Timely postemergence herbicide applications in corn

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

For several years, MSU has demonstrated the importance of timely herbicide applications to prevent the loss of yield in corn. We have shown that it is necessary to control weeds before they reach 4 inches of growth to prevent measurable yield reduction. Two-pass herbicide applications (preemergence followed by postemergence or two postemergence) or timely single postemergence applications with residual control, are most effective at preserving yield and maximizing gross margin. Information about the effectiveness and economics of preemergence and post emergence herbicide programs can be found in the three-year summary of Commercial Herbicide Program Comparisons found on the MSU Weed Science website at http://www.msuweeds.com/publications/.

Herbicide options for total postemergence weed control are dependent on the hybrid planted in the field, and the size of the corn at the time of application. Several herbicides have height limitations of 12 inches or less, such as atrazine and dicamba, while other herbicides may be applied to taller corn. Identifying the height and growth stage of the crop is important to prevent possible crop injury. Specific height restrictions for postemergence herbicides can be found on their label or in the 2007 Weed Control Guide for Field Crops in table 1J on page 52.

Timely weed control is important in minimizing yield loss due to weed competition and crop injury due to off-label herbicide applications. During ideal growing conditions, this window of opportunity may be very small, so it is important to monitor the progress of your crop and scout for weed problems before they cause lasting damage

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