A few early planted fields have been defoliated and more will follow soon. At least one field in Florence County has already been harvested.
There are two methods we use to determine when to defoliate cotton: the percent of open bolls method and the nodes above cracked boll method. Here is an excerpt from the Clemson Cotton Production Guide written by specialist Mike Jones on using these methods.
For the best results, both methods should be used. At times, as the diagram below shows, the percent of open bolls can be misleading.
Here is a field in Dillon County that is just about ready to defoliate.
Once ready to defoliate, there are dozens of combinations of products that can be used successfully. Just make sure something is being included for defoliation, opening bolls, and suppressing regrowth. Tribufos(defoliant), ethephon(boll opener), and thidiazuron( regrowth suppressant & defoliant) are usually a good combination, though there are plenty of others that will also work. These chemicals can be found on pages 83-86 of the Cotton Production Guide. A harvest aid like Aim or ET may be needed as well if there is a heavy population of morning glories present. Check labels for tank mixing compatibility.