A PCO's Guide To Ant Baits

Ants are among the most fascinating and perplexing groups of insects from a pest management perspective. About 700 ant species occur in the United States. Fortunately, only about 25 are considered to be pest species because they invade structures and/or are found in the landscape near buildings. The unique traits of ants that should be considered in a baiting program include:

• Ants are social insects living in colonies which consist of queen(s), workers, eggs, larvae, pupae and, at certain times of the year, swarmers.

• Solid food consumption in the colony is complex. Worker ants forage for solid food and liquids. However, because they are unable to digest solid food, these materials are regurgitated and fed to the larvae that are able to liquefy the food they regurgitate. The liquefied food produced by the larvae is eaten by the workers and then shared with other workers and the queen(s).

• Workers lay down a chemical (pheromone) trail that is used to guide other workers to food sources and to help them find their way back to the colony.

There are many sprays, dusts and baits available to deal with pest problems. However, baits are the products that have garnered the attention of manufacturers and pest management professionals for control of cockroaches, ants, termites and other pests.

A wide range of ant bait formulations is available, including:

• Dry granulars, which are designed primarily as a scatter bait or to be placed in trays, are very effective against many ant species.

• Gels and pastes which typically are used for ant control indoors and are formulated as either a protein or sugar bait. Small placements should be made where ant activity is detected.

• Containerized products are available for many species. Their primary limitations include the inability to place them where needed and the expense of making numerous placements. Their primary advantage is that they can be removed when they are no longer needed.

• Liquid baits are available in several formulations. The limitation of this type of bait is its tendency to lose moisture and dry out, which renders the bait ineffective.

• Do-it-yourself products, such as those containing boric acid and methoprene, suggest methods on the label for formulating bait materials.

CHANGING TASTES. Baits are designed to provide a food source that contains an active ingredient that will readily be consumed by the ant pest species. Ants typically are very selective in their food preferences.

While most species consume either sweets or honeydew and other insects, many do not feed on oils, seeds and proteins. In some cases, a species may change its food preferences from spring to fall.

The active ingredients in ant baits typically are either a toxicant, e.g., boric acid, avermectin, hydramethylnon, or an insect growth regulator (IGR), e.g., methoprene and pyriproxyfen. Baits containing toxicants must be slow acting so that the worker ant is not killed before it is able to return to the colony. This is more of a consideration with liquid baits because solid baits are not consumed directly by workers. Solid foods are fed to the larvae and after liquefaction, are eaten and distributed by workers to the rest of the colony. Baits containing toxicants kill more rapidly than those containing IGRs.

Baits that contain IGRs work on a totally different principal, i.e., they inhibit development of the larvae and can block egg production. The larvae affected by IGRs do not mature into workers and so the colony dies due to attrition.

Ant infestations can be eliminated quickly if the colony or nest can be located, removed or treated directly with a liquid product. The use of liquid sprays to treat foraging ants rarely is successful in eliminating infestations because only the foraging workers are killed and they soon are replaced. In the case of Pharaoh ants, this form of liquid application can result in colony fragmentation and the spread of the ants.

If the point of entry is located, liquid spot treatments are used to stop foraging ants from entering a structure. Liquid barrier treatments occasionally are effective in keeping ants at bay and preventing their entry into structures.

Unless the colony is treated directly, an ant infestation usually will not be eliminated or prevented through use of liquid applications. Locating a colony and making a direct insecticide application is time consuming; frequently the colony is neither located nor treated. Thus, alternative strategies must be considered. Baiting is the only other method of treatment that offers an effective and economical way of eliminating an infestation. It does not require that the nest be located — only that foraging ants be found, that they accept the bait and that a sufficient amount is transported back to the colony and distributed to other colony members.

BAITING SUCCESS. Here are some keys to making a baiting program work for you:

1. Proper identification is the key to solving ant problems regardless of the treatment method. I have been asked innumerable times how to control "sugar, red, black, small and large ants." Unfortunately, these terms do not accurately describe any ant species. Identification provides the technician crucial information on the biology and habits of the species and is instrumental in the bait selection process and the development of a treatment plan.

2. Selection of an appropriate bait is critical to the success of the pest management strategy. Despite what anyone says, all baits are not created equal. In fact, it is my experience that not all of the ant species listed on a bait product’s label will consume the bait, which then renders the treatment worthless. Frequently ants turn their gasters up in the air and go in the other direction. Selection of an effective bait is best done by trial and error as well as experience. Finally, it is important to remember that bait preferences may change throughout the season.

An example of food preferences by odorous house ants is illustrated by the following observation: ants indoors do not appear to be interested in solid baits. Instead, they appear to forage for water and readily accept liquid baits. There appears to be behavioral differences, i.e., ants outdoors prefer the solid foods and baits while those inside are looking for moisture.

