by Aaron Hager, Extension Weed Scientist
University of Illinois
The labels of most post-emergence corn herbicides allow applications at various crop growth stages, but almost all product labels indicate a maximum growth stage beyond which broadcast applications should not be made, and a few even state a minimum growth stage before which applications should not be made.
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These growth stages are usually indicated as a particular plant height or leaf stage; sometimes both of these are listed. For product labels that indicate a specific corn height and growth state, be sure to follow the more restrictive of the two. Application restrictions exist for several reasons, but of particular importance is the increased likelihood of crop injury if applications are made outside a specified growth stage or range. The following table lists the maximum corn growth stage for broadcast application of several post-emergence corn herbicides. Be sure to consult the respective product label for additional precautions or restrictions.