Bermudagrass Control with Glyphosate, Topramezone, and Mesotrione Combinations Prior to Spring Tall Fescue Seeding.

Previous research has resulted in effective bermudagrass (Cynodon spp.) control with fall herbicide combinations containing glyphosate. Limited research has explored the use of fall glyphosate applications in combination with spring applications for cool-season turfgrass establishment.  Experiments were initiated in fall of 2014 in Manhattan, KS at Rocky Ford Research Center (RF) and Stagg Hill Golf Course (SH) to determine bermudagrass control and spring cool-season establishment success through a non-selective application of glyphosate prior to winter dormancy and a subsequent application of glyphosate, topramezone, and mesotrione combinations at spring seeding of tall fescue [Schedonorus arundinaceus (Schreb.)]. Research at RF and SH was conducted on common bermudagrass (Cynodon dactylon L. Pers) maintained at 7.6 cm. Experimental design was a randomized complete block with four replications. Herbicides were applied to 1.5 x 1.5 m plots in 374 L ha^-1 water at 180 kPa with a C0₂ pressurized boom sprayer with XR 8004vs flat-fan nozzles. Treatments were glyphosate (2.35 kg ha^-1) + COC (0.75%v/v), topramezone (.036 kg ha^-1) + COC (0.75%v/v), mesotrione (0.28 kg ha^-1) + COC (0.75%v/v), glyphosate (2.35 kg ha^-1) + mesotrione (0.28 kg ha^-1) + COC (0.75%v/v), glyphosate (2.35 kg ha^-1) + topramezone (0.036 kg ha^-1)  + COC (0.75%v/v), topramezone (0.036 kg ha^-1) + mesotrione (0.28 kg ha^-1) + COC (0.75%v/v), glyphosate (2.35 kg ha^-1) + mesotrione (0.28 kg ha^-1) + topramezone (0.036 kg ha^-1) + COC (0.75%v/v), a fall only glyphosate (2.35 kg ha^-1) and a non-treated control for comparison. All treatments received a glyphosate application at 2.35 kg ha^-1 on 6 Oct 2014, excluding the non-treated control. Spring tall fescue seeding and application of herbicides were applied when non-treated control reached >80% bermudagrass green cover. Seeding and application dates were 1 May 2015 and 12 May 2015 at SH and RF, respectively. Collected data included visual percent green bermudagrass cover (0-100%), visual percent green tall fescue cover (0-100%), and visual percent weed cover (0-100%). Data was collected every 14 days after seeding (DAS). A treatment by location interaction prevented pooling data across locations. At RF and SH, non-treated control resulted in <5% tall fescue cover, 70 DAS. At RF, glyphosate + mesotrione + topramezone treatment resulted in 15% more tall fescue cover than fall only glyphosate treatment (70 DAS). At SH, glyphosate + topramezone resulted in 53% and 74% more tall fescue cover compared to fall only glyphosate treatments and the non-treated control, respectively (70 DAS).