Getting the Most Out of Your Fire Ant Bait

ANR-1161, Revised May 2003. Kathy L. Flanders, Extension Entomologist, Associate Professor, Entomology and Plant Pathology, Auburn University, and Lawrence "Fudd" Graham, Coordinator, Alabama Fire Ant Management Program, Auburn University

A fire ant bait is an inexpensive, easy, and environmentally sound way to control imported fire ants. This publication will explain how baits work, what baits are available, and when and how to apply fire ant baits. More information on pest ants can be found in Extension publications ANR-175, "Imported Fire Ants in Lawns, Turf, and Structures," and ANR-999, "IPM Tactics for Argentine Ant Control."

Fire ant baits are designed to control imported fire ants. They will not control the "sugar ants (a mix of species including Argentine ants, Pharaoh ants, and their relatives) or carpenter ants.

Fire ants usually make some kind of mound (Figure 1). In pastures, this mound can be up to 2 feet tall and 2 to 3 feet across. In a mowed lawn, fire ant mounds are usually only a few inches tall, but can easily be 1 to 3 feet wide. Other ant species such as Argentine ants and orymyrmex ants also make mounds. These ants do not sting and do not move as aggressively as fire ants move.

Figure 1. An imported fire ant mound in a pasture

Why use a fire ant bait?

Fire ant baits are safer than other insecticides that are applied as drenches, sprinkled on top of the mound, or broadcast. The insect control agent never makes up more than 1 percent of the bait, which means that 0.01 pound or less of active ingredient is used per acre.

Fire ant baits can give longer lasting control because they control the young fire ant colonies that may be too small to see. Baits have fewer nontarget effects than other control methods have because they are designed to be picked up by and consumed by fire ants. Fire ants are so efficient that they can pick up almost all the bait and carry it into the mound. This means that baits can be used around, but not on, sensitive areas such as fish ponds. In this case, it is best to spread the bait no closer than 10 feet of a sensitive area.

Fire ant baits are usually cheaper than individual mound treatments because it is time consuming to treat every mound. Individual mound treatment can cost five to ten times as much as baits, if the cost of labor is considered.

Fire Ant Biology

Fire ants live in colonies in the soil. The aboveground mound of soil is just a small part of the fire ant nest. Tunnels usually extend down to the water table and for several feet around the mound. The ants move around the nest to take advantage of the best temperature and moisture conditions. When it is too hot, too cold, or too dry, fire ants are usually deep below the ground. Fire ants do not always build mounds. When it rains after a prolonged period of drought, fire ant mounds often pop up from fire ant colonies that have been living below ground.

At the heart of each colony is the fire ant queen, a fertile female that lays all the eggs in the colony. The queen controls the colony by chemicals called pheromones. In some parts of Alabama, there are fire ant colonies where several queens share egg laying and colony leadership. A fire ant queen can live for 7 years and produce as many as 800 eggs per day.

The work is done by wingless worker ants, sterile females that defend the colony, feed the young, and hunt for food. The adult worker ants live about 60 to 90 days. Worker ants can roam far from the nest in search of food"other insects, decaying plant and animal material, and plant seeds. Plant nectar is also a food source. There can be 400,000 worker ants in a mature colony controlled by a single queen.

Fire ants have a communal system of feeding. The workers in charge of food gathering carry the food back in their mouths and share it with the rest of the colony. Liquid foods can be shared immediately with other workers, the queen, and the immature fire ants (larvae). An adult fire ant has a plate in its throat that prevents it from swallowing solid food. Solid foods are fed to the oldest fire ant larvae, which have special digestive enzymes.

In mature colonies, the queen produces unfertilized eggs, which develop into winged male fire ants. Winged females are produced from fertilized eggs, just like the workers. However, young fire ants destined to be winged females receive more food and contain higher levels of juvenile hormone than do young worker ants. Winged fire ants are produced throughout the year, but are most common in spring (April through June). The winged males and females fly high into the air and mate. The winged female is a new fire ant queen. She finds a place to land, burrows into the soil, and begins to lay eggs that will develop into the first workers in the colony.

