Synthetic pyrethroid
Synthetic pyrethroids are lab-made analogues of natural pyrethrin: bifenthrin, deltamethrin. Repellent termiticide actives, contrast with non-repellent fipronil.
Ask Chalkline about this →A synthetic pyrethroid is a lab-made analogue of natural pyrethrin, the insecticidal compound from chrysanthemum flowers. The class is the workhorse of contact insecticide chemistry: bifenthrin and deltamethrin are both synthetic pyrethroids, and both are the actives in termite-barrier products like Kordon (deltamethrin) and Biflex (bifenthrin).
Why synthetic, not natural
Natural pyrethrin degrades quickly in sunlight and air, giving it knockdown speed but no residual life. Synthetic pyrethroids are engineered for:
- UV stability (residual 8-12 years in soil for the slowest-degrading actives).
- Mammalian safety (target insect nervous-system receptors more selectively than the natural compound).
- Activity range (engineered to target specific pest groups, including termites).
The trade-off: longer environmental persistence than the parent compound.
Repellent vs non-repellent
Synthetic pyrethroids are repellent to termites: termites detect the chemical and avoid the treated zone. This is fundamentally different from non-repellent actives like fipronil:
| Synthetic pyrethroid | Non-repellent | |
|---|---|---|
| Termite response | Avoid | Walk through undetected |
| Kill mode | Direct contact on barrier | Delayed, transferred to colony |
| Coverage tolerance | Zero (any gap = bypass) | Tolerates small gaps |
| Colony impact | Foragers only | Colony eliminated |
| Service life | 8-12 yr (bifenthrin) | ~8 yr (fipronil) |
For pure-barrier termite work, pyrethroids work. For colony elimination through the transfer effect, non-repellents are required.
Common AU pyrethroid termite actives
- Bifenthrin (Biflex). The dominant pyrethroid in AU termite work. ~10 yr label life.
- Deltamethrin (active in Kordon). Pyrethroid-impregnated physical barrier.
- Permethrin. Older, lower-residual; uncommon in new termite-barrier work.
Beyond termites
Synthetic pyrethroids are also used for:
- General pest control sprays (cockroaches, ants, spiders).
- Mosquito-net impregnation.
- Public-health vector control.
Their broad insecticidal activity is also why aquatic-environment exposure is a labelled concern; pyrethroids are highly toxic to fish and aquatic invertebrates.
For a builder
- Know which chemistry your barrier installer is using. Pyrethroid barriers need 100% coverage; non-repellent barriers tolerate small gaps. The install QA is different.
- Spec Kordon (deltamethrin-impregnated) for slab-penetration sleeves as standard practice.
- Brief the owner: pyrethroid barriers don’t kill the colony; they wall it out. If the barrier fails, the colony is still active nearby.
Category: Termite management / insecticide chemistry.
Related
See also
Last updated: 2026-05-29. Verified: 2026-05-29. Quarterly review for currency.