There are several herbicide options for postemergence grass control in corn. Some require "modified" corn hybrids such as IMI (IR/IT), Liberty Link (LL), Poast Protected (PP), or Roundup Ready (RR). Other herbicide options do not require special corn hybrids and include products such as Accent, Accent Gold, Basis, Basis Gold, and even atrazine + crop oil. Accent or Beacon are very good choices for control of shattercane and johnsongrass.|
Size of annual grasses for optimal postemergence herbicide efficacy varies by species and herbicide. A general rule of thumb for grass size is 2 inches for Basis, 3 inches for Accent Gold and Basis Gold, and 4 inches for Accent. Celebrity G, the grass herbicide portion of the Celebrity co-pack, contains the same active ingredient as Accent.
Tables 1 and 2 are reprinted from Chapter 2 of the 1999 Illinois Agricultural Pest Management Handbook. Table 1 lists corn herbicide ratings for postemergence grass control, whereas Table 2 contains information on maximum grass size according to the labels of the various postemergence corn herbicides. Be sure to read the respective herbicide labels for additional information, such as spray additives to include and any application precautions/restrictions, such as if the product can be applied to corn previously treated with certain soil insecticides.--Marshal McGlamery, Aaron Hager