Minimum Corn Size for Postemergence Corn Herbicides

May 14, 1999
With corn emerging across much of Illinois, growers will soon be turning their attention to making postemer-gence herbicide applications to control grass and broadleaf weed species. Many postemergence corn herbicide options are available for growers to select from, and while we often stress maximum corn height or developmental stage for postemergence herbicide applications, some postemergence corn herbicide labels also indicate a minimum size or developmental stage the corn should be before an application is made. For example, the labels of two new postemergence corn herbicides, Distinct (diflufenzopyr + dicamba) and NorthStar (primisulfuron + dicamba), indicate that applications should be made to corn at least 4 inches in height. If you have questions about corn size (minimum or maximum) for a particular postemergence herbicide, consult the respective herbicide label.

Most postemergence corn herbicides require the addition of a spray additive for optimal activity. Although there are numerous additive choices available on the market, herbicide labels generally indicate which type(s) of additive should be included in the spray solution. Additive recommendations can vary depending on weed spectrum, crop growth stage, and prevailing environmental conditions. Choosing an inappropriate spray additive not only may result in less-than-acceptable weed control, but may also cause significant crop injury.--Aaron Hager, Marshal McGlamery

Author: Aaron Hager Marshall McGlamery