Here in south Texas we have fire ants. DH built lovely stands with legs 2 years ago. Having tried setting the legs in oil, water, kerosene, etc., and having NOT deterred the ants, we finally settled on an alternative that seems to work well.
We buy stacks of those clear plastic trays that sit under flowerpots to catch water. We fill those with granulated fire ant poison and set the legs on those. Even after a rain they are still effective. We collect a few SHB in the trays, too.
Good luck!
Summer