To Kill With Insecticides Scientists at Purdue University say cockroaches are becoming even more resistant to insecticides, and will soon be nearly “almost impossible” to kill with chemicals. Researchers say the bugs are developing a “cross-resistance” to different cocktails of insecticides used by exterminators. That resistance ends up getting passed on to the next generation of roaches. Some of those roaches are born with immunity to pesticides they’ve never even been exposed to, researchers say. Scientists recommend using other methods like traps, vacuums, or simply keeping things clean.