This article appeared in the May 1999 issue of PCT Magazine.
Elimination of Pharaoh ants is often a labor-intensive, time-consuming process. The only effective approach is through implementation of a comprehensive baiting program.
Treatment with residual insecticides will not eliminate an infestation of Pharaoh ants. Only about 5% of a Pharaoh ant colony’s workers are out foraging at any one time. Treatment with insecticide therefore only kills 5% of the workers, leaving 95% of the colony intact. The loss of its foraging workers stresses the colony and the colony splits or "buds" into two or more new colonies. Such treatments therefore make infestations difficult to control. It is very important that the customer be instructed to NOT treat foraging workers with insecticides throughout the entire baiting program. The customer must understand how the baiting program works and that the foraging workers are needed to carry bait back to the rest of the colony.
Baiting is the best and most effective strategy for eliminating Pharaoh ant infestations. The nesting sites of this ant are so varied and often so deeply hidden that finding even one colony is unusual. Hydramethylnon (Maxforce®), sulfluramid (Advance,TM FluorGard®) and boric acid (Drax,® Terro®) are the primary commercial Pharaoh ant baits available.
The Pharaoh ants in any particular situation may choose one bait over another based upon their unique preferences so pest management professionals should be prepared to switch baits when ants ignore the initially offered bait.
In homes and other small buildings, baits should be placed in all rooms of the structure. In larger buildings, such as hospitals, apartment buildings and office buildings, placing baits in all rooms is very difficult and expensive. Therefore, only the areas with ant activity and the rooms adjacent to these infested areas require baiting. It is in these large areas where a thorough inspection is most important. Prebaiting with non-toxic food baits is also very helpful in pinpointing activity in larger buildings.
Due to the mobility of Pharaoh ant colonies, it is possible for ants to move from infested areas into adjacent, uninfest-ed areas at any time during the baiting program. Colonies could already be in these seemingly uninfested areas but have not yet been noticed. For these reasons, rooms and apartments next to, above and below all sides of infested areas must be baited. In heavily infested buildings where more than 60% of the entire building is infested, it is usually best to bait the entire building to achieve the best results.
Depending on the baiting program selected, the size of the structure and the severity of the infestation, the baiting program may take only two months or as much as a year to complete. How long the baiting program is extended is a decision of the professional performing the baiting program. Most baiting programs, however, should extend at least several months, especially if Pharaoh ants have been present for awhile.
Baits should be placed along each trail of foraging workers. Remember, each trail could be from a different Pharaoh ant colony. These baits should be placed in areas out of sight and reach of children and pets. Areas where baits should be placed include cabinets and pantries, windowsills, inside wall voids where pipes are present and inside the outlet boxes of electric sockets and switches.
Baits should be placed in corners and along edges of items, such as door moldings and baseboards, as Pharaoh ants tend to trail along edges. Such placement of baits ensures that ants will more likely contact the bait.
Any baiting program for Pharaoh ants should involve several follow-up visits during the first several weeks of the program. The larger the building and areas being serviced, the more visits that will be necessary. These follow-up visits are used to check to see if ants are feeding on the bait and whether new or fresh baits need to be placed. Keep in mind that the bait may need to be changed if ants are avoiding it or are feeding on something else. The program can fail or take longer to be successful if these follow-up services are not maintained.
In addition, a floor plan diagram of the infested areas should be completed detailing each site where ant activity is noted. Each ant trail found could conceivably be from a separate Pharaoh ant colony so diagraming helps the pest management professional "see the big picture." Patterns of activity over the course of the baiting program may determine where new bait placements are needed.
Recent research has demonstrated the importance of also baiting outdoors for Pharaoh ants. In one study, the infestation was eliminated by primarily placing baits outside. A thorough inspection will determine where foraging trails are located, thus indicating where baits need to be placed.
Pharaoh ants are a difficult pest to control but with baiting expertise, creativity and a thorough inspection, PCOs can achieve success.