Bedbug on bean leaf (left); bedbug leg trapped by tiny, hairlike trichomes on leaf surface (right)
Image credit: M. Szyndler and C. Loudon / UC Irvine
Researchers have investigated an old Balkan bed bug remedy, finding that kidney bean leaves can impale and trap bed bugs. The scientists, Catherine Loudon, Robert Corn, and Megan Szyndler of The University of California-Irvine and Michael Potter and Kenneth Haynes of the University of Kentucky, are now working on synthetic materials which can do the same thing.
Their work was motivated by a centuries-old remedy for bedbugs used in Bulgaria, Serbia and other southeast European countries. Kidney bean leaves were strewn on the floor next to beds and seemed to ensnare the blood-seeking parasites on their nightly forays. The bug-encrusted greenery was burned the next morning to exterminate the insects.
Through painstaking detective work, the scientists discovered that the creatures are trapped within seconds of stepping on a leaf, their legs impaled by microscopic hooked hairs known botanically as trichomes.
Using the bean leaves as templates, the researchers have microfabricated materials that closely resemble them geometrically. The synthetic surfaces snag the bedbugs temporarily but do not yet stop them as effectively as real leaves, Loudon said, suggesting that crucial mechanics of the trichomes still need to be determined.
Theoretically, bean leaves could be used for pest control, but they dry out and don’t last very long. They also can’t easily be applied to locations other than a floor. Synthetic materials could provide a nontoxic alternative.
The study, “Entrapment of bed bugs by leaf trichomes inspires microfabrication of biomimetic surfaces” has been published in the latest issue of the Journal of the Royal Society Interface (abstract).
How did the record of the folk bed bug remedy travel to modern researchers?
According to the New York Times,
This folk remedy from the Balkans was never entirely forgotten. A German entomologist wrote about it in 1927, a scientist at the United States Department of Agriculture mentioned it in a paper in 1943, and it can be found in Web searches about bedbugs and bean plants.
The New York Times also describes how the researchers uncovered the beautiful workings of the kidney bean leaves:
The first task was to determine exactly how the hooks — the technical name is trichomes — worked. The process was viewed through an electron microscope, Dr. Loudon said. “The foot comes down onto the surface, but as it’s lifting up, it’s catching on these hooks,” she said. “The point is pointing down. So all of their legs get impaled.”
“And as soon as one leg gets caught,” she added, “they are rapidly moving legs around and try to get away on the surface. That’s when they get multiply impaled.”
The team is now working on synthetic material to mimic the way the leaves work. Brooke Borel has an interesting study in Popular Science of the mechanics of the kidney bean leaf “traps”.
It remains to be seen whether or how this technology will change bed bug treatment protocols. (Of course, it’s been patented and has already been optioned by an as-yet-unnamed company.)
An obvious use which comes to mind is a form of bed isolation — where bed bugs had to climb over a synthetic bean leaf-like material in order to get to sleeping humans.
I have to say, the Balkan cure is a lot more promising than the Ancient Hungarian Bed Bug Curse.
Here’s a video showing a bed bug getting impaled and entrapped on the kidney bean leaf (because if we know our readers, we know they really like to see bed bugs get impaled, on anything):
Update (4/15): the article “Entrapment of bed bugs by leaf trichomes inspires microfabrication
of biomimetic surfaces” is currently available for free (full-text) via the journal’s website.