Stacked herbicide resistance progresses across Midwest

Dave Ruen
Field Scientist
Dow AgroSciences

For nearly two decades, herbicide-resistant weeds have swept across the Midwest. Today, more fields than ever are facing weeds with resistance to multiple modes of action. With new postemergence technologies entering the market, farmers need to remain vigilant and avoid repetitive use of one active ingredient by using residual herbicides in a program approach to control their tough weeds multiple ways.

We’re trying to manage the expansion of glyphosate-resistant weeds — marestail, waterhemp and giant ragweed, for example. There’s no question in my mind that we’ve slowed the advance of glyphosate resistance due to the resurgent use of soil-applied herbicides, such as Sonic® herbicide in soybeans.

Some weeds, such as tall waterhemp, are developing resistance to multiple modes of action, an issue farmers must keep their eyes on.

In Kansas, some tall waterhemp plants are now resistant to HPPD inhibitors, ALS inhibitors and atrazine. Meanwhile in Illinois, tall waterhemp is documented with multiple resistance to PPO inhibitors, ALS inhibitors and atrazine.

In the last few years, we’ve seen a slow expansion of herbicide-resistant weeds, particularly in the upper Midwest. It’s important that we continue to increase the use of residual herbicides and not skimp on rates.

To stop weeds from robbing yield, carefully scout soybean fields and use a targeted program approach this season. Start with a clean field by applying a broad-spectrum, preemergence herbicide that has powerful activity on the Amaranthus species, including pigweeds, waterhemps, and Palmer and Powell amaranth. With two nonglyphosate modes of action, Sonic herbicide is proven to provide 94 percent control of waterhemp and 93 percent control of Palmer amaranth.

For more information about how your customers can take control of herbicide-resistant weeds in their soybean fields, visit

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