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Serving: IL

More weed control, more profit

Experts say farmers have more options than they think to fight waterhemp and marestail resistance. Here's a look beyond dicamba.

After two years of mostly clean fields using the dicamba herbicide platform, Bureau County, Ill., farmer Matt Foes is switching to 100% non-genetically modified soybean production.

He’s battling glyphosate-resistant marestail and waterhemp, as well as the declining effectiveness of residual herbicides through the development of metabolic herbicide resistance. While he joined neighbors in using dicamba after years of glyphosate on his mostly no-till operation, he sees chemical-only approaches as a losing battle and is making the jump to non-GMO production in 2020 for a $1.50-per-bushel premium.

“Personally, I think we’re applying a lot of selection pressure with dicamba, and it won’t be long until we see resistance issues with it here. In light of that and the market premium, I decided to go down the non-GMO path,” Foes says, adding that for the 2020 growing season, he’ll rely on three modes of action in Tricor, Dual Magnum and the PPO inhibitor Authority for residual control in his preemergence application.

He’ll spray again when the weeds are 2 to 3 inches tall — a shorter height than he would have in his second pass of dicamba in the past, but one that reasserts residual control as the summer annual waterhemp emerges across a wide window through May and June.

Foes will spray Flexstar, Select for grass control and a residual such as Outlook to “reset the residual control from the time I spray to canopy closure.”

Canopy closure suppresses further weed seedling emergence. Flexstar and Outlook will apply residual control to his waterhemp problem, too. In his previous two-pass dicamba system, he’d add a residual like Outlook on the second pass. “With the non-GMO program, I’m much heavier on preemergence residuals,” he adds.

Non-chemical tactics

Foes, who also holds a master’s degree in weed science, says his input costs won’t change. He’ll achieve diverse chemical control and will put the money he’s saved on non-GMO seed toward additional herbicides. Timeliness is also necessary to make a non-GMO program work — hence his backup plan to control weeds with a cultivator during June when summer weeds are still small. That’s a tactic that may save the day in a drought year like 2012, when residuals aren’t as effective.

Foes is deploying heavy spring vertical tillage on most of his acres as his “burndown” to effectively kill the large marestail that overwintered from the fall, as well as to incorporate fertilizer into his soil profile. He’s going to see how weather progresses before committing to tillage on his sandiest soils.

“If it’s like last year, where there’s a benefit for drying out the field for planting, then I’ll go that route,” Foes says. “I could do my preemerge herbicide pass before tilling, and just be careful not to get it too deep into the profile. Depending on timing, I may do that, but I’m planning to do my preemerge after tilling and before planting as of now.”

University of Illinois weed scientist Aaron Hager says the marestail problem may be particularly pronounced for farmers this year, requiring tillage during the preplant burndown period. He estimates most farmers couldn’t get into their fields in time to prevent many winter annual weed species (including marestail) from going to seed in 2019, and coupled with a mild winter, that means more weeds will likely be standing as farmers start planting in 2020.

Non-GMO postemergence

While Foes is using Flexstar, Ultra Blazer and Cobra also work within a non-GMO system for postemergence control and are available to farmers who want to rotate chemistries, a tactic that can help in the fight against herbicide-resistant weeds. Cobra also offers the widest application window, especially compared to Illinois’ 45-day cutoff for dicamba application after planting. 

Regardless of whether an operation is non-GMO or uses a trait platform, Karen Corrigan of McGillicuddy Corrigan Agronomics says a strong preemergence plan with multiple residual herbicides helps further the ultimate goal of stopping weed seed from being added to the seedbed.

“Strong preemerge control is necessary in any system you’re working in,” Corrigan says. “But if you have really high weed seed populations, you might want to think about something like cereal rye or some mechanical means of control.”

She points to the Harrington Weed Seed Destructor, which is not yet commercially available to U.S. growers. It attaches to combines, injuring up to 99.9% of weed seeds that get in the mill, preventing their germination. It doesn’t have a price tag quite yet, but Corrigan fears it’ll be too much for the average farmer.

As for Foes, he’s planting on 30-inch rows for a more consistent seed placement than he had with his air seeder on the 15-inch rows he used to deploy. It enables his backup plan for cultivation between the rows, which may be the deciding factor in not returning to narrow rows when he invests in new equipment.

“Ultimately, narrow-row beans might be better for high yield, but if weed control forces 30-inch rows, then so be it,” Foes concludes.

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