COMPARISON OF PYROXSULAM FORMULATIONS FOR GRASS AND BROADLEAF WEED CONTROL IN THE WESTERN U.S. Joe Yenish*1, Harvey Yoshida2, Daniel C. Cummings3, Kevin D. Johnson4, Roger Gast5; 1Dow AgroSciences, Pullman, WA, 2Dow AgroSciences, Richland, WA, 3Dow AgroSciences, Perry, OK, 4Dow AgroSciences, Barnesville, MN, 5Dow AgroSciences, Indianapolis, IN (34)


Pyroxsulam is the active ingredient in Dow AgroSciences’ PowerFlex® herbicide.  PowerFlex is labeled for use in winter wheat.  The currently available PowerFlex formulation contains 7.5% of active ingredient in a water dispersible granule.  A potential new formulation being evaluated contains 13.1% pyroxsulam.  The studies described herein were designed to compare crop tolerance and weed control of the two formulations.  Crop tolerance studies were conducted at 6 and 7 locations in 2009 and 2010, respectively.  Each formulation was applied at 18.4 g (1X) and 36.8 g (2X) pyroxsulam/ha with nonionic surfactant and ammonium sulfate.  In each year, only 1 location showed differences between formulations for crop tolerance.  In both cases, formulation differences occurred only with the 2X rate of pyroxsulam.  In 2009, the differences persisted throughout the growing season, while in 2010 differences were transitional and were not observed in ratings made later than 3 days after application.  Generally, injury ratings did not exceed 10% although there were a few exceptions.  Separate grass weed control studies were conducted at 13 locations in each year.  Pyroxsulam rates for the formulation comparison were 13.8 and 18.4 g ai/ha applied with nonionic surfactant and ammonium sulfate.  Targeted grasses were Italian ryegrass and downy brome.  Differences in grass control between formulations only occurred in 6 of the 26 locations.  Moreover, there was not a consistent pattern in which formulation provided better control nor were there consistent differences within or between rates.  Thus, in summary both formulations performed equally well for weed control and crop tolerance.