Bt is effective only when the larvae eat the B.t bacteria or protein. The insect’s alkaline (p.H 10.5) mid-gut environment processes the B.t protein and release the active toxic fragment of the protein. The toxic fragments binds with specific receptors present in the mid-gut epithelial cell and develop pores leads to upset of insect’s digestive system. The insect unable to eat and dies within a few days.

Using fermentation technology the B.t has been produced in large quantity. B.t spores and toxic proteins produced by B. thuringiensis have been used as natural insecticide by farmers throughout world. B.t is natural and its protein does not persist in the environment for longer period. Thus B.t satisfied the organic farming standard and allowed to utilize in organic agriculture as a bio pesticide for pest control. The insecticide is prepared as liquid for foliar spray and as granules for soil application. The effectiveness of the B.t is depends on the contact between B.t insecticide and target pest. If target pest have already entered into plant stem or fruit, the contact between the insect and B.t pesticide is prevented. So the possibility of larval death by B.t is avoided. This problem was overcome by using modern biotechnology tools.

Modern sciences pay the way to isolate the specific B.t gene having the insecticidal activity from the bacterium and to insert the gene into the plant genome. The Cry 1Ac and Cry 2Ab genes are highly used for insect pest control in B.t technology. The plants carrying these bacterial genes are called Genetically Modified Organisms (GMO) or transgenic plants. Thus these plants acquired built-in resistance against targeted pest. Now the toxic protein is produced all the parts of the plant throughout the life time. The toxic protein does not get washed away by the irrigation and rain water and not destroyed by the sunlight. If target pest eat any part of the plant, the toxic protein kill the pest.  The plant protected from the target pest throughout the life in all the circumstance.