Transfer effect (termite)
Termite transfer effect: contact, grooming and trophallaxis carry a non-repellent termiticide back to the colony, killing termites that never touched it.
Ask Chalkline about this →The transfer effect is the mechanism by which a non-repellent termiticide is carried back to the colony by termites that contacted the treated soil, killing nest-mates that never touched the chemical. It is the central difference between modern non-repellent chemistries (fipronil, imidacloprid) and the older repellent synthetic pyrethroids (bifenthrin, deltamethrin).
The three transfer pathways
A non-repellent chemical reaches non-foraging termites by three biological routes:
- Direct contact: a forager walks through treated soil and picks up the active on its cuticle.
- Grooming: returning to the nest, the forager is groomed by nest-mates who ingest the active.
- Trophallaxis: mouth-to-mouth food sharing distributes the ingested active through the colony.
The active has a delayed mode of action (typically 24-72 hr to lethal effect), so the forager survives long enough to return to the nest and spread the chemical before dying. A fast-acting chemical would kill the forager in the soil and never reach the colony.
Non-repellent vs repellent
| Non-repellent (fipronil, imidacloprid) | Repellent (synthetic pyrethroids) | |
|---|---|---|
| Termite response | Walks through undetected | Detects, avoids the zone |
| Lethality | Delayed, allows transfer | Fast, no transfer |
| Colony impact | Colony eliminated over weeks | Foragers killed; colony unaffected |
| Barrier role | Active treatment + barrier | Barrier only |
| Gap tolerance | Tolerates small gaps in coverage | Any gap = bypass route |
The transfer effect is why non-repellents have largely replaced pyrethroids for new soil-treated barriers under AS 3660.1.
What it means at the build
A non-repellent installer is creating a chemical-active zone, not a wall. The system works because foragers walk in, leave alive, and carry the active home. This relaxes the “100% coverage” rule that pyrethroid barriers require: a small gap in non-repellent coverage doesn’t compromise the system, since termites that bypass the gap into the building still get exposed if they return foraging through any treated zone.
Limits
- Transfer effect is colony-specific. It eliminates the colony in contact with the treated soil; it does not protect against a fresh colony moving in later.
- The protection period is still finite. Chemical degrades to below transfer-effective concentration after ~8 years for fipronil.
- Replenishment via reticulation system inlets keeps the active zone live.
For a builder
- Spec non-repellent for soil barriers by default in 2026. Pyrethroids retain a role in pre-construction blanket treatments and around penetrations.
- Brief the owner: the barrier doesn’t repel termites; it kills the colony. The mud-tube evidence may still appear during the kill window.
- Maintain the chemical-life cycle. Schedule the recharge at year 8 for fipronil, year 10 for bifenthrin.
Category: Termite management.
Related
See also
Last updated: 2026-05-29. Verified: 2026-05-29. Quarterly review for currency.