What if Engenia®, FeXapan® or Xtendimax® are Not an Option for Soybean Weed Control?
Recently the 9th Circuit Court vacated the labels for Engenia®, FeXapan® and Xtendimax® in soybean. What does that mean?
In Oklahoma, as it currently stands, existing stocks of Engenia®, FeXapan® and Xtendimax® may be applied to Roundup® Ready Xtend cotton and soybean through July 31, 2020.
What are my options if I haven’t already purchased dicamba or need to make an application after July 31st?
Currently the following products are labeled for over-top-applications in Roundup® Ready Xtend soybean:
- Roundup® (Glyphosate)
- Cadet®, Cobra®, ET®, Reflex® (fomesafen), Resource® and UltraBlazer®
- Classic®, FirstRate® and Pursuit®
- Assure II®, Fusilade® DX, Poast® and Select® (Clethodim)
Tavium® is a premix of dicamba and metolachlor. It was not included with the 9th Circuit Court ruling because it was not labeled at the time of the case filing. It is the only dicamba formulation that currently has a federal label for use in Xtend crops. Tavium® has the added benefit of including metolachlor for additional residual weed control. Depending on the weed spectrum in your area, it may be beneficial to include glyphosate with this herbicide. Controlling small weeds will still be important for success with this herbicide. Special precautions and label restrictions apply to Tavium® as with the other dicamba formulations. Tavium® can be applied over-the-top through the V4 growth stage or within 45 days after planting, whichever comes first. The preharvest interval on cotton is 100 days prior to harvest. No applications can be made to double crop soybeans.
Roundup® (glyphosate) is a non-selective herbicide that has activity on a wide range of weeds including both broadleaves and grasses. The current issue with Roundup® is the number of fields that have weeds resistant to this herbicide. However, there are many weeds currently in soybeans (especially grasses) still controlled by Roundup®. Therefore, this may still be an effective tank mix partner with other postemergence herbicides.
Cadet®, Cobra®, Reflex® (fomesafen), Resource® and UltraBlazer® herbicides (PPO) have activity on many problem broadleaf weeds in Oklahoma. Prior to introduction of Xtend soybean, these were the backbone products for control of glyphosate and ALS resistant weeds in Roundup® Ready soybean. Controlling small weeds (2 to 4 inches) is critical to the success of these herbicides, especially pigweed. Reflex is the only one of these products with significant residual activity. Future rotational crops should be considered when using Reflex®.
Classic®, FirstRate® and Pursuit® herbicides (ALS) have activity on several broadleaf weeds in Oklahoma. These herbicides provide postemergence as well as residual weed control on several weeds. Timing based on weed size is extremely important for postemergence weed control with ALS herbicides. Many weeds require applications to be made prior to 2 inches in height. The biggest weakness is ALS-resistant weeds including Palmer pigweed and tall waterhemp.
Assure II®, Fusilade® DX, Poast® and Select® (clethodim) will control most grass species when applied postemergence. These herbicides do not provide any activity on broadleaf weeds like pigweed. Size of grass control will vary by species and herbicide applied. However, except for rhizome Johnsongrass, control is generally better on grasses less than 6 inches in size.
Producers who have not planted soybeans yet may want to reevaluate their current preemergence program. A preemergence herbicide program that contains two or three different active ingredients may be the most effective option this year. Additionally, growers may want to consider adding a residual herbicide to their postemergence applications to improve season-long control.
Consult all herbicide labels for restrictions, weed size, crop stage, use rates, tank mix partners and herbicide adjuvants needed. It is also important to read labels for preharvest and crop rotation intervals.
Weed Science Extension Specialist
Weed Science Extension Specialist