An ancient Eastern European remedy for ensnaring bedbugs has been dusted off and recast as a valid chemical-free remedy for controlling bedbugs. Tiny hooks on the exoskeleton of bedbugs get ensnared on the tiny hooks on bean leaves (for example, Kidney beans - Phaseolus vulgaris L.).
The more the bug struggles, the more entrapped it becomes. The bug gets stuck on the surface of the bean leaf. It is rather like being ensnared in a spider's web or like flies being trapped on sticky paper. What a smart idea!
This natural remedy was described by a German entomologist in 1927, and it was briefly mentioned in scientific publications in the 1940s.
At this time, people with bedbug problems would simply spread bean leaves around on the floor. In the morning the leaves with the bedbugs attached would be swept up and burnt.
Recent research has revived this idea and used electron microscope images of the bean leaf surface and the legs of bedbugs. The aim of the research was to developed synthetic versions based on the same principle that could be manufactured as 'Sticky Paper for Bedbugs'. There is growing concern about the health risks of widespread use of insecticides to control bedbugs. Also their habit of hiding in cracks and crevices means that the toxic sprays are not very effective. There is also a constant battle against the problems of bedbug resistance to insecticides. The ensnarement method offers at chemical-free control method.
The research showed that the hooks on the bean plant are rather like those on the pitcher plant and other insectivorous plants they all point downwards (see the image). These microscopic hooked hairs are called trichomes. When a bedbug steps onto the surface of a bean leaf the hairs on its legs get trapped by these hooks. When the bedbug tries to lift the foot its hairs are caught up on the bean plant hooks. As soon as one leg gets caught and the bedbug struggles to get free, more and more of the legs get ensnared and the bedbug is trapped. The bedbugs can be collected from the bean leaves in the morning and disposed of.
The scientists have tried to duplicate the bean plant hooks using polymers, but so far with limited success. The natural bean leaves are best. The research work is exploring new designs.
Bedbugs are now a major problem worldwide and there are websites to warn travelers of the hazards of infected hotels. People are also warned of the risks of bringing bedbugs home with them. Infestations in hotels and homes are very hard to control and eliminate.
Hopefully mimicking bean hairs will one day soon, provide a chemical-free solution.