ANNUAL BLUEGRASS CONTROL. J. Borger*, M. Naedel, and K. Hivner, Penn State University, University Park, PA (88)

Two separate post emergence annual bluegrass (Poa annua) control studies were conducted using various materials and application timings. Both studies were conducted on a mature stand of ‘Penncross’ creeping bentgrass (Agrostis stolonifera) and annual bluegrass at the Valentine Turfgrass Research Center, Penn State University, University Park, PA. The objective of both studies was to determine if selected materials could reduce the annual bluegrass population under simulated golf course greens conditions. Both trials were randomized complete block designs with three replications. For the first study, treatments were applied on April 30 (APR), June 4 (4 WAT), July 7 (8 WAT), August 3 (12 WAT), and October 5, 2010 (20 WAT). For the second study, treatments were applied June 8 (JUNE), July 7 (4 WAT), September 20 (SEP), and October 22, 2010 (OCT). Treatments in both trials were applied using a three foot CO2 powered boom sprayer calibrated to deliver 87.12 GPA using one, flat fan, TP9508EVS nozzle at 40 psi. The test areas were maintained at 0.125 inch using a Toro triplex reel mower. Following applications, certain treatments were watered in with 0.4 inch of irrigation or natural rainfall. Additionally, turfgrass was irrigated on an as-needed basis to prevent moisture stress. Both test sites consisted of approximately 20 percent creeping bentgrass and 80 percent annual bluegrass at the initiation of the study. The annual bluegrass population was visually evaluated in the first study on April 27, 2010 and again on October 1, 2010, on a plot by plot basis, to determine the baseline population and percent change of the population in each plot. In this first study, all treated turfgrass revealed a significant reduction in annual bluegrass population. Plots treated with MRC-01 at 82 or 110 oz/A applied three times had significantly more annual bluegrass control than those treated with MRC-01 (methiozolin) at 55 oz/A, applied only once or twice, and Trimmit at 0.25 lb ai/A applied five times. Additionally, MRC-01 at 55 oz/A applied once or twice did not significantly differ from Trimmit at 0.25 lb ai/A applied five times. The second study employed a program approach to annual bluegrass reduction and control of annual bluegrass was variable. All treatments programs revealed a significant reduction in annual bluegrass populations with the exception of any treatment that was tank mixed with Ferromec. Plots treated with the program of Trimmit at 16 oz/A in June, Primo Maxx at 6 oz/A (4 WAT), and Trimmit at 32 oz/A in September and October had significantly more annual bluegrass control than all other programs in the trial. An observational non-replicated seedbed trial was also established at the Valentine Turfgrass Research Center at Penn State University to observe the effects of various herbicide treatments on annual bluegrass germination. Treatments were applied two weeks before seeding on June 28 (2 WBS), at seeding on July 15 (SEED), and two weeks after seeding on August 3, 2010 (2 WAS). The following herbicides were evaluated: MRC-01, Tenacity, Prograss, and Tupersan. Each provided some insight to the control of annual bluegrass on a preemergence basis that will be considered when designing future research in this area.