That is the seedhead of a sedge. You can control them with Dismiss, a post-emergent selective herbicide with the active ingredient sulfentrazone, which is compatible with the following lawn grasses:
- Zoisiagrass
- Perennial Ryegrass
- Tall Fescue
- Centipedegrass
- Kentucky Bluegrass
- Bermudagrass,
- Creeping Bentgrass
- Bahia Grass
Or you can use Basagran T/O, another good post-emergent, that has the active ingredient bentazon. This is compatible with the following grasses:
- Zoisiagrass
- Perennial Ryegrass
- Tall Fescue
- Centipedegrass
- Kentucky Bluegrass
- Bermudagrass,
- Creeping Bentgrass
- St. Augustinegrass
- Bahia Grass
Use as directed on the product label. I would suggest not using these if you are near a body of water, to avoid contamination.
You can also use a glufosinate based herbicide, to spot shoot plants in your lawn. This may leave a dead spots in you lawn, but will use much less chemicals.