Homemade Ant Killer: Peanut Butter and Borax

Baiting ants that are creating a nuisance in your lawn or garden is one way to control them, and mixing borax with peanut butter may form a bait that will help with your ant problem, but a few caveats are in order. The first is that not all ants like peanut butter, and the second is that boric acid is a more effective pesticide than borax. You probably have borax in your laundry room, and it might work, but if you're serious about ant control, go to the pharmacy and buy boric acid, which is derived from borax.

20 Mule Team Wagons Death Valley
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Freshly mined borax isn't as good of a pesticide as boric acid, which is derived from it

Borax vs. Boric Acid

Borax is the powdery cleaner that comes to your laundry room from the California desert courtesy of the famous 20-mule teams. It's a salt of boric acid, which is a weak acid of the element boron, and it isn't as effective for ant control. Although both boric acid and borax contain boron, which is ultimately what kills ants, boric acid is the more refined of the two compounds, and this makes it easier for ants to ingest -- and ingestion is a requirement. Contrary to myth, neither boric acid nor borax desiccate ants that come in contact with these substances. Boric acid is mildly toxic, which is why you usually find it at the drug store.

Peanut Butter as Bait

Earth is host to perhaps as many as 20,000 different species of ants, and not all of them eat the same food. Many species like sweet foods, others prefer oily ones, some eat both and still others have seasonal preferences. Peanut butter makes an effective bait primarily for ants that like greasy and oily foods, although because it contains some sugar, sweet-loving ants may also be drawn to it. To increase its effectiveness as a bait, it may be advisable to mix it with vegetable oil -- for oil-loving species -- or honey -- for sweet-loving species. To determine the best mix, you need to identify the type of ants you're trying to eradicate.

Mixing the Bait

Determine the species of ants overrunning your yard by capturing one:

  • Examine it with a magnifying glass.
  • Look it up in an ant catalog.
  • Research its feeding habits.

Once you've determined the best combination of peanut butter and other oily or sweet foods, mix up a semiliquid paste in a bowl with a little fruit juice, vegetable oil or water. Add no more than 5 percent boric acid or borax -- 1 part for every 20 parts attractant. Mixing in stronger concentrations either repels the ants or kills them too quickly, thus preventing them from feeding the bait to the colony. You may have to experiment with lower concentrations if the bait doesn't attract any insects.

Deploying the Bait Traps

Boric acid can be toxic to children and animals, so if you use it as part of the bait, you need to set the bait in a way that prevents access. One solution is to put it in closed containers with holes just large enough for ants to pass through. Another is to construct screen barricades around the bait stations through which ants can easily pass. The number of bait stations you need depends on the size of your garden and the number of ants -- there is no optimum number, but a good average is four stations for a 2,000-square-foot yard or garden. Keep the bait fresh by replenishing it as it dries out. If it works, the ant population should start to decrease in a week or two and eventually dwindle to nothing.