Boric acid functions as an insecticide primarily through two distinct mechanisms: as a stomach poison when ingested by insects, and by physically abrading their exoskeletons upon contact. These dual modes of action make it effective against a range of common household pests.
1. Stomach Poison (Ingestion)
One of the primary ways boric acid works is as a stomach poison. When insects consume baits or particles containing boric acid, the compound is ingested and interferes with their internal metabolic and digestive processes. This mode of action is particularly effective against insects that groom themselves or consume contaminated food sources.
- Target Pests: This mechanism is highly effective against pests such as ants, cockroaches, silverfish, and termites. For instance, ants might carry boric acid-laced bait back to their colony, sharing it with other ants and the queen, leading to widespread eradication within the nest.
- Internal Disruption: Once ingested, boric acid disrupts the insect's digestive system, leading to starvation and dehydration. It can also interfere with their nervous system, eventually leading to paralysis and death.
- Mechanism of Spread: For social insects like ants and termites, the slow-acting nature of boric acid allows foraging insects to return to the colony and transfer the poison to others, including larvae and the queen, through trophallaxis (food sharing).
2. Abrasive Action (Contact)
Beyond ingestion, boric acid also works through physical contact by damaging the insect's exoskeleton. This is particularly true for boric acid applied in dust or granular forms.
- Exoskeleton Damage: The fine, sharp particles of boric acid can abrade, cut, and scratch the waxy, protective outer layer of an insect's exoskeleton. This physical damage compromises the insect's natural barrier against moisture loss.
- Dehydration: Once the exoskeleton is compromised, the insect loses its ability to retain water, leading to severe dehydration. This desiccation ultimately results in the insect's death.
- Application: This mechanism is leveraged when boric acid is applied as a dust in cracks, crevices, or other areas where crawling insects frequently travel. As they move through the dust, the particles cling to their bodies, causing physical damage.
Summary of Boric Acid's Insecticidal Action
| Mechanism of Action | How It Works | Target Pests (Examples) | Key Effect |
|---|---|---|---|
| Stomach Poison | Ingested, disrupts internal metabolism and nervous system | Ants, Cockroaches, Silverfish, Termites | Starvation, dehydration, nervous system failure |
| Abrasive Action | Physical contact abrades the waxy cuticle of the exoskeleton | Cockroaches, Silverfish, other crawling insects | Dehydration (desiccation) |
These dual methods of attack make boric acid a versatile and effective option for managing various insect infestations. Its efficacy often depends on proper application to ensure insects either ingest it or come into direct contact with it.
