COCKROACH REPELLENCY OF ESSENTIAL OILS REPELLENT ACTIVITY OF ESSENTIAL OILS AGAINST COCKROACHES (DICTYOPTERA: BLATTIDAE, BLATTELLIDAE, AND BLABERIDAE) IN THAILAND Usavadee Thavara1, Apiwat Tawatsin1, Payu Bhakdeenuan1, Prapai Wongsinkongman2, Thidarat Boonruad2, Jaree Bansiddhi2, Pranee Chavalittumrong2, Narumon Komalamisra3, Padet Siriyasatien4 and Mir S Mulla5 1National Institute of Health, 2Medicinal Plant Research Institute, Department of Medical Sciences, Ministry of Public Health, Nonthaburi; 3Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, Bangkok; 4Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand; 5Department of Entomology, University of California, Riverside, California, USA Abstract. Seven commercial essential oils extracted from the plant species Boesenbergia ro- tunda (L.) Mansf., Citrus hystrix DC., Curcuma longa L., Litsea cubeba (Lour.) Pers., Piper nigrum L., Psidium guajava L. and Zingiber officinale Roscoe, and naphthalene as a control, were evaluated for repellent activity against the three cockroach species Periplaneta americana (L.), Blattella germanica (L.) and Neostylopyga rhombifolia (Stoll) under laboratory conditions. The essential oil derived from Citrus hystrix showed the best repellency over other candidate essential oils and naphthalene. The essential oil of Citrus hystrix exhibited complete repellency (100%) against P. americana and B. germanica, and also showed the highest repellency (among the essential oils tested) of about 87.5% against N. rhombifolia under laboratory conditions. In the field, Citrus hystrix essential oil formulated as a 20% active ingredient in ethanol and some additives provided satisfactory repellency of up to 86% reduction in cockroaches, mostly P. americana and N. rhombifolia with a residual effect lasting a week after treatment. Citrus hystrix essential oil has good potential for being used as a cockroach repellent. Further improvements in efficacy and residual activity may be realized with appropriate formulations. INTRODUCTION tals (Agbodaze and Owusu, 1989; Fotedar et al, 1991). There is ample evidence that sub- Cockroaches have the potential to me- stances produced by cockroaches are in- chanically carry and transmit many pathogens, volved in producing allergic symptoms such as bacteria, viruses, fungi, protozoa and (Kongpanichkul et al, 1997; Pumhirun et al, helminthes (Cochran, 1982). They also serve 1997). At least 12 species of cockroaches as potential carriers of the causes of bacterial have been reported in Thailand to date and diarrhea and nosocomial infections in hospi- the American cockroach is the most common cockroach found in dwellings in various prov- inces of Thailand (Tawatsin et al, 2001). Correspondence: Usavadee Thavara, National In- Sriwichai et al (2002) confirmed the abun- stitute of Health, Department of Medical Sciences, Ministry of Public Health, Nonthaburi 11000, Thai- dance of the American cockroach in all types land. of buildings in Bangkok, especially private resi- Tel: 66 (0) 2951 0000 ext 99245; Fax: 66 (0) 2591 dences, and found that German cockroaches 5449 were significantly predominant in grocery es- E-mail: [email protected] tablishments. Vol 38 No. 4 July 2007 663 SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH Several chemicals were studied for repel- control since it is commonly used as cock- lent effects against cockroaches, such as N, roach repellent. N-diethylphenylacetamide (Prakash et al, The essential oil of kaffir lime leaf was 1990), methyl neodacanamide, propyl selected for further evaluation against cock- neodecanamide, methyl neotridecanamide, roaches in the field because of its high effi- alkyl and aryl neoalkanamides (Steltenkamp cacy under laboratory conditions. This oil was et al, 1992), citral and eugenol (Vartak et al, prepared at various concentrations in ethanol 1994). Research regarding cockroach repel- [5, 10, 20, 50 and 100% (undiluted)] and lents, especially those derived from plant ex- tested against two cockroach species (the tracts, is quite limited at this time. Recently, American cockroach and the German cock- the essential oil of catnip (Nepeta cataria L.) roach) under laboratory conditions. For field was reported as having repellency against testing, the essential oil was then formulated adult male German cockroaches (Peterson et as 20% (w/w) liquid repellent in ethanol with al, 2002). Up to the present time, no studies some additives. have reported evaluation of repellents against cockroaches in Thailand. The present study Test cockroaches was initiated to study the repellent activity of Three cockroach species used in labora- seven essential oils, extracted from local plants tory repellent tests were laboratory-reared of Thailand, against