Action Thresholds and Residue Analysis for Integrated Pest Management In North Carolina Elementary Schools - Final Report

Disclaimer

This report was prepared by an EPA assistance agreement recipient and represents only the views of the author rather than EPA.

Principal Investigators

Dr. Coby Schal, Professor of Structural Pest Management, Department of Entomology, North Carolina State University, Raleigh, NC

Dr. Mike Linker, IPM Coordinator, Department of Crop Science, North Carolina State University, Raleigh, NC

Dr. Michael G. Waldvogel, Extension Specialist in Urban Entomology, Department of Entomology, North Carolina State University, Raleigh, NC

Report

The primary long-range goal of this project is to protect the health of children in the school environment from unnecessary exposure to pesticides that are used to control pests. We proposed to compare pesticide residues and the residues of cockroach-produced allergens that can exacerbate childhood asthma, in both conventional and IPM-based pest control services in public schools.

The first important discovery we made in this project was that it was extremely difficult to locate cockroach-infested schools. At first this was surprising to us because we had no such difficulties in earlier projects in public schools where we generated the preliminary data for this proposal. But it then became apparent that in the last 2–3 years, our School IPM Extension program—headed by Drs. Linker and Waldvogel, and implemented by Dr. Nalyanya—has had a significant impact on adoption of integrated pest management (IPM) principles in public schools throughout North Carolina. Most public schools have abandoned baseboard sprays of synthetic residual pesticides in favor of targeted, reduced-risk baiting programs. This, in turn, has dramatically reduced cockroach infestations. While this caused some initial delays in the conduct of this project, we were at the same time pleased to witness such rapid adoption of IPM in NC schools.

Dr. Godfrey Nalyanya, our research and extension associate, spent many days inspecting schools as far west as Asheville, east to Elizabeth City, and south to the Wilmington area. He finally identified several mildly infested schools that could be used in our research. The conventionally treated schools were in the Greenville area (Pitt County), whereas the IPM schools were in Wake County. We collected allergen and pesticide residue samples from 6 conventionally treated schools and 6 IPM schools. At each school we collected several samples from classrooms, kitchen and cafeteria. In total, 84 allergen samples were collected and cockroach allergen was extracted from each sample. Enzyme-linked immunosorbent assay (ELISA) determinations were initially delayed due to inconsistencies with an older lot of the allergen ELISA kits. These problems have been resolved and we will complete determinations of allergen concentrations within the next month. We will update this report at that time.

Pesticide residues were collected from baseboards and 90 cm above the baseboard (height of a child). Samples were collected in each school from the bathroom, main office, dining room, cafeteria, teachers’ lounge, and other areas such as hallways and classrooms. A sterile cotton ball was soaked in isopropyl alcohol and the cotton ball was then drawn repeatedly across a 100 cm2 surface with a latex-gloved hand. Each sample was extracted by sonication in acetone, reduced by rotary evaporator, and analyzed on a gas chromatograph. The identities of some peaks were confirmed by mass spectrometry.

In conventionally treated schools we found more propetamphos in surface swabs than any other insecticide, and it was found in all areas where it was regularly applied. Surprisingly however, propetamphos residues were also routinely recovered from almost all non-target areas that were sampled. Small amounts of acephate and chlorpyrifos were also recovered from sampled areas in the conventional schools.

In contrast to conventionally-treated schools, little pesticide deposits were found in schools under an IPM-guided service. Propetamphos residues were never recovered, and only one sample contained a small amount of acephate. Thus, environmental residues of the organophosphate pesticides acephate, chlorpyrifos and propetamphos were significantly higher in the conventionally-treated schools.

Our second aim was to gain an understanding of the relationship between trap catch and the level of the cockroach infestation, and to develop guidelines that relate trap catch to specific actions that should be taken by pest management professionals. We encountered significant problems in developing this objective. This research could only be carried out in cockroach-infested schools. Two problems arose: (1) As mentioned above, we are unable to locate heavily infested schools, and (2) the few schools that fit our criteria requested immediate remedies, pre-empting any research at these sites. Moreover, the small infestations that we found were always localized in the kitchens and not the classrooms. The only solution we could identify was to initiate this research in infested homes in the Raleigh area, and generalize results from the residential to the school environment. This was a reasonable approach, since most of our current cockroach management tactics were in fact developed in residential settings.

