Least-Toxic Control of Ants Choose a different pests

Factsheet: Least-toxic Control of Indoor and Outdoor Ants, Beyond Picnics: Controlling Ants in your Home


Pest type: Insects

In-depth Information:
There are thousands of ant species that could be nibbling on your candy bar or peanut butter at this very moment. Pharaoh ants most commonly build nests indoors. They are small, reddish-brown ants that persist through the winter months, and enjoy sweets, but are omnivorous, and will eat just about anything. Identification is key for your management strategy; if you have any questions about the type of ant in your house, call your local cooperative extension office for help with identification.

Is it a problem?

Any pest control program must include cultural control methods. You can spray the pest with the most toxic chemical you can find, but as long as you provide an environment that your pest finds attractive and a way for it to get in, it will return.

You also need to set action thresholds. In other words, at what point does the ant population get to be a problem where you need to take action. Such action thresholds can be used as a reasonable starting point, and then modified to suit the conditions. For example, outdoor ant populations may not be quite as threatening as indoor ants. If there are a few ants indoors it's possible to just wipe them up rather than spraying least toxics.

Pest prevention practices

Remove sources of water/moisture
Remove food sources
Dispose of trash
Place trash in sealed containers
Store food in air-tight, sealed containers
Remove potential habitat
Remove clutter

In-depth Information:

Locate and seal outside points of entry. Ants usually follow distinct chemical trails that they have left to easily find their way from their point of entry to their food source. Follow the ant trail, identify the points of entry into your home, and seal them out. If you don’t have a clear ant trail, place small pieces of cardboard or wax paper with syrup or a high-protein treat (depending on your ant type) out at night. In the morning, there should be a nice, thick ant trail leading to their doorway(s) into your home, and now you can seal them out. Temporary fixes include drawing a solid line with regular chalk-board chalk or putting down lines of cayenne and black pepper as repellants, or sealing entry points with duct tape, toothpaste or petroleum jelly. Silicone caulk is an excellent permanent sealant.

Locate and remove the food supply. Clean up and remove the food that is attracting the ants. Keep kitchen counters, stove tops and floors clean. Store food in glass jars with seals or gaskets and plastic containers with tight-fitting lids. Ants can climb up the threads of screw-top jars and get in if there is no gasket or liner. Put garbage in tightly sealed containers and empty it daily, and thoroughly rinse recyclables. Ants also feed on “honeydew,” a sweet substance produced by insects that feed on plant sap, such as aphids and scale. Controlling these insects and cutting branches back from your house may help control your ant problem.

Monitoring and record-keeping

Regularly inspect your home for ants or ant entry points. Check for ants near attractive food sources or moist areas. Ants may invade kitchens, bathrooms, offices, or bedrooms. Inspect under sinks, in cupboards, and along pipes and electrical wires. Look for large trails of ants or for just a few stragglers.

You can also place sticky traps and glue boards around troublesome ant areas in order to monitor existing ant infestations. Be sure to also set these traps in areas where ants have been found in the past; these traps will provide early warning signs of re-occurring ant infestation. 

Non-chemical and mechanical controls

Seal cracks and crevices
Repair holes
Create a barrier
Sticky traps
Remove trash from property
Remove clutter
Boiling water
Remove debris and habitat
Handpick and destroy

In-depth Information:
Soapy water in a spray bottle or on a sponge will kill individual ants and erase the chemical trail that lines of ants follow. You can also apply one of the various, commercially available sticky barriers to foundation walls or the legs of tables or plant stands where you see ant problems.

Use a food attractant placed in a dirt-filled, clay flowerpot to lure the ants away from your house; once they’ve moved in, kill them with boiling hot water.

Another option is cornmeal. Ants are attracted to corn meal and treat it as food, but they can't actually digest it, causing them to slowly starve. It won't kill a colony as quickly as poison, but it's incredibly cheap, and completely safe to use in a house with pets or small children.

Biological controls

Biological controls are not an effective measure for controling indoor ant populations.

Least-toxic chemical options as a last resort

  • Botanical sprays that can be used include Mint Oil, Cedar Oil, and Orange Oil. Garlic spray can be used as a repellant.
  • Desiccating dusts, such as diatomaceous earth and pure amorphous silica aerogel, kill ants by causing them to lose moisture and die. Diatomaceous earth must be food grade. Place the dust in wall voids or cracks and then seal them, or sprinkle powder lightly around the edges of carpeted areas or brush it into the carpet, wait three days, and then vacuum. In cracks, the dusts can be effective for many years, as long as they are kept dry. Once-a- year applications to carpets should suffice. When using either desiccating or silica aerogel, always wear a dust mask and goggles and cover any electronic equipment that could suffer dust damage. Do not use diatomaceous earth if you have lung problems.
  • Other least toxic options include Terro Liquid Ant Baits, which have borax as their active ingredient. Follow the instructions on the package, and place the baits nearby ant trails or wandering ants. At first, it might seem that the traps increase the population of ants, as a thick ant trail will form, but after a few days the ant population will be under control.

Boric Acid

Corn Gluten Meal

Garlic oil

Chemicals to Avoid

Look at your product labels and try to avoid products containing those chemicals listed below:

(A = acute health effects, C = chronic health effects, SW = surface water contaminant, GW = ground water contaminant, W = wildlife poison, B = bee poison, LT = long-range transport)

Abamectin/Avermectin B1 (A, C, W, B)

Acephate (C, SW, W, B)

Acetamiprid (A, C, GW, W, B)

Bifenthrin (A, C, SW, W, B)

Carbaryl (A, C, SW, GW, W, B)

Clothianidin (A, C, SW-URBAN, W, B)

Cyfluthrin (A, C, W, B)

Cypermethrin (A, C, W, B)

Deltamethrin (A, C, W, B)

Fipronil (A, C, W, B)

Hydramethylnon (C, W)

Imidacloprid (A, C, SW, W, B)

Indoxacarb (A, C, W, B)

Methoprene (W)

Permethrin (A, C, GW, W, B)

Prallethrin (A, C, W, B)

Propoxur (W, B)

Pyrethrins (C, W, B)

Pyriproxyfen (C, GW, W, B)

Sulfluramid (W)

Thiamethoxam (C, B)

Tralomethrin (A, C, W, B)

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