A new study published in the Journal of Medical Entomology is the first to report that bed bugs have developed resistance to a class of insecticides known as neonicotinoids, or neonics, the shortened name. Neonics are the most widely used group of insecticides today, and several products have been developed for bed bug control over the past few years that combine neonics with pyrethroids, another class of insecticide. Dr. Alvaro Romero from New Mexico State University and Dr. Troy Anderson from Virginia Tech collected bed bugs from human dwellings in Cincinnati and Michigan and exposed them to four different neonics: acetamiprid, dinotefuran, imidacloprid, and thiamethoxam. They also applied these neonics to a bed bug colony kept by Dr. Harold Harlan for more than 30 years without any insecticide exposure, and to a pyrethroid-resistant population from Jersey City that had not been exposed to neonics since they were collected in New Jersey in 2008. 

Unsurprisingly, the Harlan bed bugs died even when exposed to very small amounts of the neonics. The Jersey City bed bugs fared slightly better, showing moderate resistance to acetamiprid and dinotefuran, but not to imidacloprid or thiamethoxam. 

The authors believe that the detection of neonicotinoid resistance in the Jersey City bed bugs, which were collected before the widespread use of neonics, could be due to pre-existing resistance mechanisms. When exposed to insecticides, bed bugs produce "detoxifying enzymes" to counter them, and the researchers found that the levels of detoxifying enzymes in the Jersey City bed bugs were higher than those of the susceptible Harlan population. 

"Elevated levels of detoxifying enzymes induced by other classes of insecticides might affect the performance of newer insecticides," said Dr. Romero.