Insectical use has been reduced in BT crops. Why?

Explanation

Because some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), colopterans (beetles) and dipterans (Flies, Mosquitoes) `ul(B).ul("thuringienisis")` forms protein crystal during a particular plane of their growth. These crystals contains a toxic insecticidal protein. These proteins are present in inactive protoxin form, but become active toxin in the alkaline pH of insect gut. The activated toxin binds to the surface of midgut epithelial cells and create pores that -cause cell swelling and lysis and eventually cause death. Genes were isolated from B.Thuringiensis and genetically transferred to several plants such as cotton, thereby reducing the usage of insecticides.