A: Bahia, or highway grass, is one of the most despised weeds in the lawn, with good reason: If given adequate moisture, Bahia shoots up its ugly seed heads in only two or three days, leading to more frequent lawn mowing.
You should start controlling it as soon as possible after it completely greens up in the spring, usually by early to mid-May, depending on the weather. It is certainly not too late, though, to do something about it this year. It will just be a little more difficult.
When applying most selective herbicides on Bahia, your best bet is to try to suppress the weed to allow desirable grass to take over.
An immediate benefit from a herbicide is that even though it might not kill the Bahia with the first application, it will prevent any seed heads from popping up for several weeks, which is half the battle.
In most cases, you need to know what kind of lawn you have so you can match the best herbicide with your lawn.
One herbicide, imazaquin (sold as Image), can be used in the four common lawn grasses (centipede, zoysia, Bermuda, and St. Augustine). Image is rated poor to fair in control; however, this is a good herbicide option when different lawn grasses are mixed together, such as centipede and zoysia.
When using Image early in the summer, you should make a second application in about six weeks. For this late in the season, you probably won't benefit with a second application since the cooler weather will be here by then and the Bahia will be slowing down and not sending up any more seed heads.
If you have a centipede lawn, sethoxydim (sold as Poast, Vantage or Post-Emergence Grass Killer) should be your first choice for control. This product should be used only on centipede because it kills or suppresses all other grasses, including crabgrass and Bermuda. So, if you have other undesirable lawn grasses in centipede, you can take them out with sethoxydim.
For Bermuda and zoysia lawns, the best control option is MSMA or CAMA. Common brand names you will find in stores are Image with MSMA (not to be confused with regular Image) and Ortho Crabgrass Killer. After using MSMA the first time, come back in five to seven days with another application.
The best herbicide for controlling Bahia is a product containing metsulfuron and sold as Manor or Blade. The only problem is that it is packaged for commercial operators. Metsulfuron is sold in a two-ounce bottle that costs about $140. For most homeowners, this is not a practical option.
Another option is spot treating with glyphosate (Roundup) or a similar nonselective herbicide. It will kill desirable grass if you get any on it, but you might be willing to deal with the dead spots while your desirable grass grows back.
During this hot time of the year, be careful when spraying herbicides. Early morning is best. And make sure the grass is well watered before applying the herbicide.
Sid Mullis is the director of the University of Georgia Extension Service office in Richmond County. Call (706) 821-2349 or send him an e-mail at firstname.lastname@example.org.