Expert Advice for Postharvest Corn Weed Control
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As you know, once harvest is over, your work is not. After the combine is back in the shop, you have more to check off your to-do list, including fieldwork and applications. And experts recommend some of that work include herbicide applications, because giving your corn a clean field in spring starts in the fall.
“Total weed management is a year-round process, especially if we are relying strictly on herbicides to manage all of our weeds. For a no-till operation, weeds that emerge in the fall are very susceptible to herbicides while they are young, but once they’ve survived the winter, they are much more difficult to control,” says Ron Geis, a Corteva Agriscience market development specialist based in Iowa. “Additionally, several cool-season weeds, including henbit and purple deadnettle, serve as hosts for soybean cyst nematodes.”
“Total weed management is a year-round process.”
Postharvest Weed Control Benefits
Geis says a fall burndown is an excellent practice (if timing and the weather cooperate on your operation), because it can set you up to plant your corn early.
“Applying burndown products in the fall wipes the slate clean, and if a residual is added at the same time, this program can keep your fields clean so customers can plant into a drier, weed-free seedbed come spring,” Geis says. “This facilitates earlier planting — a practice shown to increase crop yield.”
And a fall burndown can help control some difficult, herbicide-resistant varieties.
“Our goal is to knock down the winter annual and biennial weeds like marestail, dandelion, mustards and henbit. You can also add a residual for spring annuals like lambsquarters, kochia and ragweed,” Geis explains. “We have farmers in northern Iowa who are able to control waterhemp well into June with a November burndown, but you won’t get away with that farther south. It all depends on where you are, the products you select and how cool the soil stays.”
“Our goal is to knock down the winter annual and biennial weeds like marestail, dandelion, mustards and henbit. You can also add a residual for spring annuals like lambsquarters, kochia and ragweed.”
Postharvest Weed Control Tips
When it comes to choosing solutions for your fall burndown application, Geis recommends starting with a mix of glyphosate and 2,4-D. For no-till fields, he advises adding Basis® Blend herbicide for residual control.
If those solutions aren’t taking care of the weeds, Geis says, you can try Elevore® herbicide, along with methylated seed oil in the fall . He says this can be especially effective for controlling tough populations of marestail and henbit.
For traditional operations, Geis explains, tillage is also an option in fall. “If aggressive tillage fits into your farming plan, it has always been a good tool to use for cool season weeds, as long as it’s done early enough,” Geis says. “Additional tillage passes may be necessary if weeds get too large for the implement. Shallow tillage, like the now popular vertical tillage equipment, is not nearly as effective at removing even small weeds. So a burndown herbicide needs to be applied in addition to most vertical tillage systems.”
Geis advises making burndown applications when weeds are actively growing and when reasonably warm temperatures are in the forecast for a few days, as you can’t apply once the ground has frozen. He says moisture also is necessary to activate any residual products.
Drought Considerations
That being said, Geis points out there are some issues to consider if you’re experiencing drought/dry weather conditions this fall. He says these four considerations may make you rethink your fall burndown application:
- Dust can coat the weed and render your knockdown product nearly useless.
- Emerged weeds may not have the active growth necessary to uptake the knockdown herbicide.
- A full flush of weeds may not yet be emerged. If a flush emerges after application, it could easily be missed by both the knockdown and the residual portions of the herbicide program.
- You’ll want to be patient and scout for weeds above ground AND below the surface to see how many new weeds are close to emerging.
Geis says a fall burndown may not be possible for you, depending on the conditions in your fields. However, if it is possible, he recommends doing it.
“Dead weeds don’t make seeds. Fall timing carries the confidence of more-complete control. And in the event the fall timing fails to give desired results, at least a follow-up application in the spring can happen in a timely manner — thus ensuring more dead weeds,” Geis explains. “For those who only apply in the spring, there have been years that weeds have already produced viable seeds before the herbicide application takes place. This puts the customer several years back in terms of weed seedbank management on that field.”
Meaning the steps you take this fall can have an impact not only in spring 2022 but also for years to come.
Basis® Blend and Elevore® 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. Always read and follow label directions.
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