| Abstract/Contents: | "Bahiagrass, a commonly used turf on highway rights-of-way in southern Mississippi, produces numerous, rapidly-growing seedheads. Bahiagrass growth may be affected by herbicide applications and mowing used to control undesirable vegetation. The objective of this experiment was to determine if bahiagrass seedhead suppression, injury, shoot length, or density are affected by application timing of AC 263, 222, glyphosphate, or sulfometuron with respect to mowing. The experiment was designed as a split-plot with application timing as main plots and treatment as subplots. Treatments consisted of 0.032, 0.047, 0.063, 0.125 lb ai/A AC 263, 222, 0.188, 0.250, 0.312 lb ai/A glyphosphate, 0.023 lb ai/A sulfometuron, 0.032 or 0.047 lb/A followed by 0.016 lb/A AC 263, 222, 0.188 lb/A followed by 0.125 lb/A glyphosphate, and 0.032 or 0.047 lb/A AC 263, 222 tank mixed with 0.188 lb/A glyphosphate. Treatments were applied 2 weeks before, on the day of, and 1 week after mowing. The day of mowing treatments were applied after mowing. Seedheads had begun to emerge when 1 week after mowing treatments were applied. An interaction was found between application timing and treatment for bahiagrass injury, density, and shoot length; however, no interaction was found for seedhead suppression. All AC 263, 222 treatments suppressed seedheads greater than 85%. Seedhead suppression with all rates of AC 263, 222 was equivalent to 0.023 lb/A sulfometuron. Glyphosphate at both 0.188 and 0.250 lb/A suppressed seedheads less than 0.023 lb/A sulfometuron; however, 0.312 and 0.188 lb/A followed by 0.125 lb/A glyphosphate were equivalent to 0.023 lb/A sulfometuron. Sequential AC 263, 222 treatments and glyphosphate tank mixtures with AC 263, 222 were not greater than a single application of AC 263, 222 for seedhead suppression. Sequential AC 263, 222 treatments did extend the length of time bahiagrass injury was observed. Bahiagrass was tolerant to rates less than 0.047 lb/A and glyphosphate rates less than 0.125 lb/A glyphosphate. Greater than 20% injury occurred with applications of 0.125 lb/A AC 263, 222. Bahiagrass shoot length was reduced with all AC 263, 222 treatments; however, only 0.125 lb/A AC 263, 222 decreased shoot length more than 0.023 lb/A sufometuron at all application timings. The sequential glyphosphate treatment reduced shoot length compared to all single glyphosphate applications when applied before or the day of mowing. This sequential treatment also reduced shoot length more than 0.023 lb/A sulfometuron. Bahiagrass density was not affected by 0.032 lb/A AC 263, 222, regardless of application date. Only 0.047 lb/A AC 263, 222 decreased density more than 0.023 lb/A sulfometuron. Generally, sequential AC 263, 222 treatments reduced bahiagrass density over single AC 263, 222 applications. The 0.032 lb/A rate of AC 263, 222 suppressed seedheads and reduced shoot length of bahiagrass but did not injure or reduce bahiagrass density. The timing of treatment relative to mowing appears to be flexible when seedhead and growth suppression are desired." |
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