hard to tell in the photo.  Is there little joints that you can pull apart every say 1 inch or so top to bottom on the entire plant ?  If so,, then yah it's joint grass, and tough to kill. Just using 24d alone will only burn down the top it won't actually "kill" the plant.

If you want to "Kill it dead",, for residual control not just burning of the top, Use 4 oz/gal of 24D  AND   4 oz/gal of spreader-sticker. The joints have a NASTY habit of not carrying the 24D thru the plant, and won't stick on the plant worth a snot either.  As was explained to me by my Chem rep. "it's like p|$$ing on a stick, the 24D just runs off."  I use spreader 90 myself but just use a 1-1 ratio of chem and spreader/sticker. AND coat the entire plant with as fine a spray as possible.  

It'll burn the snot out of the grass for a while but won't kill the grass, the jointgrass on the other hand will die DEAD.  Joint grass once it's started into the field,, it's nasty and dang tough to kill dead in a field.