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Weed control for 2023 requires diverse attack

Germination timing creates a tough operating window.

Kevin Schulz, Editor

February 22, 2023

4 Min Read
closeup of Palmer amaranth tnorns
THORN IN THE SIDE: Palmer amaranth is just one of the weeds that has become a troublesome weed for farmers, becoming resistant to commonly used herbicides in producers’ arsenal. Bruce Potter, IPM specialist, University of Minnesota Extension

There’s more than one way to kill a weed, and farmers will need to employ multiple approaches as they look ahead to the 2023 growing season.

Regardless if weed pressure comes from giant ragweed or waterhemp, Jeff Moon says the commonality is resistance. “And we think right away of glyphosate-resistant weeds, but we have weeds that are resistant to atrazine and ALS herbicides, too.”

Moon, market development specialist for Corteva Agriscience, says a weed control plan can be as different as farming practices across the landscape. Whether they be no-till, minimum till or conventional till, “We have people who want to do things in one pass or two passes,” he says. “Although we do caution farmers that a two-pass program is likely the best approach these days when it comes to ensuring effective control and mitigation of weed resistance.”

Suiting the weed control package to individual farmers is the goal of Moon and his colleagues.

Steve Snyder, fellow Corteva teammate, agrees, adding that the answer may come from outside the Corteva Agriscience offerings.

“We’re fortunate. We have good chemistry. So, 90% of the time we have the right solution with us. A lot of times, though, we’ll recommend competitors’ products to complement ours,” says Snyder, Enlist field specialist with Corteva Agriscience. “For Enlist, every meeting we have, we talk about the program approach. We want a preemerge herbicide that’ll have at least two — and a lot of times, three — active modes of action that are effective on the weed we’re trying to get.”

Snyder says Enlist One is a Group 4 mode of action herbicide. “Then, we’ll add, like, a Liberty Group 10, and we’ll add something else. We’re complementing ours with their product. … which is best for the grower. You always have the mission statement remembering who pays the bills — the farmer pays the bills, right? You follow that mission statement and it’s pretty simple. You just complement us with what’s needed.”

Building complete program

Moon says tankmixes are common, again attacking weeds from different angles. “We may not be able to cover all those weeds that someone has a problem with, so we’re going to plug in some atrazine or dicamba, or some other tankmix partner, to help round out our program — and we don’t carry those products,” he says. “Someone else does, but they’re very beneficial to helping build that complete weed control program.”

The need for a varied approach is illustrated by the resistance built by Palmer amaranth, which, according to the Minnesota Department of Agriculture website, where populations have been documented with resistance to one or more of the following classes: dinitroanilines, triazines, ALS (acetolactate synthase) inhibitors, glyphosate and HPPD (4-hydroxyphenylpyruvate dioxygenase) inhibitor herbicide.

Snyder observed a presentation in February that shows Palmer amaranth populations in Arkansas with resistance to nine modes of action.

“Since 2010, when we started talking about resistant weeds,” Snyder says, “we want three, four or five modes of action per year per crop.”

Life would be simple if farmers only had one weed species to control, or if all weeds were resistant to the same herbicide, or if the prime times to hit all weeds with a herbicide coincided. But, alas, that is not what today’s farmers face.

“You may take 40% of them [weeds] with gly[phosate], but not the other 60,” Snyder says. “But just because it’s glyphosate-resistant doesn’t mean we don’t tank-mix with gly. … we usually tank-mix with gly, because if you went with just another one to kill, then you’d have more resistance with another one.”

With that in mind, Snyder again stresses tankmixes and a preemergent application with layered residual. “The days of spending 40 bucks on a soybean herbicide program are over,” he says. “Where we have kochia and waterhemp, we’re spending $80 to $100 an acre on herbicides, if they want to do it right.”

Germination window tough to handle

Snyder says the spread of kochia and waterhemp is creating new headaches for farmers. “We’re in what we call the kochia-waterhemp zone,” he says. Farmers along the Minnesota-South Dakota border are seeing kochia heading east and waterhemp going west. “They have two very challenging weeds that are totally different emerging patterns. … There can be snow in the ditches and kochia is coming up, whereas waterhemp really doesn’t germinate until June, maybe late May.”

That germination variance makes it that much more difficult for producers. “Farmers have had one or the others, but now they’ve got both,” Snyder says. “If it’s a no-till situation, that’s tough, and it’s going to be expensive. … It’s not the weed per se, it’s the different timing.”

Moon suggests farmers willing to go back in time could handle some weed pressure by cultivation, whether it be mechanical or hoe-in-hand bean walking. Other than in organic operations, “we don’t see a lot of cultivation, but we probably could benefit from that,” he says.

About the Author(s)

Kevin Schulz

Editor, The Farmer

Kevin Schulz joined The Farmer as editor in January of 2023, after spending two years as senior staff writer for Dakota Farmer and Nebraska Farmer magazines. Prior to joining these two magazines, he spent six years in a similar capacity with National Hog Farmer. Prior to joining National Hog Farmer, Schulz spent a long career as the editor of The Land magazine, an agricultural-rural life publication based in Mankato, Minn.

During his tenure at The Land, the publication grew from covering 55 Minnesota counties to encompassing the entire state, as well as 30 counties in northern Iowa. Covering all facets of Minnesota and Iowa agriculture, Schulz was able to stay close to his roots as a southern Minnesota farm boy raised on a corn, soybean and hog finishing farm.

One particular area where he stayed close to his roots is working with the FFA organization.

Covering the FFA programs stayed near and dear to his heart, and he has been recognized for such coverage over the years. He has received the Minnesota FFA Communicator of the Year award, was honored with the Minnesota Honorary FFA Degree in 2014 and inducted into the Minnesota FFA Hall of Fame in 2018.

Schulz attended South Dakota State University, majoring in agricultural journalism. He was also a member of Alpha Gamma Rho fraternity and now belongs to its alumni organization.

His family continues to live on a southern Minnesota farm near where he grew up. He and his wife, Carol, have raised two daughters: Kristi, a 2014 University of Minnesota graduate who is married to Eric Van Otterloo and teaches at Mankato (Minn.) East High School, and Haley, a 2018 graduate of University of Wisconsin-River Falls. She is married to John Peake and teaches in Hayward, Wis. 

When not covering the agriculture industry on behalf of The Farmer's readers, Schulz enjoys spending time traveling with family, making it a quest to reach all 50 states — 47 so far — and three countries. He also enjoys reading, music, photography, playing basketball, and enjoying nature and campfires with friends and family.

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