Lately I have had several conversations on corn and soybean herbicides focusing on the “pre rapidly changing to post emergence” world of fields that were planted prior to the recent weather. A few quick review points on corn herbicides:

  • Remember that most corn herbicides with a pre-emergence label are also labeled for early post-emergence application. The exceptions are Sharpen and Sharpen-containing products, which were strictly pre emergence, and of course, a non-selective like Gramoxone.
  • Corn herbicides have post-emergence application windows either based on PLANT HEIGHT or GROWTH STAGE or sometimes a combination thereof.
  • Corn growth staging is based on visible leaf collars- starting with the round-tipped leaf as V1.  Do refer to the label, however, as at least one outside source mentions that as a few older labels apparently do not count the first round-tipped leaf.  Counting the round tip leaf as V1 is now the standard practice.
  • Excellent charts on growth stages and labels are found in the 2013 Winfield Crop Protection Guide on Pages 46-47 and in the United Suppliers Crop protection Guide on page CORN-1.

The first products to run out of timing post-emergence, unfortunately, are Balance Flexx and Corvus, that end at V2 growth stage for safe application.