Brake®: A Potential New Herbicide for Palmer Amaranth Control – What Have We Learned?

The expansion of herbicide-resistant populations of Palmer amaranth has placed significant pressure on weed control programs for southern cotton growers.  This problem is magnified because few herbicides are registered for use in cotton that provide extended residual control of Palmer amaranth.  Such lack of options limits the capacity to alternate herbicide mechanisms of action for resistance management, and has prompted efforts to develop novel and comprehensive herbicide programs.  Brake® (a.i. fluridone) is a bleaching herbicide.  Its use would represent a new mechanism of action for Palmer amaranth control in cotton.  Fluridone was originally evaluated in cotton in the late 1970’s and early 1980’s.  During that period, fluridone was reported to be a broad-spectrum preemergence herbicide with good cotton tolerance that was effective at relatively low use rates and provided good residual control.  Currently, fluridone is labeled in the U.S. as an aquatic herbicide.  In 2012, SePRO Corporation in cooperation with Cotton Incorporated and the National Cotton Council initiated a research program to evaluate Brake for Palmer amaranth control in cotton using conventional cultural practices.  Trials were conducted across the cotton belt with emphasis on determining use rates specifically targeting Palmer amaranth, and to evaluate integrated weed management programs using Brake as a base residual herbicide.  Preliminary results indicate that Brake effectively controlled Palmer amaranth when there was sufficient moisture to activate the herbicide.  Once activated with sufficient rainfall or supplemental irrigation, Brake provided long-term residual control (>8 weeks).  Weed escapes generally occurred prior to activation or under drought conditions.  Results will be reviewed and potential weed management programs using Brake will be discussed.