Fall Burndown Options Prior to Planting Corn and Soybean

Post-harvest herbicide applications in the fall can help provide a weed-free seedbed prior to planting in the spring, especially in corn and soybean no-till fields (Figure 1). Fall-applied herbicides should target fall-emerging winter annual species, biennials, and perennials.^1,2,3 Fields with heavy weed populations are the best candidates for a fall application.² Cleaning up weeds in the field after harvesting can make for a cleaner field in the spring.

Key Takeaways

• Scout corn and soybean fields in the fall to determine burndown strategy.
• Fall is a great time to control winter annuals and perennials using a burndown application.
• Control of winter annual weeds is often more difficult in the spring than in fall because of weed size and weather conditions.^1,2
• Permissible tank mixes of glyphosate, dicamba, and 2,4-D will help control weeds like palmer amaranth, marestail, and dandelion.
• Adding a residual to the tank mix can help to control later-germinating winter annual weeds that might not be present at the time of the initial application.
• Fall herbicide applications should be part of a comprehensive weed management program which could include spring burndown, at-planting, and in-crop herbicide applications. Always read and follow all pesticide label directions.

Fall Burndown Targeted Weeds

Fields that are heavily infested with winter annual weeds such as henbit, purple deadnettle, chickweed, or mustards are good candidates for a fall burndown herbicide application (Figure 2).^1,2,3,4 Winter annual weeds usually emerge in the fall after harvest, increase their vegetation during the winter, and complete their life cycle during the spring and early summer. Control of winter annual weeds is often more difficult in the spring than in fall because of weed size and weather conditions.^1,2 If allowed to grow in the spring, winter annual weeds can form a thick mat on the soil surface—blocking sunlight from warming the soil and interfering with tillage and crop establishment. For these weeds, fall herbicide treatments are often more effective than spring treatments because the weeds may have already completed their life cycles by spring and may no longer be actively growing.

Fall Management of Marestail (Horseweed)

Marestail (horseweed) is a winter or summer annual weed that can germinate in the fall or spring (Figure 3). Marestail that germinates in late summer or fall remain in the low-growing rosette stage—the stage at which they are easiest to manage with herbicides—through fall and winter before bolting (stem elongation) in the spring.³ Marestail is easiest to control with herbicides when it is small and in the rosette stage. Plants that emerge in the fall will bolt earlier in the spring, which can make them more difficult to control with a spring burndown herbicide application.

Fall Management of Dandelion, Common Waterhemp, and Palmer Amaranth

Other weeds that can be targeted in the fall include dandelion, common waterhemp, and Palmer amaranth.¹ Dandelion is a perennial weed that spreads by seeds which can germinate on the soil surface at low temperatures. Dandelion seedlings quickly develop a crown and taproot. Mature dandelion plants can live for many years and become a serious problem in minimum or no-till fields (Figure 4). Dandelions are hardy plants that grow late into the fall and tolerate fall frost. Palmer amaranth and common waterhemp are summer annual weeds but can still emerge after harvest and produce seed in as little as five to sixth weeks (Figures 5 and 6). Both species should be managed after harvest up to frost to help prevent seed production.

Benefits of Fall Burndown Applications

A fall burndown application:

• Helps to spread out the workload in the spring.
• Provides better control of perennial and biennial weeds.
• Provides more favorable conditions for control of winter annual weeds than a similar application in early spring, because weeds are usually smaller in fall and the season tends to have more suitable days for herbicide applications.¹
• Helps provide better control of marestail than spring burndown.
• Helps to improve soil temperature and soil moisture at planting.
• Reduces the potential for soybean cyst nematodes (SCN) where SCN can overwinter by removing weed hosts like henbit and purple deadnettle.

Herbicide Recommendations for Fall Burndown

Glyphosate products are effective on most grass and broadleaf weeds, though adding dicamba or 2,4-D is recommended for broad-spectrum burndown.^1,3 Some marestail or Palmer amaranth populations may be resistant to glyphosate, requiring the addition of dicamba for management. Even in fields without glyphosate resistance, including dicamba with glyphosate can help increase the consistency of marestail and Palmer amaranth control.^1,2

As fall temperatures start to get colder and foliar herbicide effectiveness decreases, the addition of a residual herbicide may be beneficial in corn or soybean rotations. Residual herbicide applications in the fall can help manage later-germinating winter annual weeds that might not be present at the time of the initial application. An effective fall application should result in a field that is mostly free of weeds—at least until temperatures begin to warm up in the spring.

