Bug Girl helpfully points us to some excellent new resources on bed bugs and pesticide resistance.
Dr. James Crow, Professor Emeritus of Genetics at the University of Wisconsin – Madison, was a pioneer in the research of pesticide resistance in the late 1940s, and was a founder of the fields of population genetics and molecular evolution.
Interestingly, Dr. Crow lived in a house with bed bugs as a grad student in the 1930s, a problem the house residents eventually solved with cyanide gas fumigation.
You can watch a 11.5 minute podcast interview in which Dr. Crow talks about about his research on pesticide resistance and evolution, below. The video was produced by the National Evolutionary Synthesis Center (NESCent). (Click here to watch on YouTube if the embedded video is not visible).
See also this article in Understanding Evolution that NESCent directs readers to.
Of special interest, the explanation of how bed bug populations become pesticide resistant, and in particular, how they became resistant to DDT and pyrethrums (Bug Girl also draws our attention to part of this passage):
Bed bug populations have been primed with the right sort of genetic variation by their evolutionary history — a history which includes extensive exposure to a different insecticide, DDT. Like pyrethrums, DDT kills insects by acting on the sodium pores in their nerve cells — and it just so happens that many of the same mutations that protect an insect against DDT also happen to protect it from pyrethrums. When DDT was first introduced, such mutations were probably extremely rare. However, with the widespread use of DDT in the 1950s and 60s, such mutations became much more common among bed bugs through the process of natural selection. Though DDT is rarely used today because of its environmental effects, these mutations have stuck around and are still present in modern bed bug populations. Because of the action of natural selection in the past (favoring resistance to DDT), many bed bug populations today are primed with the right sort of genetic variation to evolve resistance to pyrethrums rapidly.
In other words, the genetic mutations which allowed some bed bugs to be resistant to DDT are also what allow today’s bed bugs to become pyrethrin-resistant.
The article and the podcast both stress how very quickly this evolution occurs.
And note, bed bugs can become resistant to other pesticides, too. All the more reason for throwing our energy into increasing awareness about prevention and detection, improving methods of early detection, and making non-chemical approaches to treatment such as heat more available and affordable for everyone.
Unfortunately, non-chemical approaches to bed bug treatment are not the most common approaches used today against bed bugs. The majority of people are forced for financial reasons to take the option of pesticide treatment. Even if it is not always cheaper in the long run, it appears to be so, because customers often pay for single treatments or an initial course of 2-3 treatments, which often cost less than heat treatment.
And while pesticides can be used properly and effectively, pesticide applications done badly may be the least effective treatments of all. “Pray-and-spray” treatments done by “baseboard jockeys” who may overuse and misapply chemicals, can both allow bed bug problems to persist and at the same time, increase problems with pesticide resistance.
Understanding Evolution recommends the following articles for further reading (available from the Armed Forces Pest Management Board Literature Retrieval System; enter the accession number in the “advanced” search page):
Yoon, K. S., Kwon, D. H., Strycharz, J. P., Hollingsworth, C. S., Lee, S. H., and Clark, J. M. (2008). Biochemical and molecular analysis of deltamethrin resistance in the common bed bug (Hemiptera: Cimicidae). Journal of Medical Entomology. 45: 1092-1101. (LRS accesstion #185379)
Zhu, F., Wigginton, J., Romero, A., Moore, A., Ferguson, K., Palli, R. … Palli, S. R. (2010). Widespread distribution of knockdown resistance mutations in the bed bug, Cimex lectularius (Hemiptera: Cimicidae), populations in the United States. Archives of Insect Biochemistry and Physiology. 73: 245-257. (LRS accesstion #188346)
College or HS science teachers out there may also be interested in Understanding Evolution’s “discussion and extension questions” (for advanced students) or the “related lessons and teaching resources” for grades 9-12, both of which also follow the article. Please get more smart, eager young people interested in bed bug research; we need all the help we can get in this fight.
(Aren’t you glad I didn’t say we need “new blood”?!?)