(TMU) — The common German cockroach, despite being a vile carrier of bacteria and disease, is truly an impressive creature.
While a number of insects face a looming danger of extinction, many believe that the resilient roach—whose history stretches back to 300 million B.C.—could actually outlast the human race. According to extermination company Orkin, the female German cockroach can lay nearly 400 eggs in her lifetime.
And now, a team of scientists in the U.S. has determined that the common German species of roaches has rapidly evolved to become “almost impossible” to kill using chemicals alone.
And when cockroaches survive exposure to insecticides, they, as well as their offspring, become “essentially immune” to the chemicals, as a Purdue University study published in Scientific Reports found.
Michael Scharf, a professor at Purdue’s Department of Entomology who led the study, commented:
“This is a previously unrealized challenge in cockroaches.
Cockroaches developing resistance to multiple classes of insecticides at once will make controlling these pests almost impossible with chemicals alone.”
To make matters worse, the creatures are also born impervious to an array of other insecticides, including those with which they haven’t yet been in contact—a phenomenon the researchers call “rapid cross-resistance.”
The study found that cockroaches are able to rapidly evolve from one generation to the next to develop the cross-resistance to even the best insecticides developed by exterminators.
We would see resistance increase four- or six-fold in just one generation.
We didn’t have a clue that something like that could happen this fast.”
Purdue’s team conducted their study in a range of buildings across central Illinois and Indiana as well as at labs on-campus that were infested by roaches. Using combinations of different types of insecticides and studying several generations of roaches, the team concluded that the German cockroach population had almost become invincible in terms of their chemical resistance.
A press release from Purdue noted:
“If even a small percentage of cockroaches is resistant to an insecticide, and those cockroaches gain cross-resistance, a population knocked down by a single treatment could explode again within months.”
The study also refers to the German cockroach—which can carry such life-threatening bacteria as E. coli and salmonella and can cause allergies and asthma among children—as “the species that gives all other cockroaches a bad name.”
The report concludes that an integrated approach to pest management is crucial. Such an approach would include a combination of chemical treatments, traps, vacuums, and generally improved sanitation, especially in low-income communities where resources might be lacking.
“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.
Combining several methods will be the most effective way to eliminate cockroaches.”