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It's a new era in weed management

These days, soybeans sizzle with great genetics, chemistry, and traits galore. 

Somehow, though, maladies like weeds always keep one step ahead of the curve. Remember Pursuit? This Group 2 herbicide was the darling of the weed-management dance in the early 1990s, as it obliterated numerous weeds. When weeds started resisting it, the Roundup Ready system that featured glyphosate-
tolerant soybeans stepped up. Seemingly bulletproof in its early years, weeds like glyphosate-resistant marestail and waterhemp began ravaging glyphosate-tolerant soybeans.

READ MORE: Meet the $50 per acre weed

The good news? Plenty of burndown and preemergence-residual herbicides exist to get a crop off to a weed-free start. Besides glyphosate, farmers may also plant soybeans that tolerate:

Glufosinate (Liberty)

2,4-D choline (Enlist)

Dicamba (Xtend)

Headshot of farmer Brade Wade
Photo credit: Gil Gullickson
It’s important to note that in some fields, glyphosate still is effective. Farmers will also have a new tool to manage weeds with the 2,4-D choline-based Enlist system. Even though there are signs in Nebraska that dicamba isn’t as effective as it once was, it still gives excellent weed control across wide areas. Meanwhile, no glufosinate-resistant weeds have surfaced in major agronomic crops. 

Still, if a herbicide is applied time after time, its effectiveness decreases until weeds finally resist it.

“Weed control is headed to a tough spot with new resistance challenges,” says Brad Wade, who farms with his son, Jacob, near McLean, Illinois. “Just when you think you have it all figured out, everything changes.”

What to do? 

Here are four ideas Brad Wade and Bryan Young, a Purdue University weed scientist, have for managing weeds in this era. 

Have a Plan B. Burndown treatments or layered preemergence residual herbicides followed by a nonselective herbicide on herbicide-tolerant soybeans look easy on paper.

As 2019 showed, though, reality bites. Rampant rainfall closed the window for Wade’s initial plan to apply dicamba on dicamba-tolerant soybeans. He then came back with glyphosate mixed with other postemergence herbicides. 

“We lived with the results, which were remarkably good,” Wade says. “But there were a couple fields that got away from us.”

Still, having a plan made the best of a bad situation. 

“I’ve talked to growers about the importance of having a Plan A, Plan B, and Plan C,” says Young. “We have to get away from solely relying on postemergence applications. The best way to reduce the cost of a rescue soybean herbicide application is to make sure you never need a rescue herbicide application.” 

Rotate herbicide-tolerant traits. “A mistake farmers often make is they get stuck on one thing,” says Young. “If farmers continually use one herbicide, as was the case with glyphosate, weeds like waterhemp will eventually develop resistance.”

It’s here where trait technology helps. Multiple herbicide-tolerant stacks can help farmers choose which nonselective herbicide to use, says Young. 

“Five-way stacks are a reality for the future,” Young points out. 

Take a lesson from organic farmers. Without herbicides, organic farmers have to devise alternative ways to manage weeds. 

Herbicide effectiveness can be boosted with tools like cover crops or strategies to encourage weed seed decay in soils, points out Young.  

Watch new trends. This won’t immediately help soybean farmers manage weeds. Still, watching new technologies in other agricultural segments may pay dividends if they begin to become applicable to soybean production.

READ MORE: Beck's research show tops 10 tricks to boost corn and soybean yields

Wade points to smart robot use in high-value crops like grapes that may have potential someday in soybean production.

“These technologies will have to be low cost by the time they get to the commodity world,” he adds.

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