Agronomy Talk


Herbicide and Weed Management Briefs

Published on Friday, November 5, 2021


The more we add to the tank, the more chances antagonism can occur, especially when we tank-mix contact and systemic herbicides together. The larger weeds become, the greater the chance antagonism will occur. Grass or volunteer corn herbicides like clethodim can have antagonism, especially when mixed with certain Group 15 herbicides. One way to overcome the antagonism is to increase the clethodim rate to 12 oz. (2 lb. ai. product)/A. Products such as Enlist One® and Liberty® are very effective on glyphosate-resistant weeds like waterhemp and giant ragweed. However, Enlist One + Liberty will be weaker on grasses compared to Enlist One + glyphosate. One solution would be to add clethodim, but antagonism can occur when tank-mixed with Enlist One.


The plots highlighted above did not have a pre-emerge application to ensure enough vegetation was present at the post-emergence application timing. If the proper pre-emerge was utilized, the efficacy ratings could be higher. Selecting the proper residuals can help set up the post-emergence application for success. In 2021, Beck’s Practical Farm Research (PFR)® data showed Liberty® + 6 oz. (2 lb. ai.) of clethodim resulted in 90% control of fall panicum. The addition of Enlist One® to Liberty increased waterhemp control by up to 17%, thanks to the two effective SOAs. However, when Enlist One was added to Liberty + clethodim, we did see a reduction in fall panicum control. The addition of 4 oz. of clethodim to Enlist One + Liberty resulted in less than 60% fall panicum control. By increasing the clethodim rate to 8 oz., we saw a 30% increase in fall panicum control. Increasing the clethodim rate to 12 oz. resulted in the greatest fall panicum control when Enlist One was added to the tank. For fall panicum control, it took 8 to 12 oz. of clethodim to have similar results when Enlist One was added to the tank.


Tank-mixing Enlist One + Liberty resulted in the greatest waterhemp control. Enlist One + Liberty provides two effective SOAs for glyphosate-resistant (GR), weeds reducing selection pressure on both herbicides. Though we sacrifice grass control, the addition of clethodim at the proper rate did provide effective grass control. However, if the volunteer corn or grass becomes too large, a separate application may be the best option.



Adding Enlist One® to Liberty® and clethodim increased waterhemp control by up to 17%. By adding Enlist One to Liberty and clethodim, it took 8 oz. of clethodim (2 lbs. ai) to have comparable grass control. When tank-mixed with Enlist One + Liberty, increasing the clethodim rate from 4 to 8 or 4 to 12 oz. increased fall panicum control by 30% and 38%, respectively. If grasses or volunteer corn become too large, consider applying clethodim by itself.

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Jim Schwartz

Jim Schwartz

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