Last winter, I presented seven years of data collected by the WiscWeeds team, compiled and summarized by our Research Specialist and Wisconsin Herbicide Evaluation Program Coordinator, Ryan DeWerff. Based on our southern Wisconsin field trials, when a robust PRE-emergence herbicide program is applied at planting or shortly after, and the POST application of Enlist One + Liberty (don’t forget the AMS) is made in late June, targeting waterhemp at 3 inches or less, and the soybean crop is at V4 or later, we consistently observe no added benefit from including a Group 15 herbicide (e.g., Dual II Magnum, Outlook, Warrant, Zidua) in the POST tank mix.

So, should you include a Group 15 herbicide? Ask yourself the following:

• Did I spray a strong PRE or early-POST residual herbicide program?
• Is the soybean crop at V4 or more advanced?
• Is the soybean canopy on track to close within the next two weeks?
• Are you seeing only established waterhemp and no new flushes?

If you answered YES to all, our Wisconsin research suggests you can skip the Group 15 herbicide in your POST application. Apply Enlist One + Liberty, and move on.

If you answered NO to one or more, including a Group 15 herbicide is advisable to extend residual control and reduce the risk of late-emerging waterhemp.

A few additional considerations:

• If volunteer corn is present, include a graminicide (e.g., clethodim) at a higher rate to overcome antagonism with Enlist One.
• If annual grasses (other than volunteer corn) are less than 3 inches, Liberty alone (don’t forget the AMS) should provide effective control.
• If annual grasses are taller than 3 inches, consider adding a grass rate of glyphosate to achieve effective control.

Hope this helps support your soybean weed management decisions and improves both effectiveness and cost-efficiency of your program.