Evaluation of Pix Ultra and BAS130 01W on plant architecture, fruit distribution, yield, and yield components of two cotton cultivars

Plant growth regulators are commonly used to control excessive vegetative growth in cotton, Gossypium hirsutum L. Pix Ultra (mepiquat chloride plus Boron, used commercially only in California) was evaluated on Sure Grow 125 and Stoneville 474 cultivars, in field plot experiments at Mississippi State, MS in 1997 and 1998. An experimental compound BAS 130 01W (Mepiquat Penta-Borate) was evaluated similarly in 1999. Treatment levels were (1) control 0.0 L ha−1; (2) 1.16 L ha−1 split 580 ml + 580 ml; with first application applied at early bloom and second application 2 wk later; (3) 1.16 L ha−1 split 290 ml + 290 ml + 290 ml + 290 ml; (4) 2.20 L ha−1 split 440 ml + 880 ml + 880 ml; (5) 2.64 L ha−1 split 880 ml + 880 ml + 880 ml; and (6) 2.76 L ha−1 split 440 ml + 1160 ml + 1160 ml; with first application of treatment levels 3 through 6 applied at matchead square with subsequent applications 2 wk apart. Pix Ultra and BAS 130 01W significantly reduced plant architecture without reducing amount of lint. Most treatment levels produced significantly larger bolls, larger seed, and resulted in a lower lint percentage. Pix Ultra and BAS 130 01W each increased earliness 3 to 6 days (1 to 2 nodes). The year, 1997, produced low stress growing conditions and Pix Ultra had no significant effect on lint yield. In 1998, growing conditions were stressful due to cloudy weather, excessive rainfall, and high populations of tobacco budworm, Heliothis virescens F. and bollworm, Helicoverpa zea Boddie and Pix Ultra treatment levels 2 (1.16 L ha−1), 3 (1.16 L ha −1), and 4 (2.20 L ha−1) significantly increased lint yield of Sure Grow 125 and treatment level 2 (1.16 L ha −1) significantly increased lint yield of Stoneville 474. In 1999, with growing conditions similar to 1997, BAS 13 0 01W at treatment levels 4 (2.2 L ha−1), 5 (2.64 L ha−1), and 6 (2.76 L ha−1) significantly increased lint yields.