Thursday, December 6, 2012

Entomology in Knoxville: Bed bugs, Ants and Others

Bed bugs remained one of the most frequent subjects of
new research reports at the annual ESA meetings.
Continuing my earlier report on goings on at the Entomological Society of America's annual conference...

Total release foggers

In addition to health-related papers, urban entomology sessions covered many practical aspects of pest control. North Carolina State's Coby Schal, one of the top guns in urban entomology, reported on the first field study of total release foggers (bug bombs) for cockroach control. You may have heard of a parallel study done this year by Susan Jones at Ohio State University. She conducted a set of laboratory experiments with total release foggers (TRFs) against bed bugs, the results of which she recently spoke about on PCT's multimedia website.  She found that field collected strains of bed bugs were essentially immune to three common over-the-counter pyrethroid TRFs, and that even highly pesticide susceptible lab strains were largely able to survive when give basic cover as simple as a piece of paper.

Schal pointed out that TRFs are frequently misused by the public, causing four to eight home explosions per year in New York City alone. His lab looked at the impact of two TRFs on both naturally occurring cockroach populations and on "sentinel" cockroaches (lab reared cockroaches contained in open, escape-proof containers) placed in multiple locations in the treated apartments.  While the foggers did kill the pesticide-susceptible, lab-reared cockroaches, they provided little to no control of wild cockroaches (with 200-fold resistance to pyrethroids). In some treated apartments wild cockroach populations actually increased during the test. It will be interesting to see if the U.S. reevaluates registrations for TRFs in the next few years given the safety issues and dismal data coming out of university labs around the country concerning their use.

Bed bug repellents?

Conventional wisdom suggests that there are no repellents that can be sprayed on the skin to prevent bed bugs from taking a blood meal. However Changlu Wang, of Rutgers University, says "not so fast". He looked at the problem from a different angle, pointing out that there are two possible uses for repellents. Besides the traditional use of repellents applied to the skin to keep insects from biting, repellents may also be used off-host to keep bed bugs from climbing onto beds, suitcases, or other inanimate objects.  

Wang and colleagues looked at this second use. They chose several repellents including DEET, permethrin, picaridin, isolongifolenone, and other potential repellents. Although several products showed repellency, DEET was the overall winner. At 10% and 25% concentration, bed bugs were repelled from Climbup Interceptors (guarding a table with a CO2 lure) for 9 hours and 2 weeks, respectively.  While the practical use of repellents in the real world needs more experimentation, this is useful information.  DEET could conceivably be used as a repellent on some shoes (it does dissolve some plastics, so user beware) or booties to reduce the risk of hitchhiking bed bugs being picked up by technicians (or researchers!).  I expect that eventually bed bug control will be supplemented by the use of repellents as a quarantine tool or for "push-pull" tactics to get bed bugs to go where we want them to go (say, to treated harborages).  Wang cautioned that bed bug behavior may be different around a host where attraction to a live host may overcome the repellent effects he saw.

Standardized bed bug testing

One of the biggest applied bed bug research challenges today is how to standardize insecticide testing. It is common knowledge that results for nearly any insecticide can be fairly easily manipulated by selecting the right strains and using protocols that show more or less bed bug mortality. The challenge is to find protocols that are more or less predictive of a product's performance in the field. Mark Feldlaufer, with the U.S. Department of Agriculture/ARS, reported on progress being made to verify fair, standardized testing methods. This research will support the EPA in its efforts to develop standardized test protocols.

He noted that there are currently 318 insecticide formulations registered for bed bug control, 90% of which include pyrethroid insecticides. He noted that not all pyrethroids are equal, and cited as an example transfluthrin (currently unregistered in the U.S.). Transfluthrin has a high vapor pressure, which most PMP realize is likely to provide better control in difficult to reach areas like voids and crevices.  He also noted that a new combination product (metofluthrin plus clothianidin) is in the insecticide pipeline for bed bugs.

Among the USDA findings were that male and female bed bugs are approximately equal in insecticide susceptibility. This finding could allow researchers to use only one sex in tests (avoiding mortality problems with  traumatic insemination by males on females) rather than the 50/50 ratio currently recommended. Also, test results did not significantly change after seven days, suggesting that tests could be terminated after this time.

