THE INFLUENCE OF FLUOMETRON AND MSMA ON COTTON YIELD AND FRUITING CHARACTERISTICS

Field experiments conducted from 1987 through 1991 at the Delta Branch Experiment Station, Stoneville, MS, determined the effect of postemer gence topical applications of fluometuron and MSMA on cotton yield and fruiting. Herbicide treatments applied to cotton in the cotyledon to 1-leaf growth stage were 1.12 kg ai ha-1 fluometuron plus 0.25 % by vo l nonionic surfactant, 2.2 kg ai ha-1 MSMA, and a combination of 1.12 kg ha-1 fluometuron and 2.24 kg ha-1 MSMA. The commercial formulation of MSMA contained nonionic surfactant. Visual injury of cotton 14 d af ter treatment ranged from 14 to 28 % for fluometuron, 9 to 26 % for MS MA, and 22 to 34 % for the combination. Seed cotton yield at the first harvest was reduced by all herbicide treatments except in 1987 and fo r DES 119 cotton in 1990. In 1990, yield of DES 119 cotton treated wit h MSMA and the combination was less than the untreated control for the second harvest interval. Cotton yield from herbicide treatments at la ter harvests was equal to or greater than the untreated control. Only in 1988 did all treatments reduce total seed cotton yield below the un treated control. Fiber quality was not adversely affected by the herbi cides. Compared to the control, plant mapping indicated that the numbe r of sympodial branches per plant was reduced by MSMA and by the combi nation for DPL 50 cotton in 1990. Averaged over 4 experiment years, he rbicide treatments did not reduce total bolls per plant; percentage of bolls in first, second, or outer positions; highest sympodium with tw o bolls; or number of sympodium with bolls in the first or second posi tion. However, MSMA and the combination increased node number of the f irst sympodia by one and 1.5 positions, respectively, when compared to the control, indicating delayed maturity.