October 25, 2024
At a Glance
- Soybean growers must be conscious of the various weed resistances that they may have on their farms.
Earlier this year, a federal district court vacated the Engenia, Tavium and Xtendimax labels. As it stands right now, growers will not be able to legally use any of these products for soybean weed control in 2025. It is anybody’s guess what will happen with these dicamba registrations in 2025.
So, how can soybean growers manage weeds in the absence of dicamba in 2025?
Before I go any further, soybean growers must be conscious of the various weed resistances that they may have on their farms. This will determine what herbicides can be successfully used in a soybean weed control program without dicamba.
For example, PPO-resistance will negate products such as Valor (flumioxazin), Reflex (fomesafen), Cobra (lactofen), and Ultra Blazer (acifluorfen). ALS-resistance will limit the use of herbicides such as Classic (chlorimuron), FirstRate (chloransulam), Pursuit (imazethapyr), and Python (flumetsulam). I am including common names of herbicides in this article because there are also many generic formulations available.
Regardless of herbicide system, all soybean growers will benefit from starting clean -- using deep tillage, cover crops, herbicides -- planting in narrower rows (< 30”), and being timelier with postemergence (applications (weeds ≤ 3”).
I am a huge fan of narrow rows since they usually result in less late-season weed densities and higher yields. UGA research over the years has shown that soybean yields can be improved an average of 13% in narrower rows.
The key to a successful weed management program is a strong preemergence program. Soybean growers have many powerful PRE herbicides including:
Authority MTZ (sulfentrazone + metribuzin)
Authority XL (sulfentrazone + chlorimuron)
Boundary (metribuzin + S-metolachlor)
Canopy (metribuzin + chlorimuron)
Envive (flumioxazin + chlorimuron + thifensulfuron)
Fierce (flumioxazin + pyroxasulfone)
Fierce MTZ (flumioxazin + metribuzin + pyroxasulfone)
Surveil (flumioxazin + chloransulam)
Tendovo (metribuzin + S-metolachlor + chloransulam)
Tricor (metribuzin), Trivence (flumioxazin + metribuzin + chlorimuron)
Valor
By the way, it’s no coincidence that I mentioned metribuzin 7 times.
Where resistance is not an issue, the Group 15 herbicides are still very functional residual herbicides [Anthem Maxx (pyroxasulfone + fluthiacet), Dual Magnum (S-metolachlor), Outlook (dimethenamid-p), Warrant (acetochlor), and Zidua (pyroxasulfone)].
The yellow herbicides [Prowl (pendimethalin), Sonalan (ethalfluralin), and Treflan (trifluralin)] are also still on the soybean weed control table.
As for POST weed control in absentia of dicamba, I suspect that there will be significant increases in the use of Liberty (glufosinate) products and Enlist One (2,4-D choline).
Eric Prostko
Got sicklepod and morningglory? Don’t forget about Classic and FirstRate.
A friendly reminder that it would not be a great idea for PPO-resistance management to use a Valor-type herbicide PRE followed by a POST application of Cobra, Reflex or Ultra Blazer.
I would also like to remind growers that not too many moons ago, weed control in conventional soybeans was not impossible. See figure 1.
For sure, it is not a good thing when growers lose herbicide labels. Effective weed management is all about options. Fortunately, soybean farmers have options other than dicamba. Now is the time to develop your game plan.
As always, good weed hunting!
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