Control options for volunteer corn in corn
T he word "volunteer" is an odd term to describe rogue corn plants. Usually reserved for those eager beavers who provide cold refreshments at field day events, "volunteer" in this case refers to weeds that spring up in fields as a result of ear and kernel losses from the previous season.
Lodging—caused by adverse weather conditions, insects and poor stalk quality—and harvest inefficiencies contribute most frequently to problems with volunteer corn, explains Reid Smeda, a University of Missouri researcher and weed physiologist.
Research indicates that the extent of yield losses from volunteer corn varies widely, depending on field population densities. University of Missouri research conducted in 2008 and 2009 shows volunteer corn is a competitive weed capable of stealing significant corn yields—in excess of 50%, in some scenarios. Pioneer Hi-Bred research results from 2007 showed that corn yield losses of approximately 13% occurred in fields only when high volunteer corn densities were present.
Beyond yield losses, the usefulness of Bt technology can be negatively affected, says Christian Krupke, a Purdue University Extension entomologist. Volunteer corn does not necessarily express the full dose of Bt toxins, so insects may survive exposure and, over time, create a population of resistant insects, he explains.
Control options. If the previous crop you grew was conventional corn, you have more options, says Ken Ferrie, Farm Journal Field Agronomist.
For one, consider rotating to soybeans. Another option is to plant Roundup-tolerant corn and use Roundup herbicide in a postemergence application. If you grew glyphosate-resistant corn last year, plant LibertyLink corn and apply a postemergence application of Liberty.
It gets tricky, though, Ferrie adds, when you grow continuous corn with hybrids that contain both Roundup Ready and LibertyLink traits.
"Those traits stacked together can be good in a corn-soybean rotation, but in a corn-on-corn rotation you really need to separate those traits, so you can use one or the other to clean up weeds," he says.
Another option that is probably next to impossible for someone in the northern corn growing areas is to plant corn later than normal.
"Go out and get your seedbed ready. Level up that ground and just wait for the right soil temperature," Ferrie says. "At 50°F corn germinates, and at 55°F it gets really active. You want to let that volunteer corn sprout up to about two collars and then spray Fusilade or Poast or work the ground again with secondary tillage, such as a field cultivator."
Ferrie adds that today’s vertical-till harrows are not very good at removing volunteer corn and can make it worse. "It can shatter those corn ears and cause reseeding," he cautions.
Overall, Ferrie anticipates more volunteer corn in corn fields this season.
"If you had a 20-bu. or 30-bu. harvest loss when you went through the field last fall, you will have a mess this spring," he says. "Even if 90% of it was killed by frost last fall, that other 10% will have to be managed. You better be proactive to address the issue. Don’t wait until the problem’s here. Get on top of it as soon as you can."