When Corn Goes Bad

May 26, 2009 07:00 PM

Pam Smith, Farm Journal Seeds & Production Editor

Retired University of Illinois weed specialist Marshal McGlamery used to say the only sure way to rid yourself of volunteer corn was to use the "Santa Claus treatment.” Hoe. Hoe. Hoe.
That was before rope wick applicators wipers and Roundup Ready soybeans. The fact that I remember those eras tells my age. So does the fact that I remember spending my summers walking beans.
Last year I noticed teenagers were again gaining employment by way of a corn knife or garden hoe. There was something satisfying about this sight, but I'll leave my musing about righting society's lack of work ethic to another missive.
Fact is many fields once again have significant infestations of volunteer corn. It's not too hard to figure why. The widespread adoption of Roundup Ready corn has complicated the management of volunteer corn in both crops. With Liberty Link soybeans now headed to fields, the same scenario could exist with that family of technology.
Research at Iowa State University in 2007 found that one volunteer corn plant per 10-foot of row resulted in a 1.3% yield loss in corn. South Dakota State University weed specialist Mike Moechnig says research in that state has found volunteer corn to be even more competitive in soybean.
"We always suspected volunteer corn in soybeans was causing yield loss, but quantifying it actually proves the cost to be more than we expected,” says Moechnig. "It only takes one corn plant [in soybean] in a 10 ft. by 10 ft. area to justify spray applications of $6 to $9 per acre.”
Bob Hartzler, Iowa State University agronomist notes that few options, other than cultivation, are available to control volunteer corn once this year's corn has emerged. If you used an herbicide resistant trait not found in last year's hybrid (i.e. Liberty Link in 2009 following Roundup Ready in 2008), then Ignite is an option. Hartzler notes that Ignite is a contact herbicide and it will knock corn back severely, but may not always provide complete control in this situation.
For no-till fields infested with volunteer corn that are not yet planted, it's critical to know the herbicide traits in the prior year's corn. If resistant traits rule out glyphosate, either paraquat or SelectMax can be used. Hartzler notes that a six day interval is required between SelectMax application and planting to avoid injury from the herbicide residues. Other herbicides in the ACC-ase family (Poast, Fusilade, Select, Assure, etc.) are not registered for this use. Paraquat is a contact herbicide and may not provide complete control of corn.
Management of volunteer corn in soybean is much easier due to availability of the ACC-ase herbicides. Hartzler notes that Poast Plus is not as active on volunteer corn as some of ACC-ase herbides. Raptor is another good control option of volunteer corn in soybeans.
Volunteer corn is highly competitive with both corn and soybean, adds Hartzler. This means timely management is critical in order to protect crop yields infested with corn.
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