Commercial Insect Repellent Research Articles

Do Commercial Insect Repellents Provide Protection against the Tick Amblyomma sculptum (Acari: Ixodidae)?

Amblyomma sculptum is a species of public health interest because it is associated with the transmission of the bacteria that causes Brazilian Spotted Fever (BSF). The use of repellents on humans is a prophylactic measure widely used to provide protection against a series of arthropod vectors, including mosquitoes and ticks. However, in Brazil, the effectiveness of commercial repellents against A. sculptum is little known. Therefore, it is necessary to carry out specific studies to evaluate the repellency of these commercial products, registered for use against mosquitoes, against the star tick. The main goal of the present work was to evaluate the effectiveness of six commercial repellents against A. sculptum. Unfed nymphs, aged between two and eight weeks, were tested against products based on DEET (OFF!® and Repelex®), Icaridin (Exposis® and SBP®), and IR3535 (Johnsons and Henlau). Three bioassays were conducted to evaluate tick behavior: (i) filter paper, (ii) fingertip, and (iii) field. All bases tested showed high repellent activity, differing significantly (p < 0.05) from the control. It was observed the formulation with DEET resulted in the best results in the filter paper bioassay. In the fingertip bioassay, the DEET base repelled a greater number of ticks compared to Icaridin. In the field bioassay, there was no significant difference between the Icaridin base and DEET, and both formulations differed from the control (p < 0.05). The six formulations tested showed significant percentages of repellency against ticks; however, for the fingertip and field bioassays, the products OFF!®, Repelex®, and Exposis® were tested as they showed better performance in the filter paper test. OFF!® showed the best percentage of repellency (100%), followed by Repelex® (96.8%), and Exposis® (93.1%), considering the two-hour period of the bioassay-field-test. Proving the effectiveness of repellents on the market against A. sculptum presented in this study is crucial, since this is the main ectoparasite of humans that can transmit Rickettsia rickettsii when infected. The effectiveness of commercial insect repellents against other tick species that parasitize humans can also be explored.

Novel acylpiperidine analogues as potential aphid repellent agents: Rational design, synthesis and repellent activity

Odorant-binding protein (OBP) is a promising potential target and can be used as a template for developing insect control agents due to its ability to bind to and transport semiochemicals to olfactory receptors, thus triggering behavioural responses among insects. In this study, 27 novel acylpiperidine analogues were designed and synthesised by introducing the hydrophobic long chain of the aphid alarm pheromone (E)-β-farnesene (EβF) into the polar acylpiperidine group of the commercial insect repellent icaridine based on the binding cavity characteristics of an OBP of the pea aphid Acyrthosiphon pisum, ApisOBP3. Compound 14c displayed good repellent activity against the pea aphids with a repellence rate of 61.5% at a concentration of 6 μg/μL. The equilibrium dissociation constant (Ki) of compound 14c against ApisOBP3 was 20.92 μM in competitive fluorescence binding assays; this value is similar to the Ki of the commercial insect repellent icaridine (20.56 μM). Molecular dynamics simulation revealed that the EβF long chain of compound 14c showed considerable hydrophobic interactions with the binding domain of ApisOBP3. Moreover, the acylpiperidine moiety of compound 14c formed one hydrogen bond and multiple carbon–hydrogen bonds with the Phe2 and Asn109 residues, respectively. The binding free energy analysis indicated that the contribution of the van der Waals force to the binding affinity was approximately twice as great as that of the electrostatic force. These studies provide significant guidance for the rational designing and efficient identification of novel insect repellent agents.

English

Dengue is an emerging epidemic disease and among those transmitted by the Aedes aegypti mosquito, it is the one with the highest number of cases and cases with death. With the wide dissemination of the beneficial effects of medicinal plants and the use in agriculture as a pesticide, studies on the prospection of plants with toxic activity have been increasing, highlighting extracts and essential oils. The objective of this study was to evaluate the effects of Hypenia irregularis essential oil extracted by hydrodistillation, in a Clevenger-type device modified against 3rd instar larvae and adult mosquitoes of Aedes aegypti. The chemical composition of the oil was determined using the Gas Chromatography/mass spectrometer (GC/MS) technique. The major compounds were: 2, 5-dimethoxy-&rho;-cymene, thymol, o-cymene, phenol-3- (1, 1-dimethylethyl)-4-methoxy and humulene with 27.0, 21.36, 15.56, 8.89 and 5.01%, respectively. For all the tests, were applied concentrations ranging from 0.007 to 0.13 &mu;l.ml-1, for the larvicidal test was denoted LC50 0.037 &mu;l.ml-1 and CL95 0,122 &mu;l.ml-1, for the time response required to achieve 95% mortality (TL95) was 27.412 min. In the oviposition bioassay it was observed that the higher the concentration of essential oil used (0.2 &mu;l ml-1), the lower the number of eggs deposited, the less eggs being deposited as compared to the untreated tests. In addition, the action of H. irregularis oil showed better results than the commercial insect repellent composed of N, N-diethyl-m-toluamide (15 %) in 135 min of exposure to mosquitoes. Key words: Dengue, essential oil, medicinal plant, natural insecticide. &nbsp;

