Topramezone is a herbicide labeled for broadleaf and grassy weed control in corn and is currently under evaluation by BASF for use in cool season turfgrass.  Topramezone functions by inhibiting HPPD (hydroxyphenylpyruvate dioxygenase) and the formation of plant carotenoids.  Topramezone effectively controls a broad range of weed species and is safe to cool season turfgrass species.  Combinations of topramezone with triclopyr have been found to reduce whitening symptoms on susceptible plant species while increasing both grass and broadleaf weed control.

This study was conducted on two sites in 2012.  Ground ivy (Glechoma hederacea) was evaluated in tall fescue (Festuca arundinacea) at Kentland Farm in Whitethorn, VA.  Nimblewill (Muhlenbergia schreberi)  and white clover (Trifolium repens) in Kentucky bluegrass (Poa pratensis) was evaluated at the Glade Road Research Center in Blacksburg, VA.  Both trials were initiated on July 21, 2012 and sequential applications were made on August 10, 2012.  Topramezone was applied at 36 g ai/ha alone and in combination with triclopyr at 561 g ai/ha or quinclorac at 841 g ai/ha.  All topramezone treatments contained methylated seed oil.  Mesotrione was included as a comparison at 280 g ai/ha.  Non-ionic surfactant was included with the mesotrione treatment.

Initial ground ivy cover ranged from 43 to 57%.  At 2 weeks after initial treatment (WAIT), topramezone plus triclopyr controlled ground ivy 97%, whereas all other treatments did not exceed 73% control.  At 4 WAIT, all treatments controlled ground ivy between 95 and 99%.  At the conclusion of the study, topramezone alone, plus triclopyr or plus quinclorac controlled ground ivy between 99 and 100%. Mesotrione applied alone controlled ground ivy 95%.

Initial nimblewill cover ranged from 15 to 38%.  At 2 WAIT, topramezone plus triclopyr or quinclorac controlled nimblewill 80 and 80%, respectively, whereas all other treatments did not exceed 57% control.  At 4 WAIT, topramezone alone, plus triclopyr or plus quinclorac controlled nimblewill 78, 99 and 90%, respectively. Mesotrione applied alone controlled nimblewill 58%.  At the conclusion of the study, control was between 75 and 100% across all treatments.  

Initial white clover cover ranged from 20 to 35%.  At 2 WAIT, topramezone plus triclopyr or quinclorac controlled white clover 97 and 100%, respectively, whereas all other treatments did not exceed 13% control.  At the conclusion of the study, all topramezone treatments controlled white clover 100%.  Mesotrione only controlled white clover 43%.