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The first application of herbicide should take place when the bahiagrass is small and just beginning to grow. Choose a post-emergent herbicide to kill the actively-growing grass. Spray the herbicide on your lawn as per the package directions. Post-emergent herbicides are available at your local lawn and garden shop. Use metsulfuron to kill the bahiagrass without harming a bermudagrass lawn. Use metsulfuron, sethoxydim, or atrazine to kill the bahiagrass without harming a centipedegrass lawn. Use atrazine to kill the bahiagrass without harming a St. Augustinegrass lawn. Use imazaquin or metsulfuron to kill the bahiagrass without harming a zoysiagrass lawn. As the herbicide kills bahiagrass, bare patches will be left on your lawn. To ensure that these areas aren't infiltrated with other weeds, promptly fill them in. Use plugs or sprigs of sod, rather than spreading seeds, for best results. To ensure that all the seeds, rhizomes, and plants are eradicated, you'll need to apply the same herbicide again. Wait at least 4-6 weeks after the first treatment, then apply the herbicide to your entire lawn again as directed by the package instructions. The herbicide should not harm your existing grass or the new sod patches. It's important to mow the lawn frequently to keep it healthy and prevent a re-emergence of bahiagrass. Use a sharp mowing blade, as dull blades produce brown-edged grass. Keep bermudagrass and zoysiagrass at a height of 1 to 2 inches (2.5 to 5.1cm), centipedegrass at a height of 1.5 to 2 inches (3.8 to 5.1cm), and St. Augustinegrass at a height of 2.5 to 4 inches (6.4 to 10.2cm). Don't cut more than one-third of the grass height at a time, or the roots may stop growing. For instance, if you want to keep your grass at a height of 2 inches (5.1cm), cut it when it reaches 3 inches (7.6cm) tall. Watering too often can cause bahiagrass and other weeds to flourish. Wait until your lawn turns bluish-gray, holds footprints for more than a few minutes, or until the soil is dry and hard. Apply 12 inch (1.3cm) of water to the entire lawn, then wait for it to dry out before watering again. Regular lawn fertilization will prevent the bahiagrass from growing back. Use a complete fertilizer, such as 1248, 1648, or 18-24-6, once or twice per year. You can do a home soil test to determine when your lawn needs to be fertilized. The numbers of the fertilizer refer to how much nitrogen, phosphorus, and potassium, respectively, it contains.
Apply a post-emergent herbicide in May. Fill in bare spots with the desired turf. Reapply the herbicide after 4-6 weeks. Mow the lawn frequently. Water the lawn only when it shows signs of water deficiency. Fertilize the lawn once or twice per year.