Insecticides will soon become completely useless against cockroach infestation as new research shows that the household pests are growing increasingly resistant to these chemicals.
More importantly, cockroaches have appeared to develop cross-resistance to multiple insecticides, which means that most chemicals will no longer work to remove populations from households and establishments.
"This is a previously unrealized challenge in cockroaches," said study author Michael Scharf of Purdue University's Department of Entomology. "Cockroaches developing resistance to multiple classes of insecticides at once will make controlling these pests almost impossible with chemicals alone."
Cockroaches Will Be Nearly Impossible To Kill Soon
Scientists have long known about cockroaches' incredible hardiness, but it turns out they're growing even more undestroyable over time.
In a recent study published in the journal Scientific Reports, researchers led by Scharf attempted to eliminate infestations of the common German cockroach using various techniques.
Different classes of insecticides work in various ways to kill cockroaches. Exterminators often use a mix of classes or change classes with each treatment in hopes that even if some cockroaches are resistant to one class, they'll be wiped out with the use of another class.
The study authors tested these methods in multi-unit buildings in Indiana and Illinois over six months. Three treatment techniques were tested. In the first one, three insecticides from different classes were used in rotation per month. The second treatment involved using a mixture of two insecticides from different classes for six months, while the third treatment included the researchers choosing a single insecticide that cockroaches have a low resistance to and using this over six months.
All these efforts proved futile as the roaches were found to survive regardless of the treatment method used.
With the use of three rotating insecticide classes, the population of cockroaches remained the same over six months. On the other hand, the mixture of two different insecticide classes did not work at all with the population increasing greatly within the time frame it was used.
One of the single-insecticide experiments included little starting resistance to the insecticide, which resulted in the scientists nearly eliminating the cockroach population. However, in another such experiment that included 10 percent starting resistance, the populations increased.
According to the authors, cross-resistance likely played a big role in their survival. A small percentage of cockroaches would be resistant to a specific insecticide class, and their offspring would essentially be immune to this class. Surprisingly, they would also be immune to other insecticide classes, despite not being exposed to them and not having previous resistance.
"We would see resistance increase four- or six-fold in just one generation," Scharf explained. "We didn't have a clue that something like that could happen this fast."
More than just household annoyances, cockroaches can also be a health hazard. According to CDC, these insects are allergen sources and a common trigger of asthma. Little evidence links cockroaches to disease outbreaks, but they've been found to carry Salmonella typhimurium, Entamoeba histolytica, and the poliomyelitis virus.
Here's How Humans Can Cope With Indestructible Roaches
Humans aren't helpless against cockroaches, even indestructible ones. It's just that instead of relying on chemicals, households would have to be more creative in wiping out these pesky insects.
The team recommends an integrated pest management approach, which involves combining chemical treatments with the physical removal of cockroaches. This can include setting traps, vacuuming them away, and practicing better sanitation in the residence.
Schaf pointed out to Vox that if property owners and managers cut back on insecticides, it's possible that the chemicals will become effective again in a few generations. With cockroaches only living around 100 days, it may take only a short time to see their susceptibility to insecticides come back.