These proteins are very specific insecticides with activities against some species of caterpillars, mosquitoes, flies, and beetles. Recent research on Bt has followed two approaches. The first is the selection and development of Bt strains that are specific for other pests or that produce higher concentrations of the compounds. The second approach is to move the gene that controls the production of the Bt proteins into crop plants. Bt genes for control of an insect species have been incorporated into tomatoes, tobacco, cotton, and corn with good results.
Bt proteins are highly specific to particular insect species.
Therefore, to achieve control of several different insect species at one time, many different gene codes would have to be incorporated into the plant's genetic makeup. The incorporation of Bt genes into plants causes concern that insects will likely develop resistance to the Bt strain. The probability is especially high in current cases where the gene is expressed throughout the plant. For example, if three to four generations of an insect feed on the plant leaves or fruits throughout the growing season, the insect would be constantly exposed to the chemical. It is likely that the insect will develop resistance to the chemical.