See more from this Session: Turfgrass Ecology, Pest Management, and the Environment
Wednesday, October 19, 2011
Henry Gonzalez Convention Center, Hall C, Street Level
A 4-year field study was conducted at the Washington State University Turfgrass and Agronomy Research Center at Pullman, WA, to develop a program to remove ‘T-1’ creeping bentgrass from ‘Gallery’ perennial ryegrass with mesotrione (‘Tenacity’4SC). The perennial ryegrass stand was a green’s surround growing in a Palouse silt loam soil with bentgrass contamination (approx. 70%). Following 2007 Tenacity applications and overseeding with ‘Auburn Trilogy’, the plots were divided in half; one half left untreated and the other half received multiple Tenacity applications in 2008. Treatments were not applied in 2009, but were reapplied in 2010. Treatments were made with a bicycle-wheeled CO2 pressurized sprayer with 11002 flat fan spray tips at 233 L ha-1. Percentages of bentgrass cover and perennial ryegrass phytotoxicity were rated beginning at 1 wk after initial treatment (WAIT) up to 14 WAIT each year. The experimental design was a randomized-complete block with four replications and experimental units were 1.8 x 2.4 m. Not all of the creeping bentgrass was eliminated in 2007. Tenacity applied four times at 140 g ai ha-1 in 2007 was more effective at reducing the amount of bentgrass than three applications at 140 or 175 g ai ha-1. In 2008, 100% bentgrass control was achieved with Tenacity treatments applied four times each year at 140 g ai ha-1, or 3 times each year at 175 g ai ha-1. Bentgrass cover increased in all plots during 2009, prior to reapplication in 2010; however, bentgrass cover was lowest in plots treated four times with 140 g ai ha-1 in 2007 and 2008. In 2010, Tenacity applied four times at 140 g ai ha-1 resulted in complete bentgrass control by mid July. Phytotoxicity on perennial ryegrass following Tenacity applications was low throughout the study. Results indicate a multiple year Tenacity program with four applications in each of the first two years at 140 g ai ha-1 or 3 applications at 175 g ai ha-1, along with overseeding the first year, is necessary to achieve total bentgrass control. Subsequent Tenacity applications in following years are needed to prevent creeping bentgrass re-infestation from occurring.