How to classify and handle insecticide exposed bed bugs is an issue for anyone who has conducted bed bug trials. USDA classified insecticide-exposed bed bugs as alive (A), dead (D), or morbid/moribund (M/M).  The latter group consisted of bed bugs that were not completely dead, but did not behave normally or respond normally to probing. They found that if placed on untreated surfaces after exposure, between 7 and 77% of the moribund bed bugs recovered compared to 100% mortality of M/M bed bugs left on treated surfaces. This information should be useful in helping EPA decide how to require M/M to be handled. It is fascinating, and alarming, how slight differences in the way test subjects are handled and classified can dramatically influence test results.

Other interesting reports

  • Susan Jones (Ohio State) reported positive results controlling bed bugs with a new neem formulation (CIRKIL), which, PCT magazine reports, will be available in the U.S. this fall.
  • Joe DeMark (Dow AgroScience) reported on field testing of a new Recruit AG above ground bait station for termites. This product will carry 254 grams (one pound) of bait matrix per station. Of nine sites on which it was tested, all termite colonies were determined to be eliminated within four months.
  • Mike Rust (University of California, Riverside) reported on studies with the Turkestan cockroach, a species spreading throughout the southwestern states (CA to TX). They found that the Turkestan cockroach is better adapted to dry situations than the oriental cockroach, especially at higher temperatures, and may be expected to displace Oriental cockroaches in hot, dry situations.
  • Karen Vail (University of Tennessee) tested insecticides on odorous house ant.  She found fipronil provided slightly superior control to Talstar, and she observed 2-4 weeks control with the new Arilon insecticide (indoxacarb).  She also found that sprays applied with backpack sprayers targeting ant trails and structural guidelines (gutters, ledges, etc.) were as effective in controlling ants as high-volume power sprays.
  • Dini Miller (Virginia Tech) reported that a 2011 National Apartment Association survey found bed bugs as the number one concern among apartment owners (beating out concerns over property taxes). Besides control expenses, additional costs due to bed bugs include carpet wraps (to contain bed bugs on infested carpets during removal), need for heavier duty paint (to better cover fecal spots on walls), delays in rental payments, increased evictions, more abuse from residents, and loss of reputation in the community. Twenty states now have laws addressing responsibility for treatment costs for bed bugs.
  • In a study reported in the May 2012 issue of Infection Control and Hospital Epidemiology, researchers from Nebraska tested the effectiveness of chlorine dioxide gas as a fumigant for bed bugs. You may remember chlorine dioxide as the gas used in US governmental facilities after the 2001 anthrax attacks. It proved to penetrate cracks and crevices well and kill bed bugs effectively. Chlorine dioxide is used in hospitals for germ control and might find a niche use for battling bed bug infestations in medical settings.
  • Margie Lehnert, Clemson University, described a simple but (I thought) ingenious technique for studying bed bug population dynamics. She used nylon stockings inside a HEPA vacuum hose attachment to collect small bed bug aggregations in infested apartments. Once an aggregation is sucked up, the stocking can be removed and tied off and returned to the lab for counting. In this way Lehnert has developed a powerful tool to study population patterns and, perhaps, better infer reasons for bed bug dispersal away from beds. 
  • Chris Keefer, Texas A&M University, presented some of the first data I've seen on the invasive, and difficult to control, dark rover ant. This ant is thought to have entered the U.S. from Argentina in Louisiana in 1978. It is now common through most of the southern states.  Keefer, after some difficulty,  has figured out how to colonize these ants in the lab. Using his lab ants he was able to compare the effectiveness of three baits: Terro PCO gel (98% control), Advance Ant Gel (88% control) and Advance Granular Bait (large granules) (58.81% control). The best residual insecticide treatments he found during an outdoor field trial were Demand CS and Temprid, which gave 84% and 82% control, respectively. This confirms what I've heard some PMPs say about effective treatments for these ants.
Of course much more went on in Knoxville than I can report (curse those concurrent sessions!). If I've done no more than convey how exhausting it is to sit for 50 paper sessions (my count), I've given you a taste of what it's like to be there.  Next year's meetings are scheduled to be in Austin, TX, so I encourage some of my Texas colleagues to consider attending. This year the ESA planned a special event for PMPs, including an ACE prep class. Stay tuned for PMP programs for 2013.

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