Published on Friday, May 22, 2020
Farmers are itching to get back into the fields after recent rains and to finish soybean planting for 2020. As we start to put planting into road gear, we are focused on finishing the job, but what about the next step in weed management? As planting is delayed, the June 20 cut off for applications of dicamba inches closer for some states in the Midwest.
How does the cutoff date influence my weed management strategy in Roundup Ready 2 Xtend® soybeans?
If a strong foundational pre-emerge program with multiple effective SOA’s are used up front, we typically like to see the post-emergence applications applied 21 to 24 days after planting. However, as we start to plant soybeans in early June, we will not have 21 to 24 days before the June 20 cutoff in part of the Midwest.
So, what should I do with the Xtendimax® or Engenia® that I had planned in my POST trip?
Consider one weed that is also ready to jump in road gear: waterhemp. The delayed planting has allowed many fields to have large flushes of waterhemp as well as other summer annuals. Therefore, XtendiMax or Engenia could be added to an approved pre-emerge herbicide to control the flushes of waterhemp and to provide additional soil activity. For the post-emergence application, apply an in-season residual, such as a Group 15 herbicide, 21 to 24 days after the pre-emerge application. We need the in-season residual applied before the pre-emerge herbicide breaks down and prior to crop canopy to allow the herbicide to reach the soil. This provides another layer of protection to reduce new flushes of weeds.
If glyphosate-resistant weeds such as waterhemp are a concern, consider using a Group 14 + 15 pre-mix such as Warrant® Ultra or Prefix®. The PPO component in those herbicides is fomesafen, and it will provide POST activity, while the Warrant will provide in-season residual protection. Fomesafen or Flexstar-containing products will have a plant back restriction to corn. If this is a concern, consider using another Group 14 herbicide such as Cobra® or Ultra Blazer®. Some populations of waterhemp have developed resistance to POST-applied Group 14 herbicides. Therefore, preventing emergence is critical.
Example of a Dicamba-based herbicide program
Authority® XL or Valor® XLT
Xtendimax® Or Engenia®
*Use Prefix or Warrant Ultra if GR weeds have emerged. Warrant Ultra and Prefix will have a plant back restriction to corn
Whether Xtendimax or Engenia is planned, there is Power in the Pre™. Starting with an effective pre-emerge with multiple effective SOAs for the weeds you face is the key to success.
If no dicamba is planned, consider adding Gramoxone®, or another burndown product that has no plant back restriction, to your pre-emerge. Also, some pre-emerge herbicides will have greater burndown activity compared to others. Products such as Zidua® Pro contain Sharpen® and will result in great burndown activity as well as residual control. Some other products that contain good residual control with some burndown activity are Valor® XLT, Fierce® MTZ, Fierce® XLT, Trivence®. However, approved burndown tank mix partners may be needed in heavy pressure or large weed scenarios. In heavy weed pressure scenarios, apply a burndown before the pre-emerge to ensure the pre-emerge herbicide makes it to the soil.
Example of a herbicide program without dicamba
Zidua® Pro or Fierce® MTZ or Fierce® XLT or Trivence® or Valor® XLT
**Apply using the appropriate adjuvant
For more details and insights into soybean herbicide programs, please see our complete Recommended Soybean Herbicide Programs.
Author: Joe Bolte
Categories: Agronomy Talk