Bt was later isolated in Thuringia, Germany, hence the name. Bt eventually was commandeered as an organic insecticide in the war against caterpillars. Today, it is sold under the trade names of Dipel, Thuricide, and Attack, among others, and, in different strains, is effective against the larvae of Colorado potato beetles, mosquitoes, fungus gnats, gypsy moths, tomato hornworms, and imported cabbageworms. Applied as a spray or dust to susceptible plants, Bt is ingested when larvae feed on foliage. Spores pass into the gut where they multiply and produce a toxic crystalline substance that paralyzes the larval digestive system.
Infected larvae stop feeding and eventually die.
Bt has been a valuable tool for organic gardeners because of its harmlessness to animals, humans, and beneficial insects, and because most caterpillars have failed to develop immunity. However, new genetic technology introducing Bt's toxin-producing gene into commercially grown corn, potatoes, or other crops to make the plants impervious to beetle larvae may prove otherwise. Used by permission. Read our Privacy Policy .