Dithiopyr and Florasulam Combinations for Broadleaf Weed Control in Turf.

Most lawn care professionals use phenoxy-based herbicides to control broadleaf weeds in the spring but applications are often ineffective when temperatures are suboptimal.  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) when mixed with dithiopyr (S,S’-dimethyl 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-3,5-pyridinedicarbothioate) would be effective for broadleaf weed control during these conditions.  Field studies were conducted from 2007 through 2012 to determine the effect of florasulam and dithiopyr applied alone and in tank mixtures on broadleaf weed control in both cool and warm season turfgrass.  Applications were made prior to or at typical preemergence crabgrass, Digitaria sp. timing across the eastern and midwestern US.   Studies were conducted in locations that contained white clover, Trifolium repens, and dandelion, Taraxacum officinale, to assess efficacy of these herbicides applied at this early timing on key weeds common in residential turf.  Florasulam applied alone or in combination with dithiopyr controlled white clover, dandelion and other broadleaf weeds.  At this early timing, other herbicides mixtures containing 2,4-D were less effective.  Florasulam combined with dithiopyr improved weed control in an additive or synergistic manner.  These two herbicides applied together may reduce or eliminate the need for a later season postemergent herbicide treatment.