three cockroach species Periplaneta americana (L.) (the American cock- under laboratory conditions. The most prom- roach), Blattella germanica (L.) (the German ising essential oil was then further evaluated cockroach) and Neostylopyga rhombifolia for repellency against cockroaches in the field. (Stoll) (Harlequin cockroach). These cock- roaches have been reared according to the MATERIALS AND METHODS standard protocols of the Biology and Ecol- ogy Section, National Institute of Health, Thai- Essential oils for laboratory and field evaluation land, and maintained in the insectary of the Seven commercial essential oils (100%) institute. The colonies were maintained in the were evaluated for repellent activity against insectary under ambient temperature (24- three cockroach species (the American cock- 30ºC) and humidity (70-90% RH). Adult P. roach, the German cockroach and harlequin americana (aged 3-5 months), B. germanica cockroach) under laboratory conditions. These (aged 6-8 weeks) and N. rhombifolia (aged 3- essential oils were derived from lesser galanga 5 months) were employed for repellent test- (Boesenbergia rotunda (L.) Mansf.) rhizomes, ing under laboratory conditions. Both males kaffir lime (Citrus hystrix DC.) leaves, turmeric and females of each cockroach species were (Curcuma longa L.) rhizomes, Litsea (Litsea used in the laboratory tests. cubeba (Lour.) Pers.) fruits, black pepper (Piper nigrum L.) fruits, guava (Psidium guajava Laboratory tests L.) leaves and ginger (Zingiber officinale A stainless steel square-box (50x50x15 Roscoe) rhizomes. These oils were selected cm, with the top open) was employed in the for this study because the plants are com- repellent tests. All four walls of the box were monly available in Thailand and the oils are smeared with Vaseline to prevent escape of available commercially. These oils were pur- cockroaches. A piece of filter paper (Whatman chased from Thai-China Flavours and Fra- No.1, 50x50 cm) was marked by a pen to di- grances Industry Co, Ltd, Nonthaburi Pro- vide it into 2 equal parts (treated and control vince, Thailand. Naphthalene was used as a areas) and then placed at the bottom of the 664 Vol 38 No. 4 July 2007 COCKROACH REPELLENCY OF ESSENTIAL OILS box. The test repellent (1.25 ml) was applied District (36 houses) were designated as the (equal to dosage of 10 ml/m2) by placing drops treatment sites, whereas Bang Saphan Village from a pipette on the treated area to cover of Wang Thong District (50 houses) was des- the treated portion of the paper, whereas the ignated as the control site. All sites were sur- control area was untreated. Naphthalene, the veyed for cockroach species and densities control standard, is solid. Two pieces of naph- using sticky traps (HOY HOY, produced by thalene (1 g each) were placed together as a Earth Chemicals, Japan) before and after treat- treatment on the treated side. Each set of con- ment. This sticky trap has been shown to be tainers of food and drink for the cockroaches an effective tool for cockroach surveys in the was placed at both sides of the box (treated field (Tawatsin et al, 2001). The sticky trap is and control areas). Twenty adult cockroaches a simple device that can be folded into a trap- (10 males and 10 females) were anesthetized ezoid paper-house (10x15x3 cm), having four with CO2 and released into the box at the cen- entrances for cockroaches. The sticky area for tral point. The box was then placed in a Peet catching cockroaches inside the trap is about Grady chamber (180x180x180 cm) sur- 9.5x15 cm. Cockroaches are lured into the rounded by cloth curtains to keep a dark en- trap by built-in attractants located in the vironment and to prevent disturbances from middle of the sticky area. At least 36 houses surroundings. The cockroaches located in the in each experimental site were randomly treated and control areas were carefully ob- sampled for cockroaches by placing two sticky served and counted at 48 hours after treat- traps in the kitchen of each house and left ment. Repellency against the cockroaches there for one night. The cockroaches caught was calculated with the following equation: in each trap were identified by species follow- ing the handbook of domiciliary cockroach species in Thailand (Asahina, 1983) and other Repellency (%) = 100 - [T x 100] –––––––– relevant references (Cornwell, 1968; Bell, N 1981; Cochran, 1982, 1999) and then counted. Three days after the preliminary sur- where T stands for the number of cock- vey, the test repellent was applied at a dos- roaches located in the treated area and N age of 10 ml/m2 by a hand-trigger window- stands for the total number of cockroaches sprayer on the floor in the kitchen area in each used. The average repellency