What to Do if You Find Weeds in Soybean Fields at Harvest

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Dried soybeans on plant

Depending on where you’re located, soybean harvest is likely to get underway sometime in the next few weeks. While you’re in the combine harvesting your beans this fall, make sure to be on the lookout for weeds in your fields. Taking steps to control any weeds you find before winter will help set you up for a smoother spring.

But what should you do if you find weeds in your soybeans this fall? And how do your spring 2023 plans impact the steps you take now? Joe Bolte, a market development specialist for Corteva Agriscience in Missouri and eastern Kansas, has answers to those questions.

Scouting Soybeans at Harvest

Bolte says scouting from the combine is one of the best steps you can take toward creating a successful weed control program.

“If we think about scouting during soybean harvest, that’s one way we can reassess our weed control program from throughout the season, the preemergence applications, the postemergence applications,” Bolte says. “We can see how our weed control program handled overall and see if we’re happy with our program or if there are any tweaks we need to make going into next year. Maybe there’s a new weed you’re dealing with and you need to account for that.”

If you’re finding large patches of resistant summer annual weeds like waterhemp or morningglory at the end of the season, you’ll want to take measures to more carefully harvest those acres.

“If you do have weed escapes with a lot of summer annuals in your soybean fields in fall, that makes harvest much more difficult. Weeds get caught in the machinery and make your job a lot harder,” Bolte says. “You can harvest those fields with weeds in them last to help avoid spreading the seeds to your other fields. However, if resistant weeds like waterhemp have gotten a foothold in your area, you’ll want to make sure to take steps to control them after harvest as well.”

But you don’t just want to look for summer annual varieties at harvest.

“Scouting during soybean harvest can also let you know what winter annuals you’re going to be dealing with,” Bolte says. “Those winter annuals can pose a number of challenges for the next season, including being host sites for problematic pests we have to deal with in soybeans.”

Postharvest Soybean Weed Control

Bolte says no matter what weed varieties you find at harvest, taking steps to control them before winter hits is a good idea.

“I recommend using a product such as Elevore herbicide for a fall burndown, which is great against our problem weeds, particularly winter annuals,” Bolte says. “Then I also recommend adding a fall residual with that application.” 

Bolte says marestail, for example, can germinate and have flushes several times a year, emerging in fall, winter and even into early spring, “so we can burndown and control what’s there in fall and then — by including a residual with that burndown — if we do get some warmer temperatures in the winter or early spring, the residual can provide some protection from those later flushes of winter annuals.”

But which residual product should you choose for your fall application? Bolte says that depends on what you’re planning to plant in spring. 

“If you’re going to be planting corn next year, Basis Blend herbicide is a great product to use. If you’re planting soybeans next year, many of our soybean residual products at Corteva have a fall burndown label. Use an approved chlorimuron premix product in the fall, such as Trivence herbicide, Envive herbicide or Enlite herbicide, for residual control on fields that will be planted with soybeans next year,” Bolte says. “And then we could also do what I like to call a flex residual where, let’s say, you don’t know if you’re going to plant corn or soybeans, you could use a product such as Afforia herbicide, that could offer a fall residual and open you up to going corn or soybeans in spring.”

Bolte also recommends cultural weed control practices in the fall whenever possible. He says, depending on your operation, those can include crop rotation, cover crops and tillage. 

While fall weed control measures are beneficial for winter annuals, Bolte says, clean fields at harvest truly start in the spring. He says a powerful program that includes preemergence and postemergence applications with multiple modes of action and residual activity can help keep weeds out of your fields, reducing competition for your soybeans during the growing season.

“Clean fields at harvest show the benefit of running a premier, residual product such as Kyber herbicide upfront, preemergence, and then coming back with a postemergence tank mix that also includes residual activity to make sure you have that control all season and prevent those late-season weed flushes,” Bolte says. “You don’t have to worry about weeds jamming up your machinery and you’re likely to see higher soybean yield potential if you keep you fields clean throughout the season.”

Plan ahead for your 2023 soybean weed control program by visiting the soybean herbicides portfolio page on Corteva.us

Afforia®, Basis® Blend, Elevore®, Enlite®, Envive®, Kyber® and Trivence® are 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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