Potential Use of Mesotrione in Turfgrass Systems.

Mesotrione [2-(4-mesyl-2-nitrobenzoyl)-3-hydroxycyclohex-2-enone] is a pigment inhibitor herbicide that controls many common weed species by inhibiting the 4-HPPD enzyme. Recently, mesotrione received EPA registration for use on golf courses and sod farms. The objectives were to determine use rate of mesotrione and to establish tolerance of newly seeded perennial ryegrass (Lolium perenne L.). Studies were conducted at the Turfgrass Research Center, South Deerfield, MA. The existing turfgrass was killed with glyphosate (1.12 kg ha^-1) and the area was prepared for seeding. Perennial ryegrass was seeded on June 3, 2008. All treatments were applied to 1 by 3 m plots with a CO₂-backpack sprayer at a pressure of 152 kPa in 467 L ha^-1. Treatments were replicated three times in a randomized block design. PRE and POST treatments were applied on June 4 and June 20, respectively. Mesotrione formulations (480 SC, 240 SC, and 50 WG) at 175 or 280 g ha^-1 applied PRE followed by POST were tested for turfgrass tolerance. POST applications were made after the first mowing. Mesotrione treatments were safe to perennial ryegrass seedling stand. POST application of mesotrione treatments whether applied as a split treatment to PRE or POST alone exhibited slight foliar phytotoxicity (5 to 10%). Phytotoxicity from mesotrione was observed in the form of bleaching, and it typically dissipated within 1 to 2 weeks of first appearance of symptoms. Percent of turfgrass ground cover in mesotrione treated plots was similar to the untreated plot. No differences in mesotrione activity were observed with various formulations. Mesotrione at 280 g ha^-1 provided excellent control of large crabgrass and other grass weeds. In general, mesotrione provided good to excellent control of various broadleaf weeds.