A compound made from the Bt toxin has been used for over forty years as an insecticide that is applied directly to plants. Research in the past few years has allowed scientists to use genetic engineering to insert the gene that codes for the Bt toxin into plants. These plants make the toxin as part of their normal growth, and the toxin becomes incorporated into the tissues of the plant. Therefore, when an insect eats part of a Bt plant, it also eats the toxin and dies. This works as an insect control mechanism actually contained within the plant itself.
Insects have a very large gene pool and produce hundreds of offspring each time they reproduce.
One mutant insect that has a resistance to the Bt toxin can survive, reproduce and eventually create an entire population resistant to the toxin. Thus the newly engineered plant or crop with the incorporated toxin has absolutely no effect on the pests, and scientists must find a new chemical or control mechanism. Glyphosate is a unique commercial broad spectrum herbicide. This pathway is the mechanism plants use to synthesize their aromatic amino acids. This makes glyphosate relatively safe for human and animal ingestion because it only works in plants.