Warm season grasses in our area are in most cases an invasive plant that nobody wants in their yard. The two common ones in our area are Bermuda Grass and Zoysia Grass. If you are dealing with either one of these problems in your yard, NOW is the time to start taking care of this.
The first step sounds kind of strange, now that you are trying to get rid of it, water it and get it growing. You can not kill off a non-growing or dormant plant. When it greens up spray with a glyphosate product, or a more common name would be Round Up. Wait 7-10 days and spray it again, to kill off any remaing green areas. This could take a follow up third application if not all dead.
This process should start over the course of the next 3 weeks to ensure that it is not alive by the time you are wanting to seed. Mid-August is a perfect time to seed, those of you who have irrigation.
If you have any questions, please feel free to contact your Turf Manager or the office, we can assist you with all of your turf needs.