3.1. Efficacy of Alpine Aerosol in Laboratory Assays
In the direct spray bioassay, Alpine aerosol caused 93.2 ± 1.7 and 100.0 ± 0.0% mortality in bed bug nymphs at 7 and 10 d after treatment, respectively (
Figure 2). The mortality in the untreated control after 10 d was 3.3 ± 1.7%. Five-minute exposure to dry residue caused 91.6 ± 8.3, 91.6 ± 8.3, and 95.0 ± 5.0 % mortality to bed bug nymphs at 7, 10, and 14 d after treatment, respectively (
Figure 2). No mortality occurred in the untreated control after 14 d.
Figure 2.
Efficacy of Alpine aerosol against Indy strain bed bugs in direct spray and dry residue exposure bioassays.
Figure 2.
Efficacy of Alpine aerosol against Indy strain bed bugs in direct spray and dry residue exposure bioassays.
Direct spray of Alpine aerosol caused 91.3 ± 4.3% mortality of bed bug eggs (
Figure 2). No egg hatching occurred after 7 d. Only 58.0 ± 30.0% of the hatched nymphs survived at 14 d after treatment. All eggs in the control group hatched and 98.7 ± 0.8% of the hatched nymphs survived at 14 d after treatment of the eggs. The bed bugs collected from the study apartments and the Indy strain bugs used in the bioassays had similar levels of resistance to deltamethrin in a separate experiment [
19]. In that experiment, bed bugs were directly sprayed with 0.06% Suspend SC (a.i. deltamethrin) at 4.07 mg/cm
2 under a Potter spray tower. The bed bugs collected from the study apartments and the Indy strain bed bugs suffered 29% and 35% mortality at 7 d after treatment, respectively, compared to 100% mortality in laboratory susceptible strain at 2 h after treatment. More than 90% mortality in Indy strain bed bugs by Alpine aerosol in the current study suggests the effectiveness of alpine aerosol in controlling pyrethroid resistant bed bugs.
3.2. Effectiveness of a Reduced-Risk Insecticide based Bed Bug Management Program in Low-Income Housing
Many units did not have bed frames to support the box springs and mattresses or the furniture legs were too large to install interceptors directly under the legs. In these units, interceptors + visual inspection provided more meaningful and accurate counts at each visit (
Figure 3). However, total number of bed bugs found in interceptors or visual inspections during the entire study period for each apartment are also presented (
Figure 4). Bed bugs found in the interceptors or visual inspections were both removed from the apartments or killed with steam or Alpine aerosol.
Figure 3.
Bed bug count reduction (Climbup interceptors + visual inspection) in nine apartments after implementation of the bed bug management program.
Figure 3.
Bed bug count reduction (Climbup interceptors + visual inspection) in nine apartments after implementation of the bed bug management program.
The initial median (minimum, maximum) combined bed bug count based on interceptors and visual inspection of the nine apartments was 29 (1, 1,428). Four apartments were heavily infested (with ≥ 91 bed bugs). We spent a median (minimum, maximum) of 9 (4, 30) h to monitor and treat each infested apartment over the study period. A total of 283 g Alpine dust and 1,265 g Alpine aerosol were used in the nine apartments. Interceptors caught an average of 212.0 ± 90.2 bed bugs, whereas, visual inspections found 518.0 ± 240.4 bed bugs per apartment during the entire study (
Figure 4). The IPM program was highly effective in reducing bed bug numbers. It resulted in an average of 96.8 ± 2.2% reduction in bed bug counts (
Figure 3). However, elimination of bed bugs was only achieved in three apartments (Apartment 6–8) which had a low (1 to 29) number of bed bugs at the beginning (
Table 1). The 9th apartment had low bed bug numbers at the beginning and still had two bed bugs at the end of the study. This unit was enrolled late and only received service for 6 wk. The four heavily infested apartments (Apartment 1–4) still had a few bed bugs even after 5.5–6.5 months’ service. Apartment 5 had only 20 bed bugs (interceptor count 17, visual count 3) during the initial inspection. However, the resident was recently moved in from a heavily infested unit when the unit was enrolled in this study. During one month post-treatment inspection, we found 125 bed bugs hiding in unpredicted areas such as book shelves, in cracks of tables, inside plastic totes, and on a picture frame. We suspect that the failure to eliminate bed bugs in this apartment was mainly due to the very scattered bed bug distribution resulting from the recent relocation of the resident’s infested belongings.
Table 1.
Effectiveness of a bed bug management program at low-income housing
Table 1.
Effectiveness of a bed bug management program at low-income housing
Apartment no. | # occupants | # Climbups | Observation period (months) | Total treatment time (h) | Cooperation level * | Bed bug counts 1 |
---|
Initial | Final |
---|
1 | 4 | 40 | 6.5 | 30 | 2 | 1,285 | 2 |
2 | 6 | 28 | 6.0 | 24 | 2 | 342 | 7 |
3 | 2 | 22 | 6.5 | 21 | 3 | 1,428 | 4 |
4 | 4 | 18 | 5.5 | 13 | 3 | 478 | 7 |
5 | 1 | 21 | 3.5 | 9 | 1 | 20 | 1 |
6 | 6 | 21 | 1.0 | 6 | 3 | 29 | 0 |
7 | 3 | 31 | 2.0 | 5 | 1 | 1 | 0 |
8 | 5 | 16 | 1.5 | 4 | 3 | 26 | 0 |
9 | 3 | 21 | 1.5 | 7 | 3 | 10 | 2 |
Figure 4.
