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Issue No. 14, Article 2/June 26, 2009

Reminder about Corn Size and Postemergence Herbicides

The combination of ample soil moisture and very warm air temperatures has contributed to rapid corn growth and development over the past several days. As you can imagine, these conditions also promote rapid growth and development of weeds. Postemergence herbicide applications in corn are progressing as conditions allow, and we would like to offer a couple of reminders:

  • Please remember that the labels of most postemergence corn herbicides indicate a maximum corn size or development stage beyond which broadcast applications should not be made. If these restrictions are not followed, the likelihood of corn injury may increase dramatically. The sizes for many postemergence corn herbicides were listed in Table 1 of "Maximum Corn Growth Stage for Postemergence Herbicides" (the Bulletin, issue 12, June 12). Broadcast applications of atrazine-containing products or glyphosate should not be made to corn over 12 and 30 inches tall, respectively.
  • Corn stalks are often inherently "brittle" during periods of rapid growth and stem elongation. Be cautious with applying growth regulator herbicides to corn at this time, as they may enhance stalks' brittleness.

--Aaron Hager

Aaron Hager

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