Exposure to Mosquito Repellents Causes Profound Development Defects and Induces Oxidative Stress in Zebrafish

Abstract Objective The study was designed to investigate the effects of commercially available mosquito repellents on embryonic development of zebrafish. Materials and Methods Transfluthrin is a type I pyrethroid present in all commercial mosquito and insect repellents. Pyrethrins are neurotoxins that target the nervous system of insects. Three popular brands of liquid vaporizer repellents coded as compound A, B, and C that contained transfluthrin, ranging from 0.88 to 1.6% w/w, were used in this study. The effects of these compounds on the embryonic development of zebrafish were investigated. In addition, the ability of transfluthrin to induce oxidative stress was examined by analyzing the generation of reactive oxygen species in exposed embryos. Results The exposure to mosquito repellents resulted in extensive morphological defects in zebrafish embryos. The severity of the anomalies correlated with the concentration of transfluthrin in the repellents. Exposure to pure transfluthrin generated high levels of reactive oxygen species in zebrafish embryos, suggesting the induction of oxidative stress. Conclusion Liquid vaporizer repellents are generally used for control of mosquitos and are common in many households. This study demonstrated that its exposure to mosquito repellents causes severe morphological defects and embryonic lethality in zebrafish. The study also showed that transfluthrin, the active insecticide in these repellents, induces oxidative stress in zebrafish.

Aquatic life criteria derivation and ecological risk assessment of DEET in China

N,N-diethyl-meta-toluamide (DEET) is the most widely used active ingredient in commercial insect repellents. In addition to its adverse effects in insects, DEET can affect non-target organisms in surface water systems. Nevertheless, the aquatic life criteria of DEET are not available. This study conducted both acute and chronic toxicity tests on DEET in native Chinese aquatic species, and derived its criterion maximum concentration (CMC) and criterion continuous concentration (CCC). The determined CMC and CCC of DEET were 21.53 and 0.52 mg/L, respectively. The toxicity data indicated that DEET exposure posed a higher toxicity to some algae than other aquatic species. Compared with other insect repellents, DEET exposure posed a moderate toxicity to aquatic species. Therefore, the exposure concentration of DEET in Chinese surface water was collected to assess the potential ecological risk. The preliminary ecological risk assessment showed that DEET posed negligible risk to aquatic ecosystems in China. However, considering its toxic effects on the growth and reproduction to aquatic organisms, the ecological risk posed by DEET is worth further concern.

Ticks home in on body heat: A new understanding of Haller's organ and repellent action.

Ticks are second only to mosquitoes as vectors of disease to humans and animals. Tick host detection is mainly ascribed to Haller’s organ, a complex sensory structure on the tick foreleg that detects odors, carbon dioxide and heat, but these host detection mechanisms are not well understood. There is anecdotal evidence that ticks and other ectoparasites are attracted to heat, but it has never been demonstrated that they use radiant heat to detect hosts at a distance. In fact, previous attempts to do this have concluded that radiant heat was not used by ticks. Here we use a novel thermotaxis assay to investigate the detection range, temperature dependence and repellent sensitivity of heat perception in ticks and to identify the sensory organ responsible for this sense. We show that Amblyomma americanum and Dermacentor variabilis ticks can locate a human from several meters away by radiant heat sensed by the part of Haller’s organ known as the capsule, a covered spherical pit organ. An aperture in the capsule cover confers directionality and highly reflective interior surfaces of the capsule concentrate radiation on the sensilla to sharpen directionality and increase sensitivity. Commercial insect repellents provide an effective means of personal protection against potentially infectious tick bites by hindering host-seeking behavior. Low concentrations of the insect repellents DEET, picaridin, 2-undecanone, citronellal and nootkatone eliminate thermotaxis without affecting olfaction-stimulated host-seeking behavior. Our results demonstrate that the tick Haller’s organ capsule is a radiant heat sensor used in host-finding and that repellents disrupt this sense at concentrations that do not disrupt olfaction. We anticipate that this discovery will significantly aid insect repellent research and provide novel targets for the development of innovative integrated pest management programs and personal protection strategies for ectoparasites and vector-borne disease.

