Can Boric Acid Kill Insects Safely And Inexpensively?

ants on watermelon

Few things are more upsetting than to have an insect invasion of your home.

Ants, cockroaches and other insects can carry illnesses and make a homemaker feel almost helpless.

Based upon my training and experience in Pest Control Management I’d like to communicate how Boric Acid works for controlling insects.

Can Boric acid kill insects safely and inexpensively?

Yes, Boric acid is a product that can safely and inexpensively kill insects.

Whether used in powder form, as a trap or as a bait, Boric acid is an effective killer of Roaches, Ants, Fleas, Water bugs and Silverfish.

Boric acid is much safer than chemical sprays or Bug Bombs and cost pennies on the dollar when compared to hiring a Pest Control Company.

I discuss these facts:

  • Precautions to take to safely use Boric acid around humans and pets
  • Best ways to use Boric acid
  • Boric acid’s low cost
  • How Boric Acid kills insects.

Using Boric Acid Safely

Don’t confuse Boric acid with Borax, they are two different substances.

Boric acid is made from Borax by a relatively simple method of adding an acid, water and heat.

Both are effective in killing insects.

If you are interested in finding out how Borax works, I wrote an article that you can read titled, “Ant Invasions (Ant Facts, Successful Eradication, Cost And Safety)”.

Boric Acid Toxicity In Humans And Animals

In terms of ingesting enough Boric acid to cause death in an adult, Boric acid is about as dangerous as table salt.

Boric acid’s LD50 value, the amount of Boric acid that must be ingested to kill 50% of those who ingest Boric acid, is 212 grams or 0.49 pounds of Boric acid for an 80 kg, (176 pound) adult.

Common table salt has an LD50 in humans of 240 grams or 0.52 pounds of table salt for an 80 kg, (176 pound) adult.

In reviews of cases of Boric acid poisoning in humans the minimum lethal dose is said to be 2-3 grams/kg, (about 1 gram/pound), in infants, 5-6 grams/kg, (about 2.5 grams/pound), in children and 15-20 grams/kg, (about 6-8 grams/pound), in adults. (

Long-term chronic exposure to Boric acid has not shown it to be carcinogenic, cancer producing, in humans.

Boric acid only appears poisonous if taken internally or inhaled in a large amount.

The European Commission, (Bureau of Chemical Substances), has, based upon studies in rabbits, rats, and mice rated Boric Acid a Category 2 (of 4) that may impair fertility and cause harm to unborn children. (

Ingestion or inhalation of Boric acid in large amounts can be lethal in other mammals such as dogs and cats. (

Boric acid has been used as an eye wash, used in ear drops, as an anti-septic and as an anti-fungal.

This demonstrated the safety of Boric acid when used properly. (

Using Boric Acid Safely In The Home And Around The Homestead

To safely use Boric acid around the home and homestead means careful application of Boric acid powder, traps or bait to areas not easily accessible by children, pets, and livestock.

It also means only using Boric acid for the time period needed to rid the home or homestead of insect pests.

For ladies of child bearing age or who are or may become pregnant, the use of Boric acid should be carefully controlled.

This includes having another adult family member doing the Boric acid applications and preparing the Boric acid traps or bait.

The ultimate precaution for ladies of child bearing age or who are or may be pregnant would be to use Borax or Diatomaceous Earth instead of Boric acid for insect control when pregnant or during child bearing years.

Using Boric Acid To Eliminate Insects

Boric acid is used to eliminate insects in three basic methods:

  • As a powder
  • As an ant trap
  • As a bait

Boric acid in powder form is like miniature shards of glass that slowly cuts insects apart.

Powdered Boric acid will not cut humans.

When insects walk through Boric acid powder they carry some of it back to their nest where they die from the cuts.

If the insect is a cockroach, when it dies other cockroaches will eat it and ingest Boric acid which causes them to die also.

Boric acid, like Borax, is a poison to insects when taken internally.

Boric acid’s killing effect is not immediate but takes a period of time. This is important in ridding your home of ants.

The worker ants ingest Boric acid from traps or bait and carry it back to their nest where they feed it to other adult ants by a mount-to-mouth process that can result in killing all adult ants.

Using Boric Acid As A Powder

Boric acid powder is effective as an insect killer in much the same way that Diatomaceous Earth is effective as an insect killer.

Dust the Boric acid powder into cracks and crannies, behind dishwashers, washing machines and dryers, and hot water heaters.

When insects walk through it, some of it adheres to them and since the powder is like tiny shards of glass it cuts into them as they go back to their nest.

Especially in the case of cockroaches, which are cannibalistic, when a cockroach that walked through the Boric acid powder dies in the nest, other cockroaches eat the dead one and ingest Boric acid and die.

Boric acid can also be puffed into hard to get at places such as way back underneath sinks and behind refrigerators.

Insects like places where there is moisture and warmth.

Many times Boric acid powder is sold in plastic containers with a tip on them.

When some of the Boric acid powder is used and there is some air in the container pointing the tip into cracks and crannies and rapidly squeezing the container will puff Boric acid into places where it would be very hard to place it by sprinkling.

When placing Boric acid powder the goal is to leave a thin film of Boric acid powder.

If there is a pile or a ridge of Boric acid powder the insects will just walk around it.

