The Bed Bug Chronicles: Part I

Lake Tahoe is only a short drive from the casinos of Reno.

One of the meetings I try to make every year is the Entomological Society of America annual conference.  It's the only place in the world where you can see more entomologists than bugs in a given day--over 2400 of them this year.  This year's meeting took place in Reno, the prettier of the two big gambling destinations in Nevada.

The ESA conference is lots of great information packed into a grueling marathon of paper sessions that seem to go on forever.  So today you're the lucky ones because you get to experience ESA without the gluteus maximus crampus (sore patootie).

For a week there were more entomologists than insects
in Reno.

This year's bed bug theme is a continuation of last year, though I think the papers and the research are getting better scientifically every year.  Of course no one person can take in the whole conference, so my highlights are admittedly selective.  There were many good talks on urban entomology that I did not attend.

• The lab of Changlu Wang (Rutgers University) continues to be a great source of practical research relating to bed bugs (BB) and other urban pests. This meeting Changlu reported on practical uses of carbon dioxide to control bed bugs. He found that putting 3 lbs of dry ice in a 42 gallon (3 mil-thick) garbage/yard waste plastic bag was sufficient to suffocate all stages of bed bugs in up to 22 lbs of clothes, when held for 24 hours. This amounts to a cost of approximately $4 to disinfest 22 lbs of clothes or other items that would fit in the bag. This adds another practical method for do-it-yourselfers looking for an inexpensive way to ensure disinfestation of personal items.
• In a related study, Dini Miller from Virginia Tech, found that Nuvan Prostrips (dichlorvos) achieved incomplete BB adult (4%), nymph (6%) and egg (45%) mortality when used at the label rate on clothing in 42 gal. yard waste bags. On hard items (e.g., books, computers, shoes and other personal items) Nuvan strips at the label rate achieved 48% mortality for adult BBs, 84% mortality for nymphs and 100% mortality for eggs. [According to Miller, to follow the label rate for a 42 gal. bag, one must cut a single Nuvan strip into 22 pieces (1/22 strip/bag)] If a whole strip is used in the bag (22X label rate), and the strip is held for 14 days, all nymphs and adults were killed, but only 63% of eggs were killed. Nuvan is commonly used as a fumigant by our industry, and does kill BBs; however this study suggests that it will not guarantee a kill of all BB life stages, even at higher than label rates (which we would, of course, never suggest).
  
• Susan Jones from Ohio State University tested bed bugs from six populations (five pyrethroid resistant populations, and one susceptible population) and found that three commonly sold “bug bombs” (total release aerosols) were ineffective in killing resistant bed bugs (0-30% mortality) held in open containers only 2-7 feet away from the aerosol emitter. The susceptible strain (unlikely to be found today in the field) was killed (100% mortality) under the same conditions.
       When provided with harborage to hide in during application, even the susceptible strain had very low (10-15%) mortality. These results confirm current recommendations by most Extension publications that “bug bombs” do not provide effective control for bed bugs for consumers.
  
• Joell Olson, of Ecolab in MN, reported on the effectiveness of cold temperatures for killing BBs. She found the egg stage to be the most resistant to cold. Her research suggested that items to be disinfested be held in a chest freezer (<= -13 degrees C) for a minimum of four days. This is longer than previously reported freezing times for BBs. 
• Many conference participants came away from the meeting with a greater appreciation for bed bug resistance to commonly used insecticides. Pyrethroid-resistant BBs are now predominant throughout the United States, with few susceptible populations remaining. Although I was unable to attend many of the resistance papers, I did catch one by Reina Koganemaru, a PhD student Dini Miller’s lab (Virginia Tech). With the aid of scanning electron microscopy she documented increased cuticle thickness in pyrethroid resistant bed bugs. Steven Kells (University of Minnesota) collected a different kind of data that supports Koganemaru's findings. Using both BBs and German cockroaches, Kells exposed both pests to Phantom insecticide (chlorfenapyr). He then washed and cut up his subjects and found 9X more insecticide on the outside of bed bugs compared to cockroaches. Similarly 9X more insecticide was found internally in the cockroaches compared to BBs. So, in addition to known target site (kdr) and enzyme-based detoxification resistance mechanisms, resistant bed bugs are thick-skinned as well. This suggests to me that surfactants/penetrants added to current bed bug insecticides might be one way to increase the effectiveness of existing products.
• I unexpectedly came away from this meeting with a much greater appreciation for the role of bacteria in entomology. Bacteria got my attention during the Founder’s Memorial Award lecture by Angela Douglas, from Cornell University. In talking about the role of bacteria in the bodies of insects, Dr. Douglas stunned me with the fact that 90% of the cells in an insect are bacteria (the same ratio is reported for humans). This is possible because of the tiny size of bacteria compared to the cells in our bodies. The relationship between insects and bacteria is far more complex and important to the ecology of pest control than I’d previously appreciated. Wolbachia, an intracellular parasite (lives in the cells of its hosts) is a type of rickettsial bacteria that has now been found in bed bugs. This same genus plays an important role in mosquito biology and reproduction. In some cases, Wolbachia has evolved to play important symbiotic roles (beneficial to both host and parasite) in insects. For example, some mosquitoes are unable to reproduce successfully without this bacterium in their bodies, while males of some mosquitoes are rendered sterile by Wolbachia infections. We don’t know exactly what roles Wolbachia plays in the ecology of bed bugs, but its presence opens up some doors for possible biological control options for bed bugs. Indeed Wolbachia is thought to play a role in the bed bug immune system. Remove Wolbachia and the survivorship of bed bugs goes way down after traumatic insemination (the bed bug equivalent of rough sex).

My next post I will cover some of the papers related to monitoring for bed bugs.