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Boric Acid & Borate Insecticides

- Boric acid is an effective, low toxicity, natural insecticide -

Summary: Borate (borax) is a mineral salt of boric acid and a very effective insecticide and wood preservative. It can be used as a powder, incorporated into baits, or applied to building materials.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)
my resume

Boric acid is a mineral

Boric acid usually exists as a salt called borate. Borate is a mineral mined from the earth and 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, in addition to natural pesticides and wood preservatives. The full chemical name of one form of borate is disodium octaborate tetrahydrate, or orthoborate.

Boric acid is poisonous to insects

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 powder 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.
Death Valley National park

Death Valley National Park near where natural borate is mined. Photo by Elizabeth DeAngelis.

Borates are relatively  safe

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

Borate is toxic to plants

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 insecticides.

Uses for boric acid insecticides

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 (see Timbor Insecticide and Bora Care Insecticide for more information).

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Jack DeAngelis, PhD,  , email:  [email protected]

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