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Serving: MO
Bradley-SIZED.jpg University of Missouri Extension
SCIENTIST SPEAKS: Over the years, University of Missouri Extension state weed specialist Kevin Bradley has given talks regarding dicamba crops and damage during field days and farmer meetings. He is offering his take on the latest California court ruling on three dicamba products.

MU weed scientist Kevin Bradley weighs-in on court’s dicamba ruling

There are weed control options for those who planted dicamba-tolerant crops.

On Wednesday of this week, the U.S. Court of Appeals for the 9th Circuit vacated the labels of XtendiMax, FeXapan and Engenia, which are three of the primary products that are used for postemergence weed control in Xtend-traited soybean and cotton. 

Here is the most recent information I have available at this time:

1. UPDATED: On June 8, the EPA released a statement allowing some use of these chemicals through July 31, 2020. The details can be found here: epa.gov/newsreleases

2. This ruling does not apply to Tavium, which is an approved dicamba product registered for use on Xtend crops that contains dicamba + S-metolachlor (Dual II Magnum). Tavium can be applied up to the V4 growth stage of soybeans or within 45 days after planting, whichever comes first. Tavium can also be applied through the 6-leaf stage of cotton or within 60 days after planting, whichever comes first.

3. Our biggest weed problem in the state of Missouri is waterhemp, which occurs as the predominant weed in most fields everywhere outside of the bootheel of Missouri. In the bootheel, the predominant weed is Palmer amaranth. Both of these species exhibit wide-scale resistance to post-emergence applications of the group 14, PPO-inhibiting herbicides, as well as glyphosate and other herbicides. For this reason, in my opinion the most effective post-emergence herbicide option remaining in Xtend soybean would be Tavium. But keep in mind, this can only be applied up to the V4 growth stage in soybean. As far as non-dicamba options, the next best option for control of these species would be a tank-mix of glyphosate plus one of the group 14 PPO-inhibiting herbicides like fomesafen (Flexstar, others), lactofen (Cobra, others), or acifluorfen (Ultra Blazer) with the understanding that PPO-resistant populations will not be controlled. The addition of a group 15 herbicide to this mix will provide residual control of any pigweeds that might emerge after the application, but will not control emerged pigweeds that are present at the time of the post-emergence application. Regardless of the post-emergence mix you use, making applications to pigweeds that are less than 4 inches in size is critical.

4. I expect there will be appeals and there could be some changes to all of this in the near future, but we will just have to wait and see. We will update you and provide recommendations as we learn more.

Bradley is the University of Missouri Extension state weed specialist. This article appeared in the latest Integrated Pest Management newsletter.

 

TAGS: Soybeans
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