Trifloxysulfuron-sodium (TFS), an acetolactate synthase-inhibiting herbicide, utilized postemergence in cotton (Gossypium hirsutum L.) to control certain broadleaf weeds, has been reported to cause stunting visually similar to mepiquat chloride (MC) application. The objective of this research was to examine cotton response, in multiple environments to POST broadcast application timings and rates of TFS with and without MC, to determine if TFS application alters the need for MC application. Six TFS treatment combinations were evaluated in Virginia and North Carolina in 2005 and 2006, including an untreated check, and a fifth node application (FNA) or eighth node application (ENA) with rates of 5.3 g ai ha-1 or 7.9 g ai ha-1, with or without MC. Trifloxysulfuron-sodium application had no influence on plant height, height-to-node ratio, or maturity; however, the number of apical main-stem nodes increased with the FNA compared to untreated cotton. Mepiquat chloride application reduced harvest plant height by 10%, reduced height-to-node ratio by 8%, and hastened maturity as measured by nodes above white flower. Lint yield and lint percentage were not altered by TFS or MC application, while fiber quality results were mainly unaffected. These results suggest that TFS application does not have the season-long effects on plant growth and maturity attributed to a MC application.