Fire ant control products are often criticized because they control fire ants for a while, and then the fire ants come back. The lack of permanent control relates back to fire ant biology. There will always be new, winged fire ant queens looking for somewhere to start new colonies. In a fire ant infested area, fire ant workers from local colonies can kill more than 99 percent of new fire ant queens. A queen is most likely to succeed in an area where all the other fire ants have been controlled. Fire ant baits usually can give 6 to 18 months of control.

There are several other reasons why fire ants come back. Some fire ant control methods kill many fire ant workers, providing temporary relief. However, the queen can produce more workers that will rebuild the colony. If a fire ant infestation redevelops in a few weeks, this may be the case. Fire ant control strategies that rely on treating every mound will also frequently miss the very small colonies, consisting of the queen and relatively few workers. With the larger colonies
no longer competing for food, these small colonies can
grow rapidly.

How do fire ant baits work?

A fire ant bait has three parts: a food source, an insect control chemical, and a carrying particle. Fire ant workers see the bait particle as food and carry it back to the nest. Inside the nest, the insect control chemical is passed around the colony, and it eventually reaches the queen.

Fire ant baits will not work unless the worker ants pick them up. Therefore, it is important to put the fire ant bait out when fire ant workers are most actively searching for food (between 70 and 90 degrees F).

The food source is what attracts the fire ants and causes them to carry a bait particle back to the nest. The food source is usually soybean oil. If the oil becomes rancid, the bait will not be picked up by the fire ants. Soybean oil becomes rancid if it is exposed to the air for a prolonged period or if it gets too hot. That is why it is important to store bait in a tightly sealed package in a cool, dry place.

Mixing the fire ant bait with fertilizer granules at first may seem to be a time-saving idea. However, the dust from the fertilizer granules reduces the attractiveness of the fire ant bait. Again, the treatment will not be effective if the workers do not pick up the bait.

The insect control chemical is different for each fire ant bait. It may be a slow-acting insecticide or an insect growth regulator or a combination of the two. The slow-acting insecticide kills workers and larvae that have come into contact with it. The insect control chemical has to act slowly so that workers have time to feed it to the queen before being killed themselves. The queen will die if she eats enough of the slow-acting insecticide. An insect growth regulator will not kill the adult worker ants or the queen. However, it will stop the queen from laying fertile eggs and prevent the immature fire ants from developing.

The carrier particle is usually made from ground corncobs. The carrier will start to disintegrate if it becomes wet. Therefore, it is important to wait until the dew has dried before spreading the fire ant bait. Also, bait should not be applied if rain is expected within the next 6 hours.

What brands of fire ant bait are available?

Currently, seven insect control chemicals are used in fire ant baits (Table 1). Not all baits are cleared for use in all situations. It is important to read the directions on the bait package carefully to see if the place you want to apply a bait is listed. The directions on the label are federal and state laws. If the place is not listed, it is illegal to apply the bait there. Baits also differ in cost. Extension publication ANR-175-A, "Fire Ant Control Materials for Alabama Homeowners", compares the cost of baits that are readily obtained by homeowners. You can find or order other baits at farm supply stores.

Hydramethylnon (Amdro, Amdro Pro, Siege), spinosad (Justice, Eliminator Fire Ant Killer Bait, Ortho Fire Ant Killer Bait Granules, Fertilome Come and Get It! Fire Ant Killer), and fipronil (Chipco Firestar Fire Ant Bait) are slow-acting insecticides. The effect of these materials will be seen within a few weeks because the active ingredient kills most of the workers and the queen. Any remaining workers will die of old age or starvation.

Fenoxycarb (Award, Logic), S-methoprene (Extinguish), and pyriproxifen (Distance, Spectracide Fire Ant Killer Plus Preventer, Esteem) are insect growth regulators. The effect of these materials will not be seen for 6 to 12 weeks. That is because the workers are not killed as a result of ingesting the bait. The queen stops laying fertile eggs but continues to control the actions of the workers. Eventually, the workers die of old age and the queen starves.

Abamectin (Clinch, Varsity, Ascend) is an insect growth regulator-like compound. When broadcast at labeled rates, effects are seen in 6 to 12 weeks. A quicker response will occur if the material is applied as an individual mound treatment because, if the doses are high enough, workers will be killed.

