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Here are tips for getting stronger performance against tough weeds with preemergence corn herbicides.

Tom J. Bechman, Editor, Indiana Prairie Farmer

February 21, 2024

4 Min Read
A close-up of young corn crops in a field
BETTER CONTROL: If you want clean cornfields like this one, it may require enhancing your herbicide mix to target your toughest weeds. Tom J. Bechman

What if you like the weed control delivered by an older, cheaper preemergent product for the most part, but you see more grass escapes than you like? Or maybe your preemergent controls everything well except giant ragweed and cocklebur. Then again, perhaps it’s letting more waterhemp through than you like. Is it time to scrap your strategy and start over? Or is there another option?

“For many of these products, you can add another active ingredient that works especially well on your toughest target weed and stay with what you’re doing,” explains Bill Johnson, Purdue Extension weed control specialist. The first step is to check efficacy tables in the 2024 Weed Control Guide for Ohio, Indiana, Illinois and Missouri.

Suppose you are applying SureStart, but you know you have waterhemp. Strong on many weeds, SureStart only rates 7 of 9 on waterhemp control, meaning you can expect around 70% to 80% control. Atrazine rates an 8, so you could bump up control by adding atrazine.

The tables for soil-applied residual products assume you’re going to come back with another product postemergence, so they rate early-season performance, not season-long performance, Johnson notes. Before adding a product selected to boost control based on ratings, check the labels of each product to make sure combining them is allowed.

Earlier corn residual herbicides

Here is a rundown of several soil residual herbicides used over time that could still be used today. The list of product names isn’t all inclusive because these active ingredients are off patent. Several different companies sell these active ingredients under a different name.

For each one listed here, Johnson indicates active ingredients at the labeled rate, plus top options for enhancing performance. “Applying labeled rate is crucial to obtaining optimum performance,” he explains. “If you shave rates, don’t expect the same results.”

Bicep II Magnum 5.5L at 2.1 quarts per acre. Ingredients include 1.3 pints of Dual II Magnum 7.64 EC and 1.6 pounds of a.i. atrazine. To enhance control on large-seeded broadleaves like giant ragweed and cocklebur, and on waterhemp and triazine-resistant lambsquarters, add Balance, Hornet or Callisto. Or for most of these weeds, add atrazine up to a maximum rate of 2 pounds per acre.

Harness Xtra 5.6L at 2.4 quarts per acre. Ingredients are 1.86 pounds of a.i. acetochlor and 1.5 pounds of a.i. atrazine. The same comments for enhancing weed control as for Bicep II Magnum apply here.

Lexar 3.7L at 3 quarts per acre. Ingredients are 1.35 pints of Dual II Magnum 7.64 EC, 1.3 pounds of a.i. atrazine and 5.3 ounces of mesotrione 4L. Adding more atrazine would pick up morningglory and large-seeded broadleaves.

Acuron 3.44L at 3 quarts per acre. Ingredients are 1.7 pints of Dual II Magnum 7.64 EC, 0.75 pound of a.i. atrazine, 5.76 ounces of mesotrione 4L and 0.045 pound of a.i. bicyclopyrone. Consider adding more atrazine up to the maximum amount allowed for a single application.

Corvus 2.63SC at 5.6 ounces per acre. Ingredients are 5.3 ounces of Balance Flexx 2L and 0.032 pound of a.i. thiencarbazone. Adding atrazine helps, especially for broadleaf control.

SureStart 4.25L at 2.5 pints per acre. Ingredients are 1.17 pounds of a.i. acetochlor, 0.12 pound of a.i. clopyralid and 0.7 ounce of Python 80 WDG. Add atrazine for help on large-seeded broadleaves. Adding more acetochlor would help on grasses and small-seeded broadleaves.

Resicore 3.29L at 2.5 quarts per acre. Ingredients are 1.75 pounds of a.i. acetochlor, 0.12 pound of a.i. clopyralid and 6 ounces of mesotrione 4L. More atrazine or Sharpen could help, especially on giant ragweed, morningglory and waterhemp.

Acuron Flexi 3.26L at 2 quarts per acre. Ingredients are 1.5 pints of Dual II Magnum 7.64 EC, 5.1 ounces of mesotrione 4L and 0.04 pounds of a.i. bicyclopyrone. Consider adding atrazine.

Newer corn residual herbicides

Here are some newer options:

Maverick 2.2L, 20 ounces per acre, preplant, pre and post up to V6 corn. Ingredients are 3.3 ounces of Zidua SC, 4.11 ounces of mesotrione 4L and 0.11 pound of a.i. clopyralid. Add Balance or a Group 15 herbicide, like Dual or Outlook, to boost grass control. Atrazine or Sharpen could help on broadleaves.

TriVolt 3.65SCV, 20 ounces per acre, preplant, pre and post up to V2 corn. Ingredients are 5.7 ounces of Balance Flex, 0.44 pound of a.i. flufenacet and 0.036 pound of a.i. thiencarbazone. It can stand alone for grasses and small-seeded broadleaves. Enhance with atrazine for large-seeded broadleaves.

Storen 3.2ZC, 2.1 quarts per acre, preplant, pre and post up to V8 corn. Labeled for 2024, this new herbicide features four active ingredients: 1.44 pints of S. metolachlor, 2.4 ounces of Zidua SC, 5.2 ounces of mesotrione 4L and 0.039 pounds of a.i. per acre of bicyclopyrone. See comments for Maverick.

Surtain 1.6L, 14 ounces per acre, preplant and pre, pending for post. Registration was granted for this herbicide in early February. Ingredients are 3.3 ounces of Zidua SC and 3 ounces of Sharpen. Johnson suggests atrazine could help on broadleaves, and Balance or a Group 15 for enhanced grass control.

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About the Author(s)

Tom J. Bechman

Editor, Indiana Prairie Farmer, Farm Progress

Tom J. Bechman is editor of Indiana Prairie Farmer. He joined Farm Progress in 1981 as a field editor, first writing stories to help farmers adjust to a difficult harvest after a tough weather year. His goal today is the same — writing stories that help farmers adjust to a changing environment in a profitable manner.

Bechman knows about Indiana agriculture because he grew up on a small dairy farm and worked with young farmers as a vocational agriculture teacher and FFA advisor before joining Farm Progress. He works closely with Purdue University specialists, Indiana Farm Bureau and commodity groups to cover cutting-edge issues affecting farmers. He specializes in writing crop stories with a focus on obtaining the highest and most economical yields possible.

Tom and his wife, Carla, have four children: Allison, Ashley, Daniel and Kayla, plus eight grandchildren. They raise produce for the food pantry and house 4-H animals for the grandkids on their small acreage near Franklin, Ind.

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