Building the Perfect Fall Burndown Tank-Mix

After harvest, the temptation is to park the sprayer and call it a season. But fall burndown might be the most underutilized tool in a corn-soybean farmer's toolbox. A well-planned tank-mix this fall sets the table for cleaner fields, a healthier seedbed, and a less stressful spring.

Start with the Right Burndown Chemistry

A solid fall burndown starts with a non-selective foundation paired with a synthetic auxin herbicide to broaden your weed spectrum. Glyphosate remains the workhorse for most operations, but relying on it alone leaves you exposed—particularly as glyphosate-resistant marestail (horseweed) has become widespread across the Corn Belt.

The standard recommendation from extension weed scientists is to pair glyphosate with either dicamba or 2,4-D. Dicamba excels on perennials like Canada thistle and dandelion, while 2,4-D provides strong control of annual broadleaves like wild mustard, chickweed, and henbit. Together, they address the two main categories of fall weed pressure in a single pass.

For fields with documented glyphosate resistance, consider building your program around paraquat + dicamba + 2,4-D instead. This combination is especially effective against hard-to-kill marestail populations. Clethodim is another option to layer in when volunteer corn or annual grassy weeds are part of your weed spectrum.

Timing matters. Iowa State University Extension recommends treating on sunny days when temperatures are above 55°F during the day and above 40°F overnight. Glyphosate and 2,4-D both move more slowly through the plant in cold conditions—apply while weeds are still actively growing for best control. If conditions aren’t ideal, consider switching from a glyphosate-based burndown to a paraquat based burndown.

Should You Add a Residual?

The case for residuals in fall burndown is situation-dependent. University weed scientists generally caution that fall-applied residuals offer inconsistent benefits compared to spring applications—most weed species aren't germinating yet, so the residual window can expire before it's most needed.

That said, there are scenarios where residuals earn their place in the tank. Fields with heavy marestail seed banks, operations planning no-till corn rotations, or fields with a history of early-emerging problem weeds can see real value from adding a PPO inhibitor like flumioxazin or sulfentrazone. For corn-following-corn or corn following soybeans, layering atrazine into the fall mix provides both burndown activity and a residual bridge toward spring—if your rotation supports it. When using atrazine in the fall, be mindful of local annual maximums so that you don’t over-apply this chemistry.

The bottom line: match residual use to your field history and rotation plan, and always check plantback restrictions before adding any product with soil activity.

"Heat Up" Your Mix with the Right Adjuvants

Adjuvants are where a lot of fall burndown programs lose effectiveness—or where farmers spend money on the wrong products.

Read more