Wallaces Farmer

Multiple SOAs: The best weed control option

5 Min Read

Benjamin Franklin once said, “An ounce of prevention is worth a pound of cure.” This quote can be applied to weed management today. Preventing weeds from emerging protects yield. University data indicates that growers will sacrifice 2.5% of their final yield for every leaf stage that a post-emerge application is delayed. When making a post-emerge application, the best weed to control is a weed that never emerged.

No matter which trait platform you select, greater success will occur when the post-emerge trip is used to clean up a few escapes versus being relied on to do the heavy lifting of weed control in your fields. Given the ever-growing list of resistant weeds, taking selection pressure off current effective herbicide options is more critical than ever. The first step in ensuring a successful post-emerge application starts with the Power in the Pre™.


When utilizing various SOAs (sites of action), Beck’s Practical Farm Research (PFR)® data shows a 29% increase in waterhemp control with two SOAs and a 37% increase in control with three SOAs, versus using just one SOA. Each herbicide group has strengths and weaknesses when it comes to weed control, so it’s important to select herbicide groups that are effective for the weeds you face. For instance, Group 2 residual herbicides are very effective on large-seeded broadleaf weeds such as cocklebur, morningglory, giant ragweed, etc. Other SOAs, such as metribuzin, a Group 5 herbicide, as well as PPOs or Group 14 herbicides (Valor® and Authority®), are very effective on small-seeded broadleaf weeds like waterhemp. However, metribuzin and PPO herbicides will struggle on grasses. Group 15 herbicides such as Dual II Magnum®, Outlook®, Warrant®, and Zidua® are very effective on waterhemp and grasses but struggle on large-seeded broadleaf weeds. Selecting herbicide premixes with multiple SOAs will utilize the strengths of various herbicide groups. Ultimately, resulting in greater control across a broader spectrum of weeds as well as increasing waterhemp control.

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When selecting a pre-emerge herbicide, select a product with two or three “effective” SOAs. Select SOAs or actives targeting your problematic weeds versus selecting a random pre-emerge with one, two, or three SOAs. Weeds such as waterhemp have developed resistance to various herbicide groups. For instance, Group 2 herbicides are very effective on large-seeded broadleaf weeds, but many waterhemp populations are resistant to Group 2 herbicides. If we select a 2 + 14 pre-emerge herbicide and the waterhemp population is resistant to Group 2 herbicides, how many “effective” SOAs do you have?

In 2020, one “effective” SOA resulted in 85%, two “effective” SOAs resulted in 90%, and three “effective” SOAs resulted in 95% waterhemp control 28 DAT of post-emerge application (GR population). Ultimately, this resulted in fewer escapes and less selection pressure on the post-emerge application. Developing a residual program with multiple “effective” SOAs for your problematic weed will help lay a powerful pre-emerge foundation for a successful post-emerge application.

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So, in summary, the most important takeaways to remember this spring are:

  1. A successful pre-emerge application lays the foundation for a successful post-emergence application.

  2. Beck’s PFR data shows a 29% increase in waterhemp control when using two SOAs and a 37% increase when using three SOAs, versus using only one SOA.

  3. Waiting to control weeds with a post-emergence application can cost 2.5% of your yield for every growth stage of delayed weed control.

While weed control continues to provide new challenges with each growing season, you have the option to bring the power to your soybean platform. Put the Power in the PRE and let your pre-emergence applications do the heavy lifting this season.

For more information on recommended herbicide programs and options for soybeans, check out Beck’s 2021 Recommended Soybean Herbicide Programs guide.


Innovation has always been at the heart of farming. Dreaming, inventing, and experimenting with new tools, equipment, and products is what allows farmers to continue improving their operations. Beck’s family of employees thrives on innovation too, which is why they developed the Practical Farm Research (PFR program. Today, Beck’s provides a truly comprehensive, innovative, and practical agronomic research program that helps farmers with decisions that can improve profitability. By evaluating hundreds of new management practices and inputs, we deliver unbiased agronomic data to help farmers make better decisions and increase profitability.

Beck’s is the largest family-owned retail seed company in the United States that serves farmers in Arkansas, Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Mississippi, Missouri, Ohio, South Dakota, Tennessee, and Wisconsin. According to a recent seed industry survey, Beck’s ranks as the third largest corn and soybean brand in the United States. At their core, all Beck’s employees are Farmers at Heart. It stands for something special. It has soul. It has truth. And it represents a community of farmers, employees, and dealers who strive each day to seek challenges, push boundaries and innovate. Beck’s has, and always will be, proud to serve a community of farmers who love what they do and who are proud to be… Farmers at Heart. For more agronomic new and information, visit Beck’s Agronomy Talk page or blog at BecksHybrids.com.

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