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Comparison of Contact and Spatial Repellency of Catnip Oil and N,N-Diethyl-3-Methylbenzamide (Deet) Against Mosquitoes

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Comparison of Contact and Spatial Repellency of Catnip Oil and N,N-Diethyl-3-Methylbenzamide (Deet) Against Mosquitoes University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln U.S. Department of Agriculture: Agricultural Publications from USDA-ARS / UNL Faculty Research Service, Lincoln, Nebraska 2005 Comparison of Contact and Spatial Repellency of Catnip Oil and N,N-Diethyl-3-methylbenzamide (Deet) Against Mosquitoes Ulrich R. Bernier University of Florida, [email protected] Kay D. Furman USDA-ARS Daniel L. Kline USDA-ARS Sandra A. Allan USDA-ARS Donald R. Barnard USDA-ARS Follow this and additional works at: https://digitalcommons.unl.edu/usdaarsfacpub Part of the Agricultural Science Commons Bernier, Ulrich R.; Furman, Kay D.; Kline, Daniel L.; Allan, Sandra A.; and Barnard, Donald R., "Comparison of Contact and Spatial Repellency of Catnip Oil and N,N-Diethyl-3-methylbenzamide (Deet) Against Mosquitoes" (2005). Publications from USDA-ARS / UNL Faculty. 962. https://digitalcommons.unl.edu/usdaarsfacpub/962 This Article is brought to you for free and open access by the U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Publications from USDA-ARS / UNL Faculty by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. BEHAVIOR,CHEMICAL ECOLOGY Comparison of Contact and Spatial Repellency of Catnip Oil and N,N-Diethyl-3-methylbenzamide (Deet) Against Mosquitoes ULRICH R. BERNIER, KAY D. FURMAN, DANIEL L. KLINE, SANDRA A. ALLAN, AND DONALD R. BARNARD USDAÐARS, Center for Medical, Agricultural, and Veterinary Entomology, 1600 SW 23rd Drive, Gainesville, FL 32608 J. Med. Entomol. 42(3): 306Ð311 (2005) ABSTRACT Nepetalactone, the primary component of catnip oil, was compared with the repellent N,N-diethyl-3-methylbenzamide (deet) for its ability to affect the host-seeking ability of Aedes aegypti (L.). A triple cage olfactometer was used to bioassay each substance and to assess its attraction inhibition (spatial repellent) attributes when combined with the following attractants: carbon dioxide, acetone, a blend of L-lactic acid and acetone, and human odors. Repellent tests were conducted with each substance against female Ae. aegypti, Anopheles albimanus Weidemann, and Anopheles quadri- maculatus Say. Catnip oil and deet were both weakly attractive to Ae. aegypti, catnip oil was the better spatial repellent, whereas deet was a more effective contact repellent in tests with all three species of mosquitoes. KEY WORDS olfactometer, inhibition, nepetalactone, repellents CATNIP, Nepeta cataria L., is a member of the mint are not involved in the detection of attractive host family (Lamiaceae) that is used as a food additive, in odors (Boeckh et al. 1996). traditional medicine, and as a stimulant for felids Less attention has been directed toward the dis- (Tucker and Tucker 1988, Leung and Foster 1996). covery of spatial repellents (synonymous here with One possible basis for the use of catnip by felids might attraction inhibitors; Kline et al. 2003) compared with be for defense against mosquito attack (Weldon 2003, the discovery of topical repellents (Gouck et al. 1967, Weldon et al. 2003), and if so, other species, e.g., Schreck et al. 1970). Hoffmann and Miller (2002, 2003) humans, may beneÞt from this means of protection demonstrated spatial repellency attributable to vapor against predators by concealment or cloaking of odors phase release of deet. Attraction inhibitors have a (Eisner et al. 1978). Nepetalactone, a primary com- primary effect that results in a reduction of the num- ponent of catnip oil, has been reported recently to ber of mosquitoes that take ßight in the presence of an repel cockroaches (Peterson et al. 2002) and mosqui- attractant; this is accomplished possibly by masking toes (Peterson 2001). the attraction at a cellular level. Because a totally Synthetic and natural products have been evaluated effective inhibitor has yet to be discovered, a percent- as repellents throughout the years (Peterson and age of mosquitoes are still activated to ßight upon Coats 2001), and N,N-diethyl-3-methylbenzamide detection of attractive odors even in the presence of (deet) is one of the most successful (McCabe et al. an inhibitor. However, these mosquitoes have greater 1954). In laboratory-based sensory physiology studies, difÞculty orienting to and locating the attractive odor deet inhibits favorable response to mosquito attract- source compared with mosquitoes in the absence of an ant(s), such as L-lactic acid as a host attractant for inhibitor (Kline et al. 2003). Aedes aegypti (L.) (Davis and Bowen 1994) and ethyl A Feinsod & Speilman olfactometer (Feinsod and propionate as an oviposition attractant (Kuthiala et al. Spielman 1979) modiÞed to identify attractants, in- 1992). Two neuron classes of the antennal grooved hibitors, and repellents was used to demonstrate in- pegs on Ae. aegypti are reported to respond to lactic hibition of mosquito