In the last 30 years, there haven't been any new modes of action (MOAs) introduced from chemical companies. However, recently, growers have some new tools available to them to mix up their MOAs using existing technologies, notes Debalin Sarangi, weed science postdoctoral research associate at the University of Nebraska-Lincoln.

"Many of them have one or two new active ingredients, but no new mode of action. They're using the same herbicide chemistry we've had for last few decades, just making a cocktail," Sarangi says. "In one herbicide premix, you get multiple modes of action, and it can provide a broad-spectrum weed control."

COCKTAIL MIXES: Debalin Sarangi discusses new premix herbicide technology at a recent Weed Management Field Day at UNL's South Central Agricultural Lab. "Many of them have one or two new active ingredients, but no new mode of action. They're using the same herbicide chemistry we've always had, just making a cocktail," Sarangi says.

At a recent Weed Management Field Day at UNL's South Central Agricultural Lab near Clay Center, Sarangi outlined some of these new technologies, including Syngenta's Acuron, FMC's Anthem Maxx and Bayer Crop Science's DiFlexx Duo.

Acuron has four active ingredients and three modes of action, including atrazine (AAtrex), S-metolachlor (Dual II Magnum), mesotrione (Callisto) and bicyclopyrone — a new active ingredient which provides residual and burndown control, giving growers additional options for broad-spectrum weed control. Acuron may be used preemergence or early postemergence in field corn, seed corn and silage corn to control annual grasses and problematic broadleaf weeds including glyphosate-resistant common waterhemp, giant ragweed, marestail and Palmer amaranth. It can be used in sweet corn and yellow popcorn, but only preemergence.

Then there are Bayer Crop Science's DiFlexx Duo and FMC's Anthem Maxx. DiFlexx Duo, a selective preemergence and postemergence herbicide for control of annual broadleaf and grass weeds, includes a premix of dicamba (DiFlexx) and tembotrione (Laudis). Anthem Maxx, a new formulation of Anthem, is a premix of pyroxasulfone (Zidua) and fluthiacet (Cadet) for preemergence or early postemergence control of annual grasses and some small-seeded broadleaf weeds in corn and soybeans.

With multiple active ingredients and modes of action already built into these premix herbicides, Sarangi notes they provide additional options for broad-spectrum weed control, helping combat weeds resistant to glyphosate and ALS-inhibitors.

"That's the advantage of having this cocktail mix," Sarangi says. "Those prepackaged mixes are really good because it will provide you with different modes of action and different chemistries."

Acuron and DiFlexx Duo also include crop safener technologies to minimize crop injury — benoxacor and Crop Safety Innovation, respectively.

"That means you have an opportunity to apply it a little late. For example, DiFlexx Duo can be applied from emergence up to, but not including, V7 growth stage or 36-inch-tall corn — that's pretty amazing; it even can be applied from V7 to V10 stages with directed application," Sarangi says. "That's the beauty of those crop safeners. It gives a little extra period to control the weeds."

Because these prepackaged mixtures allow for preemerge and postemerge applications, they provide additional options for greater residual and foliar control of weeds throughout the growing season.

Moving forward, preemerge applications with multiple modes of action, followed by postemerge applications with foliar-active herbicides tank-mixed with residual herbicides for overlapping residuals, will be key to achieving broad-spectrum weed control, keeping fields clean and preventing resistance from developing, Sarangi says.

"Look at the emergence patterns of waterhemp and Palmer amaranth. They start emerging in May and continue emerging until the middle of August — that's really bad for the farmer," he says. "If you spray a preemerge in May during planting, you'll have one to 1.5 months of residual activity. Initial control is necessary because most weed seeds are photoperiod-sensitive — if they get light, they emerge. If you start with a clean field early in the season, later the canopy will close and there will be a fewer weeds emerging — and you can always come back with a postemergence herbicide application."