The best time to apply herbicides in the fall is on days when the morning low is above freezing.¹ The best foliar herbicide activity will occur if applications are made in the middle of multi-day periods of warm daytime air temperatures (50 °F or higher), because the foliar activity of herbicides like glyphosate and 2,4-D is reduced in lower temperatures.¹ If applications are made in cooler conditions, residual products may be permissibly tank mixed with foliar products when weather conditions might allow additional weed emergence.¹

In fields with heavy corn residue, increase spray volume or decrease speed to increase carrier volume.¹ Many weeds will be shielded by residue, so spray coverage can be compromised if adjustments are not made.¹ Using residual products in residue-heavy fields may also increase the consistency of winter weed control, because precipitation can wash these products off the corn residue and into the soil where they can still be effective.¹

The earlier the fall application is made, the more benefit a soil-residual herbicide can provide since emergence of winter annual weeds is often not complete. Applications later in the fall often diminish the need for a soil-residual herbicide, since most of the winter annual weeds have emerged by that time. However, there can be significant germination of winter annual weeds throughout the winter months depending on the year’s weather conditions.

Autumn™ Super Herbicide is one option that provides burndown of emerged weeds with residual activity to help create a clean seed bed at planting. Other herbicides that provide residual activity on winter annuals include metribuzin and chlorimuron ethyl, sulfentrazone, and flumioxazin. These herbicides can also be tank mixed with glyphosate, dicamba, and 2,4-D for improved control of emerged weeds. Convintro™ herbicide contains a breakthrough active ingredient (diflufenican) with residual control to help manage resistant Palmer amaranth and waterhemp in corn and soybean in the US that has a site of action in group 12 PDS inhibitors. Combining Convintro™ herbicide with appropriate tank mix partners helps to broaden the spectrum of weed control. For corn, tank mix options include atrazine and labelled fall residuals. For soybean, permissible tank mix options include metribuzin and labelled fall residuals.

The application of residual herbicides in the fall does not remove the need for residual herbicide applications in the spring.² Residual herbicides applied in the fall generally provide little to no control of summer annual weeds the following year, especially in soybean. Fall herbicide applications should be part of a comprehensive weed management program which could include spring burndown, at-planting, and in-crop herbicide applications. Programs should be designed to help minimize the risk of weed resistance and weed species shifts.

Be sure to read the herbicide label for any plant back restrictions and corresponding seed trait systems to avoid any carry over that could injure corn or soybean planted the following spring.

Tips for Good Application Practices

• Timing: Spray post-harvest once crop residue settles and weeds actively emerge, but before a hard killing frost or frozen ground.
• Temperature: Ensure daytime highs are consistently above 40 °F to 50 °F so weeds can metabolize and move the chemical.
• Adjuvants: Include proper drift control and surfactants to improve contact through leftover crop stubble.²
• Spray Volume: Use adequate water carrier volumes (10 to 15 gallons per acre) to get maximum contact coverage.

Sources

¹Zimmer, M. and Johnson, B. 2022. Fall applied herbicides and winter weed control. Purdue University Extension. https://extension.entm.purdue.edu/newsletters/pestandcrop/article/fall-applied-herbicides-and-winter-weed-control-2/
²Anderson, M., Hartzler, B., and Jha, P. 2022. Fall burndown treatments for winter annual weeds. Iowa State University Extension. https://crops.extension.iastate.edu/cropnews/2022/09/fall-burndown-treatments-winter-annual-weeds
³Lingenfelter, D. 2025. Fall weeds: Burndown and control in cover crops. Pennsylvania State University Extension. https://extension.psu.edu/fall-weeds-burndown-and-control-in-cover-crops
⁴Copes, J., Stephenson, D. O., and Miller, D. K. 2018. Fall and spring burndown considerations. Louisiana State University, LSU AgCenter. https://www.lsuagcenter.com/profiles/aiverson/articles/page1517843467900
Web sources verified 10/01/2026. 1123_154368