Anointing with commercial insect repellent by free-ranging Cebus capucinus in Manuel Antonio National Park, Quepos, Costa Rica.

Fur rubbing or anointing is a well known behavior in capuchin monkeys (Cebus and Sapajus), and may have medicinal and/or social functions. Observations of anointing in capuchins have recorded the application of substances derived from both plants (orange, onion, garlic, citronella, and lemongrass) and animals (ants and millipedes). The present study reports on anointing behavior in free-ranging white-headed capuchins, Cebus capucinus, which involved a commercial insect repellent. After looting a bottle of repellent from the bag of a visitor to the Manuel Antonio National Park in Costa Rica, an adult male bit open the bottle and rubbed the leaking liquid over its entire body, focusing mainly on its belly. Other members of the group rubbed themselves against the male's body and were eventually able to retrieve the bottle of repellent and anoint themselves. The repellent is composed mainly of extracts of eucalyptus and citronella. The capuchins may have been attracted by the strong citric scent of the citronella, which is known to stimulate fur-rubbing behavior in these monkeys. This is reinforced by the fact that the sequence of events was quite distinct from that associated with an earlier event, in which a juvenile male looted, tasted, and then discarded a stick of lip gloss and a tube of sunblock. Overall, the observations indicate that the citric scent of the repellent was attractive to the capuchins, especially in comparison with other man-made substances. As the animals partially ingested all the substances, there is clearly a need for more effective regulation of the contact between animals and visitors in the park.

Chemical Composition and Repellency of Origanum vulgare Essential Oil against Cimex lectularius under Laboratory Conditions

The common bed bug (Cimex lectularius), a nocturnal blood-feeding ectoparasite, is considered an urban pest with public health importance in human environments. We aimed to determine the repellency effect of oregano essential oil, Origanum vulgare, against this pest under laboratory conditions. The essential oil was prepared from dried leaves using hydro-distillation method. A gas chromatography-mass spectrometer (GC-MS) was used for analysis and identification of oregano essential oil compounds. Treated surface method in Petri dish was carried out to evaluate repellency potential of the oil using 4th and 5th instar nymphs and adults. The concentration-repellency response of oregano essential oil was calculated and compared with a commercial insect repellent stick containing 33% N, N-diethyl-meta-toluamide (DEET). The oregano essential oil consisted of 158 compounds with terpineol (22.85%) and α-terpinene (20.60%) being the major components by volume. The EC50 and EC99 of oregano oil (effective concentrations causing 50% and 90% repellency of bed bugs) were 1.61 and 6.57mg/cm2 at 9h after application, respectively. The 40% oregano essential oil exhibited 100% repellency against bed bug at 3, 5, 9 and 24h after application while the repellency index of DEET 33% was 100% at 3 and 5h and it decreased to 80% and 27% at 9 and 24 hours. Oregano oil 40% exhibited more repellency compared to commercial insect repellent stick containing 33% DEET. Further studies are warranted to confirm the effectiveness of oregano essential oil in personal protecting against bed bug biting.

Activity of Origanum vulgare essential oil, as a safe green-friendly repellent for personal protection against common bed bug

The common bed bugs have become a public health concern in urban communities recently. The use of repellent compounds is the recommended way to prevent biting and in order to personal protection against insect biting. So, we aimed to determine the protection time of oregano essential oil, Origanum vulgare, against the common bed bug, Cimex lectularius L. on animal and human hosts. Oregano essential oil 39% (99% repellency of bed bugs in Petri dish test) was used against 4th, 5th instar nymphs and adults of bed bug using rabbit and human host. The results were compared to a commercial insect repellent stick (DEET 33%). The data were recorded at 20 min intervals and continued until the second bed bug bite was happened. The protection times were calculated 454.33 ± 10.97 and 430.33 ± 16.5 min using oregano oil 39% and commercial insect repellent stick (DEET 33%) against the bed bug in the animal test, respectively. The protection times were decreased in the human test, hence calculated 175 ± 3 min for oregano oil 39% and 6.85 ± 1.34 min for commercial DEET 33% against the bed bug biting. The lower harmful side-effects of botanical products on humans and environment have attracted considerable attention in recent years. With a proper formulation of plant essential oils, these compounds can be recommended as potential repellents against the blood-sucking insects.

