Biological warfare against insects is both high and low tech.
The low tech part is bizarre, basically getting 500 gallons of a type of insect in a stainless steel vat, mashing them, then seeing is anything grows on the mash. If it can eat the mashed insects, it might be able to eat the living ones.
The home, low tech version, used against fire ants, is to get a quart glass jar, put some honey in it, and set it next to an anthill. When there are a bunch of ants in it, pour in some boiling water to kill them, seal the jar, and put it in a cool, dark place for a couple of weeks. Then, when a fungus or something grows on the water, pour the water over the nest. Typically it will wipe out both that nest, and several other nests within about 10 yards.
It will be a bit trickier with crazy ants, since they do not make obvious nests, just using small holes in the ground over their massive, underground nest. However, it would be worth it to try the same technique.
Worth a try.