The Utility of Stance™ for Managing Growth of New Earlier Maturing Cotton Varieties In Georgia.

Stance™ is a plant growth regulator (PGR) commonly used in cotton. It is generally applied at lower rates than mepiquat-containing PGRs, as it contains over twice the concentration of Mepiquat Chloride (MC) plus cyclanalide which acts as a synergist to MC. Since it contains two active ingredients and is applied at lower rates than standard MC products, it is generally thought to be more forgiving in regard to the risk of over-suppressing vegetative growth, especially when dry conditions prevail after application. Now that Georgia’s predominant cotton variety, DP 555 BR, has left the market, several of the now-common varieties planted in Georgia are somewhat earlier maturing than DP 555 BR, thus less aggressive in terms of vegetative growth potential. When DP 555 BR was widely planted, growers generally implemented an aggressive PGR management strategy to suppress growth of DP 555 BR, using generally higher MC rates in multiple applications. A similar strategy used on the newer earlier maturing varieties could increase the risk of over-suppressing growth, therefore forcing the crop into a premature cutout and preventing the formation of an adequate number of fruiting sites necessary to achieve optimal yields. Since Stance™ is generally less-suppressive than MC products, the use of Stance™ may be more appropriate for these early maturing varieties if a PGR application is needed to suppress plant height, whereas MC may be more appropriate for later maturing or more aggressive varieties. Experiments were conducted in 2009 through 2011 in Tifton, GA and Midville, GA, to investigate the response of an early maturing variety and a late maturing variety to various PGR management strategies. Trials were conducted using a randomized complete block design containing four replications. The objective of the first experiment was to determine if Stance™ is more appropriate for pre-bloom PGR applications for earlier maturing varieties. The treatments consisted of a non-treated control, Stance™ applied at a rate of 2 oz/A to 9-10 leaf (lf) cotton, followed by Stance™ at 3 oz/A at early bloom (EB); Stance™ applied at a rate of 2 oz/A to 9-10 lf cotton, followed by 16 oz/A MC at EB; Stance™ applied at a rate of 3 oz/A to 9-10 lf cotton, followed by 16 oz/A MC at EB; MC applied at a rate of 8 oz/A to 9-10 lf cotton, followed by 16 oz/A MC at EB; and lastly MC applied at a rate of 12 oz/A to 9-10 lf cotton, followed by 16 oz/A MC at EB . The varieties included in this experiment were DP 1050 B2RF (later-maturing) and FM 1740 B2F (early maturing). The objective of the second experiment (2009 and 2010 only) was to determine if Stance™ used season-long is more appropriate for earlier maturing varieties whereas MC used season-long may be more appropriate for later maturing or more aggressive varieties. PGR treatments used in this experiment included a non-treated control; 2 oz/A Stance™ applied to 9-10 lf cotton fb 2 oz/A Stance™ at EB fb 2 oz/A Stance™ at EB+2wk; 3 oz/A Stance™ applied to 9-10 lf cotton fb 3 oz/A Stance™ at EB fb 3 oz/A Stance™ at EB+2wk; 4 oz/A Stance™ applied to 9-10 lf cotton fb 4 oz/A Stance™ at EB fb 4 oz/A Stance™ at EB+2wk; 8 oz/A MC applied to 9-10 lf cotton fb 8 oz/A MC at EB fb 8 oz/A MC at EB+2wk; and 12 oz/A MC applied to 9-10 lf cotton fb 12 oz/A MC at EB fb 12 oz/A MC at EB+2wk. The varieties included in this experiment were DP 555 BR (later-maturing) and FM 1740 B2F (early maturing). The results from the first experiment suggest that Stance™ applied during the pre-bloom period may adequately suppress plant height for both varieties, especially FM 1740 B2F, when followed by MC at EB. However, preliminary data in 2011 suggests that the use of MC for the EB application, following a pre-bloom application, may suppress plant height adequately, regardless of the product or rate used for the pre-bloom application. Evaluation of plant growth will continue for the remainder of 2011 to verify these preliminary results. Results from the second experiment indicated that season-long use of Stance™ at the 2 oz/A rate on FM 1740 B2F resulted in similar plant height to that of DP 555 BR treated with 8 oz/A MC season-long, suggesting that the use of Stance™ may be more appropriate for earlier maturing varieties like FM 1740 B2F.