I don’t think there is anyone in this industry that would disagree the use of Plant Growth Regulator (PGR) in cotton is more of an art than a science. Because cotton growth is such a complex interaction of variety, rainfall, temperature, soil fertility, boll load, etc there is no right recommendation for every situation. I’ve seen this year, that some people think like myself and want to get PGR in the plant early and often while others prefer to wait much later in the season for the first application. The farmer usually has the best sense of these factors on his farm and can develop the “art” of PGR application. There is not a consistent yield response to PGR use, but it definitely makes a difference in harvesting and “where” the cotton is located. Dr. Jarod Whitaker, University of Georgia Extension Agronomist provided the attached guidance document showing relative PGR requirements for currently available cotton varieties. This is a basic summary of when to start applications, and how frequently we might make applications depending on the variety. Of course the other factors of soil fertility and rainfall are very important as well.
If you would like more information about cotton management particularly the use of PGRs and how they impact plant development, please see the YouTube video of Dr. Whitaker. An update from February 2013. (33)