Issue No. 5, Article 6/April 28, 2006
Control of Volunteer Corn
Many cornfields around the state soon greened up following the 2005 harvest, not because of weed growth but because of the season's "second crop": volunteer corn. While some corn seed was lost due to fall germination and some additional seed was lost during the winter months, volunteer corn may be a common weed problem in soybean fields and cornfields during 2006. This may not be much cause for alarm to everyone, but some volunteer corn plants may contain traits that reduce the effectiveness of certain herbicides. It might be timely to review options for volunteer corn control in soybean and corn.
Control in Soybean
Control of volunteer corn is usually much easier and more complete in soybean than in corn. Several soil-applied and postemergence herbicide options are available that can provide excellent control of volunteer corn in soybean. Postemergence soybean herbicides are generally more effective than soil-applied herbicides. Keep in mind, however, that volunteer corn often grows in clumps near the corn ear. Complete control of clump corn is sometimes more difficult to achieve than control of individual plants because it is harder to thoroughly cover clump plants.
Some soil-applied soybean herbicides that can provide suppression or control of volunteer corn include Scepter (or premixes containing imazaquin), Treflan (trifluralin), Command, Classic (or premixes containing chlorimuron), and Pursuit (or premixes containing imazethapyr). Most of these products can be surface applied without incorporation in no-till systems, and absence of soil disturbance may help reduce the amount of volunteer corn emergence.
The postemergence grass control herbicides Assure II, Fusion, Fusilade DX, Select Max, and Poast Plus are effective options for volunteer corn control, even volunteer glyphosate-resistant corn. It should be noted that control of volunteer corn with these herbicides may be reduced when these products are applied in combination with certain postemergence broadleaf herbicides. Other postemergence soybean herbicides that can suppress or control volunteer corn include Scepter, Raptor, and glyphosate. Scepter and Raptor will not provide much control of volunteer ClearField corn, and glyphosate will not provide acceptable control of volunteer glyphosate-resistant corn. Efficacy ratings, application rates, and volunteer corn heights for these products appear in Table 1.
Control in Corn
In conventional corn, no selective corn herbicide will selectively control volunteer corn. If second-year corn will be planted, control of volunteer corn in the 2006 corn crop can be enhanced with the use of herbicide-resistant/herbicide-tolerant hybrids that allow the use of herbicides that normally control corn. Table 2 lists some options for volunteer corn control in the 2006 corn crop.--Aaron Hager and Dawn Nordby