With the evolution of glyphosate-resistant weeds, cotton producers now rely on multiple applications of soil-residual herbicides tank-mixed with postemergence (POST) herbicides. However, the current soil-residual herbicides represent a relatively low number of herbicide mechanisms of action (MOAs), with the same few MOAs being utilized year after year. Therefore, it is important to introduce new MOAs to slow the likelihood of further resistance development. A field experiment was conducted in 2012 and 2013 to determine if fluridone, a bleaching herbicide currently not used in any agronomic cropping system, applied preemergence (PRE) would provide effective season-long control of Palmer amaranth as well as reduce the number of POST applications throughout the season. Fluridone PRE at 224, 336, and 448 g ai ha-1 did not eliminate the need for POST herbicides for Palmer amaranth control in cotton in either year. Fluridone, regardless of rate, provided comparable control to fluometuron in 2012; however in 2013, fluometuron provided less control than fluridone. Although moderate season-long control was observed in 2013, greater seed cotton yields were obtained in 2013 than in 2012, which is likely a result of greater control during the critical period for weed control. Based on this experiment, fluridone will not provide effective season-long Palmer amaranth control in the absence of a multiple POST-herbicide program.
