The boll budworm, pink bollworm and tobacco budworm, together, account for only about a quarter of the losses of cotton crop. If further gene transfers were developed to control other insects, significantly more pesticide use could be avoided. Although cotton farms occupy only 5% of US farmland, these farms account for about half of all pesticides used in the United States.
The best known cotton pest is the boll weevil. Weevils are beetles. Although the Bt toxin presently produced by Bt cotton doesn't affect weevils, there are other Bt toxins that would kill it, occurring in other natural varieties of Bacillus thuringiensis. But this is not particularly important because in the United States the boll weevil has been almost completely eradicated. Meanwhile research is underway to discover how to transfer the genes for other pest specific toxins.