| Abstract/Contents: | "A study was conducted in 1995 on a golf course in North Florida to evaluate two different types of PGR's for annual bluegrass (Poa annua L.) seedhead suppression in overseeded perennial ryegrass (Lolium perenne L.) turf. Treatments included mefluidide (Embark 2SC) at 0.125 lb ai/A plus X-77 at 0.5% v/v; and paclobutrazol (TGR 50WP) at 0.5 lb ai/A. Treatments were applied weekly to separate plots from 11 January to 08 February. Treatments, in a randomized complete block design, were replicated four times. Plot size was 5ft x 10ft. Plots were evaluated for perennial ryegrass density (%) and color (1 to 10, where 10=best and 5=minimum acceptable) and Poa annua seedhead control (%). Ratings commenced five weeks after initial (WAT) application. Perennial ryegrass density five WAT following mefluidide treatment were 70%, 75%, 80%, 81%, and 85% for 11, 18, and 25 January and 01 and 08 February treatment timings, respectively. Paclobutrazol treatments had density ratings of 79%, 79%, 76%, 76%, and 75% five WAT for 11, 18 and 25 January and 01 and 08 February treatment timings, respectively. Perennial ryegrass color rated five WAT following mefluidide treatment was 6.5, 7.0, 9.0, 8.5, and 8.5 for the 11, 18, and 25 January and 01 and 08 February timings, respectively. Also rated five WAT following paclobutrazol treatment were 8.0, 8.0, 8.0, 7.8, and 7.5 for 11, 18, and 25 January and 01 and 08 February timings, respectively. Early January treatments of mefluidide exhibited minor perennial ryegrass tipburn. However, this was temporary and was removed when mowed. Paclobutrazol treated perennial ryegrass exhibited no visible phytotoxicity. Poa annua seedhead control five WAT following mefluidide application was 94%, 100%, 97%, 29%, and 68% for 11, 18, and 25 January and 01 and 08 February treatment timings, respectively. Paclobutrazol rated five WAT was 85%, 75%, 90%, 75%, and 97% seedhead control for 11, 18, and 25 January and 01 and 08 February treatment timings, respectively. Overall, early January mefluidide treatments provided the best Poa annua seedhead suppression but did exhibit temporary (~2 weeks) minor perennial ryegrass tipburn damage. Paclobutrazol treatments did not effect the perennial ryegrass but provided better Poa annua suppression of the two materials when applied in late January or early February. Future research includes sequential timing of applications throughout the growing season and tank mixtures with iron or nitrogen to reduce turf phytotoxicity." |
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