When there is a thin film of Boric acid powder the insects will walk through it and it will attach to their body.

Using Boric Acid As An Ant Trap

Boric acid as an ant trap is very effective against those little black Pharaoh ants that are found in kitchens and around sink drains.

Making your own Boric acid ant traps are very inexpensive and save lots of money over hiring a Pest Extermination Company.

ants tending eggs in the nest
Ants in their nest

To make the ant trap mix 1 teaspoon Boric acid powder (link to read reviews on Amazon) with 10 teaspoons sugar and 2 cups of water.

Spread the mixture on cardboard or, better yet, absorb it onto cotton balls.

Place the ant traps in areas where you know ants have been found.

They will ingest some of the Boric acid sugar solution and take it back to their nest to share with other adult ants.

Do not add more Boric acid powder than the recipe calls for to the mixture!

If you do, it can kill the ants before they get back to their nest and have a chance to share it with the others.

The ants need to share the mixture with the nest worker ants for you to get a complete kill of all the adults in the nest.

Important: Place the ant traps where children and pets will not get to them!

It is important to keep ant traps in place for at least 2 weeks to be sure of a complete kill of the entire nest or colony of ants.

The cotton balls will need to be replaced every day or two during this time.

If you would rather not bother with making the ant traps there is another way you can kill ants effectively by using Zap-A-Roach Boric Acid Roach and Ant Killer – Odorless and Non-Staining. (link to read reviews on Amazon)

Using Boric Acid As A Bait

Boric acid works great as a bait to kill cockroaches.

Here is one recipe for making a Boric Acid Cockroach Bait.

Mix together:

  • 2 tablespoons solid vegetable shortening or lard
  • 1/2 small onion finely chopped, (about 3 tablespoons onion)
  • 1 teaspoon sugar
  • 2 tablespoons Boric acid powder (link to read reviews on Amazon)

Mix the ingredients together in a small bowl using a metal fork.

With a metal spoon place 1/2 tsp of this mixture in a small lid or on aluminum foil.

You should get 8 or more baits from this mixture.

Place the baits where you frequently find cockroaches such as inside cupboards, behind the refrigerator, stove, water heater, and in the back of cupboards in kitchen and bathrooms.

Be sure the baits are not where pets or children can get to them!

Replenish the bait area every two weeks or more frequently if all the bait is eaten.

In a few days to a week you should notice a decrease in the number of cockroaches seen.

Keep baits out for at least a month. If cockroaches reappear, re-bait them.

dead cockroach
Boric acid baits kill cockroaches dead

Here is another recipe for Boric Acid Cockroach bait:


  • 1 cup maple syrup
  • 2 cups Boric acid powder (link to read reviews on Amazon)
  • 4 teaspoons flour to thicken the mixture

Mix these ingredients together with a metal fork and stir well.

You will end up with a mixture that resembles peanut butter in appearance.

Spread this mixture in every room of the house, behind the stove, refrigerator, water heater, washer, dryer.

Place in the back of cupboards underneath sinks and in the far corners of kitchen cupboard – especially those cupboards where food is stored.

Caution! This looks like peanut butter and smells like maple syrup.

This means kids and pets will eat it so do not place it where they can get to it!

Don’t want to make your own bait or have the time to make cockroach baits?

You can purchase Zap-A-Roach Boric Acid Roach and Ant Killer instead (link to read reviews on Amazon) to effectively do the job for you.

Cost Effective Pest Control

Boric acid powder (link to read reviews on Amazon) can be purchased inexpensively.

Boric acid can last for a few years depending upon how much of it you use and how often it has to be used.

When you add the cost of water, sugar and cotton balls for the Boric acid ant traps or the cost of onion, shortening or lard, sugar or maple syrup, flour and water for the Boric Acid Bait for cockroaches, you are substantially under the cost of one trip from a Pest Control Company.

Related Questions

I have little flying insects swarming at my house. How can I know if they are termites or ants?

There are some ants that have wings and swarm.

So not all swarming insects are termites.

Here is an article that I wrote, “Ant Invasions (Ant Facts, Successful Eradication, Cost And Safety)” that tells how to identify swarming ants from termites.

I understand there is more than one type of Diatomaceous Earth and I would like to use it instead of Boric acid. Where can I find information on Diatomaceous Earth?

The only type of Diatomaceous Earth that is effective against insects is Food Grade Diatomaceous Earth.

For a detailed article I wrote on Diatomaceous Earth you can read, “Does Diatomaceous Earth Work As A Method Of Pest Control?”

Where can I learn more about ants and getting rid of them?

We have an article on ants and how to control them. Visit, “Ant Invasions (Ant Facts, Successful Eradication, Cost And Safety)”

I understand that cockroaches love to inhabit areas that are not clean.
Where can I learn more about cockroaches?

Here is a good article that I wrote, “How To Rid Your Home Of Cockroaches: In-Depth Facts & Control Methods” that goes into detail about cockroaches.

John Brownlee

John is a retired Lawyer, Health Care Provider and has a certificate in Pest Management Technology. He teaches people how to locate, evaluate, and purchase Country and Homestead Property. He and his wife, Linda, share their knowledge of homesteading skills and safe pest management.

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