Many pest problems occur in homes. Among them, cockroaches and rodents are two of the most frequently reported pest problems. The German cockroach, Blattella germanica (L.), is a carrier of varied pathogens (Elgderi et al. 2006). Rodents cause property damage and food contamination. Both cockroaches and rodents produce allergens that are an important trigger for indoor allergy and asthma (Rosenstreich et al. 1997, Huss et al. 2001, Berg et al. 2008, Matsui 2009). In addition, bed bugs emerged as a new problem in many communities the past 10 to 15 years.
Historically, conventional insecticide spray treatments caused development of insecticide resistance among cockroach populations. Resistance to pyrethroids and other pesticides such as DDT, diazinon, and malathion have been reported in previous studies (Collins 1973, Umeda and Hirano 1988, Scott et al. 1990). Compared to conventional chemical treatments, gel baits and Integrated Pest Management (IPM) are preferred for cockroach management in apartments nowadays. In a study by Sever et al. (2007), the median cockroach count from sticky traps in apartments treated by researchers using gel bait decreased from 426.5 to 0 in six months. In contrast, the median cockroach count decreased from 308.5 to 56 in apartments treated by commercial contractors using hydramethylnon gel baits, insect growth regulators and pyrethroids; and increased from 205.5 to 285 in the non-treated control group. In a study conducted by Wang and Bennett (2006), IPM and bait-only treatments reduced cockroach trap counts during a short period (16 weeks) by 100% and 94.6%, respectively.
In spite of the highly effective cockroach management tools and methods that are available, German cockroach infestations remain prevalent in apartment buildings. Why are they so prevalent? How do we achieve a high level of elimination? In this study we investigated the prevalence of pests and evaluated a community-wide cockroach IPM program in a low-income community over a seven-month period.
MATERIALS AND METHODS. The study site was an apartment complex managed by New Brunswick Housing and Redevelopment Authority (New Brunswick, N.J.). The occupants consisted of low-income families or seniors. The complex contained 258 units within 40 buildings. As with many other low-income communities in New Jersey, this community had disproportionately higher pest infestations. The existing pest control provider hired by the housing authority came once a month to control pests based on a list of resident complaints provided by the management office. They would apply gel baits in kitchen cabinets for cockroach control and place glueboards for rodent control. If residents were not at home at the time of the visit, the pest control technician would not enter the apartments. Based on our conversation, only about two tubes (60 grams) of cockroach bait was used per month. About two technicians spent half to one day a month to service the whole complex. We conducted community-wide household pest surveys in October 2015 and May 2016. A total number of 225 and 205 apartments were accessed during the two surveys, respectively. Some apartments were not accessed because they were vacant, had private locks installed by tenants, or the tenant refused our access. During the initial survey, tenants who had ongoing indoor pest issues were asked the following questions: 1) Do you see any of the following pests in your apartment (rodents, cockroaches, bed bugs)? 2) Have you used pesticides to control pests in the past half year? 3) Are you satisfied with the pest control service provided by housing? To evaluate the program’s effectiveness, we asked the same questions to the same group of residents at the end of the study if the residents were at home. We also visually assessed the sanitation level (clean, normal, dirty) and clutter level (low, medium, high) in the kitchen of each these apartments in October 2015 and May 2016.
We inspected signs of bed bug infestation in bedrooms and living rooms. Apartments with bed bug infestations were recorded. If signs were present but no live bugs were found, ClimbUp insect interceptors (Susan McKnight, Inc., Memphis, Tenn.) were installed under bed and sofa legs, and inspected approximately two weeks later.
Trapper monitor & insect traps (1/3 of the whole piece) (Bell Laboratories, Madison, Wis.) were placed in every apartment with confirmed or suspected cockroach infestation. Six traps (labeled as 1-6) were placed in certain locations in the kitchens and bathrooms and checked 1-4 days later, depending on our schedule and availability of housing staff for assistance in accessing the apartments. The locations of the six monitoring traps were: 1) kitchen cabinet under the sink, 2) kitchen cabinet above the sink, 3) under the stove, 4) behind the refrigerator, 5) on the kitchen floor next to the heater or trash can, and 6) behind toilet in the bathroom. All cockroach trap counts were adjusted to one-day counts during analysis.
