| Abstract/Contents: | "AC 263,222 (trade name Plateau) was evaluated for winter weed control in roadsides maintained by the Mississippi Department of Transportation. The experimental design was a randomized complete block with a split-plot arrangement of treatments with 4 replications. The experiment was conducted three times with bermudagrass turf at two locations and bahiagrass at the other. The main plots were application timing as follows: first application timing was in October, prior to frost when turfgrass still retained their green color; second application timing in January when both turfgrasses were dormant; third application timing in March just prior to turfgrasses resuming active growth following dormancy. Applications made in October were generally made PRE to winter annuals, while January or March applications were POST to winter annuals. Sub-plot treatments made within each application date were 0.125 to 0.188 lb ai/A AC 263,222, 0.047 lb ai/A sulfometuron, 0.5 lb ai/A glyphosate, 0.125 or 0.188 lb ai/A AC 263,222 + 0.5 lb/A glyphosate, or 0.047 lb/A sulfometuron + 0.5 lb/A glyphosate. October applications of AC 263,222 controlled winter annuals poorly. At 7 months after initial treatment (MAIT), 0.188 lb/A AC 263,222 controlled Carolina geranium 40%, compared to 48% with the January application and 90% with the March application. Results were similar with sulfometuron, with 43% or less control from the October or January applications and 80% control of Carolina geranium with the March application. Regardless of application date, glyphosate did not control Carolina geranium more than 20%. Sulfometurin controlled horseweed 80% or greater 8 MAIT regardless of application date, and glyphosate provided 80% or greater control when applied in January or March. AC 263,222 did not control horseweed more than 60% regardless of application date. While sulfometuron applied at any date controlled wild chervil 80% or greater, AC 263,222 or glyphosate had to be applied in January or March to provide 80% or greater control at 7 MAIT. AC 263,222 or glyphosate applied in October controlled wild chervil 35% or less. At 7 MAIT, common vetch and hop clover were not controlled more than 43% by AC 263,222 applied in January or March, or glyphosate applied in March controlled common vetch 80% or greater. Unlike control of winter annuals, tall fescue control was best with the October treatments of AC 263,222, sulfometuron, or glyphosate. AC 263,222 at 0.188 lb/A, glyphosate, or sulfometuron controlled tall fescue 83% at 8 MAIT, compared to 68% or less with the same treatments applied in January or March. March tank-mixes of AC 263,222 or sulfometuron + glyphosate were the only January or March treatments which controlled tall fescue 80% or greater. At one location, the October treatments of AC 263,222 or glyphosate did not significantly increase bermudagrass density (% green cover) at 8 MAIT compared to the untreated. January or March treatments of AC 263,222 resulted in 60 to 65% density of bermudagrass while the same treatments applied in October or the untreated plots had 45% or less density of bermudagrass. Best bermudagrass density (68%) observed at 8 MAIT occurred where tank-mixes of AC 263,222 + glyphosate were applied in March. At the other bermudagrass locations, best bermudagrass density (78%) was also observed with AC 263,222 + glyphosate treatments applied in March. The 0.188 lb/A rate of AC 263,222 applied in January or March, glyphosate applied in January or March, the tank-mixes of AC 263,222 + glyphosate applied in January or March, or sulfometuron + glyphosate applied in January were equivalent to the best bermudagrass density observed at both locations at 8 MAIT. At the bahiagrass location, October applications of 0.188 lb/A AC 263,222 or either rate of AC 263,222 + glyphosate resulted in 23 to 33% bahiagrass density. This was less than the untreated at 43% density. Generally, all other treatments did not affect bahiagrass density 10% compared to the untreated, or glyphosate applied in January, which increased bahiagrass density 12%." |
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