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Delayed spring planting brings herbicide considerationsDelayed spring planting brings herbicide considerations

K-State agronomists have advice for farmers and some options for weed control.

Jennifer M. Latzke

June 1, 2022

4 Min Read
Corn being planted
CORN PLANTING: Kansas farmers may have been waiting on much-needed rain to get their planters into the field for their fall crops. But that delay may require them to consider the timing of their herbicide applications so they will be most effective. Kansas State University agronomy experts have advice to share. Jennifer M. Latzke

Despite a rainy end to May, the state of Kansas is still facing widespread drought across the western two-thirds of the state.

According to the U.S. Drought Monitor, a strong upper-level trough moved across the contiguous U.S. the week of May 18-24. It brought surface low pressure systems and cold fronts, and the complex trough tapped Gulf of Mexico moisture to spread above-normal precipitation across parts of the Plains. Two inches or more of precipitation fell across southern and eastern parts of Kansas, central Colorado and northeast Nebraska, while half an inch or more was widespread across North Dakota. This was just enough to bring optimism to spring planting.

Kansas State University agronomy experts have advice for these farmers racing to the field to manage their herbicide applications and their fall crops.

Herbicides in corn

Sarah Lancaster, K-State Extension weed science specialist, and Jeanne Falk Jones, multicounty agronomy specialist, warn corn farmers to be sure to not get too far ahead of the sprayer to ensure the full effectiveness of their preemergence herbicide applications.

“The speed of planting coupled with unusually windy conditions can potentially interfere with preemergence herbicide applications,” the two write in the May 12 Agronomy eUpdate.

Residual herbicides are the foundation of weed management programs, according to Lancaster. Fortunately, many residual products that are applied preemergence to corn, can also be applied to small corn. These include:

  • Atrazine

  • Group 15 herbicides such as acetochlor (Harness, Warrant, others), dimethenamid-P (Outlook, others), pyroxasulfone (Zidua, others) and S-metolachlor (Dual, others)

  • Group 27 herbicides such as isoxaflutole (Balance Flexx, others) and mesotrione (Callisto, others)

  • Premixes that contain various combinations of these products, such as Acuron, Anthem, Armezon Pro, Corvus, Lumax or Lexar, Resicore and SureStart II.

If you’re in a situation where you need to apply a weed control product to emerged corn, do not use any products that contain flumioxazin, like Valor, according to Lancaster. And if you’re considering making an application to control emerged weeds in the field, remember paraquate, saflufencail and tiafenacil cannot be safely applied to emerged corn.

Also, be wary of activation requirements for the products you do apply, since Kansas may be facing drier-than-normal conditions that continue through the summer, Lancaster and Jones advise.

Herbicides in cotton

Kansas farmers who are new to planting cotton must remember that unlike other fall crops they may be used to, cotton can be slower to canopy — and that makes early-season weed control all the more critical. According to Lancaster and Stu Duncan, retired K-State Extension crops and soils specialist, weeds not only rob cotton of water, nutrients and sunlight, but they can also contribute to trash and lint discoloration at harvest. That can reduce the value of the lint from docked quality grades.

While farmers to the south may use tillage in their early-season weed control toolbox, the majority of Kansas cotton acres are in conservation tillage. That calls for effective burndown herbicide applications before planting, and residual herbicides applied at planting to manage or delay the development of herbicide-resistant weed populations.

Read more about Lancaster and Duncan's recommendations.

Volunteer corn in soybeans

Volunteer corn plants can be much more of a nuisance than just sticking out like a sore thumb in an otherwise beautiful soybean field. Lancaster says research from South Dakota puts soybean yield loss at 8% to 9% when volunteer corn density was at just one plant per 10 square feet. “Yield loss increased to 71% at volunteer corn densities of about one plant per square foot,” she writes in the May 19 Agronomy eUpdate.

How do you manage volunteer corn when it very well may be resistant to glyphosate or glufosinate? You have three chances:

1. Burndown. Paraquat products will control volunteer corn that has emerged prior to soybean planting. Glufosinate will also do the trick, as long as the corn is not a glufosinate-resistant variety like LibertyLink. To achieve full effect, apply burndown herbicide in contact with the growing point on the corn, so make sure it is at V6 stage at least.

2. At planting. University of Nebraska research shows that preemergence applications of sulfentrazone in combination with imazethapyr, cloransulam, metribuzin or chlorimuron (Authority Assist, Authority First, Authority MTZ or Authority XL) reduced volunteer corn growth compared to non-treated controls.

3.Over the top. If you’re delayed, you still have an option to use Group 2 herbicides for very effective over-the-top options for volunteer corn control in soybeans. Just be sure to use the maximum labeled rate, or use a more aggressive adjuvant.

You can read more in the May 19 Agronomy eUpdate.

Kansas State Research and Extension contributed to this article.

About the Author(s)

Jennifer M. Latzke

Editor, Kansas Farmer

Through all her travels, Jennifer M. Latzke knows that there is no place like Kansas.

Jennifer grew up on her family’s multigenerational registered Angus seedstock ranch and diversified farm just north of Woodbine, Kan., about 30 minutes south of Junction City on the edge of the Kansas Flint Hills. Rock Springs Ranch State 4-H Center was in her family’s backyard.

While at Kansas State University, Jennifer was a member of the Sigma Kappa Sorority and a national officer for the Agricultural Communicators of Tomorrow. She graduated in May 2000 with a bachelor’s degree in agricultural communications and a minor in animal science. In August 2000 Jennifer started her 20-year agricultural writing career in Dodge City, Kan., on the far southwest corner of the state.

She’s traveled across the U.S. writing on wheat, sorghum, corn, cotton, dairy and beef stories as well as breaking news and policy at the local, state and national levels. Latzke has traveled across Mexico and South America with the U.S. Wheat Associates and toured Vietnam as a member of KARL Class X. She’s traveled to Argentina as one of 10 IFAJ-Alltech Young Leaders in Agricultural Journalism. And she was part of a delegation of AAEA: The Ag Communicators Network members invited to Cuba.

Jennifer’s an award-winning writer, columnist, and podcaster, recognized by the Kansas Professional Communicators, Kansas Press Association, the National Federation of Presswomen, Livestock Publications Council, and AAEA. In 2019, Jennifer reached the pinnacle of achievements, earning the title of “Writer of Merit” from AAEA.

Trips and accolades are lovely, but Jennifer says she is happiest on the road talking to farmers and ranchers and gathering stories and photos to share with readers.

“It’s an honor and a great responsibility to be able to tell someone’s story and bring them recognition for their work on the land,” Jennifer says. “But my role is also evolving to help our more urban neighbors understand the issues our Kansas farmers face in bringing the food and fiber to their store shelves.”

She spends her time gardening, crafting, watching K-State football, and cheering on her nephews and niece in their 4-H projects. She can be found on Twitter at @Latzke.

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