[University Research] Is there a new bed bug answer?

Throughout history, bed bugs have been squirted and sprayed with everything from alcohol to arsenic. Mercury, kerosene and gasoline were also used, and more than a few people died and buildings burned in the process.

Most of the early bed bug killers had no residual action. Sprays had to be applied repeatedly in order to contact the insects directly — a process which was both difficult and inefficient. That changed in the 1940s with the discovery of DDT. For the first time, bed bugs residing in hidden locations and nymphs hatching from eggs succumbed after resting or crawling on previously treated surfaces. One application normally did the job, and re-infestation was unlikely since the residual effect lasted several months or years. When bed bugs displayed resistance to DDT in the 1950s, residual products like malathion, diazinon and lindane were effective replacements. Provided spraying was thorough, a single application usually was successful and the bed bug threat all but vanished.

DEPLETED ARSENAL. The regulatory restriction of organochlorine, organophosphate and carbamate insecticides has diminished our options for dealing with today’s bed bug resurgence. In terms of residual indoor sprays, most of what’s left is pyrethroids. While pyrethroid insecticides are efficacious against many pests, results against bed bugs have been inconsistent due to high levels of resistance in some field populations within the United States (see “Insecticide-Resistant Bed Bugs: Implications for the Industry,” PCT July 2007). The specter of bed bug resistance is especially worrisome because we have few alternatives today, underscoring what can happen when pests resurface after entire classes of insecticide are removed from the market.

ENTER PHANTOM. BASF’s Phantom (chlorfenapyr) has been used in recent years to control such pests as cockroaches, ants and termites. To our knowledge, it is the only water-based residual spray labeled for bed bugs with a different mode of action from a pyrethroid. Phantom has been evaluated against bed bugs in the laboratory by the University of Kentucky and others. Results of these lab studies have shown the product to be lethal but relatively slow acting, often taking a week or two to cause high levels of mortality. On the other hand, bed bugs did not avoid Phantom residues, and when we exposed pyrethroid-resistant bed bugs to chlorfenapyr most died, suggesting Phantom could be an effective management option (Romero, unpublished data). The logical next step was to evaluate Phantom in a rigorous, real-world setting — bed bug-infested apartments.

FIELD TRIAL. In 2007, 15 bed bug-infested apartment units in Cincinnati, Ohio, were identified and selected for treatment. Four of the units were located within the same apartment building, three were from another building, two units each were from two other buildings, and the remaining four were from separate buildings around the city. Only two of the 15 infested units were located on the same floor within the same building.

Most of the apartments were rented by tenants in the low- to mid-income range. Each unit was thoroughly inspected before initial treatment, recording numbers of live bed bugs (adults and nymphs) residing on beds, furniture, floors, walls, ceiling and other locations. Pretreatment infestation levels varied from a low of six live bed bugs found in one apartment unit to more than 1,000 found in another (five units had initial pre-treatment counts of 22 bed bugs or less, five had 27 to 99 bugs, and five had 155 to 1,076). Adjoining units were also inspected and treated if necessary in a manner similar to the test units.

Prior to treatment, residents were asked to remove, bag and launder bed linens and clothing. Some tenants complied with this request while others did not. Tenants were not asked to disassemble beds or dispose of bed bug-infested mattresses, box springs, couches or other belongings. One tenant did throw out a heavily infested bunk bed and another disposed of a moderately infested couch. While throwing out infested items is sometimes advisable, it can be financially impractical for residents, including many of those involved in this study. Retaining infested beds, couches, etc., further allowed us to determine if they could be successfully treated with Phantom. No bed encasements were installed on mattresses or box springs while insecticide treatments were being evaluated.

All 15 apartments were treated with Phantom (0.5 percent chlorfenapyr) as the sole liquid insecticide. Applications were made according to label directions, targeting areas where bed bugs were found or likely to crawl or hide. This included seams, folds, edges and crevices of mattresses, box springs (including beneath dust covers), bed frames and headboards; along and beneath baseboards and molding; seams, folds, and crevices of upholstered chairs, couches and wood furniture (excluding surfaces where people are prone to laying or sitting); ceiling-wall junctures; and behind wall-mounted objects such as mirrors and picture frames. The average amount of Phantom applied per apartment on the initial service was 0.4 gallon (between 0.25 gallon and 0.75 gallon), whereas follow-up applications averaged 0.25 gallon (between 0.06 gallon and 0.5 gallon). Nine of the 15 apartments also received limited initial treatment with Bayer Environmental Science’s Drione (silica gel plus pyrethrins). The only areas receiving this desiccant dust (about a hand-duster’s worth) were behind outlets and switch plates, and under baseboards/carpet edges. No Drione was applied to the bed complex, upholstered furniture or elsewhere in the apartment. One unit also inadvertently received a single treatment with MGK’s Bedlam (d-phenothrin plus synergist).

Several follow-up inspections were made of each apartment. Inspections were performed bi-weekly or monthly depending on the severity of the infestation and the service schedule arranged with the client. Additional Phantom applications were made as needed, usually monthly. The number of live bed bugs found in specific areas was recorded on each service visit. (All inspections, counts and treatments were performed by Permakil Pest Control, Covington, Ky., and the authors, primarily W. Wickemeyer.)

