A Programmed Approach to Controlling Broadleaf Weeds in Cool Season Turfgrass Utilizing Granule and Liquid Formulations of Florasulam.

Most turf managers use phenoxy-based herbicides to control broadleaf weeds but applications are often ineffective when temperatures are cool in the early spring or late fall of the year.  This research was initiated to determine if florasulam (N-(2,6-difluorophenyl)-8-fluoro-5-methoxy (1,2,4)triazolo(1,5-c)pyrimidine-2-sulfonamide) applied  as a granule or sprayable liquid formulation  with or without dithiopyr (S,S’-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedicarbothioate) would  control broadleaf weeds under these conditions.  Six field studies were initiated the fall of 2013 to determine the effect of florasulam, applied alone or with dithiopyr either as an impregnated fertilizer granule or in a liquid tank mixture, on broadleaf weeds in cool season turfgrass.  Applications were made in October 2013 with or without follow-up applications in early spring of 2014.  Studies were conducted in locations that contained white clover, Trifolium repens, and dandelion, Taraxacum officinale, to assess efficacy of the herbicides applied at these timings on weeds commonly found in residential turf.  Florasulam liquid applied alone or in combination with dithiopyr controlled white clover, dandelion and other broadleaf weeds regardless of when applications were made.  Control of dandelion from the granule formulation was optimized when a fall application was followed by a second application in early spring.