Bed bugs have developed a resistance to neonicotinoids, a group of the most widely used insecticides, according to a new study published in the Journal of Medical Entomology.
Products developed over the past few years to control bed bugs combine neonicotinoids, or neonics, with pyrethroids, another class of insecticide.
The newly found resistance to neonics has real implications for people who need to control the pest, which are most often found in human dwellings such as apartments or condominiums, single-family homes and hotels or motels, according to the 2015 Bugs Without Borders Survey. Neonics are the most commonly used insecticide to fight the already elusive and resilient bed bugs, and if they no longer work, bed bugs will continue to thrive despite exterminators’ efforts.
Study authors Alvaro Romero, from New Mexico State University, and Troy Anderson, from Virginia Tech, discovered the resistance by collecting bed bugs from human dwellings in Cincinnati and Michigan and exposing them to four different neonics: acetamiprid, dinotefuran, imidacloprid and thiamethoxam.
Romero and Anderson applied the same neonics to a bed bug colony kept by entomologist Harold Harlan for more than 30 years without exposure to insecticide, and to a pyrethroid-resistant population from Jersey City, New Jersey, that had not been exposed to neonics since 2008.
Harlan’s bed bugs died after exposure to small amounts of neonics. The Jersey City bed bugs died when exposed to imidacloprid and thiamethoxam but resisted the other two neonics.
According to Romero and Anderson, the neonic resistance in the Jersey City bed bugs could be credited to pre-existing resistance mechanisms. Bed bugs produce “detoxifying enzymes” to counter exposure to insecticides, and the researchers found that the Jersey City bed bugs had higher levels of the enzymes than did the Harlan bed bugs.
“Elevated levels of detoxifying enzymes induced by other classes of insecticides might affect the performance of newer insecticides,” Romero said.
The bed bugs collected from Cincinnati and Michigan proved to be tougher, with a much higher resistance to neonics than the Harlan and Jersey City bed bugs. Compared with Harlan’s bed bugs, the Michigan creatures were 462 times more resistant to imidacloprid, 198 times more resistant to dinotefuran, 546 times more resistant to thiamethoxam and 33,333 times more resistant to acetamiprid.
Similarly, the Cincinnati bed bugs were 163 times more resistant to imidacloprid, 358 times more resistant to dinotefuran, 226 times more resistant to thiamethoxam and 33,333 times more resistant to acetamiprid.
Romero said insecticide companies should be “vigilant for hints of declining performance of products that contain neonicotinoids”.
“For example, bed bugs persisting on previously treated surfaces might be an indication of resistance,” he said. “In these cases, laboratory confirmation of resistance is advised, and if resistance is detected, products with different modes of action need to be considered, along with the use of non-chemical methods.”