Ask Mr. Smarty Plants

We had several previous answers in our Mr. Smarty Plants section similar to this. We believe you are suffering from an onslaught of leaf cutter ants. Two of those questions were from areas in Texas south of you. Here is an excerpt from one of those questions:

"We went looking for leaf cutter ants, and found that it is an enormous problem. Like fire ants, these creatures are imported from Central and South America and have no natural enemies in our area. This very comprehensive site from Texas A&M AgriLIFE Extension, Leaf Cutting Ants, has a lot of information that you should read. The pest control people you have been talking to probably either don't know how to approach the problem or realize it is bigger than they can easily control.

To quote from the above site:

'Defoliation by leaf cutting ants can resemble damage produced by several other leaf chewing insects, particularly sawflies and leaf cutting bees. Trees defoliated by the leaf cutting ant usually are within sight of an ant nest and the ants themselves may be seen carrying leaves. Foraging trails will be littered with pieces of leaf tissue that can be traced to a feeder hole. Considerable damage to a plant can occur in a few hours. Small- to medium-sized trees can be stripped in one night. One researcher in South America estimated that a large leaf cutting ant colony harvested approximately 13,000 pounds of leaves over a 6-year period. This same colony excavated 802 cubic feet of soil weighing over 44 tons.'

First of all, let's make sure we're talking the right bug. Take a look at this page of Images of leaf cutting ants and see if that is what is going on in your yard.

The most recent information we found on those ants was that they were threatening pine forests as near as East Texas and on east into Georgia and Florida. They apparently choose one particular plant to chow down on, but the reason they take so many leaves is not for food and not for nest lining but for their own version of farming. They go back to the colony, chew the leaves and spit them out and on this base a fungus grows which is the only food of the ants, including the young. When a queen ant flies, she takes a "starter" from this fungus, establishes a new little hole, and plants her garden. Then, the workers come in and begin the fresh tunneling. Because they eat nothing but the fungi, putting out bait is not successful. Because they have such a large and intricate colony of underground tunnels, spraying down the holes in the conical mounds doesn't go far enough to do any real good."

Since we are not entomologists and this falls outside of our expertise in native plants, we would suggest you contact the Texas A&M AgriLIFE Extension Office for Bexar County.  As these non-native ants seem to be getting a foothold in Texas, perhaps the County Extension office will have some suggestions.