Another grassy weed to contend with...
 

Does anyone know what this is, and if there is a selective herbicide to get rid of it?
Thanks

These are very common in Florida.

https://www.youtube.com/watch?v=fi1e3qv_9j4

Thank you!

Kyllinga, a species of Nutgrasses

Killing Nutsedge
 

I use Certainty and get good results, there is also a herbicide called Sedge Hammer.

Kyllinga is used to treat:
diarrhea in Malaysia;
stomach and intestinal problems in India;
joint pain and rheumatic problems in various places in Polynesia; and
common colds, bronchitis, malaria, arthritis, injuries and dysentery in China.


Just don't eat it if you are pregnant.

Use Sedgehammer, or the first frost will kill it.

Ground clear kills everything.

The picture that you posted is not the same plant as that in the video link that was posted in response to your question.

The picture you posted appears to be false green kyllinga. Recommendations for controlling it depends on how much of it you have. I’ve used Sedgehammer in my backpack sprayer if I have a lot of it. I’ve also had success with Ortho Nutsedge Killer. It’s more for spot treatment of individual plants and it works quickly. Sedgehammer takes a little more time.

Can Sedgehammer be used on St. Augustine?

Yes.
Can Sedgehammer be used on St. Augustine? - Google Search