Summary: Pyrethrins are six natural compounds found in pyrethrum flowers (Tanacetum cinerariifolium). They break down quickly in sunlight and are permitted in organic agriculture under many standards. Pyrethroids (permethrin, cypermethrin, deltamethrin…) are synthetic molecules modelled on pyrethrins but far more stable, persisting longer in the environment, and they are not allowed in organic farming.

The two names sound alike and are often confused, even on product labels. Understanding the difference helps growers, distributors and buyers choose the right material for their purpose.

Table of Contents

1. What are pyrethrins?

“Pyrethrins” is the collective name for six natural esters: pyrethrin I, pyrethrin II, cinerin I, cinerin II, jasmolin I and jasmolin II. They are concentrated mainly in the achenes (seeds) of the flower head, typically at around 1–2% of dry flower weight depending on variety and growing conditions. Learn more: pyrethrum in Vietnam.

2. What are pyrethroids?

Pyrethroids are a group of chemically synthesised active ingredients designed on the pyrethrin structure to overcome its rapid breakdown. Allethrin (1949) was the first synthetic pyrethroid; later generations such as permethrin, cypermethrin and deltamethrin are much more light-stable and are now used very widely.

3. Quick comparison

Criterion	Pyrethrins (natural)	Pyrethroids (synthetic)
Origin	Extracted from pyrethrum flowers	Chemical synthesis
Stability in light	Degrade quickly (hours to days)	Stable, persist for weeks
Mode of action	Insect nerve sodium channels (IRAC group 3A)	Same group 3A
Organic farming	Permitted (EU, USDA NOP – with conditions)	Not permitted
Resistance risk	Exists, but short persistence	High due to wide use and long persistence
Toxicity to fish, bees	Toxic, but break down quickly	Toxic, persist longer

4. Why pyrethrins are valued in organic growing

Rapid degradation under UV light and oxygen, leaving few residues on produce.
Botanical origin, in line with the trend of reducing synthetic chemicals.
One of the few naturally derived actives listed as permitted in many organic standards (note: some standards do not allow formulation with the synergist piperonyl butoxide – PBO).

5. Common misconceptions

“Natural means harmless”: false. Pyrethrins are still toxic to fish, aquatic life and bees; they must be used correctly, away from water and outside bee foraging hours.
“Pyrethroids are extracted from chrysanthemums”: false. Pyrethroids are synthetic, even though the name derives from pyrethrum.
“The more concentrated, the better”: efficacy depends on formulation, dose and target; products must be registered and used according to the label.

6. Thao Duoc Xanh and pyrethrum

Thao Duoc Xanh (Blue Herbs) is developing trial pyrethrum plots in Moc Chau, Dien Bien and Ha Giang (now part of Tuyen Quang province) in northern Vietnam, aiming to supply pyrethrin-rich dried flowers to extraction plants. For dried flowers, seeds or growing partnerships, please contact us or browse our products.

Note: this article provides general knowledge. Thao Duoc Xanh’s pyrethrum products are currently raw/botanical materials and are not registered plant protection products; they must not be used as a substitute for registered pesticides. When using any insecticidal product, follow the label and applicable regulations.

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Pyrethrins vs Pyrethroids: Natural vs Synthetic Insecticides Explained