The rod is inserted into the mound and the toxicant released. Although these systems are more expensive, this method is a fast-acting mound treatment, and the potential for exposure to and runoff of surface residues is reduced. Commercial hot water mound injection systems also provide control. This liquid sinks into the mound, because it is heavier than air, and vaporizes. Ants are killed quickly, but the degree of penetration into the colony may depend on the wetness of the soil.
Vaporization is less complete if the soil is saturated.
Methyl chloroform also kills grass and other plants that it contacts in the application process. Noninsecticidal controls have been proposed as a part of the on-going effort to suppress fire ants. Anything that disturbs the colony may cause mound relocation. Mixing the contents of two mounds may cause relocation or removal of queens and brood. Cereals, such as rice, grits, or meal, are sometimes thought to aid in fire ant control when sprinkled on the mound.