Thursday, November 8, 2007 - 8:15 AM

Use of Mesotrione at cool-season turfgrass establishment for annual bluegrass control.

Stephen Hart, Foran Hall, 59 Dudley Rd., Rutgers State University Accounts Payable, Rutgers University, Department of Plant Biology & Pathology, New Brunswick, NJ 08901 and Patrick McCullough, Plant Biology and Pathology, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901.

Field studies were conducted in the fall of 2006 and 2007 to evaluate the response of newly seeded and seedling Kentucky bluegrass, perennial ryegrass, and tall fescue to mesotrione applied at planting (PRE), four weeks after turfgrass emergence (4 WAE) and a sequential treatment at both timings. Mesotrione was applied at rates ranging from 0.14 to 0.56 kg ai/ha using a single nozzle CO2 pressured sprayer calibrated to deliver a total of 375 L ha-1.  Nozzles used were 9504E and CO2 regulators were set for 220 kPa. Experimental design was a split-block with four replications.  Treatments were a factorial combination of four seedings (main plots, 1.8 x 68-m) with 12 mesotrione applications (sub-plots, 1 x 7.2-m). A non-seeded check strip was also included as a main plot for weed control evaluations. Turfgrass chlorosis was rated on a percent scale where 0 equaled no chlorosis and 100 equaled complete chlorosis.  Turfgrass and weed cover were rated visually on a percent scale. Overall, mesotrione caused minimal turfgrass cover reductions applied PRE. However, 4 WAE applications at the higher mesotrione rates tended to cause chlorosis on both tall fescue and perennial ryegrass and in some experiments significant stand reductions especially on Kentucky bluegrass and tall fescue. Control of winter annual broadleaf weeds such as chickweed and henbit were nearly complete with all mesotrione treatments. Mesotrione exhibited potential to selectively control annual bluegrass applied PRE especially at the 0.28 and 0.56 kg/ha application rate. Annual bluegrass control was lower with 4 WAE applications than PRE applications. The most complete annual bluegrass control was observed with PRE applications followed by sequential applications 4 WAE at 0.28 and 0.56 kg/ha. In the fall 2005 and 2006 experiments these treatments provided 94 to 99 and 73 to 91% annual bluegrass control the following spring.