RESPONSE OF TALL FESCUE CULTIVARS TO MESOTRIONE APPLIED AT ESTABLISHMENT. K.A. Venner*, S. Hart, and C.J. Mansue, Rutgers University, New Brunswick, NJ (32)


   Field studies were conducted in the fall of 2009 and 2010 in order to evaluate the response of eight newly seeded tall fescue cultivars to mesotrione applied at planting (PRE), and PRE followed by sequential treatment four weeks after turfgrass emergence (WAE) at rates ranging from 0.14 kg ai/ha to 1.125 kg ai/ha.  All applications were made with a single 9504EVS nozzle CO2 pressured sprayer calibrated to deliver a total 178 L/ha at 222 kPa.  Experimental design was a strip plot (tall fescue cultivar x mesotrione application regime) with 4 replications.  Tall fescue cultivars ‘Rebel Advance,’ ‘Cochise II,’ ‘Hounddog,’ ‘Bullseye,’ ‘3rd Millenium,’ ‘Faith,’ ‘Falcon V,’ and ‘Mustang IV’ were seeded on September 9, 2009 at a rate of 295 kg/ha in 1.8 m wide rows using a drop spreader.  PRE application was made on September 9, 2009 and PRE + 4 WAE on October 6, 2009.  Tall fescue was visually evaluated for cover and injury at 4 and 8 weeks after seeding, as well as in the springtime on a scale of 0 (no cover or injury) to 100 (complete cover or injury).   In this study, reductions in establishment were visible for some of the cultivars at 1.125 kg ai/ha applied PRE or PRE + 4 WAE.  The most severe reductions occurred in the PRE + 4 WAE were visible in cultivars ‘Rebel Advance’ and ‘Hounddog,’ with 17.2% and 20%, respectively.  There is some degree of intraspecific variability, with cultivars ‘Bullseye,’ ‘3rd Millenium,’ ‘Faith,’ and ‘Mustang IV’ showing the most tolerance to 1.125 kg ai/ha applied twice while ‘Rebel Advance’ and ‘Hounddog’ were more sensitive.  The results of this study suggest that although differences in tolerance to mesotrione was observed in some cultivars, these differences were minor, suggesting that tall fescue cultivars should all respond similarly to mesotrione (Tenacity) applications.