Boric Acid Pesticides: What To Know Before You Buy

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Is boric acid for you? Learn how it works, and whether it's safe for your family and pets.

Boric acid is a mineral found widely in nature, from seawater to soil. But when we talk about it as a pesticide, we’re referring to a chemical compound that has been mined and refined from boron-rich deposits near volcanic areas and arid lake beds. Though used as an herbicide, the mineral form occurs naturally in many plants and almost all fruit.

Humans use boric acid in applications from manufacturing fiberglass to preserving wood. Here, we’ll discuss its pros and cons as a pesticide.

What Is Boric Acid?

Boric acid is a chemical compound created with the element boron. It’s most commonly used as an insecticide, herbicide, fungicide, antiseptic and flame retardant. It’s sometimes called orthoboric acid, hydrogen borate or boracic acid.

As an insecticide, it’s mostly used to kill cockroaches, ants, silverfish, termites and fleas. As an herbicide, it’s best on molds, fungi and some kinds of weeds.

Boric Acid vs. Borax

Like boric acid, borax is also a form of boron, though it’s generally not used as an insecticide.

“They are two entirely different chemical compounds,” says Wyatt West, a board certified entomologist with Ehrlich Pest Control. “Borax is generally less effective than boric acid as an insecticide. If you are going to purchase either of them, boric acid would be the way to go.”

Borax is most commonly used in laundry detergent, hand soap, cosmetics and fertilizer.

How Do Boric Acid Pesticides Work?

When insects come into contact with boric acid, it sticks to them. When they clean themselves, they ingest it. Then it disrupts their stomach function and affects their nervous system. Because boric acid needs time to build up in their bodies, it can take a few days or more to start working.

Boric acid will kill any arthropod (insect, spider, tick, mite, millipede) that ingests it. But only arthropods that groom themselves are likely to ingest it, so it’s unlikely to work on spiders, centipedes and ticks. Boric acid can also be used to scratch insects’ exoskeletons, which impedes their ability to retain water. If this is the goal, West says, there are more effective solutions.

Boric acid products come in many forms, including powder, gel and tablet. “Typically, you will see boric acid used in insect baits,” West says.

How To Use Boric Acid for Roaches and Other Pests

First, decide whether you want to use gel, powder, tablet or trap. This will depend on the type of insect, plus the location and environment where you’re applying it.

It is extremely important to read and follow the directions carefully. Boric acid is poisonous and potentially harmful to people and pets. “Mixing more doesn’t mean it’s more effective,” says Bernie Holst III, CEO at Horizon Pest Control in Midland Park, New Jersey.

For your greatest chance of success, the keys are:

  • Proper placement. Observe where your pests are traveling. With ants, this might be along corners and floorboards. For cockroaches, it might be under the sink.
  • Thoroughly clean the areas that are attracting bugs. This will help prevent a recurrence.

If you’re using boric acid powder:

  • Handle it carefully. Wear goggles, a mask, gloves and a long-sleeved shirt to ensure you don’t inhale or touch it.
  • Sprinkle it where insects travel.
  • Vacuum it up in 24 to 48 hours.
  • Do not let kids and pets enter the area before it’s cleaned up.

Other safety considerations:

  • Do not use boric acid near pet dishes or on food-prep surfaces.
  • Don’t leave it where kids or pets can get to it.
  • Don’t use boric acid on decorative surfaces. It can create stains or cause discoloration.
  • If you are exposed to it, follow instructions on the label and contact the Poison Control Center at 1-800-222-1222 for more advice.

“Use common sense,” says Holst. “Don’t apply products outside before it rains. And you would not want to spray a product or use a granular product near a body of water, because of drift issues and or rain water carrying the granular product into the water.”

Is Boric Acid Safe For Pets and Children?

Yes and no. When properly used, boric acid can be a safe pest control product, but it should never be inhaled or ingested.

“In terms of pesticides, boric acid is going to be one of the ‘safest’ around,” says West. “We have to remember that at the end of the day, all pesticides are poisons, but when used correctly, they carry minimal risk. Always follow the label! Don’t take unnecessary risks.”

To minimize risk:

  • Always follow the instructions for proper mixing, application, storage and disposal.
  • Remember pets and children are closer to the floor, and may be more prone to picking up residues on carpets.
  • Keep children and pets out of areas where boric acid is being used, until you are certain it is no longer in the environment.

Can I DIY a Boric Acid Pest Control Formula?

Yes, but why bother? Boric acid must be mixed with a bait that will attract pests to it, so some people mix it with powdered sugar or other foods.

“I would just recommend purchasing a pre-made bait instead of going through the hassle of trying to create your own,” West says. “In terms of the time and cost associated with making your own, I am not sure you would be saving very much.”

Also, mixing it wrong can be counterproductive. “Mixing at the wrong ratio for the species of pest present can treat one aspect of the problem, but never truly eliminate the issue,” says Dr. Nancy Troyano, a board certified entomologist and director of operations, education and training for Ehrlich Pest Control.

Is Boric Acid Environmentally Friendly?

Mostly. “Boric acid naturally occurs in the environment in soil, water and plants, so in that regard, it is a ‘green’ product,” says Holst. “However, in certain formulations and quantities, it can potentially kill plants.”

While plants naturally use small amounts of boric acid, even slightly elevated levels in the soil can be toxic to them. So any addition of boric acid to your plants or soil will most likely tip the balance from nutrient to herbicide.

It’s also worth noting that boric acid is not known to emit harmful vapors into the atmosphere. It’s believed to be minimally toxic to most birds, fish and amphibians.

“That is unusual when talking about pesticides,” says West. “However, I would not make a habit of going around haphazardly using any compounds containing any derivative of boron. Too much of anything is never good for the environment.”

Karuna Eberl
Karuna writes about wildlife, nature, history and travel for magazines, newspapers and websites including National Geographic, National Parks, Discovery Channel, Atlas Obscura and the High Country News. She's also produced a number of independent films and directed the documentary The Guerrero Project, about the search for a sunken slave ship. She and her husband, Steve, wrote an award-winning guidebook to the Florida Keys and are currently completely renovating an abandoned house in a ghost town. She holds a B.A. in journalism and geology from the University of Montana. Member of OWAA, SATW.