In order to start a new mound and tunnels, a bred fire ant queen needs a bare patch of ground. This is why wood mulch works so well at keeping fire ant mound numbers under control. Try to not overuse your chicken range because when you do and the chickens kill the grass and dethatch an area it just provides new places for fire ants to start mounds.
Fire ants do not, in fact they cannot eat solid food like corn meal. This old wives tail got started because oily corn meal is the food base that the fire ant poison is mixed with. The fire ants gather the poisoned corn meal and feed it to the ant larva. This kills the larva. You must first kill the larva because they regurgitate a portion of the food they are fed in a liquid form. The adult ants feed on this "ant milk" and this is were the adult fire ants get ALL their nourishment.
Killing the larva therefor results in the adult aunts, queen(s) included dying from starvation. It's too good of an end for them if you ask me. Someone on this forum reported on trying to kill fire ants by putting several hundred of them in a jar of DE and agitating the devil out of the DE for 30 minutes, the idea being to cut or whack the ants into tiny wee pieces with the flying DE. The poster reported that the only result seemed to be agitated fire ants. Anyway, fire ants live and dig in earth and I believe that they think of all earth, DE included like Walt Disney's Brer Rabbit in Song of the South viewed the briar patch. Have a good day and check out this link.
http://www.ces.ncsu.edu/depts/ent/notes/Urban/ifa.htm