host-seeking behavior by deet acid, possible skin acids, and essential oils, and these (Dogan and Rossignol 1999, Dogan et al. 1999). In our also are inhibited by deet (Davis and Bowen 1994, triple cage, dual-port olfactometer system (Posey et al. Sutcliffe 1994). Deet not only affects cells responsible 1998), we test for attractants and can test for attraction for detection of attractants but also inhibits cells that inhibition by combination of the candidate inhibitor with established attractants (Bernier et al. 2001). Peterson (2001) found that in laboratory bioassays with a glass tube olfactometer, Ae. aegypti were less This paper reports the results of research only. Mention of a chem- ical compound does not constitute an endorsement for use by the likely to land on the side that contained deposited USDA, nor does it imply registration under FIFRA as amended. nepetalactone compared with the side that had deet. May 2005 BERNIER ET AL.: CONTACT AND SPATIAL REPELLENCY OF CATNIP OIL 307 The same work also demonstrated that a higher dosage petitive bioassays. The mosquitoes trapped in each of of deet was required to be as effective as a lower the ports, and those remaining in the cage were dosage of nepetalactone. Stimulated by this work, we counted after each 3-min bioassay. Data were re- compared commercially available catnip oil with deet corded as a percentage of the mosquitoes attracted to by using our protocols for topical repellency (USDA each port out of the total number of mosquitoes ini- 1977) and spatial repellency (attraction inhibition) in tially in the cage. Treatments consisted of 500 ␮lof both competitive and noncompetitive bioassays catnip oil, 500 ␮l of deet, 5 ml/min carbon dioxide (Gouck et al. 1967, Schreck et al. 1970, Kline et al. (Gillies 1980), the binary blend of 200 ␮gofL-lactic 2003). We chose the popular repellent deet to serve as acid plus 500 ␮l of acetone (Bernier et al. 2003), and the standard by which comparisons of repellency combinations of catnip oil or deet plus carbon dioxide, were made. L-lactic acid and acetone, and odors from the arm of a human subject. The dosage of were selected to provide a dose of deet equivalent to 1 ml of a 50% deet Materials and Methods product. The dosage of catnip oil was chosen to pro- Chemicals. Chemical reagents are listed with the vide a sufÞcient dose of nepetalactone for an observed Chemical Abstracts number in brackets following the effect. As little as 50 ␮l of this substance produces chemical name. Acetone [67-64-1] Ͼ99.5% A.C.S. re- inhibition (U.R.B., unpublished data). The binary agent grade was purchased from Aldrich (Milwaukee, blend composition and dosage was selected from pre- WI). L-(ϩ)-Lactic acid [79-33-4] Ͼ99% was pur- vious experiments (Bernier et al. 2001, 2003). All chased from Fluka (Milwaukee, WI). A 2 ␮g/␮l L- chemical samples, except carbon dioxide, were dis- lactic acid stock solution was prepared in reagent pensed onto a porous plastic block made of polyeth- grade methanol UltimAR [67-56-1] Ͼ99.9% ylene and polypropylene (GenPore, Reading, PA) and (Mallinckrodt Chemical, Phillipsburg, NJ). Carbon manufactured for controlled release of 1-octen-3-ol in dioxide [124-38-9] was delivered from a compressed the Þeld (Armatron International, Melrose, MA). Car- gas cylinder (Airgas South Inc., Gainesville, FL). Deet bon dioxide was delivered from a cylinder, through a [134-62-3] was obtained from our stock supply (Vir- Þnely controllable metering valve (Nupro Co., Wil- ginia Chemical Inc., Portsmith, VA) and prepared as loughby, OH) and measured on a calibrated ßowme- a 25% (vol:vol) solution in ethanol [64-17-5] (190 ter set to deliver 5 ml/min. In noncompetitive tests, proof, for Molecular Biology, Aldrich). Catnip oil (Ca- the blank port contained a slow release dispenser, but nadian catnip) consisting of Ϸ80% nepetalactone plus no treatments. Both the blank port and treatment nepetalactone isomers was purchased Essential Oil ports have an identical ßow of conditioned air through University (New Albany, IN). them. Provided that there is no contamination, very Attraction and Attraction Inhibitor Bioassays. Tests few if any mosquitoes were trapped in this control port were conducted in a triple cage, dual-port olfactom- during the course of an experiment. Data presented in eter (Posey et al. 1998). Each cage allows for a single tables are untransformed means. Percentages were experiment to be conducted. The mosquitoes either arcsine transformed before analysis. remain in the cage or ßy upwind to be captured in one Repellency Bioassays. Repellency, reported as min- of the two ports, each containing either a treatment or imum effective dosage (MED), was determined ac- control substance. cording to standard protocol (USDA 1977). The MED Air drawn from outside the laboratory was Þltered, is the lowest dosage that resulted in three or fewer cooled or heated, and humidiÞed or dehumidiÞed as bites through a repellent-treated cloth, which is held necessary by the air handling system to produce a above, but protected from contact with skin.
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