| Abstract/Contents: | "Herbicide usage on highway right-of-ways plays a vital role in the management and control of vegetation along South Carolina roadsides. The removal of noxious and tall weeds like annual ryegrass and little barley are needed because they detract from the beauty of state roadsides and can ultimately pose a hazard to motorist by obstructing unforeseen hazards along the grass shoulders of highways. The removal of these weeds also helps reduce the frequency of mowing and can help release lower growing species. Clemson University, in cooperation with the South Carolina Department of Transportation, is exploring options in dealing with problematic winter weeds along state roadsides. In 2005, Clemson University performed a postemergence trial to control various winter weeds on a right-of-way located on Interstate 95 near St. George, SC. The trial was initiated on January 19th to evaluate selected postemergence herbicides for control of annual ryegrass (Lolium multiflorum), little barley (Hordeum pusillum), cats' ear dandelion (Hypochoeris radicata), and Carolina geranium (Geranium carolinianum) in a 'Pensacola' bahiagrass (Paspalum notatum) right-of-way mowed at 6 in. Treatments were applied in a randomized complete block with 3 replications using a CO2 backpack sprayer calibrated to deliver 20 GPA. Treatments (oz product/acre) included single applications of the following herbicides: Roundup Pro 4L (16.0), Oust 75 DG (1.0), Telar 75 DG (1.0), Roundup Pro (8.0) + Oust (0.25), Roundup Pro (8.0) + Oust (0.25) + Telar (0.25), Campaign 3.1L (64.0), Escort 65 DF (1.0), Revolver 0.19L (17.0), Monument 75 DF (0.3), Hoelon 3EC (42.5), QuikPRO 75.2 WG (72.0), Overdrive 70 WG (6.0), Plateau 2L (6.0), and Journey 2.25L (16.0). Weed control was rated on a 0-100% scale where 100% = complete control. Bahiagrass was rated for percent initial green-up density where 100% = full green-up and percent seedhead suppression where 0% = no seedheads present. For annual ryegrass, at 86 days after treatment (DAT), Oust, Roundup Pro + Oust, and Journey provided 100% control. Also providing excellent control (>92%) were Roundup + Oust + Telar, Plateau, Revolver, Hoelon, and QuikPRO. Telar, Escort and Overdrive provided <45% control of annual ryegrass. For little barley, Roundup Pro, Roundup Pro + Oust, Plateau, and Journey provided >=92% control. Oust, Roundup Pro + Oust + Telar, Campaign, and QuikPRO completely controlled little barley through 86 DAT. Telar, Escort, Revolver, Hoelon, and Overdrive were unsuccessful in controlling little barley at <10% control. Only, Oust completely controlled both grasses through 86 DAT. For cat's ear dandelion, Escort and Roundup Pro + Oust + Telar provided >98% control at 86 DAT followed by Oust, Campaign, and QuikPRO at 92%. For Carolina geranium, Campaign and QuikPRO yielded 100% control through 86 DAT. Also providing good (>=92%) control of Carolina geranium was Oust, Telar, Roundup + Oust + Telar, Escort, and Overdrive. Revolver, Monument and Hoelon failed to provide sufficient control at <=10%. The initial spring bahiagrass green-up at 98 DAT was delayed by Oust, Escort and QuikPRO at <20% bahiagrass density compared to 50% of that of the untreated. By 135 DAT, Escort, Oust, and Overdrive continued to provide a slight delay in bahiagrass green-up at 61, 60 and 58%, respectfully compared to the untreated at 73%. At 168 DAT, Oust and Escort provided significant seedhead suppression at 30 and 27%, respectfully. In conclusion, Roundup + Oust + Telar, Oust and QuikPRO all provided >90% control of all 4 weeds evaluated in this trial. Roundup Pro + Oust, Plateau, and Journey provided >90% control of little barley and annual ryegrass while, Escort and Campaign provided >90% control of cats' ear dandelion and Carolina geranium. Oust, Escort and QuikPRO delayed green-up for up to 6 weeks following initial green-up of the bahiagrass. Since Roundup Pro + Oust + Telar did not delay bahiagrass green-up and provided excellent control of all 4 weeds, it can be concluded that it was the best overall treatment in this trial. Despite Oust and QuikPRO performing equally as good controlling winter weeds, delaying bahiagrass green-up poses a further risk of weed invasion from summer weeds and permanent stand density reduction." |
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