Non-chemical methods, like keeping food secure, repairing cracks where roaches get in, and vacuuming up large infestations, can also increase the chances of success. “Some of these methods are more expensive than using only insecticides, but if those insecticides aren’t going to control or eliminate a population, you’re just throwing money away,” Scharf said. “Combining several methods will be the most effective way to eliminate cockroaches.
But while scientists have documented cross resistance in German cockroaches in the lab, these roaches were able to cross-resist a variety of insecticides across different classes to a degree not documented before, according to the paper.
And that’s really bad news for the future of roach eradication. “This is a previously unrealized challenge in cockroaches,” lead author Michael Scharf said in a release from the University of Purdue. “Cockroaches developing resistance to multiple classes of insecticides at once will make controlling these pests almost impossible with chemicals alone.
The bug scientists used a variety of strategies and different insecticides to root out real-life infestations of the German cockroach (Blattella germanica), but found that the roaches were able to survive nearly all of their efforts.
At three roach-infested apartment complexes in Illinois and Indiana, they either used a rotation of three professional-grade insecticides, rotating every month for six months; sprayed two insecticides at the same time monthly; or laid down monthly gel baits with an insecticide that the roaches were previously shown to be susceptible to.