtendimax® Herbicide with VaporGrip® Technology or Engenia® to your program. Both herbicides can be added to an approved tank-mix pre-emerge (add approved DRA if required) product to increase the control of waterhemp, marestail, and giant ragweed. Dicamba products such as Xtendimax will also provide up to 14 days of soil activity to control weeds that are present while also reducing future weeds when paired with an approved tank-mix pre-emerge application or an in-season residual as a post-emergence application.

*An approved tank-mix DRA was added*

Untreated Control

Engenia® + Roundup PowerMAX® - 35 DAT

In-Season Residuals. Crop canopy closure is one of the best ways to fight weeds. However, we may not always have crop canopy closure by the time the residual begins to break down. Group 15 herbicides such as Dual II Magnum®, Outlook®, Warrant®, and Zidua® can provide in-season residual activity.

Group 15s are most effective in controlling grasses and small-seeded broadleaf weeds like waterhemp. These products will provide roughly four weeks of activity, allowing enough time for full canopy closure. Beck’s PFR data shows a 6% increase in weed control at the end of the season when a Group 15 was used in season. Though 6% may not sound substantial, remember that a waterhemp plant can produce over 800,000 seeds and thus, just a few plants will result in millions of seeds that can remain viable in the soil for four to six years.

Freedom in the Post. Contrary to popular belief, you can have success with the Roundup Ready® Xtend Crop System without using dicamba in your post-emergence application. By using Xtendimax or Engenia in your pre-emerge, you will have the freedom to come back with a different herbicide and still obtain very effective post-emergence weed control. In-season products that contain fomesafen such as Flexstar® and other PPOs such as Cobra® or Ultra Blazer® are great post-emergence options for waterhemp control when targeting weeds 4 in. or less. But because some populations may be resistant to PPOs in the post-emergent application, applying the pre-emerge is very important.

The success of your pre-emerge program also depends on getting enough rain for activation and also how much rain occurs throughout the season. Other crucial keys to controlling waterhemp are using an in-season residual and planting early to ensure early canopy closure. The photos below demonstrate that early planted soybeans that received a successful pre-emergence application still obtained successful weed control at the end of the season, even waterhemp is suspected to be resistant to Cobra and glyphosate. However, the Roundup Ready Xtend System provides the flexibility for farmers to utilize other control options such as Xtendimax and Engenia. If your in-season residuals do not provide the protection you need, a post-emergent application of Xtendimax or Engenia can be used to control any weeds that have escaped.

Fierce® MTZ at Harvest

Warrant® Ultra at Harvest

Trivence® at Harvest

Authority® MTZ at Harvest

*All treatments were sprayed with Cobra and Roundup PowerMAX.
Waterhemp population is suspected to be resistant*

I encourage you to check out this great video by Cody Evans, Weed Management Tech Development Rep with Bayer, to learn more about the value of a proper burndown and what type of soil activity you can expect when using XtendiMax and the Roundup Ready Crop System.


Contact your local Beck’s representative to learn how to successfully manage your Roundup Ready 2 Xtend soybean fields in 2020.



Fierce® and Cobra® are registered trademarks of Valent USA LLC. Zidua®, Engenia®, and Outlook® are registered trademarks of BASF. Warrant® and Roundup PowerMAX® are registered trademarks of Monsanto Technology LLC. Trivence® is a registered trademark and service mark of Dow AgroSciences, DuPont or Pioneer, and their affiliated companies or their respective owners. Authority® is a registered trademark of FMC Corporation. Xtendimax®, Vapor Grip®, and Roundup Ready Xtend® are registered trademarks of Bayer Group. Dual II Magnum® and Flexstar® are registered trademarks of Syngenta. Ultra Blazer® is a registered trademark of UPI-USA.


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Author: Joe Bolte

Categories: Agronomy, Agronomy Talk


Joe Bolte
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