If the first application time is missed, weed competition can be reduced by applying nicosulfuron with drop nozzles when the corn is 2 to 3 feet tall to control secondary flushes of seedlings in the row. Cultivating the furrows after application and avoiding the use of nicosulfuron year after year in the same field will help prevent the development of resistance in johnsongrass to this material. The use of glyphosate-tolerant varieties of corn offers an inseason option for managing johnsongrass. Some of the common broadleaves in corn include redroot pigweed , common lambsquarters , green amaranth, common sunflower , common purslane , horse purslane, annual morningglory , cocklebur , hairy nightshade , black nightshade , velvetleaf , and field bindweed . Alachlor and metolachlor are mainly grass herbicides.
Cultivation is important in controlling many small broadleaves.
Dicamba and 2,4-D are low cost options but be careful because they can easily drift or volatilize onto sensitive crops and cause severe injury. Weeds must be in the seedling stage or no larger than the size of a quarter. It could be a good choice used as a buffer near sensitive crops. Bromoxynil alone does not do an adequate job of controlling redroot pigweed. Corn has a greater tolerance for metribuzin than for bromoxynil.