Boric Acid & Borate Insecticides

What is boric acid?

Boric acid usually exists in a salt form called "borate". Borate is a mineral mined from the earth. A single company, Rio Tinto Borax, mines about 50% of the world's supply of borates from mines near Death Valley National Park in the southwestern US. Borates have many industrial uses, for example as an additive in glass, in addition to natural insecticides and wood preservatives. The full chemical name of one form of borate is disodium octaborate tetrahydrate. You'll also sometimes see the term orthoborate.

How does boric acid work?

Unlike many insecticides that work on contact, boric acid must be eaten to be effective. While it is a relatively safe compound for humans and other animals, boric acid is highly toxic to insects. The mode of action in insects is not completely understood, however.

Insects typically ingest boric acid when they groom themselves, or during feeding. If borate dust (roach powder, TimBor, Borid, etc.) is used, insects pick up particles when they walk through it. They ingest the particles when they later groom legs and antennae. They can also ingest the toxin directly when it is applied to food sources or in baits.

Are borate insecticides safe?

Borate insecticides are generally safe especially when compared to older, synthetic pesticides. They don't vaporize and get into the air; however, you should avoid breathing the dust. When applied as a liquid to wood surfaces they are quickly absorbed into the surface. They are, however, highly water soluble so care should be taken to avoid situations where large amounts could be washed into water.

While boric acid is a necessary plant micronutrient, high soil levels of elemental boron are toxic to plants. Therefore, take care not to contaminate landscape soil with boric acid.

What are boric acid insecticides used for?

Boric acid-based insecticides and wood preservatives are mainly used in structural pest control for termites, carpenter ants, powderpost beetles, wood-rot fungi and in nuisance pest management as crack and crevice and bait treatments for ants and cockroaches.

Boric acid insecticides (right, various brand names) are very effective supplements to cockroach baits in single family dwellings and along with crack and crevice treatments in commercial buildings. Very effective and low cost ant baits incorporate boric acid as the toxicant. And, there are several sprays that use boric acid to protect wood against wood-destroying insects. Timbor and Bora Care are two such products. Bora Care combines borate with a glycol penetrant and is more expensive than Timbor.

Can I purchase borate insecticides?

Yes. Common brand names are: Borid, Timbor, Bora Care, EZ Bor, Shell-Guard, and Armor-Guard. Borid, Timbor and Armor-Guard are 98% borate powders, Bora Care and Shell-Guard are liquid concentrates plus a glycol penetrant, while EZ Bor is a ready-to-use liquid.

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