Wednesday, November 7, 2007 - 8:30 AM
265-3
Effect of Sulfosulfuron and Bispyribac-Sodium on Cultivars of Poa trivialis.
Bispyribac-sodium and sulfosulfuron have recently been labeled for Poa trivialis control, but cultivar variability could potentially affect the efficacy of both of these herbicides. Our objective was to compare effectiveness of bispyribac-sodium and sulfosulfuron on different Poa trivialis cultivars. This study was conducted starting in June 2006 and will be repeated in 2007. Adjacent studies were done under 1.25 cm or 5.0 cm mowing heights. Experimental design was a randomized split-plot design with three replications. Main plots were cultivars of Poa trivialis and subplots were herbicides treatments. In addition to the eight Poa trivialis cultivars, the 1.25 cm study included creeping bentgrass and the 5.0 cm study included Kentucky bluegrass for comparison. Herbicide treatments included an untreated control, sulfosulfuron at 13 kg a.i. ha-1 applied twice on a two week interval and bispyribac at 37 kg a.i. ha-1applied four times on a two week interval. At 1.25 cm in summer 2006, ‘Laser’ was more tolerant to sulfosulfuron than all other cultivars in the study. Six weeks after initial treatments (WAIT), bispyribac-sodium applications decreased cover of all cultivars at 1.25 cm to less than 2% cover except for ‘Laser’, which had 17% cover. At 5 cm in 2006, bispyribac-sodium decreased Poa trivialis cover more than sulfosulfuron at the 5 cm mowing height. Bispyribac-sodium decreased cover on all cultivars to less than 34% by 7 WAIT except for ‘Winterlinks’, which had 47% cover. However, sulfosulfuron appeared to affect all cultivars similarly at 5 cm. By 12 WAIT, cultivars mowed at 5 cm almost completely recovered, unlike cultivars mowed at 1.25 cm.
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