Many fields in southern Iowa have significant infestations of volunteer corn.

Research at Iowa State University in 2007 found that one volunteer corn plant per 10-foot of row resulted in a 1.3 percent yield loss. South Dakota State University researchers found that volunteer corn was much more competitive in soybean than corn, thus management is critical in both corn and soybean to protect yields.

The widespread adoption of Roundup Ready corn has complicated management of volunteer corn in corn. Few options, other than cultivation, are available to control volunteer control once this year’s corn has emerged. If this year’s hybrid carries an herbicide resistant trait not found in last year’s hybrid, then the appropriate herbicide can be used (e.g. use of Ignite/Liberty on LL corn in 2009 when RR corn was planted in 2008). Ignite often does not provide complete kill of corn since it is a contact herbicide, but it will greatly reduce the plant’s competiveness by killing emerged leaves.

For no-till fields infested with volunteer corn that are not yet planted, knowing the herbicide traits in the prior year’s corn is critical. If resistant traits rule out glyphosate, either paraquat or SelectMax can be used. 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. Like Ignite, paraquat is a contact herbicide and may not provide complete control of corn.

Management of volunteer corn in soybean is much easier than in corn due to the availability of the ACC-ase herbicides. Poast Plus is not as active on volunteer corn as the other ACC-ase herbicides. Raptor also provides good control of volunteer corn.

Volunteer corn is highly competitive with both corn and soybean. Timely management is critical in order to protect crop yields infested with this plant.

Bob Hartzler is a professor of weed science with extension, teaching and research responsibilities. He can be contacted by e-mail at hartzler@iastate.edu or phone (515) 294-1164.