by: Dr. Mark Loux, OSU Extension
Having to issue a retraction to previous C.O.R.N. article where we thought we had it right is always fun. About a month ago we ran an article that covered the legality of POST glyphosate and glufosinate applications to the LL-GT27 soybean, which is resistant to both herbicides. The issue at that time was the legality of applying a mix of both herbicides, based on questions we had received. Cutting to the quick, our conclusion was that because it was legal to apply the mixture since both herbicides could legally be applied and labels did not prohibit mixing. We were naïve apparently, because that article caused the issue over whether it was actually legal to apply glyphosate to the LL-GT27 soybean to be raised. Since then, ODA, USEPA, and the companies who are the involved registrants have been working to come to a solution that clarifies this issue and keeps us all moving forward toward a resolution. The issue here seems to be this – wording on most glyphosate labels specifies application is allowed to “Roundup Ready” and “Roundup Ready 2 Yield” soybeans, and since the LL-GT27 soybean is not designated as such, those glyphosate products could not legally be applied. After a month of deliberation, the USEPA issued some guidance which took the form of the following:
“Users of pesticide products containing glyphosate should refer to the pesticide product labels of herbicide products containing glyphosate for the specific registered uses on pesticide-resistant crops such as soybeans with glyphosate-resistant trait(s). Regardless of the herbicide product name (brand name), if the label of the glyphosate product states it is for over-the-top (post-emergent) use on glyphosate-resistant soybeans, and it is not otherwise restricted by other label statements/directions for use, it can be used on any soybean that has a glyphosate-resistant trait. However, if the label of the glyphosate product states it is for use on crops such as soybeans, with specific glyphosate-resistant traits by name, then the glyphosate product can only be used on those crop(s) with those traits specifically identified on the label. Ultimately, growers and commercial applicators must comply with the entirety of the pesticide label. Please let us know if you have any questions.”
Questions – yes – excuse us while we look for the head scratching emoji. We can try to interpret in real-life speak. Here’s what it comes down to:
– the important part of the glyphosate label here is the use-specific directions, or the section within the larger “Roundup Ready” part of the label that deals with soybeans.
– If the soybean section of the glyphosate product label does not mention specific genetics by trade name, but just the wording “glyphosate-resistant” or “glyphosate-tolerant”, then it is legal to apply that product to the LL-GT27 soybean.
– if the soybean section of the label restricts use to certain genetics by trade name – “Roundup Ready”, “Roundup Ready 2 Yield”, etc, then it would not be legal to apply to the LL-GT27 soybean.
– if the wording on the label is along the lines of “For Use on Soybeans with the Roundup Ready gene”, or similar wording with other specific genetics, it would not be legal to apply to the LL-GT27 soybean.
Our not exhaustive search through glyphosate product labels indicates that most if not all do not contain any wording about “glyphosate tolerance” in the soybean section, and indicate use is specifically on “Roundup Ready” or “Roundup Ready 2 Yield” or “Soybeans with the Roundup Ready gene”. This includes Roundup PowerMAX, Durango DMA, Abundit Edge, Credit Extreme, and Cornerstone to name a few. Manufacturer reps with a glyphosate product label that varies from this are free to contact us so we know.
The inability to use glyphosate on the LL-GT27 soybean affects primarily growers who bought it for the genetics or other traits and not the LibertyLink trait, who might have planned to use only glyphosate POST. Most of the utility of this soybean on problem broadleaf weeds comes from the LibertyLink trait though (and it’s definitely legal to apply glufosinate POST). There’s plenty of generic clethodim around to help out with grass. We assume label language will adapt over time to take care of the glyphosate issue. We’re not even sure this issue would have come up if we hadn’t tried to clarify the tank-mix legality and stepped right in it. There appeared to be some confusion in the field about this though, with different stories being told, and better to just clear it all up way in advance of the season. Stay tuned for the next chapter. Offer void where not legal. Legality may vary by state. Your mileage may vary. Side effects may include confusion, apathy, anger, and spontaneous profanity.