IPM IMPLEMENTATION. We provided one-page brochures on cockroach prevention and control, pesticides and human health and home pest control. During home visits, we orally instructed residents to clean the floors, reduce clutter, put away pet food during the night, and stop using pesticides by themselves.
All infestations with 10 or more cockroaches in monitoring traps during the first survey were treated with Advion cockroach gel bait (Syngenta Crop Protection, Greensboro, N.C.) and Borid boric acid dust (FMC Corporation, Philadelphia). Cockroach bait was applied mostly in kitchens and bathrooms where most cockroach activities were present. Boric acid dust was applied using a duster behind the refrigerator, stove and toilet. The average amount of bait and boric acid dust applied per apartment during the initial treatment was 20 grams and 6 grams, respectively. The amount of insecticide used was based on the severity of the infestations. We swept the area around the refrigerator using a broom before applying boric acid dust if it was dirty.
For light infestations (with 10 or fewer cockroaches in monitoring traps), we used mass trapping instead of bait and insecticide dust. Six traps were placed in the same locations as the monitoring traps, and four more traps were added to the kitchen counter, closet in the living room beside the kitchen, and refrigerator.
We monitored the results by visiting each cockroach-infested apartment approximately every two weeks. On the first day, traps were placed following the same protocol as before. On the second day (or fourth day based on previous visit date), traps were examined and discarded. Additional treatments (baiting, dusting, placing new traps) were made depending on trap counts. If trap count was zero, then the traps were left continuously in the apartments for detecting very low level infestations. Cockroach elimination was considered achieved when there were no cockroaches in traps during a one-month trapping period. The follow-up monitoring and re-treatment lasted 25 weeks. All treatments were carried out by licensed Rutgers University researchers.
The existing pest control provider hired by the housing authority provided bed bug and rodent control. The contractor visited the infested apartments on a monthly basis based on the list provided by the housing staff. They used Transport Mikron (active ingredient: acetamiprid, bifenthrin) to treat bed bugs and rodent bait or glueboards for rodents. We advised the housing authority to request that the contract adopt more effective IPM strategies for managing bed bugs and rodents. A short list of cost-effective, non-chemical and chemical bed bug control methods was provided to the contractor. But these recommendations were not adopted based on our observations.
RESULTS. Based on interviews and examination of monitoring traps at 0 month, German cockroaches are the No. 1 pest. A total of 62 apartments (28%) had German cockroaches. Rodents and bed bugs were the second and third most common household pests. Residents from 24 apartments (11%) reported rodent issues. A total number of 17 apartments (8%) were infested with bed bugs. Considering the fact that many tenants were not home during our visit, the actual rodent infestation rate should be higher. During our cockroach treatments, rodent infestations were either found by the sticky traps or through complaints by the residents in 14 out of 64 (22%) treated apartments. Among those 14 apartments, 11 were not found during our first survey. Ants were extremely common indoor insects based on examination of cockroach traps, but only seven residents (3%) mentioned ant issues in our survey. It was apparent that residents were not concerned about ants as much as other pests. Only one resident complained about termite issues in his house.
A total of 64 apartments were treated for cockroaches. This includes the initial 62 identified apartments and two more apartments that were subsequently added during the treatment process upon request by tenants at week 9 and 19. After our treatment, the average cockroach count (one-day trapping period) per apartment decreased rapidly (see Fig. 1). The mean count was reduced by 64, 84, 96, 97, and 100% at week 2, 4, 7, 9, and 29, respectively. During the 7-month period, an average amount of 35 grams of bait (1.2 tubes) and 35 grams of dust were used in each treated apartment. The average time spent per apartment per visit (including the time between apartments) ranged from 11 to 14 minutes (two researchers worked together most of the time) and was relatively constant throughout the study period.