If you need relatively fast fire ant control, use fipronil, hydramethylnon, or spinosad baits. These materials give 3 to 9 months of control. If you can wait, one of the insect growth regulator baits could be a better option. These materials can give 9 to 18 months of control. The longer control is probably because the worker fire ants linger in the treated area, defending the territory from incoming fire ant queens.

How do I apply fire ant bait?

Many of the baits are applied at a rate of 1 to 2 pounds per acre (approximately half an ounce per 1,000 square feet, 15 to 25 bait particles per square foot). Exceptions include Spectracide Fire Ant Killer Plus Preventer, which must be applied at 10 pounds per acre, Justice (2.5 to 5 pounds per acre), Ortho Fire Ant Killer Bait and Fertilome Come and Get It! (4 pounds per acre), Amdro Fire Ant Bait Yard Treatment (29 pounds per acre), and Chipco Firestar (1.5 to 15 pounds per acre). Just as a reminder, an acre is 43,560 square feet. To determine the square footage of your yard, multiply the length in feet by the width in feet.

Fire ant baits are usually applied by spreading them across the area where fire ants are feeding (a broadcast application). Baits can be applied in different ways, and at different times, depending on your objectives.

One strategy is to apply a broadcast application of fire ant bait in spring and fall. A calendar schedule like this would be very appropriate for areas where children play or around a house inhabited by someone who is allergic to fire ant stings. This treatment would be most effective if an insect growth regulator bait were used.

If you can only afford one fire ant bait application, consider waiting until most of the spring mating flights have occurred, then apply your fire ant bait in mid-June to mid-July. This strategy leaves fire ants to defend the territory from most of the incoming fire ant queens.

Another strategy is to apply the bait in September or October for a relatively fire ant free spring. This strategy is especially helpful in hayfields where the highest quality hay is harvested in spring.

Studies in Texas have shown that a 50:50 mix of an insect growth regulator bait and a slow-acting insecticide bait give results as fast as the slow-acting insecticide bait alone. In addition, the duration of the control is similar to that of an insect growth regulator bait alone.

Fire ant baits can be used as individual mound treatments. The instructions for each bait will show how to spread a few tablespoons of bait around, but not on a fire ant mound. This strategy works well if you only have a few mounds to treat but becomes cost prohibitive if you have to treat too many mounds.

Fire ant baits and individual mound treatments with a fast-acting insecticide can be used in combination as a two-step method. A bait can be applied that will be carried by the workers to all colonies. Then, a few days later, a fast-acting insecticide (see Extension publication ANR-175-A, "Fire Ant Control Materials for Alabama Homeowners") can be used on the most annoying mounds to kill the workers. Read the label carefully to make sure it is legal to use a particular insecticide to kill fire ants on your site.

Apply bait when fire ants are searching for food (at temperatures between 70 and 90 degrees F) and when the foliage is dry. Make sure that the bait is not rancid. To determine if the ants are foraging, scatter 1 to 2 tablespoons about 5 feet from a fire ant mound. Watch the bait to see if it is picked up by fire ants. If no ants are observed picking up the bait within 10 minutes, this is not a good time to put out the bait. If you see fire ants approaching a bait but not picking it up or picking it up then dropping it, the bait may be rancid. You will need to buy new bait.

Avoid disturbing the fire ant colonies before you apply a fire ant bait. When colonies are disturbed, the workers rush to protect the queen and the brood and to rebuild the mound. This takes workers away from their normal foraging activities.

