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Preventing and Managing Ant Infestations

Ants roaming inside your home or business is not only annoying, but can also lead to ruined food and damaged property or result in a stinging bite. Permanently eradicating ants requires a little knowledge, some patience, and targeted removal tactics.

The first step to reclaiming your home or office space is identifying the type of ant infestation. The two main types of infestation include ants that live outside the building but forage inside, or ants that both forage and nest inside. Some ants live outside most of the year, but come indoors to search for food or shelter from inclement weather. The method you use to effectively get rid of problematic ants depends on the kind of infestation and ant species you’re dealing with.

How to Differentiate Ant Invasions

• If you observe ants entering through a crack in a window or door, this is a good indication that they live outside and are foraging inside for food.
• If you notice a trail of ants coming to or from a crack in a cabinet, wall, electrical outlet, or floor, there is a possibility that ants are nesting inside your home. Once you have located the points of entry, you will be better equipped to determine which method of ant control will best suit your needs for treatment, removal, and prevention.

Low Impact Approaches

The following ant control measures are effective when implemented in combination to disrupt the ant life cycle and kill ants and their colonies. Prevention is key to avoiding indoor ants.

Home Cleaning

Keep the kitchen and food preparation areas clean by putting sweets and proteins into tightly sealed containers or into the refrigerator to eliminate ant attractants. Keep counter-tops clean. Empty garbage regularly and otherwise make sure garbage is tightly sealed. Wash empty food cartons before discarding. Wipe up food spills and wash dirty dishes. Sweep and mop floors regularly to remove crumbs and any scout ants. Create a moat around pet food dishes and potted plants that are attracting ants by surrounding the dish in a larger one filled with a soapy water solution.

Ant Control Pesticides

If your house is so old and full of cracks and crevices that you simply can’t caulk them all, pesticide baits will complement your ant control efforts. Avoid aerosol sprays of pesticides or foggers. They indiscriminately contaminate all surfaces in the treated area and are an inhalation and asthma hazard.

Potential Consequences of Ant Control Pesticides

Recognize that when you use ant control pesticides, you should be ready to deal with these potential consequences:

• Use of aerosol sprays or foggers guarantees exposure to the pesticidal active ingredient, through inhalation of the spray droplets and contamination of exposed surfaces. See US EPA’s page on foggers.
• If bait stations are left out in the open, children or pets can be exposed to pesticides if they put a bait station in their mouths and chew on it.
• Boric acid pesticides are toxic to plants and if this type of pesticide is placed inside a potted plant or other area where water may carry the pesticide to plants, your plants will be affected.

Precautions to Take When Using Ant Control Pesticides

If you determine that pesticides are necessary, take these precautionary steps to reduce the potential for adverse effects:

• Always read and follow the label instructions on the pesticide product to avoid harm to yourself, children, pets and others. The label is the law and you could be liable for any damage resulting from not following the label instructions.
• Use only US EPA approved products (see Regulatory Update below for details).
• Indoors, place pesticide bait stations only in locations that are completely inaccessible to children and pets—inside walls, under heavy appliances, or in enclosed crawlspaces. Never put baits where they can contaminate food.
• Once all signs of pests are gone, remove bait stations promptly to avoid attracting new populations of ants.

Baits and Gels

Baits are formulated as granules or solid blocks, gels, or liquids. Some bait products already have the active ingredient in the bait station, and others are packaged as a liquid that you pour into a bait container provided in the package. The likelihood of exposure to the chemicals is lower if you use the bait stations that don’t require you to handle the product other than to set it out.

When using bait stations or gels, you’ll have to resist wiping up all of the ants for a short while—you’ll need to be sure there are enough ants to bring the bait back to the nest. Place the bait station near the line of ants close to their point of entry, so they have to crawl over it, but be sure it is out of reach of children and pets and not near food that could become contaminated. Place gels in cracks and crevices behind and under appliances, cabinets, sinks, or closets. Within a few hours, the ants will be carrying the bait back to the nest. It may take a few days to eliminate the line of ants entirely, but the visible population will drop fairly quickly.

There are several different pesticide active ingredients used in ant baits. If you use the same kind of pesticide every time, the ants will become resistant to the pesticide and it will no longer work well. To solve this problem, buy several different bait products containing different active ingredients. The first time you put baits out, select one of them and use it. Next time, use a different product, and rotate through the products as needed. If you find that one isn’t working very well, switch to another one—you may have ants that are already resistant.

The different types of active ingredients used in ant baits and their toxicity properties are described below:

Boric acid or other borates: Baits containing borax or boric acid active ingredients are usually mixed with sugar or syrup, and are highly attractive to Argentine ants year-round. Borates are also used against grease ants. These baits draw forager ants that bring the bait back to the colony, killing it and the queen. Boric acid and other borates occur naturally in the diet and have relatively low acute toxicity. They are not absorbed through the skin; however, ingestion of small amounts of boric acid every day over several months has been shown to reduce sperm counts in laboratory animals. Borates are toxic to plants.

Insect growth regulators: Methoprene and pyriproxyfen are insect growth regulators that work by inhibiting the development of insects from one stage to the next. They are used primarily for control of fire ants. Insect growth regulators generally have low acute and longer-term toxicity to humans. They are toxic to aquatic life, so it is important to dispose of used baits properly so they don’t make their way into water.

Hydramethylnon: Hydramethylnon is used in baits packaged as gels, liquids, and granules for use against Argentine ants, carpenter ants and fire ants, among others. It has low acute toxicity to humans and is not extensively absorbed through the skin. It is toxic to the developing fetus and interferes with reproduction at moderate doses.