Total number of bed bugs counted from Climbup interceptors or visual inspections for each apartment during the entire study period.
Figure 4.
Total number of bed bugs counted from Climbup interceptors or visual inspections for each apartment during the entire study period.
The results achieved in this study are comparative to bed bug reduction and elimination rates reported in other IPM studies [
3,
7,
8]. Wang
et al. [
3] reported bed bug reduction by 97.6 ± 1.6 and 89.7 ± 7.3% in the diatomaceous earth dust-based IPM and chlorfenapyr spray-based IPM, respectively. Bed bugs were eradicated from 50% of the apartments in each group after 10 wk. In a more recent study, the IPM program consisting of non-chemical treatment and 0.075% Temprid SC (imidacloprid and cyfluthrin), Tempo dust (1% cyfluthrin) or diatomaceous earth dust eliminated bed bugs from 44% of the apartments and reduced bed bug counts by 99.9% [
7]. Wang
et al. [
8] evaluated another IPM program consisting of non-chemical treatment and chemical treatment (Tempo dust and Alpine aerosol). Bed bugs were eliminated from 25% of the apartments and bed bug counts were decreased by 92% over 12 wk. Our IPM program also resulted in a similar (96.8%) level of reduction compared to an insecticide only study reported by Potter
et al. [
6] (95.6%). Moreover, we achieved these results with a 96% reduction in pesticide usage compared to their study. Similarly, the current study reduced pesticide use by 94% compared to chemical only treatment in another study conducted in eight one-bedroom apartments in a high rise building [
20].
All of the previously reported bed bug IPM studies [
3,
7,
8] were conducted in studio or one-bedroom apartments with only one or two adults occupying each unit. What makes our study unique is that it was carried in family-style housing which is not only larger, but also presents a variety of different obstacles including, more beds, occupants, children and pets. Still we only used an average 172 g of formulated reduced risk-pesticide per apartment, much less than used in studies in smaller apartments but achieving similar levels of control.
Interception devices are typically thought of as a monitoring tool for the detection of bed bugs. However, in our study, interceptors caught an average of 43.7 ± 11.4% of the total bed bugs (interceptor + visual) found per apartment (
Figure 4). In separate studies, Wang
et al. [
3,
8] demonstrated the effectiveness of bed bug interceptors in reducing bed bug numbers. To what degree, interceptors contributed to overall population reduction is unclear and was not specifically measured in this study, however, we do believe that interceptors should be viewed not only as a detection tool but also as an important part of the IPM program from a control perspective.
Pre-treatment interviews show 100% of the residents (n = 9) in the infested units were bothered by bed bug bites. The majority of residents described bed bug bites as itchy, painful, and caused loss of sleep. At the end of the project, nobody complained about bed bug bites despite the presence of low numbers of bed bugs in six apartments. All surveyed residents were satisfied with our service and level of control and hoped their apartments would continue to be inspected periodically for bed bugs. None of them used pesticides since we started this project. All residents indicated they learned some non-chemical methods for preventing or controlling bed bugs.
The quality of the bed bug program was compromised by lack of cooperation by both the residents and property management. Only two out of nine residents were fully cooperative. For example, during each visit, bed bug infested bed linens and sheets were bagged and residents were asked to launder them. The majority of the residents did not launder and continued using infested sheets and linens from bags. Property management failed to provide encasements for all beds as initially agreed upon and did not provide access to all apartments during scheduled visits. These are some of the limitations associated with research in low-income housing, which makes the cooperative relationship required in a true IPM program challenging [
7]. The results of this and previous studies suggest that while high level population reduction is possible with little cooperation from residents and management, the same is not true for successful elimination of bed bug infestations. Lack of cooperation contributes to slow elimination even with the best treatment efforts. Other challenges encountered in this study were: (1) presence of old furniture with many cracks, crevices, and holes; (2) lack of a bed frame to support the mattresses and box springs; and (3) relocating infested furniture within an apartment. The financial constraints, physical or mental challenges, and culture of the residents contributed to these conditions. No cooperation from residents in five out of nine apartments suggests our education did not significantly alter the residents’ level of cooperation during the study period (
Table 1). Surprisingly, we did not find signs of bed bug infestations in the six apartments adjoining to the four heavily infested units after two consecutive biweekly inspections using interceptors and visual inspections. Wang
et al. [
4] found that 45% of the apartments in a high rise building became infested within 41 months of the first confirmed bed bug introduction and 53% of apartments adjacent to infested apartments had bed bugs. Among the infested apartments, an average of six bed bugs was detected dispersing through apartment entry doors every 4 wk. The lack of dispersal observed in our study might be due to the differences in building structure. There were only one or two adjacent units for each apartment in this study.
Our study indicates infestations can be significantly reduced and sometimes eliminated without using large amounts of pesticides and that efficiency of elimination also appears to be associated with the extent of the infestation. Apartment (6–8) had low (1 to 29) number of bed bugs at the beginning. It took less than 2 months to eliminate bed bugs from these three units. In contrast, infestations in apartments with initial counts over 300 bed bugs (Apartment 1–4) were still not eliminated even after 5.5–6.5 months of service (
Table 1). These four apartments had 16 to 86 bed bugs at two months after initial treatment (
Figure 3). Although the sample size is small, the data clearly suggest the time required to eliminate an infestation is closely related to the infestation levels. Multiple visits and treatments are necessary to eliminate high level infestations. Similar findings were reported by Wang
et al. [
3] and Potter [
15]. Therefore, proactive monitoring to identify unreported or new infestations is very important to prevent low level populations from becoming heavy infestations and to minimize the spread of bed bugs.