Virginia cotton producers use plant growth regulators to promote earliness, while also trying to control plant height and increase yield potential. A new low rate plant growth regulator, Reign has been tested recently on cotton (Gossypium hirsutum L.). A combination of two active ingredients is used in Reign, mepiquat chloride and cyclanilide, which are mixed at a 4:1 ratio. While mepiquat chloride is a standard in plant growth regulation, cyclanilide, which is also used in Finish 6 Pro harvest aid, is an auxin transport inhibitor and gibberillin synthesis inhibitor that inhibits cell growth, but not cell division. Bayer CropScience has received product registration for Reign, which was tested as TADS 15338, and expects to market the product in 2006. Label application rates are 1.5-3 fluid ounces per acre, with application timing and plant growth determining the preferred rate.

In 2005, a field test evaluating the effectiveness of Reign was performed in Suffolk, Virginia at the Virginia Tech Tidewater Agricultural Research and Extension Center. The objective of this study was to evaluate the effect of multiple treatments of Reign compared to a standard mepiquat chloride plant growth regulator (Mepex) and an untreated check, on Delta Pine 444 BR/RR. The application rates of Reign ranged from 1.5 to 3 fluid ounces per acre compared to the Mepex rates of 4 to 16 fluid ounces per acre. A total of three applications of these products were made at the same growth stage and timings for all treatments, including match-head square on June 23rd, 7-14 days after treatment on June 30th, and early bloom on July 15th. Mepiquat chloride rates were equivalent for the first two applications and increased in Mepex rates for the third application.

All treatments were evaluated on control of plant growth, maturity, and boll retention. Measurements of plant height, nodes above white flower, and plant mapping were taken to provide adequate data for these evaluations. The results of plant height showed that the Reign and Mepex treatments ranged from 65-71% of the height of the untreated. The earliness profile of Reign and Mepex treatments was enhanced. Yield and plant mapping data will be reported.