Bed Bugs Are Becoming Resistant to Some Insecticides

A new study finds bed bugs are becoming resistant to neonicotinoids, which are commonly used for extermination. U.S. Centers for Disease Control

Bed bugs are the stuff of nightmares for many (if not most) people, so perhaps the only thing worse than spotting these pests in one's home is finding out the chemicals sprayed to kill them don't work. New research suggests we may be headed in that direction. A study published Thursday in the Journal of Medical Entomology finds that bed bugs appear to be developing a resistance to neonicotinoids, which are frequently used to combat infestations.

Neonicotinoids, also known as neonics, are a group of insecticides often combined with pyrethroids, another man-made insecticide. These combined products have become incredibly popular in the pest control market in the U.S. Neonics, a group of neuroactive chemicals that were first introduced to the market in 2009, cause certain receptors in the bugs to fire repeatedly until they fail, eventually leading to paralysis and death.

For the study, researchers at New Mexico State University and Virginia Tech collected bug samples from pest control companies and also through friends of friends who were contending with bed bug infestations. The bloodsuckers came from homes in Cincinnati and Troy, Michigan, and the researchers exposed them to four different types of neonics: acetamiprid, dinotefuran, imidacloprid and thiamethoxam.

Additionally, the researchers tried these various chemicals on a bed bug colony cultivated in a laboratory for more than 30 years and never exposed to insecticides. They also tested a colony that hailed from Jersey City, but hadn't been exposed to neonics since 2008 when they were initially collected.

The goal of the experiment was to see how strong a dose of the chemical would actually be needed to kill 50 percent of the bed bugs in each sample.

The researchers found the bed bugs from the lab died even with an incredibly small dose of chemicals. The bugs from New Jersey showed some resistance to acetamiprid and dinotefuran, but not to imidacloprid or thiamethoxam.

However, the bed bugs from homes in Cincinnati and Troy proved to be much more resilient. While it only took 0.3 nanograms of acetamiprid to kill off half of the laboratory-bred bugs, the researchers needed to use 10,000 nanograms to destroy the bugs that came from the homes. Overall, the bed bugs from Troy were 462 to 33,333 times more resistant to various neonics, while the Cincinnati bugs were 163 to 33,333 more resistant. The researchers saw a similar trend with the other types of neonic chemicals they tested.

Dr. Alvaro Romero, an assistant professor in urban entomology at New Mexico State University and co-author on the study, says more research is needed to understand the mechanisms at play that cause these bugs to build up resistance. However, he and his fellow researchers suspect the bugs produce what's known as a "detoxifying enzymes" when they're exposed to certain chemicals. These enzymes help the bugs metabolize the chemicals without their lethal effects. Research has found genes related to these enzymes are typically mutated in insecticide-resistant bed bugs.

In the 1940s and 1950s, DDT and pyrethroids were the chosen poison for bed bug infestations, but over time they have become much less effective and insects have built up a resistance to these chemical agents. In the past 15 years, experts say, there has been a resurgence of these creepy pests—and the fact that they are now turning impervious to neonics means these scourges appear perfectly capable of building up multiple chemical resistances as gene mutations are passed down from one generation to the next.

Spraying insecticides needs to be just one component of addressing an infestation, says Romero. It's important to do a thorough cleaning of all permeable items and clothing in a household, and use non-chemical approaches such as applying heat and steam, which both kill the bugs.

Romero says the next step in his team's research is to partner with people who can collect bugs in other states and regions of the U.S. in order to see how widespread the problem is. "People need to be aware of the performance of these formulations in the field," he says. "We're not saying that everything is resistant."