Why Rotate Herbicide Modes of Action?
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As far as we know now, there are a finite number of herbicide modes of action available to farmers to control weeds in their corn and soybean fields. That’s why herbicide stewardship and resistance management are important practices.
Many Midwestern farmers have come to realize they need a multipass program with several modes of action and residual activity to keep their fields clean and their yield as high as possible. They also know that herbicide resistance management is about more than controlling weeds for one season. It’s about working to ensure those species can be controlled in the future.
Rotating Herbicide Modes of Action
Kacee Kreischer is a retail product agronomist for Brevant® seeds. She says one great way to protect future weed control practices is by switching up the herbicide modes of action you use. “Many different products are used to control weeds in corn and soybeans, and you have to make sure you are rotating your modes of action to help fight resistance to these herbicides,” she says.
Kreischer says using the same mode of action over and over allows weeds to get the upper hand on it.
“If we continue to repeatedly use the same types of herbicides, weeds gain the ability to become resistant to those herbicides — thus making the weeds difficult to control,” Kreischer says. “In utilizing different modes of action, we can help prevent these dominant species from becoming tolerant.”
“In utilizing different modes of action, we can help prevent these dominant species from becoming tolerant.”
By rotating modes of action, Kreischer says, farmers can get cleaner fields in both the short and long term.
“Not only does this make it easier to control to these species, but rotating modes of action also allows us to preserve the efficacy of these herbicides for a longer period of time,” she says. “The more variation you can create in your herbicide programs by incorporating different modes of action year over year, the better. The results you have should be better in not only the control of your weed management but also in extending the efficacy of the herbicides themselves for future use,” Kreischer explains.
Effective Modes of Action
When building your weed control program, Kreischer recommends including a burndown as well as preemergence and postemergence applications with residual activity and, yes, multiple modes of action.
And when it comes to those modes of action, she says, quality is more important than quantity. They need to actually work.
“It’s inevitable that you will always have a certain percentage of a weed population that has natural tolerance to a particular herbicide mode of action. However, if your application program has two or more effective modes of action, effective being key here, instead of selecting for that weed, you will kill it,” Kreischer says. “Resistance management will only work if multiple components of the mix are effective against the target weeds. Growers need to be sure they are selecting effective modes of action and not just the number of modes of action.”
“Resistance management will only work if multiple components of the mix are effective against the target weeds. Growers need to be sure they are selecting effective modes of action and not just the number of modes of action.”
Kreischer says it doesn’t matter how many modes of action you have if they can’t control the weeds you need to control. That’s why, she says, it’s important to find the right solutions with effective modes of action. For example, Sonic® herbicide has two effective modes of action against some of the toughest weeds in soybean fields - including waterhemp.
Kresicher says taking steps like this will help keep your fields clean well beyond just next season. And now is the time to talk with your ag retailer about which weeds you need to control and which herbicides will do the job. You can also reach out to your local Corteva Agriscience territory manager to find solutions that fit the way you farm.
Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Consult the label before purchase or use for full details. Always read and follow label directions.
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