This chapter discusses the candidate molecular targets of pyrethroids and the chemistry and insecticidal actions of these compounds. The vast majority of pyrethroids are esters of carboxylic acids. Fast-acting pyrethroids are designated good knockdown agents. Knockdown by a pyrethroid is the characteristic immobilization of the insect, and although it often precedes a lethal action, this is not always the case. Knockdown may result from actions on the central nervous system of insects. Based on the symptoms of pyrethroid action on whole insects, two distinct classes of pyrethroids (Type I and Type II) have been postulated. Type I compounds include pyrethrins, S-bioallethrin (1R, cis) resmethrin, kadethrin, the 1R, (1) trans and 1R, (1) cis isomers of tetramethrin, phenothrin and permethrin, and an oxime O-phenoxybenzyl ether. Narahashi (1980) proposed the following terminology: Type I for the pyrethroids that induce repetitive firing and Type II for those pyrethroids that depolarize the resting membrane.
ASJC Scopus subject areas
- Insect Science