Beltwide Evaluation of Commercially Available Plant Growth Regulators

Plant growth regulator (PGR) use has become common in cotton (Gossypium hirsutum L.) production over the past 30 years. Plant growth regulators are widely used to manage plant height and suppress vegetative growth in cotton. However, the commercial introduction of new PGRs has prompted questions regarding comparative product performance in regard to height reduction, yield, and fiber quality. The objective of this study was to compare the effect of several commercially available PGRs on cotton growth, development, yield, and fiber quality. Field research was conducted in 2007 and 2008 at 22 locations representing 12 states. Products evaluated included mepiquat chloride, mepiquat chloride plus kinetin, mepiquat chloride plus cyclanilide, and mepiquat pentaborate. A non-ionic surfactant was included with all PGR applications, as well as alone, for comparison purposes. A non-treated check was also included. Application of all PGRs reduced end of season plant height. Plant height reductions varied depending on location. The total number of mainstem nodes was reduced due to PGR application in the Southwestern and Southeastern United States; however, no differences in lint yield, micronaire, or uniformity were observed due to PGR application in any region. Minor differences were present in nodes above cracked boll, fiber length, and fiber strength. No single product provided superior performance in regard to growth regulation, yield, or fiber quality.