Pyrethroid pesticides have strong chiral characteristics and usually contain multiple chiral enantiomers. Although these enantiomers have exactly the same physical and chemical properties, they exhibit completely different insecticidal activities and biological properties in vivo. Toxicity and environmental residue levels. Such as Cypermethrin, Beta-Cypermethrin, Alpha-cypermethrin; beta-cypermethrin, cyhalothrin; Beta Cyfluthrin, cyfluthrin, etc.

Cypermethrin
Cypermethrin is the most widely used pyrethroid pesticide. Its molecular structure contains 3 chiral centers and 8 enantiomers. Different enantiomers show significant differences in biological activity and toxicity.
The 8 optical isomers of Cypermethrin form 4 pairs of racemates. There are obvious differences in the killing effect and photolysis speed of different isomers of Cypermethrin on insects. Their insecticidal activity from strong to weak is cis, trans Formula, cis-trans cypermethrin.
Among the eight isomers of Cypermethrin, two of the four trans isomers and the four cis isomers are highly efficient.
However, if the single high-efficiency isomer of Cypermethrin is used as a pesticide, not only can its insecticidal activity be greatly improved, but also the toxicity to non-target organisms and adverse effects on the environment can be reduced. Therefore Beta-Cypermethrin and Alpha-cypermethrin came into being:

Alpha-cypermethrin
Alpha-cypermethrin separates two low-efficiency or ineffective forms from a mixture containing four cis-isomers, and obtains a 1:1 mixture containing only two high-efficiency cis-isomers.
Alpha-cypermethrin has twice the insecticidal activity of Cypermethrin.

Beta-Cypermethrin
Beta-Cypermethrin, English name: Beta-Cypermethrin
Beta-Cypermethrin is also called high-efficiency cis-trans cypermethrin. It converts the ineffective form of the technical cypermethrin containing 8 isomers into a high-efficiency form through catalytic isomerization, thus obtaining high-efficiency cis isomers and high-efficiency cypermethrin. A mixture of two pairs of racemates of trans isomers contains 4 isomers, and the ratio of cis and trans is approximately 40:60 or 2:3.
Beta- Cypermethrin has the same insecticidal properties as Cypermethrin, but its insecticidal efficacy is about 1 times higher than that of Cypermethrin.
Beta-Cypermethrin is much less toxic to humans and animals, and its toxicity to sanitary pests is equal to or greater than Alpha-cypermethrin, so it has certain advantages in the prevention and control of sanitary pests.

Summarize
Since the biological activity of the cis-high-efficiency form is generally higher than that of the trans-high-efficiency form, the order of insecticidal activity of the three brothers of cypermethrin should be: Alpha-cypermethrin≥Beta-Cypermethrin>Cypermethrin.
However, Beta-Cypermethrin has better hygienic pest control effect than the other two products.