Hydrogenation of Naturally-Derived Nepetalactone as a Topical Insect Repellent

Dihydronepetalactone (DHN) is a safe and effective topical insect repellent,(5,6,8) comparable in efficacy to that of N,N-diethyl-m-toluamide (DEET). The latter is the most commonly used active ingredient, found in many commercial insect repellents for a broad range of biting insects. DHN can be produced by hydrogenating nepetalactone (NL), which is the primary ingredient of the essential oil obtained from the renewably sourced catmint plant, Nepeta cataria. Optimizing the hydrogenation reaction to produce DHN from catmint oil is a key economic driver for the process. Prior to the study described here, Six Sigma methodologies were used to select palladium on carbon (5% Pd/C) as the catalyst of choice. The hydrogenation step was studied as a function of critical process variables and the composition of the oil. As described in this article, a robust, two-step hydrogenation process was developed to maximize the yield of the desired DHNs from treated catmint oil. It was observed that the composition of the catmint oil, vis-à-vis, the relative amounts of trans–cis and cis–trans-nepetalactone isomers, had a major impact on the activity and selectivity of the catalyst. This study also focused on minimizing the formation of a less desirable byproduct, puleganic acid. On the basis of the process variables tested in this study, temperature was found to have a strong effect on the activity and selectivity of the catalyst. Higher pressure enhanced the activity of the catalyst but it did not significantly impact the formation of undesired byproducts, such as puleganic and nepetalic acids. Spiking experiments with suspected catalyst poisons, such as dimethyl sulfide, dimethyl sulfoxide, nepetalic acid, and puleganic acid were also performed to study catalyst deactivation. Sulfur was identified as the main factor for the catalyst deactivation. Possible reaction mechanisms for the formation of less desirable puleganic and nepetalic acids have been suggested.

Repellency of 29 Synthetic and Natural Commercial Topical Insect Repellents Against Aedes aegypti (Diptera: Culicidae) in Central Mexico.

In Mexico, the use of repellents to prevent insects from landing and biting is a common practice. However, variation in the efficiency of natural and synthetic repellents has been observed. In this study, we evaluated the repellency and protection time of 16 synthetic and 13 natural-based commercial products against Aedes aegypti (L.) from an endemic dengue area (Jojutla, Morelos) in Central Mexico. The "arm exposure" cage test was used to assess the efficacy of the repellents. Tests were conducted by three adult volunteers. Results showed that DEET (N, N-Diethyl-3-methylbenzamide) repellents provided the highest protection and duration times against Ae. aegypti. However, low repellency and short-time protection was observed (when compared with the manufacturers' protection times). Natural-based products did not repel (either landing or biting) mosquitoes for >30 min. These results show that most of the repellent products did not provide satisfactory levels of personal protection against mosquito bites. Frequent reapplication of repellents (synthetic and natural-based) may compensate for their short duration of action. Repellent efficacy data must be integrated into the decision-making process for an optimal response to the local (or specific region) situation.

Responses of the aquatic midge Chironomus riparius to DEET exposure

N,N-diethyl-3-methylbenzamide (DEET) is the active ingredient of many commercial insect repellents. Despite being detected worldwide in effluents, surface water and groundwater, there is still limited information on DEET’s toxicity toward non-target aquatic invertebrates. Thus, our main objective was to assess the effects of DEET in the life cycle of Chironomus riparius and assess its biochemical effects. Laboratory assays showed that DEET reduced developmental rates (reduced larval growth, delayed emergence) of C. riparius larvae and also caused a decrease in the size of adult midges. Concerning the biochemical responses, a short exposure to DEET caused no effects in lipid peroxidation, despite the significant inhibition of catalase and glutathione-S-transferase activities and of total glutathione contents. Moreover, inhibition of acetylcholinesterase activity was also observed showing neurotoxic effects. Environmental risk assessment of insect repellents is needed. Our results showed moderate toxicity of DEET toward C. riparius, however, due to their mode of action, indirect ecological effects of DEET and of other insect repellents cannot be excluded and should be evaluated.

Infodisruption of inducible anti-predator defenses through commercial insect repellents?

