Q: I am trying to kill bermudagrass that is spreading thru the centipedegrass in my lawn. I have been told that putting black plastic over the area for two weeks will kill what bermudagrass remains after spraying with herbicide.
A: Bermudagrass is VERY tough to kill. I know of one lawn service that controls weeds in bermudagrass by spot-spraying the weeds with Roundup. Though the weed is killed outright, the bermudagrass usually recovers from this powerful herbicide in a couple of weeks.
Your method of covering the grass with plastic is called “solarization”. It works best with annual grasses, particularly when you use clear plastic and cover the soil for six weeks. However, I do not have confidence that anything less than twelve weeks of covering would have an effect on bermudagrass, with or without spraying herbicide beforehand. Honestly, I don’t think solarization will kill bermudagrass in any situation.
My best recommendation is to allot two months to your bermuda-busting effort. Spray the plot with Roundup three times at four week intervals and you should be free of the invasive grass. Plant centipedegrass sod in the area and it will be pristine once again.