Enlist One and Enlist Duo Re-Registration: What Do We Need to Know?

by Tommy Butts, Extension Weed Scientist, Tom Barber, Extension Weed Scientist, and Jeremy Ross, Extension Soybean Agronomist - January 18, 2022

UPDATE — Some of the labeling guidelines below were amended by the US EPA on March 29, 2022. Find details in the blog post for the Enlist Herbicide Update.

Enlist herbicides [Enlist One (2,4-D choline) and Enlist Duo (2,4-D choline + glyphosate)] were recently granted amended seven-year registrations for over-the-top applications on Enlist corn, cotton, and soybean. This is great news for individuals who are using the Enlist cropping system. However, there were numerous counties (including several in western Arkansas) in which the use of Enlist herbicides has been prohibited by the EPA due to their updated Endangered Species Act risk assessment. Additionally, there were some new labeling guidelines everyone should be aware of that were implemented to reduce the impacts of off-target and runoff movement.

Both Enlist One and Enlist Duo are officially prohibited from being used in the following 11 Arkansas counties at this time (Fig. 1):

• Crawford
• Franklin
• Johnson
• Little River
• Logan
• Montgomery
• Polk
• Scott
• Sebastian
• Sevier
• Yell

Counties in Arkansas that are NOT listed above, do not fall under these restrictions and Enlist herbicides are permitted for use in accordance with the label.

Fig. 1. Counties (shaded in blue) in which Enlist herbicides are prohibited in 2022.

This is extremely unfortunate news for growers in these counties. With glufosinate (Liberty) prices skyrocketing and its limited availability for 2022, the ban on Enlist herbicides leaves minimal if any, effective POST herbicide options for PPO-inhibitor-resistant Palmer amaranth control. If you farm in the affected counties listed above and had Enlist crops in your plans for 2022, we recommend the following:

• Start clean; make sure to effectively eliminate weeds that emerged prior to planting.
• Use a strong residual program with multiple, effective modes of action. Soybean pre-mix products such as Trivence, Boundary, and Fierce, among others, and cotton tank-mixtures of Cotoran, Caparol, or Diuron + Brake are great candidates and will also control a diverse weed spectrum.
• Overlap residuals (Dual Magnum, Zidua, Outlook, etc.) between 2 and 3 weeks after the PRE application. Reduce or eliminate the need for POST products as much as possible.
• If you have access to and the budget allows, use an application of glufosinate (Liberty) to clean up your field. If PPO-inhibitors are still effective on your Palmer amaranth, Flexstar would be a great option POST in soybean for multiple weed species that also includes some residual activity.
• If pigweed is PPO-inhibitor-resistant and glufosinate is not viable this year, consider switching to an XtendFlex variety. Dicamba rules have remained unchanged from last year, so the cutoff remains June 30, but be aware of surrounding crops and other vegetation, and make sure to follow all label requirements.

Other changes to the Enlist labeling affecting all applicators are aimed at reducing the potential risk of non-target species, mitigating runoff, and protecting pollinators. These federal changes and additional information regarding the seven-year EPA registrations can be found in this article, New Enlist Registrations: EPA Gives Enlist Herbicides New Seven-Year Registrations, or visit the Enlist Weed Control System website at https://www.enlist.com.

Additionally, the EPA noted in their news release that the new Enlist registrations are among the first herbicides to have undergone a full EPA analysis of their effect on endangered species and critical habitats. As a result, we all must be aware moving forward that these area/county-wide bans may become more commonplace with future herbicide registrations and re-registrations.