Naturally occurring fungus may help where chemical pesticides are failing
By Summit Voice
SUMMIT COUNTY — The resurgence of common bedbugs is partly due to their increase resistance to insecticides — like many other nuisance species, they’ve evolved to develop an immunity to the toxins. But a team of researchers at the University of Pennsylvania say they may have discovered the key to effective biocontrol of the nuisance bugs — a natural fungus that causes disease in insects.
In the study, the researchers used an airbrush sprayer to apply spore formulations of the Beauveria bassiana fungus to paper and cotton jersey, a common bed sheet material. Then control surfaces, again paper and cotton jersey, were sprayed with blank oil only. The surfaces were allowed to dry at room temperature overnight.
Three groups of 10 bed bugs were then exposed to one of the two surfaces for one hour. Afterward, they were placed on clean filter paper in a petri dish and monitored. The researchers found that all of the bed bugs exposed to the biopesticide became infected and died within five days.
“They are natural diseases that exist in the environment,” said entomologist Nina Jenkins. “They are relatively easy to produce in a lab and stable, so you can use them much like chemical pesticides.”
“We exposed half of a population of bed bugs to a spray residue for one hour and then allowed them to go into a harborage with unexposed individuals,” Jenkins said. “The fungal spores were transferred from the exposed bug to their unexposed companions, and we observed almost a hundred percent infection. So they don’t even need to be directly exposed, and that’s something chemicals cannot do.”
Also, there were no prominent differences in susceptibility by feeding status, sex, strain or life stage. Most importantly, the infected bed bugs carried the biopesticide back to their hiding places, infecting those that did not go out in search of blood.
This result is important because bed bugs live in hard-to-reach places.
“Bed bugs tend to be cryptic, and they’ll hide in the tiniest crevices,” said Jenkins. “They don’t just live in your bed. They hide behind light switches and power sockets and in between the cracks of the baseboard and underneath your carpet.”
The speed of mortality with B. bassiana is as fast as Jenkins has seen in any application, but it doesn’t even need to be that fast.
“If you are trying to protect a farmer’s field, he wants the insects that are eating his crop dead immediately,” said Jenkins. “Obviously, if you have bed bugs in your house, you don’t want them there for any longer than you have to, but what you really want to know is if they’ve all gone at the end of the treatment, and I think that’s something that this technology could offer.”
Next, the researchers will test the effectiveness of brief exposure times and look at entire populations where natural harborages are established. Then they will begin field work.
“It’s exciting, and it definitely works,” said Jenkins. “We’re working on the next step, and we have more funding to support these studies.”