A new way to combat resistant pests stems from discovering how the widely used natural insecticide Bt kills insects.



Figuring out how Bt toxins punch holes in the cells of an insect's gut was the key to designing the new toxins, according to a Mexico-U.S. research team.



Some insects have developed resistance to Bacillus thuringiensis toxins, naturally occurring insecticides used worldwide to combat pests of crops such as cotton and corn and also disease-carrying mosquitoes.



"This is the first time that knowledge of how Bt toxins work and how insects become resistant have been used to design toxins that kill resistant insects," says research team member Bruce Tabashnik of The University of Arizona in Tucson.



The Mexico team developed the designer toxins by tweaking the gene that codes for the toxin, a protein. The researchers then teamed up with Tabashnik to test their modified toxins on university's colony of Bt-resistant pink bollworms, major cotton pests.



Combating Bt-resistant pests without using broad-spectrum insecticides can make agriculture safer for farm workers, better for the environment and more profitable for growers, Tabashnik says.