Commercial insect repellents like DEET (N,N-diethyl-m-toluamide), EBAAP (IR3535®, (3-[N-butyl-N-acetyl]-aminopropionic acid, ethyl ester)) or Icaridine (picaridin, Bayrepel, 1-piperidinecarboxylic acid, 2-(2-hydroxyethyl), 1-methylpropyl ester) are used worldwide to protect against biting insects and ticks. The detection of these repellents in surface waters in concentrations up to several μg/L levels has caused concern that these substances might affect non-target organisms in freshwaters. Daphnia sp., a keystone organism in lakes and ponds, is known for diel vertical migration (DVM) and life-history changes (LHCs) as inducible defenses against predation by fish. Here we test whether (i) environmentally relevant concentrations of DEET, EBAPP or Icaridine have repellent effects on Daphnia magna and (ii) if these repellents are infodisruptors for DVM and LHCs. Using concentrations of up to 44 μg/L, the repellents neither had effects on juvenile somatic growth nor on clutch size. In thermally stratified water columns with a repellent-free hypolimnion, no repellent effects of the test compounds on D. magna were observed. The presence of fish-born infochemicals induced LHCs, which are characterized by a reduced size at first reproduction, and DVM in D. magna. These effects were not affected by the presence of either repellent. Hence no evidences for infodisruption of the chemical communication of fish and Daphnia by DEET, EBAAP or Icaridine were found.

Characterization of an ultraviolet irradiation chamber to monitor molecular photodegradation by Raman spectroscopy

ABSTRACTA homemade ultraviolet chamber is reported to induce photochemical changes with characterization by Raman spectroscopy. The equipment has compartments for ultraviolet-A (UV-A) (8 lamps of 8 W) and for UV-A + ultraviolet-B (UV-B) irradiation (4 lamps of 26 W and 1 lamp of 15 W). The irradiance was measured 3, 5, and 10 cm from the light sources. The maximum irradiance was obtained at 3 cm (UV-A: 2.66 mW/cm2 and UV-A + UV-B: 4.30 mW/cm2). The chamber internal temperature was stabilized at 30°C after 1 hr of operation with an internal relative humidity of approximately 45%. 10% Collagen was irradiated with UV-A at 2.0 mW/cm2 for 3 hr with changes in Raman peaks at 1253, 1271, 1453, and 1660 cm−1 indicating changes in conformation. 5% Atenolol was irradiated with UV-A + UV-B at 4.30 mW/cm2 for 8 hours with changes to Raman peaks at 822, 1186, 1206, 1248, and 1618 cm−1. A commercial insect repellent was irradiated with UV-A + UV-B at 4.30 mW/cm2 for 8 hr and decreases in Raman intensity were observed at 526, 690, 1003, and 1606 cm−1 due to degradation of N, N-diethyl-m-toluamide. The results demonstrate proper operation of the irradiation chamber with Raman spectroscopic monitoring.

Insecticidal and repellent action of allyl esters against Acyrthosiphon pisum (Hemiptera: Aphididae) and Tribolium castaneum (Coleoptera: Tenebrionidae)

In this project, three allyl esters from middle-chain fatty acids (allyl octanoate, allyl heptanoate and allyl hexanoate) and two from aromatic acids (allyl cinnamate and allyl 2-furoate) were investigated against two differential pests. Lethal and sublethal repellent effects by topical and ingestion exposure were tested against the pea aphid Acyrthosiphon pisum (Harris) and the red flour beetle Tribolium castaneum (Herbst) as these represent two insect pest orders of Hemiptera and Coleoptera each with a specific feeding behavior using piercing–sucking and biting–chewing mouthparts, respectively.Significant mortalities against aphid nymphs were produced when fed via diet containing allyl cinnamate, allyl 2-furoate and allyl heptanoate at 0.1mgmL−1, and in dose–response tests allyl cinnamate was the most active with an LC50 of 0.03 (0.02–0.05) mgmL−1. Although topical application on aphids was only effective at doses of 0.1mg aphid−1 for allyl cinnamte, beetles of T. castaneum adults were sensitive to all allyl esters assessed with LC50's ranging between 0.1 and 0.2mg insect−1.In binary choice bioassays, none of the allyl esters produced repellent effects on A. pisum aphids, neither by ingestion (0.1mgmL−1 in the diet) nor by contact (100μgcm−2 on filter paper). In contrast, all allyl esters, except allyl hexanoate, showed high to moderate repellence effects on T. castaneum beetles at 10μgcm−2. Interestingly, the repellent activity of allyl cinnamate was equal to the commercial insect repellent N,N-diethyl-m-toluamide (DEET). The data obtained suggest a possible role of allyl esters in insect pest control.

