insecticide is poured directly into the tunnels. Mound drenches are most effective after rains when the ground is wet and the ants have moved up into the drier soil in the mound. During excessively dry weather, effectiveness of the treatment may be enhanced by soaking the soil around the mound with water before treatment. One problem with this technique is that the queen may be too deep to be reached with the drench. This may be especially true if the colony is disturbed prior to an application. In this case the workers may move the queen deeper into the colony in order to avoid a potential threat.
Granular formulations are also available for individual mound treatment. In this case once the recommend dose is applied to the mound it should be watered thoroughly in order to reach the worker ants and queen that occur deeper in the colony. The dissolved granules must come into direct contact with the ants to have any effect. As in mound drenches, care must be taken not to disturb the colony prior to application.
A few insecticides are marketed as injectants. In
this case they may be injected using a "termite rig" with a
soil injector tip, a standard 1-3 gallon compressed air sprayer with a fire
ant injector tip, or a special aerosol soil injector system. The mound is injected
in a circular pattern, usually at 3 to 10 points. A new product combines
insecticide treatment with high temperature vapors to increase
Fumigants are readily available in most states for fire ant control. These are usually more effective than surface applications or mound drenches but are also more expensive and can be dangerous if not handled properly.
Depending on the state a number of fire ant baits are available. These can be used for treating individual mounds or for broadcast treatment of larger areas. The bait should be uniformly applied around the mound 0.3 to 1.0 meters away and not on the mound itself. Baits are much slower acting than the control methods listed above but are generally safer, cheaper and more effective in the long run.
Water - The use of
boiling water has been examined on several different occasions resulting in
varying degrees of success. In one experiment over a 50% of treated mound were
eliminated by pouring approximately 3 gallon of hot water directly into the
mound. The use of steam produced by a
steam generator produced similar results.
Regardless both techniques are far less effective the use of drenches,
fumigants, granular formulation or baits are
cumbersome in the field are not practical when dealing with large
populations of these pests. Area wide flooding with water has not proven to be
effective, impractical in most situations and can led to spreading of the
population due to the rafting ability of these insects.
Broadcast Treatments - A number of fire ant baits (Figure 10) are commercially available for broadcast treatments (again depending on the state). Baits are composed of an inert carrier-attractant (corn carrier and soybean oil) and toxicant. The active ingredient (either a slow-acting insecticide or an insect growth regulator) is incorporated into the oil. These baits can be applied either by a hand operated granular fertilizer spreader or larger equipment. Once foragers find bait they carry it back to the nest, ingest it and begin feeding other ants in the nest. Because the active ingredients are slow acting, they are spread around the nest before the desired effect. This formulation and means of application has a number of advantages. Unlike individual mound treatments, colonies need not be "located" in order for them to be treated and as a result this method is less time intensive and consequently less expensive than individual mound treatments. On the other hand broad cast treatment has the potential of affecting non-target organisms. It is also slow acting and the effectiveness of the bait is greatly reduced when they come in contact with water from rain, irrigation or other sources. Finally baits are only effective during those times of the year or temperatures when the ants are readily foraging. Ge