Managing Late Season Cotton Growth

A number of calls have came in this week regarding management of late season cotton growth.  For the greater part of the growing season, fruit retention has been outstanding in the 2016 MS cotton crop.  However, about two weeks ago significant levels of shed started to occur.  Up to that point, plant growth regulator applications had been minimal in many cases due to the high level of fruit retention.  It has been said many times that a good fruit load is the best plant growth regulator on the market and this has been proven once again in 2016.

Several things should be taken into account when considering management of late season cotton growth.  At this point in the growing season, the calendar date is of utmost importance.  Considering the time required for a fruiting form to develop into a mature boll, August 20th – 25th is generally considered the latest that you can count on a white flower developing into a boll that will end up in the picker basket.  Keep in mind, the weather can have a dramatic impact of that number.  Having said all of that, we do not need additional nodes on cotton plants at this time.  The goal at this time should be to get flowers to climb cotton stalks and bloom out the top by the dates outlined above.  Any flowers that occur after these dates may or may not develop into mature bolls and be harvested.

The internode between the fourth and fifth node downward from the terminal is considered the youngest fully expanded internode.  If this internode is less that 2.5″ in length, a PGR application may not be warranted.  The exception to this would be when you have a crop that has experienced a large amount of shed.  The plant will likely try to add additional vegetative growth which can result in a “switch” that is of little to no value given that fruit on this part of the plant will likely not mature prior to harvest.  If you have a crop that has relatively short internodes but has experienced shed, a PGR application may help minimize unneeded vegetative growth.

Close examination of plants in a given field, knowledge about varietal growth habits, and understanding the productive potential of a given field as well as the information above should all be factored into the decision of whether or not to apply a PGR late in the season.