Invading Bermuda grass is a problem for anyone in the South who likes a thick, full lawn of St. Augustine. Getting rid of it can be just as big of a problem. While there are a couple of different strategies, it will take a substantial amount of diligence. Fortunately, if your lawn is afflicted with areas of Bermuda grass, the solution is relatively inexpensive.
Identify the Grass
Bermuda has a medium to fine texture and does not tolerate shade very well. Therefore, if the blades of the grass appear thinner than the known St. Augustine grass, and it does not grow in the shade, chances are it is Bermuda. Another tell-tale sign is if there is a yard full of Bermuda in close proximity.
Most of the steps involve shading the yard as much as possible, because Bermuda does enjoy full sun. Therefore, cutting grass at the highest level the mower allows will significantly shade the Bermuda and stifle its growth. In some cases, where the grass is only spotty, this may take care of the problem altogether. This solution, of course, will require more frequent mowings.
Herbicide can be used in areas where Bermuda grass has completely overtaken the St. Augustine. However, the chemical should be used carefully, as it is also capable of killing the grass you want. It may take several applications of herbicide in order to completely kill off the Bermuda grass.
Once you have applied the herbicide, it is best two wait a week or two before replanting St. Augustine plugs. Otherwise, the residual chemical could kill any new plugs. Once this is done, using shade should help stifle any Bermuda that may be tempted to reemerge. Putting down a preemergence herbicide may help, but check with your local nursery or lawn and garden store to make sure it will not affect adult St. Augustine grass.