During our 7-month survey, 16 apartments were identified with cockroach infestations. Among them, 10 were newly found infestations and six were treated by us but were never eliminated. Out of the 10 new infestations found during the 7-month survey, five of them were not accessible during the 0 month survey. Therefore, the initial survey failed to identify 7% (5 out of 69) of the infested apartments. Among the 64 units that were treated, cockroaches were eliminated in 46 apartments, 8 apartments still had cockroaches, and 12 apartments were not inspected during the final survey due to lack of access. The confirmed elimination rate was 85% (44 out of 52).
After 7 months, 9 apartments had bed bug infestations (47% reduction), and 20 apartments had rodent infestations (17% reduction). These numbers suggest that the bed bug and rodent control methods were ineffective.
We were able to interview the same 21 residents both at 0 and 7 months. At 0 month, 91% of the residents treated cockroaches using over-the-counter pesticides including sprays, insect bombs, baits, and dusts; only 29% of the residents were satisfied with the existing pest control service provided by the management office. At 7 months, 14% of the residents still saw traces of cockroach activity, only 19% of them used pesticides by themselves after we initiated the IPM program, and 91% of the residents were satisfied with our cockroach control service (see Fig. 2).
We compared the sanitation and clutter levels at 0 and 7 months in the 21 apartments. Five apartments showed some improvement in sanitation or clutter levels, 5 apartments became worse, 9 apartments were similar as before, and 2 apartments were not evaluated. Overall, the education did not significantly improve the sanitation and clutter level in the residents’ apartments.
DISCUSSION. The community-wide cockroach IPM program reduced cockroach counts by 96% at the fourth visit (7 weeks after initial treatment), which is similar to previous studies in low-income communities (Wang and Bennett 2006, Wang et al. 2013). By providing effective pest control the percentage of residents who used pesticides reduced by 79% (from 91% to 19%), resident satisfaction increased by two times.
However, complete cockroach elimination for the whole community is hard to achieve. After 7 months, cockroaches were never eliminated in a few apartments, and new infestations were found. Lack of cooperation was the major obstacle in eliminating cockroach infestations on a community-wide scale. Below are some factors that contributed to the failure in cockroach elimination:
NO ACCESS TO APARTMENTS. During our treatment, 12 out of 64 apartments were not accessible for at least one visit. Failing to access apartments caused a delay in our treatments.
Lack of housekeeping cooperation. Despite our education on the importance of cleaning, some apartments were still dirty and cluttered at the end of the treatment. In a few apartments, structural damage, such as broken cabinets or leaking pipes, provided an ideal environment for cockroaches. They were sometimes not repaired in a timely manner.
MISSING MONITORING TRAPS. Disturbed or lost monitoring traps were a common problem. Disturbed traps were usually found relocated, flipped, flattened, or wet. According to tenants’ reports, some traps were thrown away because children and pets played and chewed on them, or live mice were caught in them. When using sticky traps as monitoring tools in apartments such factors should be considered when deciding where to place them.
CONCLUDING REMARKS. While pest management faces many challenges in low-income communities, most roach infestations (85%) were able to be eliminated by adopting a community-wide IPM program in a 7-month period in our study. The majority of the cockroach populations (97%) were eliminated after just four visits. Follow-up monitoring is critical in confirming elimination success. A community-wide pest survey is valuable for identifying new and missed infestations.
The low elimination rates in rodent and bed bug infestations suggest the pest control provider should adopt similar IPM strategies as our cockroach control program. Implementation of a more effective IPM program changed residents’ behavior and attitude towards pest control. On the other hand, the effect of education on sanitation and clutter was not as effective, suggesting other measures must be taken to change residents’ behavior towards sanitation and clutter.
Acknowledgements: The authors thank Syngenta Crop Protection for donating gel baits. Staff from the New Brunswick Housing and Redevelopment Authority provided biweekly assistance in our field visits. This study was sponsored by a Community-University Research Partnership grant from Rutgers University.
The authors are from Rutgers University. Chen Zha and Desen Wang are Ph.D. students, Changlu Wang is associate extension specialist, and Amanda Eiden is a postdoctoral student. Email them at firstname.lastname@example.org.