Volunteer corn: whether it pops up in corn or soybeans, it’s a weed and it could steal precious bushels at the end of the season. Keep your trait package in mind as that will affect your herbicide options and gain control before yield is lost. Your management strategy will be different in corn versus soybeans, and your risk varies by crop, too. Learn how and why to gain control in each crop with tips from the University of Nebraska Extension. Controlling volunteer corn in soybeans.
Unwanted corn competes with soybeans by acting as a weed. In addition, it can attract and encourage corn rootworm beetles to lay eggs in soybean fields—which increases their threat to corn the following year. Nebraska Extension also notes that volunteer corn in soybeans will likely express a reduced level of the Bt toxin compared to the corn the year before—which could select for resistance. Perhaps the most immediate impact, though, is just one volunteer corn plant every 3.5’ leads to a 20% yield loss in soybeans. Thanks to graminicides (grass killers), volunteer corn is easier to control in soybeans. Nebraska Extension lists Select Max, Poast, Assure II, Fusilade and Fusion in Roundup Ready or Roundup Ready 2 Xtend soybeans. In some cases, you can use Liberty to control corn, too. But, last year’s corn cannot have the LibertyLink trait, and you can’t use it in non-LibertyLink soybeans—unless you want a dead crop. According to the current Liberty label you can apply 87 fl oz per acre each growing season, or two applications at 32 to 43 fl oz per acre in LibertyLink soybeans. Control is more challenging in continuous corn. That’s probably obvious since you can’t use corn killer to kill volunteer corn in corn. You do have some options, however. Volunteer corn competes with your corn crop for sunlight, water and nutrients, which can limit yield potential. If you used Roundup Ready corn last year, and Roundup Ready with LibertyLink this year a simple Liberty application can manage last year’s break-throughs. If you used a stacked variety last year this method isn’t effective. Farmers using Enlist corn have a new option. Because the traits include tolerance for FOPs (aryloxphenoxypropionates), an ACCase inhibitor, you can spray that on corn that was stacked with Roundup and LibertyLink last year. Nebraska Extension says the following FOP herbicide is approved: Assure II, applied at five to 12 fl oz per acre and must include crop oil concentrate (1% v/v) or a nonionic surfactant (.25% v/v) to emerged Enlist corn between V2 and V6. Note, applicators need to maintain a 36’ downwind buffer between the last treated row and the nearest downwind field edge in the direction the field is blowing.