Nowadays, pyrethroids, which are synthetic versions of chrysanthemum-derived pyrethrins, are used in many insecticide formulations. For example, the house-brand wasp and hornet killer I used lists two active ingredients: tetramethrin (a pyrethroid ester) and a phenoxybenzyl cyclopropanecarboxylate. Raid’s product includes tetramethrin and a chlorinated carboxylate.
Other manufacturers blend tralomethrin, a brominated pyrethroid ester, and allethrin, a related compound that does not contain halogens, in products marketed as stinging-bug killers. But those same products, in nearly the same concentrations (no more than 0.05%), are also found in some roach and ant killers and spider killers. A key difference between the crawling- and flying-critter control agents, however, is packaging. Antiroach products are applied as gentle mists. In contrast, wasp exterminator comes in cans with propellants and nozzles designed to deliver the poison in a 20-foot stream–just in case a couple of angry bugs get away.
Although a great variety of insects are knocked down quickly by pyrethroids, pyrethrins, and other compounds, some of them get back up after a while. To keep bugs down for good, chemists have long blended poisons with compounds described as “synergists.” These substances lack significant insecticidal character on their own, but team up with primary pest-control agents to produce potent insecticide formulations.
Visit “What’s That Stuff” to learn more about the chemistry of bug spray.
Excerpted with permission, Chemical & Engineering News
Copyright © 2002 American Chemical Society