Abstract: A method for killing fire ants in subterranean tunnels includes fogging the subterranean tunnels with an insecticidal amount of thermal aerosol fog through a boot covering the subterranean tunnels and then blowing hot air into the subterranean tunnels whereby the thermal aerosol fog is forced further into the subterranean tunnels. The apparatus used in the method includes a heat generator unit capable of producing thermal fog and a boot with skirt connected to said generator and which covers said subterranean tunnels. A dye may be added to the fog to provide a color marking for each fire ant mound treated by the fog.