Dont let the bed bugs bite
Scientists here have determined that combining bed bugs’ own chemical signals with a common insect control agent makes that treatment more effective at killing the bugs.
The researchers found that stirring up the bed bugs by spraying their environment with synthetic versions of their alarm pheromones makes them more likely to walk through agents called desiccant dusts, which kill the bugs by making them highly susceptible to dehydration.
A blend of two pheromones applied in concert with a silica gel desiccant dust proved to be the most lethal combination.
In the past decade, bed bugs have become an increasing problem in industries ranging from agriculture and housing to travel and hospitality, so much so that the Environmental Protection Agency hosted a National Bed Bug Summit in April of this year.
The species, Cimes lectularius, also is developing resistance to the insecticides approved to spray infested areas, treatments that belong to a group of compounds called pyrethroids.
Desiccant dusts that are sprinkled in infested areas, however, are among the oldest forms of insect control and are still considered effective killers as long as the bugs walk through them.
“Once we put the alarm pheromone in the places bed bugs hide, boom, they instantly started moving around and moving through the desiccant dust,” said Joshua Benoit, lead author of the study and a doctoral candidate in entomology studying under David Denlinger at Ohio State University.
“Consistently, the addition of a pheromone blend to desiccant dust was more effective than adding either chemical by itself or by using desiccant dust alone.”
The research is published in the current issue of the Journal of Medical Entomology.
The two bed bug alarm pheromone ingredients are known as (E)-2-hexenal and (E)-2-octenal. When bed bugs are disturbed or excited, they secrete these two pheromones and tend to want to move around.
While some pheromones are known to attract species for reproductive purposes, these particular pheromones act more as a repellent, Benoit explained.
“These pheromones also can be bought from any chemical company. They’re well-established chemicals, are easy to make in the lab, and are readily available,” he said.
Two types of desiccant dusts were used in the experiments: diatomaceous earth, a naturally occurring, chalky substance, and a compound called Dri-die, made from a silica gel. Desiccant dusts are designed to disturb the bed bugs’ cuticle, particularly the waxy outer layer on insects that allows bugs to stay hydrated. Without the waxy protection, insects are more prone to dry up and die.
The researchers first tested the chemical combination on five bed bugs at a time for 10-minute exposures in petri dishes. They tested both types of desiccant dusts as well as each pheromone component alone and in a blend more typical of natural secretion.
Bed bugs exposed to Dri-die and a blend of pheromones lost water at a much faster rate than did bed bugs treated with the desiccant dust alone. The scientists found that bed bugs exposed to Dri-die alone lost 21 percent more water than untreated control bugs. Water loss nearly doubled with either (E)-2-hexenal or (E)-2-octenal applied alone and tripled with a blend of both pheromones.
Young bed bugs exposed to the combination died in about a day, three days earlier than control bed bugs. Adult female bed bugs exposed to the combination survived for about 6 ½ days, compared to females exposed only to the desiccant dust, which lived for an average of 17 days.
In petri dish tests, the scientists found that the combined treatments using Dri-die consistently worked better than those using diatomaceous earth at generating rapid water loss in the bed bugs.