Preserving Aesthetics with a Novel Method to Transition Overseeded Turfgrass Tyler L. Mittlesteadt, John B. Willis, and Shawn D. Askew; Virginia Tech, Blacksburg VT The Problem In transitional climates like Virginia, clients expect green turf throughout the year as is typical for cool-season grasses. Turf managers overseed warm-season grasses to meet this expectation. Grasses used for overseeding, like perennial ryegrass, competitively displace bermudagrass over time if left in place. In cooler climates, ryegrass continues to compete with bermudagrass during the summer and must be controlled with herbicides. Conventional method (total kill of ryegrass) Partial kill using drip Partial kill using sponge Partial kill using strips Two weeks after strip kill Partial kill using drip Partial kill using sponge Not Treated Vamont bermudagrass shows bare ground after ryegrass dies. This transition occurs during prime golfing conditions and golfers find the bare ground, which may last 2 to 6 weeks, unacceptable. The aftermath of a GCSAA funded study that evaluated perennial ryegrass transition methods on Midiron bermudagrass in VA. Clearly, bermudagrass health suffers if ryegrass is not controlled. Traditional Transition Overseeded ryegrass must be controlled to release bermudagrass from competition as it breaks dormancy. However, dead or dying ryegrass is unsightly and leaves bare ground and straw-colored bermudagrass in its’ wake due to winter kill and slow spring growth of post-dormant bermudagrass. Turf managers then must race against the clock to grow in bermudagrass for improved aesthetics and playing conditions. Bermudagrass cover was increased by partial control treatments at every rating date. Note the lack of visual impact by partial control treatments in the images above. Perennial ryegrass turns yellow before dying from a blanket spray of foramsulfuron. This dying ryegrass will leave behind approximately 30% of green bermudagrass. In late June or early July, turf managers will blanket spray to kill ryegrass only to find a weak bermudagrass base. Partial Transition  Devices were built to allow for controlled application of selective herbicides to remove 20 to 30% of existing overseeded perennial ryegrass.  Herbicides were applied with drip, sponge, and strip methods in repeating patterns.  The overwhelming effect of remaining perennial ryegrass is to mask the partial control event and maintain aesthetics of the turf. Objectives  Evaluate three new methods of herbicide application in turfgrass to give partial kill of overseeded perennial ryegrass.  Determine if partial kill of overseeded ryegrass in May, will increase bermudagrass cover when remaining ryegrass is killed in June/July. Patterns of controlled perennial ryegrass were produced with drip (A), sponge (B), and strip (C) application methods. These methods were used to control 20 to 30% of existing perennial ryegrass. A B C Materials and Methods  RCBD field trial at Farmington CC, Charlottesville, VA in  Strip, drip, and sponge treatments applied Apr 26 and May18. Subsequent broadcast treatment of Foramsulfuron at 17 oz/A on Jul 7.  Treatments included a nontreated check and strip, drip, and sponge pretreatments in the following scenarios:  Foramsulfuron at 17 oz/A at 30% fb 30% coverage  Foramsulfuron at 17 oz/A at 20% fb 20% coverage  Foramsulfuron at 17 oz/A at 30% coverage (Apr 26)  Monument at 0.33 oz/A at 30% coverage (Apr 26)  Visually-estimated bermudagrass cover and turf color were assessed. Results  Pretreatments always increased bermudagrass cover compared to the nontreated check regardless of application method.  Bermudagrass cover after the broadcast Revolver treatment in July was 80 to 90% in plots that received partial control treatments compared to 68% from plots that did not.  Only strip treatments reduced visual turfgrass color. Control (%) LSD = 0.8 Nontreated RevolverMonument SpongeDripStrip % kill Apr 26 fb May 18 Note the maximum visual effect occurs on strip (A) and sponge (B) plots when looking down on the plot soon after treatment. Within two weeks of these treatments, bermudagrass starts to fill in the strips (C) and sponge dots (D). Conclusions  Pretreatments are an effective method to avoid transition problems.  Further research is warranted to refine application equipment, timings, and percent of partial control needed for best results. ABC D