Plant Growth Regulator Use in Cotton

Plant growth regulator use has become commonplace in cotton production over the past 30 years.  However, as PGRs have become inexpensive, over application has occurred in some instances.  While some areas of the state have enjoyed adequate rainfall this year, others have went long periods of time with very limited rainfall.  In areas where drought has been an issue, caution is urged with respect to PGR use.  The following is offered with respect to PGR use in cotton:

1.  Let the plant dictate application timing and rate.  The youngest fully expanded internode occurs between the fourth and fifth node down from the terminal.  If this internode begins to exceed 2.5″ in length, a PGR application may be warranted.  The longer the length of this internode, the greater the application rate warranted.
2. Be mindful of weather conditions in the 14 days following PGR application.  If dry weather is predicted in the 14 days following a PGR application, you may consider cutting the rate back or delaying the application altogether.
3. Use whatever product you like best.  Research at Mississippi State has shown that no one product offers superior performance to another.  If you prefer to go as cheap as possible, by all means do so.  If you would rather handle less product, use a formulation that is typically applied at 2-4 oz/A versus 8-16 oz/A.
4. A good fruitload is the best PGR on the market.  Maintaining a good fruitload will help naturally regulate growth and development of the cotton plant.  If areas where the fruitload is reduced, PGR applications may be warranted to prevent excessive vegetative growth.
5. Do not apply a PGR with the intention of increasing yield.  A quick search of previous research will reveal that PGRs may increase yield, decrease yield, or have no effect on yield.  Plant growth regulators should be applied to manage vegetative growth.  Period.  Managing excessive vegetative growth will help with penetration of insecticides, aid in leaf removal at the end of the year, and facilitate a quicker harvest.