Baits are applied at a very low rate, usually 1 to 2 pounds per acre. Sometimes, the hardest part is to figure out how to cover the area that needs to be treated with such a tiny amount of bait. At this rate, there will be only 20 to 30 bait particles per square foot. Fire ant bait can be broadcast by hand (wear a pair of plastic or rubber gloves). For larger areas, various seeders or fertilizer spreaders can be adapted to apply fire ant baits at the labeled rate. For areas smaller than 1 acre, a small, hand-cranked seeder/ spreader can be used, such as a Republic EZ Handspreader (Figure 2). For larger areas (1 to 5 acres), you will want something with a wider swath width and a larger bait hopper such as a Cyclone seeder or a Spyker seeder. For even larger areas, a seeder/spreader with an electric or gas motor instead of a hand crank will be useful. Two such examples are a tractor- or ATV-mounted Herd seeder equipped with a fire ant plate (Figure 2) or a Solo backpack spreader (Figure 3). Calibrate the equipment by figuring out how much bait you are applying to a given area. Your county Extension agent can provide assistance on calibration. For those baits applied at 1 to 2 pounds per acre, such as Amdro, Amdro Pro, Award, or Logic, start calibrating by adjusting the seeder at the bottom of the bait hopper to about 316. If this opening spreads more than the recommended amount of bait, decrease the width of the opening the bait goes through or increase your speed. If this spreads less bait than needed, decrease your speed or increase the width of the opening. Repeat the calibration until you are applying the desired amount of bait. Extinguish particles are a bit smaller, and you will need to make the slit slightly narrower than 316, if you can. Distance is slightly larger than Amdro, Award, and Logic, so the spreader opening needs to be a bit larger than 316. Clinch and Varsity particles are the largest"you can either make two passes over the same area with the spreader opening set to about 316 or open the spreader wider to let more fall through in a single pass. Because Chipco Firestar is a small, light granule it is easy, unfortunately, to apply too much.

		Figure 2. Seeders or spreaders that can be used to apply fire ant bait are (a) electrically powered seeder suitable for large areas; (b & d) hand-cranked seeders suitable for medium-sized areas; (c) a small, hand-cranked spreader for small areas (less than 1 acre).
		Figure 3. A backpack applicator with a small engine that can be used to apply fire ant bait to larger areas

Do I have to broadcast the fire ant bait over the entire area?

Management of fire ants on large areas such as athletic fields, golf courses, commercial landscapes, camp sites, cattle ranches, and parks can be different from management on a small, home lawn. It may not be necessary to spread the bait across the whole site. To get the most fire ant control for the least amount of money, apply the bait in the spots where it is most needed. Make a map of your site. Then walk the site and indicate on your map where the fire ant mounds are. Also note where you most want to keep out fire ants (children,s play areas, for example). Apply bait to the areas where fire ant control is most wanted or most needed. Consider leaving ant colonies in the areas where land use is not frequent. Leaving some ants in the area can help slow reinfestation. Wait 1 month and evaluate the effect of hydramethylnon, spinosad, or fipronil baits. Wait 2 to 3 months before evaluating the effect of the other ant baits, which are insect growth regulators. Map the remaining fire ant mounds and repeat treatment in the most heavily infested areas. This technique is most effective if you make the first bait application in late June or early July. Using the mapping method, some landscape managers in Alabama have reduced their fire ant control costs to 10 percent of what they were.

Steps to the Successful Use of Fire Ant Baits Store ant bait in tightly sealed containers. Place them in a cool, dry place. Store them away from gasoline and tobacco products because these can quickly taint the baits and reduce their effectiveness. Do not buy more bait than you can use in 1 year. Apply the bait when ants are searching for food (when soil temperatures are between 70 and 90 degrees F). In summer, a late afternoon or evening application is best. Do not disturb the fire ant mounds before you apply the bait. Do not apply the bait with other materials, such as fertilizer granules or sand. Do not apply bait when the foliage is wet, or just before a rain. Give the bait enough time before deciding if it has been effective (Table 1).

Use pesticides only according to the directions on the label. Follow all directions, precautions, and restrictions that are listed. Do not use pesticides on plants that are not listed on the label.

The pesticide rates in this publication are recommended only if they are registered with the Environmental Protection Agency and the Alabama Department of Agriculture and Industries. If a registration is changed or canceled, the rate listed here is no longer recommended. Before you apply any pesticide, check with your county Extension agent for the latest information.

Trade names are used only to give specific information. The Alabama Cooperative Extension System does not endorse or guarantee any product and does not recommend one product instead of another that might be similar.

For more information, contact your county Extension office. Visit http://www.aces.edu/counties or look in your telephone directory under your county's name to find contact information. Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The Alabama Cooperative Extension System (Alabama A&M University and Auburn University) offers educational programs, materials, and equal opportunity employment to all people without regard to race, color, national origin, religion, sex, age, veteran status, or disability.