By Amit Jhala
Extension Weed Management Specialist
Figure 1. Several herbicide options are available for managing volunteer corn in soybean. Management in corn will be more challenging.
Volunteer corn is a competitive weed in the corn/soybean cropping system and if not controlled, may result in yield penalty. In addition, volunteer corn encourages the dispersal and survival of western corn rootworm and gray leaf spot disease, limiting the benefits of a corn-soybean rotation. Therefore, it is important to control volunteer corn.
Control of Volunteer Corn in Soybean
Control of volunteer corn in soybean is easier because a number of graminicides (grass herbicides), such as Select Max, Poast, Assure II, Fusilade, and Fusion are labeled for this use. For more information on application rates of grass herbicides for control of volunteer corn in Roundup Ready or Xtend Soybean, see Volunteer Corn in Soybean: Impact and Management.
LibertyLink soybean is also available in the marketplace and Liberty can control volunteer corn, but ONLY if the hybrid corn planted last year was NOT LibertyLink-resistant. Liberty is a nonselective, contact, postemergence herbicide for broad-spectrum weed control in LibertyLink soybean. An update to the Liberty label allows a maximum cumulative rate of 87 fl oz/acre per growing season. Two applications, each of 32 to 43 fl oz/acre, could be made in LibertyLink soybean.
Remember that Liberty can only be applied in LibertyLink soybean NOT in Roundup Ready or Roundup Ready 2Xtend soybean. Application of graminicides (Assure II, Select Max, Poast, Fusilade, Fusion) will be the only option for controlling volunteer corn in
Roundup Ready or Roundup Ready 2Xtend soybean.
Control of Volunteer Corn in Corn
Control of volunteer corn in continuous corn is difficult because volunteer corn is also selective to corn herbicides.
- If only a Roundup Ready corn hybrid was planted the previous year and Roundup Ready + LibertyLink hybrid corn is planted this year, Liberty can be applied for control of glyphosate-resistant volunteer corn. Two applications, each of 32 to 43 fl oz/acre, could be made in LibertyLink corn.
- Remember that Liberty will NOT be effective if Roundup Ready + Liberty Link hybrid corn was planted last year.
Control of Volunteer Corn in Enlist Corn
- Enlist™ Corn is a new multiple herbicide-resistant corn. Enlist corn is resistant to 2,4-D choline, glyphosate, and aryloxyphenoxypropionates (FOPs), an acetyl CoA carboxylase (ACCase) inhibitor. Enlist corn is commercially available for the first time for the 2018 growing season. If Enlist corn is grown this year in a field that was under Roundup Ready/LibertyLink corn last year, volunteer corn can be controlled by applying aryloxyphenoxypropionates (FOPs).
- Assure® II is the only grass herbicide labeled to control volunteer corn in Enlist Corn. It can be applied at 5 to 12 fl oz/acre in Enlist Corn for selective control of volunteer corn. Assure® II must include crop oil concentrate (1% v/v) or nonionic surfactant (0.25% v/v). Apply Assure® II to emerged Enlist™ field corn that is at the V2 through V6 stage of development.
- The applicator must always maintain a 36-foot downwind buffer between the last treated row and the nearest downwind field edge (in the direction the wind is blowing).
- Remember that Assure II can NOT be applied in Roundup Ready/LibertyLink corn. To know more about application requirements of Assure II, see the product label.