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Mitigating and preventing herbicide resistance is key to effective long-term weed control. Find strategies for your acres with this expert advice.

April 1, 2024

4 Min Read
Managing weed resistance: 5 expert tips
Submitted by Corteva Agriscience

As resistant weed varieties continue spreading to different geographies each season, researchers continue discovering new cases of resistance. For growers like you, a sound management strategy is key to staying ahead of this ongoing challenge.

“Most growers understand the importance of using different chemistries. However, it takes more than applying different herbicide brands. It takes a familiarity with local weed populations and a solid understanding of herbicide classifications,” says Brett Gordon, an Enlist® field specialist based in Arkansas. “Additionally, it’s critical to employ a diverse weed control program approach.”

Gordon says a first step to creating an effective program is choosing a trait technology that provides several herbicide tolerances. Enlist E3® soybeans and Enlist® cotton varieties offer tolerances to 2,4-D choline, glufosinate and glyphosate. Enlist® corn offers the same tolerances plus an additional tolerance to FOP herbicides. Enlist One® herbicide and Enlist Duo® herbicide are the only 2,4-D herbicides approved for use with crops with the Enlist® trait.

“For example, Palmer amaranth is one of the most troublesome, resistant weeds in the South. To control it, you need to start with a burndown or tillage. Then apply preemergence residual herbicides and overlap residuals post,” Gordon says. “For good stewardship of the Enlist system, always tank-mix Enlist herbicides with another effective mode of action to reduce the odds of developing resistance.”

Gordon advises carefully selecting herbicides to include different active ingredients, from different herbicide groups in your pre- and postemergence applications. This balances weed control effectiveness with resistance management.

Here are five reminders for resistance prevention:

  1. Choose herbicide traits carefully and consider your rotations. If you rotate crops, make sure you’re not inadvertently encouraging resistance development by continually using the same active. Enlist E3 soybeans, Enlist corn and Enlist cotton varieties, for example, all offer tolerance to multiple herbicides. This gives you application flexibility and allows you to switch up active ingredients in back-to-back crops.

  2. Site of action vs. mode of action: Know the difference and know what you’re applying. Mode of action (MOA) refers to how the herbicide controls the weed, such as inhibiting cell division; site of action (SOA) refers to the place in the plant where the action occurs, such as a specific protein. Effectively managing resistance involves using a combination of herbicides with different SOA or multiple MOA.

  3. Avoid letting resistant weeds go to seed. Remove them by hand or through application of a product known to control the resistant weed. Thoroughly clean equipment to avoid bringing seeds from one field to another.

  4. Don’t assume single resistance. Cross-resistance can occur. So, don’t assume if a resistant population appears, then you can simply apply a different herbicide for control. Work with your local advisers to find effective tools to control resistant weeds.

  5. Remember that resistance is proportional. The longer a resistant weed variety is allowed to thrive in a field, a greater percentage of that total weed population will develop resistance.

In closing, Gordon says, the best resistance management plan is the one that uses a diverse program built on a foundation of weed control best practices.

“In addition to effective herbicides, I recommend cultural practices, like cover crops or narrow row spacing, to diversify your weed control program,” Gordon says. “When growers utilize several robust tools, this mitigates herbicide resistance, prevents new resistance development and helps extend the longevity of powerful technologies like the Enlist system.”

Learn more about managing resistance with the Enlist® weed control system by watching the video How Multiple Modes of Action Keep Resistant Weeds in Check. You also can contact your Corteva Agriscience representative for local information.

™ ® Trademarks of Corteva Agriscience and its affiliated companies. The transgenic soybean event in Enlist E3® soybeans is jointly developed and owned by Corteva Agriscience and M.S. Technologies L.L.C. Enlist Duo® and Enlist One® herbicides are not registered for sale or use in all states or counties. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your area. Enlist Duo and Enlist One herbicides are the only 2,4-D products authorized for use with Enlist® crops. Consult Enlist® herbicide labels for weed species controlled. Always read and follow label directions. ©2024 Corteva.  019429  BR (04/24)  CAAG4NLST067

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