Horticulture/Bed Bug control with Bean Leaves (trichomes)
QUESTION: Hi Susan,
You may know, the recent interest in the Balkan practice of controlling bed bugs with bean leaves (which have trichomes) and trap the bed bugs.
Well, my question is : Is it just Kidney Bean Leaves that have trichomes (and hence are effective) or do all any other/ all bean leaves have trichomes?
ANSWER: Hi Sam,
Thanks for sending me such an interesting question. First, many different types of beans/legumes have trichomes, in varying degrees. There are 2 types of trichomes; Unciform (hooked), and Acicular (straight, needle-like). Not just legumes, but many other plants have trichomes.
The above is an account of the trichome density study done in Puerto Rico.
I have presently growing yardlong beans (which are actually an edible pod cowpea) and Louisiana Purple Pod Pole Snapbean. The leaves of the pole snap bean stick to my clothing (and each other) on BOTH sides of the leaf. The yardlong bean leaves barely stick on the underside.
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QUESTION: Hi Susan,
Thank you for your detailed answer and the weblink.
After reading it, and other web-sites, I believe that the bed bug studies were with trifoliates with high-density aciculars. Red Kidney Bean leaves therefore become the first choice, am I right? And the next question would be which bean types would not have aciculars, i.e. would not/poorly serve the bed-bug trapping purpose?
Even though the practice is historical, research into it is recent. I'm sure you know that Kidney Beans, Kentucky Wonder, Yellow Wax, Navy, Black, Blue Lake, etc. are all "P. Vulgaris". I cannot find a study where distinction is made between them with respect to trichomes in the leaves. I did find where Soybeans (Glycine max), and Hycianth bean (Dolichos lablab) were mentioned as also being somewhat effective against bedbugs.
My assumption would be as a rule of thumb that less refined varieties would contain more trichomes. My reasoning is that beans are cultivated for the pods (although many cultures eat the leaves). Often, when plants are bred to show a specific characteristic, other characteristics are changed or lost.
It would certainly make for an interesting experiment!