Growth Stage Cutoffs for Herbicide Applications in Corn (06/10/21)
Despite our challenging start to 2021, many early planted corn fields are rapidly approaching the growth stage and height-restriction cutoffs for postemergence corn herbicides. If we go off of growth stage restrictions, we start losing many popular options once we reach V5 to V6 corn (5 to 6 visible leaf collars). If we base our staging on height, then some of the earliest cutoff timings are 8-inch corn for broadcast applications of 2,4-D, and any atrazine must be applied before corn reaches 12-inches in height. If corn is 12 inches or taller, the atrazine must be left out of the tank. Many premix herbicides also have a cutoff of 11-inches which is driven by the Group 15 (acetochlor) product in the premix. Keep in mind that the cutoff for many products is based on growth stage or corn height, whichever comes first. There are plenty of options available to apply to later growth stages, but be sure to know the cutoff for your product of choice. See the “When to Apply” column on pages 22 through 24 in the 2021 NDSU Weed Control guide for height and growth stage restrictions of postemergence herbicides in corn.
Extension Weed Specialist