Volunteer corn: A growing soybean weed problem

Members of the Weed Science Society of America identified volunteer corn as a notable weed problem in soybeans for the first time in its 2025 survey. Volunteer corn can cause yield loss, grain dockage and, potentially, fuel corn rootworm populations in soybean fields.

Many farmers believe their tank mix will control volunteer corn, but unlike troublesome soybean weeds such as waterhemp — which are gradually gaining resistance to multiple herbicide groups — volunteer corn comes from the dropped seeds and ears of last fall’s hybrids, which are bred to tolerate an increasing number of herbicides. That makes control harder.

Use effective chemistry wisely

Fortunately, soybean growers still have effective chemical tools such as clethodim or quizalofop. Their value depends on proper use rates, grass herbicide antagonism and herbicide-tolerant trait stacks.

Farmers commonly spray graminicides such as quizalofop or clethodim, in tank mixes with broadleaf herbicides like 2,4-D choline (Enlist One® herbicide), dicamba, glyphosate or glufosinate. Some tank-mix combinations can create antagonism, reducing grass (volunteer corn) control.

Rate changes needed

Higher application rates of clethodim are also critical as volunteer corn height increases. Apply it at the following rates based on volunteer corn growth stage:

8 oz. per acre of clethodim if volunteer corn is V4 or less (12 inches tall)
12 oz. per acre on V5 to V7 corn (24 inches tall)
16 oz. per acre if volunteer corn is V8 or higher (36 inches tall).

Paying attention to adjuvant use is also critical. Many clethodim labels call for either a crop oil concentrate or a nonionic surfactant in the tank mix and an ammonium sulfate product may be added. Be sure to read and follow all herbicide label requirements.

Sequential applications

Sequential applications of 2,4-D choline and quizalofop offer another way to overcome antagonism at lower herbicide rates.

“Finding time to make an application and pay for another post application creates challenges to using quizalofop, compared to just increasing the rates of clethodim to avoid a second spray and achieve good volunteer corn control,” said Debalin Sarangi a University pf Minnesota weed scientist.

University of Minnesota Extension Crops Educator Ryan Miller said he is receiving more questions from farmers about a new wrinkle in volunteer corn. Advanced seed trait technology, such as Vorceed Enlist corn or PowerCore Enlist corn, adds tolerance to 2,4-D, glyphosate, glufosinate and FOP herbicides, plus rootworm control.

“If these hybrids have header or ear loss that produces volunteer corn the following year, using a FOP herbicide like quizalofop is no longer an option,” Miller said. “The primary control tool for Enlistvolunteer corn becomes clethodim.”

The other big issue with volunteer corn is that it becomes a viable host for corn’s most problematic insect pest. “Corn rootworm can actually complete a life cycle if volunteer corn grows too long into the season,” Miller said. “If they pupate in early to mid-July, then rootworm will be there in next year’s corn crop.”

Volunteer corn in corn

Volunteer corn in a subsequent corn crop creates its own challenges. Fewer herbicide options exist for volunteer corn in corn, but control is possible through correct herbicide tolerance trait selection and trait rotation. Examples could include quizalofop in Enlist corn to control volunteer corn that does not include the Enlist trait or using glyphosate to control conventional volunteer corn in glyphosate-tolerant corn. Know your previous year’s corn traits, check with your crop protection adviser, and always read and follow label directions.

Precision application technology offers another avenue, particularly where separate applications aren’t practical.

University of Nebraska research used see and spray dual-tank technology to accomplish two separate applications in one pass. The volunteer corn in the corn trial compared single-tank versus dual-tank applications of quizalofop + 2,4-D choline (Enlist One) at two rates: 5 oz. per acre and 10 oz. per acre. The products were applied separately (in different tanks and with different nozzles) and as a tank mix to test for antagonism.

The tank-mix control ratings (20 days after post application) showed 76% control at the 5 oz. rate and 93% control at the 10 oz. quizalofop rate, proving the antagonistic effect at the lower rate. When the herbicides were sprayed from individual tanks and nozzles, both the 5 oz. per acre and 10 oz. per acre rates achieved 99% control

Dial in your combine

The combine is an important tool in volunteer corn control in the following year’s soybean crop. Proper header settings, crop moisture levels and speed should keep kernels and ears from hitting the ground.

“If we pick the right hybrids, don’t cheat the herbicide rates, harvest at the right time, don’t have a storm, and our combines are set appropriately, we shouldn’t have a ton of volunteer corn every year,” Miller said.