Plant Growth Regulator Use in Cotton

Numerous questions have came in over the past 7-10 days regarding managing cotton growth with plant growth regulators.  While every situation can be unique with respect to cotton growth and development and subsequent plant growth regulator use, the slides given below were developed in order to serve as a general guide for variety management.

The biggest benefit from plant growth regulator use is managing vegetative growth.  There is no question that use of reputable products at appropriate rates will help manage excess vegetative growth.  With respect to effects of plant growth regulator use on yield, the data are variable.  Most data suggests that plant growth regulator use does not directly affect yield.  However, in some situations yield may be increased or decreased due to plant growth regulator use.  In short, use these products to manage the height of your crop but do not expect to see direct yield effects on a consistent basis from these applications.  The biggest issue I see on cotton with respect to plant growth regulator use is when plant growth regulators are not early in the season and excessive internode lengths (3″+) are present on the lower portion of the plant then high plant growth regulator rates are used later in the season and internode lengths of 1-2″ are present (on upper portions of the plant).

When deciding what rate to apply, several factors must be considered including variety, potential productivity (think how strong or weak your soil is), irrigation availability, and crop growth stage.  Some varieties are known for aggressive growth – on these varieties, 12-16 oz/A of mepiquat chloride at pinhead square is appropriate particularly on strong ground where irrigation is present.  However, if you have soils that may limit vegetative growth and do not have irrigation, little to no mepiquat chloride may be warranted at pinhead square.  Furthermore, be sure to examine the crop in the field to determine how well it is coming along.  Examine the internode length between the 4th and 5th node downward from the top of the plant – if this length exceeds 2″ a plant growth regulator application is warranted.  Adjust your rate taking into account the previously mentioned factors.  Follow the link below for guidance on plant growth regulator use in cotton.

Cotton Management Slides