3. Proper bait placement is also critical to the success of the baiting program. Baits need to be placed where ants are actively foraging for food. Using the shotgun approach, i.e., placing bait randomly, is costly and rarely successful in the elimination of an ant infestation.

4. Sufficient quantities of bait must be used to ensure that the ants do not abandon the food source. Depending on the species of ant and the type of bait product used, baits may need to be replenished within several days. Ants must take sufficient quantities of bait back to the colony in order for the treatment to be effective.

5. Follow-up is the final and most important aspect of a baiting program. It is important to know if the baiting program was successful, if bait needs to be replenished and relocated and if there are new areas of activity. When a "reinfestation" occurs, proper identification of the ants must once again be made in order to determine if they are a different species.

CASE HISTORIES. The following case histories are based on products that have worked for me. They are not product endorsements. Other products may work effectively. The important thing is to remember that ant bait preferences may change and what works in one situation might be ineffective in another.

The product that has worked most effectively for this species is Whitmire Micro-Gen’s Avert Ant Bait. Workers readily accept it when it is applied outdoors; indoors, however, they have been observed to walk right through the bait without touching it.

This species has responded best to Maxforce Granular Ant Bait both indoors and out.

I have observed this species to accept only one type of bait — Drax Carbohydrate Bait (the brown tube) which is a gel bait containing boric acid that is readily accepted by the species indoors.

Due to the size of the colonies, multiple queens and colonization by budding, this ant species is one of the most difficult to eliminate from structures. The only method of treatment is by baiting. I prefer to prebait with mint apple jelly and peanut butter in order to determine food preferences and areas of activity. Prebait areas should be inspected about two hours after placement, then baits applied to areas where activity is noted.

Pharorid (methoprene) is once again available; the product is mixed with either peanut butter or mint apple jelly, depending on the results seen in the prebait period. An alternative bait matrix is suggested on the label.

Alternatively, Advance Dual Choice Ant Bait Stations can be placed where ant activity is noted. The limitation to this product is the ability to place bait stations in close proximity to ant activity.

Of the several species of this ant, the black carpenter is the most common species in my area, Washington, D.C. Bait acceptance by this species typically is very sporadic.

The Advance Carpenter Ant Bait has worked well when applied outdoors in areas where foraging trails are observed. Bait acceptance indoors is limited.

OTHERS’ OBSERVATIONS. Because in my area of the country I don’t have the opportunity to deal with other pestiferous ant species, e.g., fire ants, Argentine ants and white-footed ants, I consulted with Dr. David Williams, Ph.D., research leader for the Imported Fire Ants Section of the United States Department of Agriculture’s Medical and Veterinary Entomology Research Laboratory, about baits for these pests. A summary of his comments follows.

Methoprene (Extinguish) recently was registered for use on imported fire ants. Although slower than other baits, it is effective and has a unique label, i.e., it can be applied as a broadcast application to field crops and gardens.

Baits containing pyriproxyfen (Distance), fenoxycarb and abamectin are available for fire ant control. Hy-dramethylnon (Amdro) provides the fastest kill for fire ants, but reinfestation is much faster when this product is used.

These ants typically prefer to feed on sugars and do not respond very well to baits. Reportedly, John Klotz of University of California Riverside has been successful in baiting Argentine ants with a sugar solution containing 0.5 percent boric acid. Apparently the trick is preventing the bait from drying out. Klotz has accomplished this by using capped and slotted PVC pipes containing cotton wicks soaked in the bait solution. This strategy has kept the baited wick wet for four to five days.

These ants also are difficult to control because of their large colony size and multiple queens. They prefer to feed on sugar and in order to be successful, baiting must continue over a long period of time. For a yet-to-be-determined reason, they do not move bait readily through the colony. According to industry consultant Harry Katz, the boric acid (1.0 percent) liquid bait manufactured by JT Eaton, which incorporates caffeine into the bait matrix, has proven very effective against this species.

CONCLUSION. These comments represent my (and others’) observations in the field. I’d be interested in hearing from other PCOs and manufacturers about their ant baiting experiences. E-mail me at the address below with your ant baiting stories and PCT will publish the results on pctonline.com in the future.

According to USDA’s Williams, the future for ant baits does not appear bright since few new active ingredients are being tested as ant baits. Most manufacturers are reworking existing active ingredients.

However, fipronil is one new bait that maybe registered for fire ant control within the next year. In field tests, this product has out-performed all the existing products hands down. As a bait, it is effective at very low concentrations. Applied as a granular at a rate of 2 to 3 pounds per acre, it has provided up to nine months control.

When used correctly baits can be the most effective tool in your arsenal for the eradication of ant infestations.