PBO (Piperonyl Butoxide) Synergist

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Target Pests / Scope

PBO does not kill insects on its own. It enhances the effectiveness of pyrethrins (3-5x boost), pyrethroids (2-3x boost in resistant populations), and some other insecticide classes. Most valuable against insecticide-resistant populations where the insect enzymes are actively detoxifying the killing agent.

Products and Recommendations

PBO is an ingredient in products, not sold alone to consumers. Found in: most pyrethrin aerosols (CB-80, PT 565, PyGanic), many flea sprays, lice treatments, bed bug sprays (Bedlam Plus), some professional concentrates. When you see pyrethrin products listing two active ingredients - pyrethrins AND piperonyl butoxide - the PBO is the synergist.

Safety

Low mammalian toxicity. PBO has been used in consumer products since the 1950s with an excellent safety record. Found in human head lice treatments applied directly to children. The EPA classifies it as a Group C possible human carcinogen based on high-dose animal studies, but real-world exposure levels are far below concern thresholds.

Why it matters: Without PBO, most pyrethrin products would be only marginally effective. The natural pyrethrins from chrysanthemum flowers are quickly detoxified by insect enzymes. PBO blocks those enzymes, allowing the pyrethrins to reach lethal concentrations in the insect nervous system. It is the reason pyrethrin aerosols work as well as they do.

Example

0.5 oz

per gallon

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Detailed Guide

How insects detoxify pesticides: Insects produce cytochrome P450 enzymes (mixed-function oxidases) in their gut and fat body that chemically modify insecticide molecules, rendering them harmless. This is the same enzyme system that detoxifies plant chemicals in the insects natural diet. PBO jams this defense system by binding to P450 enzymes irreversibly, leaving the insecticide free to reach its target in the nervous system.

Resistance management: In insecticide-resistant pest populations, P450-based metabolic resistance is one of the most common mechanisms. Adding PBO can partially or fully restore the effectiveness of insecticides against resistant populations. This is why many bed bug spray products include PBO - bed bug populations have developed significant pyrethroid resistance, and PBO helps overcome it.

Reading labels: When you see a product listing Pyrethrins 0.5% + Piperonyl Butoxide 4.0%, the PBO concentration is intentionally much higher than the pyrethrin concentration because the synergistic effect requires an excess of PBO relative to the active insecticide.

PBO with pyrethroids: While PBO is most commonly paired with natural pyrethrins, it also synergizes synthetic pyrethroids - particularly against resistant populations. Products like Bedlam Plus (sumithrin + PBO) and some professional tank mixes exploit this to improve performance against pyrethroid-resistant bed bugs and cockroaches.

Key takeaway: PBO was discovered in 1947 and is derived from safrole, a compound found in sassafras trees. It transformed pyrethrin from a marginally effective natural product into a powerful commercial insecticide. Without PBO, the modern natural insecticide industry based on pyrethrins would likely not exist - the pyrethrins alone would be too easily detoxified by target insects.

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Reviewed by Derek GiordanoContent reviewed by a licensed pest management professional. Last reviewed: April 2026.