Wednesday, November 23, 2011

The Bed Bug Chronicles: Part II

Yesterday I presented some of my highlights of the 2011 Entomological Society of America (ESA) annual conference, most of which had to do with bed bugs.  Today I wanted to share some notes on bed bug monitoring, a subject which I think will be key to developing effective IPM programs for this pest.

Some of my almost indecipherable notes from a bed bug
talk at ESA
Apparently I'm not alone in this belief.  There were several papers at ESA this year on monitoring-related topics. The ability to detect bed bugs early, before they become abundant in an apartment or hotel room, is critical to quick elimination of infestations. A good monitoring method should be inexpensive (if it's to be deployed in hundreds of hotel rooms or apartments), easily checked, and effective at detecting bed bugs at low infestation levels.  To date, the ideal monitoring tool does not exist; but much work is going into the search.

For cockroaches, the simple sticky trap has performed quite well as a cheap and effective monitoring tool.  Unfortunately, bed bugs are not readily captured with sticky traps, for reasons that have not been well studied.  The best alternative approach so far is use of various pitfall trap designs.  Pitfall traps consist of a container into which insects fall and cannot get out.  These work well with bed bugs because bed bugs are not very good climbers on slick surfaces. The first successful manufacturer of pitfall traps was the ClimbUp Insect Interceptor trap, sold by Susan McKnight Inc., and designed to be placed under bed posts.  When placed correctly it traps bed bugs either exiting or climbing on to beds.

Narinderpal Singh and Changlu Wang (Rutgers University) have been using the ClimbUp to investigate ways to make pitfall traps more attractive to bed bugs.  They found that CO2 was more effective at luring bed bugs to ClimbUp pitfall traps than heat. However they also tested several volatile compounds as potential lures. The compounds nonanal, spearmint oil, octenol, and coriander mixed together was more effective than any of the compounds individually.  They also found that when these compounds were added to CO2 they attracted more bed bugs than CO2 alone. Of these four compounds, nonanal (aka nonanaldehyde or pelargonaldehyde) was the most attractive. This compound is emitted by humans and was recently found to be highly attractive to Culex mosquitoes.

Figuring out how to take basic scientific research like this and turn it into a successful product for PMPs has generally been role of the specialty products industry.  The chemical manufacturer FMC has been busy doing just that with bed bug monitoring.  For over two years FMC has been developing technology to build a better bed bug trap. The result of this project is a prototype of a new bed bug trap they announced to bed bug researchers at the meeting.  Tentatively called Verifi™, the trap uses a combination of CO2, pheromone (scent produced by other bed bugs) and kairomones (host odor components) to tempt bed bugs to enter their trap.

The Verifi™ trap design is based on the idea that bed bugs have two basic search behaviors: host searching when looking for a meal, and harborage seeking after consuming a meal. When searching for a host, bed bugs use both CO2 and host odors as orientation cues. When searching for harborage, they use scents associated with groups of other bed bugs, called aggregation pheromones. The good folks at FMC claim to have identified and produced two lures that effectively mimic host odors and aggregation pheromone. The aggregation pheromone is cleverly vented through one side of the trap to lure bugs into a dark harborage area. The kairomone and CO2 canister are designed to lure bugs into a pitfall trap. When the trap is checked by a PMP both harborage and pitfall sections of the trap can be observed to detect and monitor bed bug activity.

Data presented at the meeting by university personnel who tested a trap prototype in field situations looked promising.  One of the major advances that FMC seems to have made is in the technology needed to provide a slow release of attractants used in the lures. One of the big questions I was left with, however, was cost.  A lot of engineering has gone into this trap and cost will certainly be a factor. Nevertheless, I hope the industry will put this product through the most rigorous testing protocol--the real world--when it comes out in 2012.

Unfortunately for science, discovery of compounds that are attractive to bed bugs is a lucrative, and therefore often secretive, activity. For this reason, FMC is not sharing its “secret attractants” with others. Even some university researchers, like Emma Weeks (University of Florida), who is working on bed bug aggregation pheromones, are remaining tight-lipped about their research results until the research, and presumably patents, are published.  Weeks reported finding some 21 compounds that were active in attracting bed bugs to filter paper.  Meanwhile, until more is known and better options come around, we should all work on our visual bed bug inspection skills, perhaps the most basic and indispensable monitoring technique of all.

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