To this end, we recruited homes in Southeast Raleigh to participate in this study. However, it became apparent that the spatial distribution of infestations in residential kitchens differs markedly from infestations in school cafeterias and kitchens. The scale is much smaller (several m² vs. hundreds of m²), and the propensity to aggregate is much less. That is, in infested residential kitchens cockroaches are so widely dispersed, the space is so small, and the number of traps that can be used is so small that it is difficult to generate an algorithm that predicts bait use based on trap catch. We did, however, develop a satisfactory algorithm based on whole-apartment trap catch in 18 traps throughout the kitchen (6 traps), living room (6 traps) and one bedroom (6 traps), as follows:

Alogrithm of Required Treatment Amounts Based on Infestation Level.
Number of cockroaches	Grams of gel bait	Grams of bait per cockroach
50	60	1.20
100	90	0.90
200	120	0.60
300	150	0.50
400	180	0.45
500	210	0.42
600	225	0.38
700	240	0.34
800	255	0.32
900	270	0.30
1000	300	0.30

We are currently validating this approach, and the results to date are highly promising. Cockroach reductions based on this approach have ranged between 95 and 100% in the first month after treatment with reduced-risk bait formulations.

In summary, we showed that elementary IPM programs, based on monitoring and reduced-risk pesticides, are as effective as a conventional pest control program, based on monthly applications of residual pesticides. The IPM program, however, used significantly less pesticides, the pesticides had much lower mammalian toxicity, and they resulted in significantly less environmental and off-target residues. The IPM program thus created a safer environment for children than the conventionally-serviced schools. The benefits of an IPM approach far outweigh the convenience of a conventional, calendar spray-based approach, and should be adopted by school systems and pest management professionals.

This project also had significant impact on the conduct of pest management operations in North Carolina. It facilitated meetings of the NC School IPM Committee, which (a) developed and signed an MOU with the NC Pest Control Association, NC PTA, and NC Department of Agriculture to adopt safer pest management procedures in schools; (b) conducted a survey of pest control companies to find out their most preferred training dates and locations, and whether they would be interested in an IPM credentialing program; 99% of the responding companies were interested in a credentialing program, which we initiated. The goal of this program is to train pest control technicians and school maintenance employees in IPM techniques and to provide school districts with a mechanism of select qualified personnel to conduct pest control in schools; (c) reviewed and adopted policies for School IPM for easy adoption by school boards and School IPM Services contract that is now available to school districts; and (d) developed a School IPM Website (http://schoolipm.ncsu.edu/).

This project also facilitated extension and research presentations to numerous stakeholders in North Carolina, including annual talks to the NC Pest Control Association (audience ~800), and research projects aimed at understanding the biology and environmental distribution of cockroach allergens. Exposure and sensitization to cockroach allergens is an important risk factor for allergic disease in humans. We documented the tissue distribution of Blattella germanica allergen 1 (Bla g 1), a perennial indoor environmental allergen. ELISA was used to quantify the Bla g 1 contents of feces and various anatomical tissues, and Northern blot analysis was used to elucidate tissue-specific expression of Bla g 1. Results showed that the Bla g 1 protein is most prevalent in the midgut, and the Bla g 1 gene is exclusively expressed by midgut cells. Although Bla g 1 is produced by both sexes and all life stages of the German cockroach, adult females produce and excrete in their feces significantly more Bla g 1 than males or nymphs, even when corrected for body mass or mass of voided feces. Our results demonstrated that the concentration of Bla g 1 in feces of adult females is 6–7-fold and 30-fold higher than in adult males and nymphs, respectively, probably because females process more food than other life stages of the German cockroach.

We also examined another potent German cockroach protein aeroallergen, Bla g 4. It is expressed only in the adult male reproductive system and changes in relation to mating. Because exposure to juvenile hormone stimulated production of this allergen, we are now delineating whether use of insect growth regulators in pest management programs might stimulate the production of allergenic proteins. Results from these studies will be of immense practical importance to pest management in residential and school environments.

