5 MIN READ

Benefits and Limitations of Late Burndown Herbicide Applications

February 4, 2025

Ideally, burndown herbicide applications should be made four to six weeks prior to planting. However, burndown applications may be delayed due to wet soils or poor environmental conditions. A late burndown application could occur a couple of weeks—or even just a few days or hours—before planting and crop emergence. A late burndown herbicide application is still important even if the typical application window is missed and planting is delayed due to weather conditions.

Q. Why is it important to include a late burndown herbicide application when an early burndown application is missed, and what are the major limitations?

A major limitation of late burndown applications is that weeds can be larger and more difficult to control. Weeds grow fast. If they are allowed to get a head start and grow with the crop, they can have an advantage when competing for resources for the rest of the season. If weeds are large, burndown herbicide rates may need to be increased and more aggressive herbicide mixtures may be required for good control.1 Herbicide plant back restrictions can further limit the herbicide choices available for later burndown applications, as they must be balanced against the need to plant as soon as possible.2

Why not just wait and spray after planting to avoid any further delay in planting the crop?

If possible, it is better to make a late burndown herbicide application before the crop is planted. Weather can quickly change after planting and prevent a post-plant application, allowing existing weeds to adversely affect the crop. Planning burndown herbicide applications after the crop is planted can be risky, as it is easy to become busy with other operations and the weeds will only become harder to control with further delays. The risk of crop injury from some herbicides can also increase if the burndown application is made after planting.2

Why is it important to scout fields before making late burndown herbicide applications?

Fields should be scouted to determine the weed spectrum and size in order to select the right burndown herbicide program. While winter annual weeds are often the focus of early burndown herbicide applications, they will likely already be setting seed with a late application. If this occurs, the focus of weed management may then switch to summer annual weeds such as common lambsquarters, common ragweed, velvetleaf, and pigweed species.3 Additionally, it may be important to have a plan to control glyphosate- and multiple herbicide-resistant horseweed (marestail), waterhemp, and Palmer amaranth. Marestail may be six to eight inches tall or more by the time of a late burndown application, and waterhemp and Palmer amaranth may just be starting to emerge.3 The burndown herbicide program needs to be selected to control the largest or the most difficult-to-control weeds in the field. Tillage could also be considered under these conditions, if doing so fits within the cropping system.

Can growth regulator herbicides be used in late burndown applications in corn?

When using 2,4-D and dicamba, it is important to be conscious of the label precautions and observe the plant back restrictions. For corn, you generally need to wait 7 to 14 days before planting when using 2,4-D or dicamba in a burndown application.

What are some herbicides that can be used as a late burndown on corn products that do not possess herbicide tolerant traits?

DiFlexx® herbicide can be used in corn through V10 or 36 inches tall, whichever occurs first, preplant, preemergence, or post emergence. Early post emergence application is recommended for best weed control when weeds are less than three inches tall.

What are the weed management considerations when making late burndown herbicide applications in corn?

There are more herbicide choices for effective weed control in corn than soybean.3 Late burndown herbicide applications in corn can be very effective and safe to the crop. Residual herbicides such as atrazine and mesotrione can provide good activity on emerged weeds.1,2 Additionally, there are many postemergence herbicide options available depending on the weed spectrum to be controlled. Some of the products available for use in corn include: Capreno® herbicide, Laudis® herbicide, and TripleFLEX® II herbicide. As always, read and understand the label of any pesticide that is to be used.

What are the weed control considerations when making late burndown herbicide applications in soybean?

For Roundup Ready or glyphosate-resistant products, Roundup PowerMAX® 3 Herbicide can be used as a late burndown application.



Sources

12019. Adapting burndown herbicide programs to wet weather delays. Ohio State University Extension. https://agcrops.osu.edu/newsletter/corn-newsletter/2019-11/adapting-burndown-herbicide-programs-wet-weather-delays

2Hager, A. 2019. Weed management reminders in a wet spring. University of Illinois. The Bulletin. https://farmdoc.illinois.edu/field-crop-production/weeds/weed-management-reminders-in-a-wet-spring.html

3Burns, E. and Sprague, C. 2019. Weed control recommendations for late and prevented planting. Michigan State University Extension. https://www.canr.msu.edu/news/weed-control-recommendations-for-late-and-prevented-planting

Additional Resources

Steckel, L. 2019. Late burndown in corn. University of Tennessee Extension. https://news.utcrops.com/2019/03/getting-late-early-for-burndown-in-corn/

Web sources verified 11/21/24. 1323_101086