Synthetic Pyrethroid Insecticides

Synthetic Pyrethroids:  Botanically-produced pyrethrins were seldom used for insect control purposes because of high production costs of and their instability in sunlight.  When synthetic alternatives were developed, they were rapidly adopted for use in agriculture. Today, synthetic pyrethroids are used for many purposes because of their efficacy, low use rates, low cost, broad spectrum of control, and relatively low mammalian toxicity.  The historical development of pyrethroids was a long process.  The first widely-used pyrethroid insecticides were allethrin (Pynamin®), tetramethrin (Neo-Pynamin®), resmethrin, bioallethrin, fenvalerate (Pydrin®) and permethrin (Ambush®).  The next generation of pyrethroids greatly influenced agriculture.  They are still very important for insect control in commercial agriculture and include cypermethrin (Ammo®), bifenthrin (Capture®), lambda-cyhalothrin (Karate®), cyfluthrin (Baythroid®) and deltamethrin (Decis®).

The mode of action of pyrethroids is similar to that of DDT, affecting the function of sodium channels in nerve cells.  Most entomologists consider the synthetic pyrethroids to be the most versatile and effective insect control materials ever developed.  However, some important insect species have developed resistance to these chemicals, including the tobacco budworm (Heliothis virescens).