Agronomy Talk


Herbicide and Weed Management Briefs

Published on Friday, November 5, 2021


XtendFlex® provides farmers the opportunity to utilize an approved dicamba formulation such as XtendiMax® or Engenia®, as well as Liberty® and glyphosate. Though some of our problematic weeds are resistant to glyphosate, there are several that glyphosate remains highly effective against. Glyphosate is also strong on many of the weeds that Liberty is weak on, such as cocklebur, velvetleaf, and grasses. Growth regulators such as Engenia or XtendiMax will be highly effective on broadleaf weeds but have no activity on grasses. The XtendFlex system allows farmers the opportunity to utilize Engenia or XtendiMax in the pre-emerge or early post-emergence application, providing short-term residual with no potential crop response. An additional option could include applying Liberty, separately, in-season to control any escaped weeds.



Beck’s Practical Farm Research (PFR)® demonstration plots were conducted with no pre-emerge to ensure enough weeds were present at the post-emergence application timing. Not applying a pre-emerge herbicide resulted in lower ratings, showcasing why a pre-emerge herbicide with two to three “effective” SOAs must be utilized in any herbicide system. Utilizing The Power in the Pre™ would likely have resulted in fewer weeds, thus increasing the success of the post-emergence herbicide application. Beck’s recommendations for the XtendFlex® system shows greater than 90% waterhemp control when a pre-emerge with two to three SOAs was used, followed by Liberty® or Liberty + glyphosate in the post-emergence application. For the post-emergence only study, Liberty alone resulted in 85% control of waterhemp and 80% control of fall panicum by 28 DAT. Though clethodim does not have waterhemp activity, the addition of crop oil concentrate (COC) with clethodim did increase the crop response as well as waterhemp control.


The addition of clethodim increased Liberty’s control of fall panicum by 11%. Substituting clethodim with Roundup PowerMAX® provided another SOA for glyphosate-susceptible broadleaf weeds while still providing grass control. Compared to Liberty alone, Liberty + glyphosate increased waterhemp control by 11% and fall panicum control by 15%. Though the population was suspected to be resistant to glyphosate, we still had approximately 20% control on this waterhemp population. We did not see antagonism with Liberty + glyphosate. However, if grasses become too large or drought-stricken, Liberty and glyphosate should be applied in a separate application.


Engenia® or XtendiMax® can provide another effective SOA for glyphosate-resistant (GR) waterhemp. In a heavy weed pressure scenario, Engenia resulted in 83% control. However, Beck’s XtendFlex herbicide system study shows greater than 90% control when an effective pre-emerge herbicide was used, followed by Engenia + Roundup PowerMAX. Products like Flexstar® can provide control of GR waterhemp, but some populations may be resistant to PPO herbicides. Regardless, PPOs were still effective on the waterhemp population in which the study was conducted. The addition of Flexstar® to Engenia did increase waterhemp control by 4%.


The addition of Roundup PowerMAX® to Liberty® increased waterhemp control by 11% and fall panicum by 15%. Adding glyphosate to Liberty resulted in broader spectrum control in comparison to clethodim. However, glyphosate will not control glyphosate-tolerant volunteer corn. When spraying Liberty + glyphosate, run a 1:1 ratio (32 oz. Liberty: 1.125 lb. a. e. glyphosate), 2-3 lbs AMS, 20 Gal./A. on weeds less than 4 in. tall. Tank-mixing Flexstar with Engenia increased waterhemp control by 4%.

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Jim Schwartz

Jim Schwartz

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