Establishment of cool-season turfgrass in summer months can be a daunting task due to weed pressure, especially from annual grasses. Three trials were conducted during 2009 and 2010 in Pennsylvania to determine the potential use of mesotrione for use in hydroseed applications.

   In 2009, one trial investigated the safety of perennial ryegrass (Lolium perenne; PRG) and weed control of mesotrione used at establishment with a hydroseeding application and again 21 days following. There were six treatments including: 1) mesotrione sprayed with a flat fan nozzle at 0.156 lb ai/A (5 floz/A) on bareground and then hydroseed mix (i.e. seed, water, fibers) applied at 6 lb seed/1000 ft² on top of the treated soil; 2) hydroseed mix applied at 6 lb seed/1000 ft² and then mesotrione sprayed with flan fan nozzle at 0.156 lbai/A on top of the hydroseed mix once dry on the same day; 3) mesotrione applied in the hydroseed mix at 0.156 lb ai/A; 4) conventionally seeded at 6 lb seed/1000 ft² with no mesotrione; 5) treatment 3 applied twice over the plots (mesotrione at 0.312 lbai/A and 12 lb seed/1000 ft²); and 6) hydroseeded at 6 lb seed/1000 ft² with no mesotrione. Hydroseed treatments were applied using a 50 gallon tractor mounted Turbo Turf Hydro Seeder. Plots were seeded 16 June 2009. The sequential application of mesotrione was applied on 7 July 2009. All plots receiving mesotrione at seeding had no ragweed (Ambrosia spp.) plants per plot which was significantly less than the conventionally seeded and hydroseeded-alone plots. All plots receiving mesotrione treatments had significantly less smooth crabgrass (Digitaria ishaemum) coverage on every rating date. Data from this trial indicate that mesotrione may have the potential to be recommended for use in hydroseeding applications with PRG. 

   In 2010, two separate trials evaluated weed control and establishment safety of 1) PRG and 2) a mixture of tall fescue (Festuca arundinacea), Kentucky bluegrass (Poa pratensis) and PRG. The mesotrione rate for all treatments was 0.156 lb ai/A. There were six treatments: 1) mesotrione sprayed with a flan fan nozzle prior to hydroseeding; 2) mesotrione sprayed with flat fan nozzle prior to hydroseeding followed by a sequential application; 3) mesotrione applied in hydroseed mixture; 4) mesotrione in hydroseed mixture followed by a sequential application applied with a flat fan nozzle; 5) untreated (no herbicide at or following seeding); 6.) mesotrione sprayed with a flat fan nozzle at sequential timing (i.e. rescue treatment). Plots were seeded on 30 April and sequential applications occurred on 25 May 2010. In both trials, no significant injury was observed to desirable grasses. Mesotrione treatments were effective in reducing ragweed and smooth crabgrass when applied prior to hydroseeding or in the tank with hydroseed mixture.