Neonicotinoids: Imidacloprid, clothianidin, acetamiprid and thiamethoxam are neonicontinoid pesticides, used primarily in indoor ant control as gels or liquids. These products are labeled for use on Argentine ants and carpenter ants, among others. The neonicotinoids have moderate acute toxicity to humans and are absorbed through the skin to some extent. They are toxic to the nervous system, and imidacloprid has been shown to reduce sperm counts in laboratory animals with long-term exposure.

Avermectin: Avermectin-containing baits are used to treat fire ants, Argentine ants, and carpenter ants. They are often packaged as granular formulations. Avermectin (also known as abamectin) has high acute toxicity in pure form, but the concentrations used in ant baits  (less than 0.01%) have low acute toxicity. Avermectin is toxic to the nervous system and to the developing fetus at very low doses. It is not absorbed through the skin to any great extent.

Fipronil: Fipronil is used for control of fire ants, Argentine ants, and carpenter ants, among others. Products are formulated as gels, granular, liquids, and impregnated materials. Fipronil is moderately acutely toxic by ingestion, but not absorbed substantially through the skin. It is toxic to the nervous system and has been classified as a Possible carcinogen by US EPA.

Metaflumizone: Metaflumizone baits are used for fire ant control and are packaged as granular and pelleted formulations. It has low acute toxicity and there is some evidence of toxicity to reproduction and development at moderate to high doses.

(S)-Indoxacarb: Indoxacarb baits are used for fire ant control and are packaged as granular formulations. Indoxacarb has low acute toxicity.

Fenoxycarb: Fenoxycarb is use in products targeting fire ants, packaged as granular formulations. It has low acute toxicity and is not well absorbed through the skin, but with longer-term exposure, it is toxic to the liver and is a Probable carcinogen.

Aerosol Sprays and Foggers

Use of aerosol sprays or foggers is not recommended, due to the high probability of harm during the application from inhaling the aerosol. Fogging also leaves pesticide residues that remain distributed throughout the home environment and is an explosion risk in homes with gas appliances. Outdoor sprays can drift away and pose a risk to non-target wildlife such as bees or other beneficial insects.

Botanicals: Several naturally occurring substances are available as aerosol sprays including limonene, phenylethyl proprionate, thyme oil, capsicum oleoresin (hot pepper extract), pyrethrins, cinnamaldehyde, neem oil, eugenol (clove oil), linalool (from mint and citrus plants), and allyl isothiocyanate (a garlic extract). Contamination of surfaces with these common components of foods is not a problem, but inhalation of the spray can be problematic.

Pyrethroids: Many pyrethroid pesticides are used in aerosol sprays or foggers for insects. While they will kill the insects that are sprayed, they will die before returning to the nest, so will not deplete the population significantly. If you find an active ingredient that ends in “-thrin,”it is a pyrethroid: Allethrin, bifenthrin, permethrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, esfenvalerate, imiprothrin, tetramethrin, tralomethrin, and phenothrin. Most products also contain a synergist such as piperonyl butoxide that increases the toxicity of the active ingredient. Because these chemicals are typically packaged as aerosols, the likelihood of exposure via inhalation and contamination of surfaces is high. Pyrethroids have been implicated as causing asthma attacks and for setting off allergic reactions in sensitive individuals.

Organophosphates and carbamates: Several popular consumer products containing the organophosphate chemicals chlorpyrifos (Dursban products) and diazinon were removed from the market in 2001 and 2002 because of their hazards to children. The remaining chemicals in this group are neurotoxic at relatively low doses, and several are Probable or Possible carcinogens (propoxur, DDVP, malathion).

Regulatory Updates on Ant Control Pesticides

Pyrethroid pesticides applied as perimeter barrier sprays outside around homes and other buildings have been found in water runoff  and in the sediment in urban creeks, resulting in high toxicity to the small invertebrates that serve as an essential part of the food web for fish and other aquatic animals. In response to this environmental impact, in August 2012, the US EPA required manufacturers to revise the Directions for Use on labels for pyrethroid pesticide products in an effort to reduce ecological exposures through runoff and drift. A specific list of pyrethroids was subject to reregistration under these updated requirements, affecting over 2000 end-use products.

Several ant-control products have been highlighted by US EPA as unregistered and illegal to use in the U.S.

• Fast Ant Bait: Sales of this bait made people ill in Washington state. The product contains the now-banned chemical Mirex. More information about Mirex can be found at the ATSDR web site.
• Insecticidal chalk: Also known as “Miraculous Chalk” or “Chinese Chalk,” these products are often for sale in Chinese grocery stores. The chalk can contain several different insecticides, but because it is not labeled, you won’t be able to find out what the active ingredient is. The problem with this chalk is that it looks exactly like regular chalk, and children have been poisoned by eating the chalk.

On October 29, 2008, the EPA released a statement that stated that the seven products containing sulfluramid currently being sold will stop December 21, 2013. All products containing sulfluramid will be phased out by 2016.

References and Additional Resources

• University of California, Davis IPM Online: Pests of Home, Structures, People, and Pets
• National Pesticide Information Center: Understanding and Controlling Ants
• Fluoride Action Network Pesticide Project: Sulfluramid
• eXtension – Managing imported Fire Ants in Urban Areas
• California Department of Pesticide Regulation: School IPM HELPR Potential Environmental Health Impacts of Management Alternatives for: Other ants
• US Environmental Protection Agency:
  • Baits for Ant, Cockroaches and Crickets
  • Environmental Hazard and General Labeling for Pyrethroid Non-Agricultural Outdoor Products
  • Notice of Advisement Purchase of a Potentially Dangerous Pesticide