The EPA funded project also facilitated studies in residential settings. Exposure to cockroach allergen is the most important risk factor for asthma in inner-city households. The National Cooperative Inner-City Asthma Study found that asthma morbidity was highest in children with both a positive skin-test response and a high exposure to cockroach allergen in the bedroom. These findings suggest that reducing exposure to cockroach allergen could be an effective strategy for improving the health among inner-city residents. However, cockroach control alone does not seem to be effective in lowering allergen levels, and there are no proven methods for allergen abatement in infested homes. In collaboration with the NIEHS, we sought to develop intervention strategies to implement clinically relevant reductions in exposure to cockroach allergen. A trial with 16 intervention and 15 control homes was conducted. The interventions consisted of occupant education, placement of insecticide bait, and professional cleaning. From 0 to 6 months among intervention homes, allergen concentrations decreased on kitchen floors, on living room floors/sofas, on bedroom floors, and in bedroom beds. A subsequent study showed that allergen reductions could be sustained with cockroach control alone. Thus, substantial reductions in cockroach allergen levels can be achieved in homes. In this study, allergen levels were reduced below the sensitization threshold in beds, arguably the most relevant site for exposure, and below the asthma morbidity threshold on bedroom floors and living room floors/sofas.

Findings from this research should offer new approaches for the control of cockroach infestations, reduction of environmental allergens associated with them that are responsible for asthma, lessening the potential for transmission of pathogenic bacteria, and elimination of pesticide residues in areas that children might contact.

Publications acknowledging this grant:

Fan Y., J. C. Gore, K. O. Redding, L. D. Vailes M. D. Chapman and C. Schal. 2005. Tissue localization and regulation by juvenile hormone of German cockroach, Blattella germanica (L.), allergen Bla g 4. Insect Molecular Biology (in press).

Gore J. C. and C. Schal. 2004. Gene expression and tissue distribution of the major human allergen Bla g 1 in the German cockroach, Blattella germanica L. (Dictyoptera: Blattellidae). Journal of Medical Entomology 41: 953–960.

Gore J. C. and C. Schal. 2005. Expression, production and excretion of Bla g 1, a major human allergen, in relation to food intake in the German cockroach, Blattella germanica (L.). Medical and Veterinary Entomology (in press).

Gore J. C. and C. Schal. 2005. Cockroach allergen biology and mitigation in the indoor environment. Annual Reviews of Entomology (invited).

Nalyanya G., M. Linker, M. Waldvogel and C. Schal. 2003. Integrated Pest Management for North Carolina Schools. North Carolina Cooperative Extension Service (49 pages). http://ipm.ncsu.edu/urban/cropsci/SchoolIPM/schoolipm_manual.pdf

Williams, G. M., H. M. Linker, M. G. Waldvogel, R. B. Leidy, and C. Schal. 2005. Comparison of conventional and integrated pest management programs in public schools. Journal of Economic Entomology (in review).

Publications related to this grant:

Arbes S. J., Jr., M. Sever, J. Archer, E. H. Long, J. C. Gore, C. Schal, M. Walter, B. Nuebler, B. Vaughn, H. Mitchell, E. Liu, N. Collette, P. Adler and D. C. Zeldin. 2003. Abatement of cockroach allergen (Bla g 1) in low-income, urban housing–a randomized controlled trial. Journal of Allergy and Clinical Immunology 112: 339–345. http://www.cals.ncsu.edu/entomology/schal/program/schal/2003ArbesJACINIEHS.pdf

Commentary by Peyton Eggleston: http://www.cals.ncsu.edu/entomology/schal/program/schal/2003ArbesEgglestoncommentary.pdf

Arbes S. J., Jr., M. Sever, J. Mehta, J. C. Gore, C. Schal, B. Vaughn, H. Mitchell and D. C. Zeldin. 2004. Abatement of cockroach allergens (Bla g 1 and Bla g 2) in low-income, urban housing: Month 12 continuation results. Journal of Allergy and Clinical Immunology 113: 109–114. http://www.cals.ncsu.edu/entomology/schal/program/schal/2004Arbes12Months.pdf

NCSU article: http://www.cals.ncsu.edu/agcomm/magazine/spring04/study.htm

NCSU press release: http://www.ncsu.edu/news/press_releases/04_01/011.htm