Caption: Pigweed-infested soybean field

In the fight against resistant corn and soybean weeds, one of the best ways to combat herbicide resistance and maximize yield potential is to diversify your weed management program. Herbicide rotation alone is not enough to protect your yield potential against resistance.

Weeds are constantly adapting and developing resistance to the most commonly used herbicides. Some of the most troublesome resistant weeds that have affected corn and soybeans in recent seasons are:

• Waterhemp: resistant to ALS inhibitors (Group 2), glyphosate (Group 9), PPO inhibitors (Group 14), HPPD inhibitors (Group 27) and photosystem II inhibitors (Group 5)
• Palmer amaranth: resistant to ALS inhibitors, HPPD inhibitors, glyphosate, PPO inhibitors and photosystem II inhibitors
• Kochia: resistant to ALS inhibitors, glyphosate, photosystem II inhibitors and synthetic auxins (Group 4)
• Marestail: resistant to ALS inhibitors and glyphosate

To most effectively manage resistant weeds, it’s important to consider combining multiple management strategies, like planting cover crops, using narrow rows and starting clean with a burndown herbicide.
Another key component of any successful chemical weed management program is herbicides with multiple effective modes of action (MOAs). It’s vital to keep in mind that overreliance on one particular MOA can select resistant types and create more widespread resistance. To prevent this from occurring, overlap your residuals by applying a pre- and post-emergence herbicide, both containing multiple effective MOAs. Additionally, each MOA in an herbicide program should have activity against the target weeds that are present in order to be as efficient as possible.

By incorporating cultural practices and effective herbicides into your weed management program, you can better protect your yield potential from resistant weeds. Syngenta offers a comprehensive portfolio of herbicide programs that contain multiple effective modes of action, designed to target resistant weeds. For additional information on battling weed resistance, you can use Resistance Fighter^®, an educational program from Syngenta that provides local recommendations to help growers and retailers manage resistant weeds in their area.

To learn more about weed resistance management tools in soybeans and corn, contact your local Syngenta expert for a custom plan or visit www.ResistanceFighter.com.

Nate Prater is an Illinois-based agronomy service representative at Syngenta. He educates growers on pests, weeds, diseases and other agronomic issues that affect corn and soybean production.

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