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Recent Ruling On Dicamba Products By The U.S. Court Of Appeals For The 9th Circuit
DR. KEVIN BRADLEY
COLUMBIA, MO.
On Wednesday of last 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 post-emergence weed control in Xtend-traited soybean and cotton. I had intended to hold off on writing anything about this until we knew more and until I received clarification from the Missouri Department of Agriculture (MDA), but the calls and emails keep coming in and MDA is still looking for guidance from the EPA on this issue. So briefly, here's all I can say about what I (think I) know at this time:
1. As I read and understand this ruling, it means that any farmer in Missouri who intended to use Xtendimax, Fexapan, or Engenia for weed control can NO LONGER legally do so as of June 3. Until we learn otherwise from MDA and/or EPA, it seems pretty clear that this is the stance we need to take at this point in time.
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. ∆
DR. KEVIN BRADLEY: Associate Professor, University of Missouri
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