TREATMENT OUTCOME. Successive inspections and treatments produced a slow but steady decline in bed bug numbers (see Figure 1). In 12 of the 15 apartments, live bed bugs could no longer be found 20 weeks (about five months) after initiation of treatment. Three apartments continued to have bed bugs (25, 39 and 59 adults and nymphs) beyond this period, although treatment in these units was hampered by excess clutter, lack of preparation and overall poor tenant cooperation. Compared to the total initial number of bed bugs found in the 15 apartments (2,719), a 78 percent overall reduction was observed after four weeks, 87 percent fewer bugs were found after eight weeks and 96 percent fewer after 12 weeks. However at the four, eight and 12-week evaluations, 14, 11 and 10 apartments, respectively, continued to have some live bed bugs. The seven apartments that received a follow-up inspection two weeks after initial treatment exhibited only a 49 percent overall decline at that time in bed bug numbers — further reinforcing the delayed action of the compound under field conditions. As is often the case with bed bugs, apartments with low-level infestations tended to be more efficiently managed than infestations that were severe.

Figure 2 summarizes the distribution of bed bugs found within all apartments. As expected, the greatest amount (73 percent), were associated with beds — close to what we found in an earlier apartment study where 70 percent of all bed bugs were associated with the bed complex (see “Battling Bed Bugs in Apartments,” PCT, August 2006). Substantially more bed bugs were found this time on mattresses (48 percent) than on box springs (6 percent), bed frames and headboards (8 percent) or bedding/bed skirts (11 percent). In the previous apartment study, more bugs were found on box springs (35 percent) than on mattresses (22 percent) or bed frames/headboards (13 percent). Clearly though, the bed complex is a top priority for treatment, whether with insecticides, vacuums, steam, cold, disposal or encasement. Couches and upholstered chairs yielded the next largest number of bed bugs (12 percent) followed by walls and ceilings (8 percent), and baseboard areas (4 percent). Other places where bed bugs were found in the study included dressers, nightstands, television stands, appliances, clothing, shoes, boxes and rehabilitation equipment. Some of these harborage sites were several feet from sleeping areas, underscoring the importance of inspecting well beyond beds.

LABEL INTERPRETATION. Phantom is labeled for indoor use as a low-pressure spot or crack and crevice spray to “breeding areas, nesting sites, hiding places, runways, and other places where pests are found or can infest.” Bed bugs are listed as a target pest on the label, although specific mention of where it is permissible to treat is subject to interpretation. Eighty-five to 90 percent of the bed bugs in our two apartment studies were found on bed components, couches and upholstered furniture — ironically, the same places that many of today’s insecticides are not to be used. Treatment of mattress seams, folds and edges is permissible with Phantom, but the label instructs not to make (general) surface applications to mattresses. No specific mention is made of treating box springs, couches or upholstered furniture, but according to the manufacturer (BASF), such items can be treated provided application is made with spot or crack and crevice treatments, and surfaces where people will be laying or sitting or are prone to normal human exposure must not be treated.

When using Phantom, it’s also important to remember that the label states not to reapply more often than every four weeks. When servicing more frequently (as is often the case with bed bugs), applicators will need to utilize other products or methods.

LESSONS LEARNED. It was encouraging to see that bed bugs could be reduced to low, often non-detectable levels under the challenging conditions of this study. Few infested items were discarded, and other useful tactics such as encasing beds, steaming and vacuuming were not employed. Moreover, Phantom was the only liquid insecticide used in order to delineate the effects of the product when applied by pest managers.

The field study supports observations in the laboratory that Phantom is slower acting than some other insecticides, including pyrethroids. Nonetheless, recent lab experiments by the University of Kentucky (Romero et al., unpublished data) indicate that the time in which bed bugs succumb to Phantom can vary depending on field strain, life stage and perhaps other factors. When adult bed bugs from seven different populations were exposed continuously to dry residues, some persisted for two or more weeks while other populations exhibited substantial mortality in less than 7 days. We have also observed that young nymphs emerging from Phantom-treated eggs typically die within 72 hours — substantially faster than older nymphs and adults. To hasten elimination, however, it still would be advisable to incorporate faster-acting chemical and non-chemical measures such as Sterifab (Noble Pine), Bedlam (MGK), Kicker (Bayer ES), ExciteR (Prentiss), pyrethrum-based aerosols, vacuuming, steaming, freezing, encasement or disposal.

Finally, it bears repeating that bed bugs in apartments can be maddeningly difficult to eradicate. Large numbers of people living in close proximity, perpetual turnover of tenants, guests and belongings, clutter, communal use of laundry facilities, and poor tenant cooperation are “worst case” for bed bug management. Because of these factors, there is no “standard” or “guaranteed” timeframe in which infestations can be eliminated. To achieve the reported outcome in this study, thorough inspections and repeated applications were made using quite a lot of insecticide. The amount of time spent in each apartment on the initial service ranged from one to two man-hours, with each follow-up service typically lasting an additional hour (sometimes much more). Actual time spent depended on the severity of infestation and amount of clutter and tenant cooperation.

Phantom may not be the “silver bullet” for today’s bed bug problem, but it’s ammo worth having considering the depleted state of the arsenal. Should resistance to pyrethroids become rampant, it could become more valuable.
 
All photos © M. F. Potter

Michael F. Potter and Kenneth F. Haynes are professors at the University of Kentucky. Alvaro Romero is a Ph.D. student at the same institution. Erich Hardebeck and Wayne Wickemeyer are vice president and service manager, respectively, of Permakil Pest Control, Covington, Ky. Funding for the study was provided by BASF Corporation. Potter can be reached at mpotter@giemedia.com.

References
Potter, M.F., A. Romero, K.F. Haynes and W. Wickenmeyer. 2006. Battling bed bugs in apartments. Pest Control Technol. 34(8): 44-52.

Romero, A., M.F. Potter, D.A. Potter, and K.F. Haynes. 2007. Insecticide resistance in the bed bug: a factor in the pest’s sudden resurgence? J. Med. Entomol. 44(2): 175-178.

Romero, A. M.F. Potter and K.F. Haynes. 2008. Insecticide-resistant bed bugs: implications for the industry. Pest Control Technol. 35(7): 42-46.