How does Bt technology differ from conventional insecticides in controlling pests?

Conventional insecticides are generally sprayed on the crops to destroy pests. The shortfalls in this system are many. Insecticidal sprays are effective only during a brief window between the hatching of larvae and its penetration into the fruit and shoot of the plant. Once the larva bores into the plant, it is impervious to insecticidal sprays. To avoid this possibility, farmers tend to resort to saturation spraying, a process that not only adversely affects the environment, but also their health and that of the end consumers. These sprays also destroy non-target insects and organisms that are otherwise beneficial to agricultural plants and the local ecology. In Bt brinjal, the insecticidal protein is expressed by the plant itself and the borer is killed as it tries to bore into the plant. However, Bt brinjal is harmless to the beneficial insects and non-target organisms.