How Drought and Dry Weather Impact Soybean Weed Control

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Dry weather soy control

Soybean farmers in several states across the Midwest struggled with drought and extremely dry weather in 2021. And, forecasts show, dry conditions may still be a problem for the 2022 season, depending on the location.

North Dakota was hit particularly hard by drought this summer. Bridgette Readel is a territory manager for Corteva Agriscience covering eight counties in North Dakota and the Red River Valley of west-central Minnesota. She says 2021 was one of the driest summers in her territory in decades, and it created a lot of challenges.

“This summer, we experienced probably our most severe dry weather and longest-term dry weather we’ve had, certainly, since the late 1980s,” Readel says.

Although Readel’s territory has received some much-needed rain this fall, she says there are important lessons to be taken from the drought conditions earlier in the year. It’s unclear just what Mother Nature holds for 2022, but depending on your location, you may struggle with dry weather.

Weed Control in Drought

One big challenge drought creates for soybean farmers is that dry conditions can make weed control more difficult. Like crops, weeds are affected by the weather, and you can often see the impact just by looking at them.

“The leaves start to shrivel up, and the weed will start to kind of pull back into itself as protection from the heat and to try to conserve moisture,” Readel says. “It’s important that we just remember that the soybean crop canopy is thin during drought. And, so, you don’t have as much crop competition to shade out those weeds. Those weeds are going to be a bit more prolific, and they will try to take any available water and nutrients from crops.”

Besides competing with soybeans for precious little moisture during drought, Readel says, some weeds will literally toughen up, making them harder to control.

“You’ll see weeds, particularly weeds like kochia or ragweed, with a thick cuticle on the leaf. So, it’s harder for a herbicide to be absorbed. We’re also seeing a thickening in the stem — the stems get thicker and tougher because they want to survive,” Readel explains. 

And, she says, it’s not just the herbicides that have a harder time getting through those weed leaves and stems. “Even when you’re doing tillage, the weeds just don’t die quite as easily because they are tougher because of the drought and the stress that they’re under,” Readel says.

Overcoming Drought Difficulties

Knowing these dry conditions could likely continue into 2022, what can farmers do to ensure the best possible soybean weed control? Readel says there are a couple of very important items to remember. One of those is to try to control weeds before they grow too large, because the smaller they are, the easier they are to control.

“You also have to adjust to make sure you’re using plenty of water when spraying. I know that’s hard to do when we’re all trying to conserve and be safe with water, but water coverage matters when we want to cover the multiple growing points on the weeds,” she explains. “Because it’s tougher to get through the weed cuticle, quality adjuvants matter when you’re using herbicides. The adjuvant helps to break through that cuticle and get the absorption into the plant.”

It’s also a good idea to plan out a weed control program approach that includes strong residual herbicides with multiple effective modes of action during drought. Sonic® and Trivence® herbicides, for example, are soybean premergence solutions that contain multiple modes of action.

Readel advises talking through your program plans with your trusted advisors this winter too. She says it will be particularly important to use strong, preemergence solutions with multiple modes of action and residual activity to balance out any supply chain shortages for certain postemergence products. Readel says you’ll want to have a plan B in place if you need to change things up. 

Even if you’re planning to use powerful, high-quality herbicides, drought can still create challenges when it comes to keeping weeds under control. But, remember, there are measures you can take in the future to make sure your herbicides are as effective as possible, even when the weather’s dry.

Readel says: “Control weeds when they’re small, use enough water when spraying, use quality adjuvants to control those weeds and remember that the crop canopy is thin and allows those weeds a little extra foothold than they might normally have.” 

Sonic and Trivence not registered for sale or use in all states. 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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