Dialkoxybenzene and Dialkoxyallylbenzene Feeding and Oviposition Deterrents against the Cabbage Looper, Trichoplusia ni: Potential Insect Behavior Control Agents

The antifeedant, oviposition deterrent, and toxic effects of individual dialkoxybenzene compounds/sets and of hydroxy- or alkoxy-substituted allylbenzenes, obtained through Claisen rearrangement of substituted allyloxybenzenes, were assessed against the cabbage looper, Trichoplusia ni , in laboratory bioassays. Most of the compounds/sets strongly deterred larval feeding, with some exhibiting mild toxic and oviposition deterrent effects as well. Some of the compounds/sets were more active than the commercial insect repellent, DEET (N,N-diethyl-m-toluamide), as both feeding and oviposition deterrents against the cabbage looper. On the basis of the obtained oviposition data a general hypothesis was proposed regarding the oviposition sites: one binding mode with the alkyl and allyl groups on the same side of the benzene ring resulted in deterrence, the other with alkyl and allyl groups on opposite sides of the benzene ring resulted in stimulation. The results suggest some structure-activity relationships useful in improving the efficacy of the compounds and designing new, nontoxic insect control agents for agriculture.

Is there a risk associated with the insect repellent DEET (N,N-diethyl-m-toluamide) commonly found in aquatic environments?

DEET (N,N-diethyl-m-toluamide) is the active ingredient of most commercial insect repellents. This compound has commonly been detected in aquatic water samples from around the world indicating that DEET is both mobile and persistent, despite earlier assumptions that DEET was unlikely to enter aquatic ecosystems. DEET's registration category does not require an ecological risk assessment, thus information on the ecological toxicity of DEET is sparse. This paper reviews the presence of DEET in aqueous samples from around the world (e.g. drinking water, streams, open seawater, groundwater and treated effluent) with reported DEET concentrations ranging from 40-3000 ng L(-1). In addition, new DEET data collected from 36 sites in coastal waterways from eastern Australia (detections ranging from 8 to 1500 ng L(-1)) are examined. A summary of new and existing toxicity data are discussed with an emphasis on preparing a preliminary risk assessment for DEET in the aquatic environment. Collated information on DEET in the aquatic environment suggests risk to aquatic biota at observed environmental concentrations is minimal. However, the information available was not sufficient to conduct a full risk assessment due to data deficiencies in source characterisation, transport mechanisms, fate, and ecotoxicity studies. These risks warrant further investigation due to the high frequency that this organic contaminant is detected in aquatic environments around the world.

LABORATORY EVALUATION OF 21 INSECT REPELLENTS AS LARVICIDES AND AS OVIPOSITION DETERRENTS OF AEDES ALBOPICTUS (DIPTERA: CULICIDAE)

Twenty-one commercial insect repellent products, including 12 botanical, 6 DEET-based, and 3 synthetic organics, were evaluated as larvicides and as oviposition deterrents of Aedes albopictus. Ten of the 12 botanical products at 0.1% concentration provided 57-100% mortality of laboratory-reared 4th-stage Ae. albopictus larvae at 24 h after treatment. Five of the 6 DEET-based products and 3 synthetic organic repellents at 0.1% concentration induced 88-100% larval mortality at 24 h after treatment. All 12 botanical products proved highly effective oviposition deterrents of Ae. albopictus, resulting in 76-100% effective repellency at 24 h after exposure. The 6 DEET-based repellents and the 3 synthetic organic repellents caused 84-100% effective oviposition repellency of Ae. albopictus at 24 h after exposure. Several botanical repellents previously shown to have minimal protection from mosquito bites proved effective oviposition deterrents. Some commercial topical repellents have good potential for development and use in management of container-inhabiting mosquitoes because they deter oviposition and kill larvae.

Analysis and mass spectrometric characterization of the insect repellent Bayrepel and its main metabolite Bayrepel-acid

Insect repellents such as N,N-diethyl- m-toluamide (DEET) which are used as protection against mosquitoes or ticks were detected in all wastewater and anthropogenically influenced surface waters analyzed. In Germany, the concentrations of DEET have constantly decreased since 1999, when DEET was substituted by Bayrepel (1-piperidinecarboxylic acid, 2-(2-hydroxyethyl), 1-methylpropyl ester; KBR 3023) in commercial insect repellent formulations. A sensitive quantitative method was developed in order to study the occurrence and fate of Bayrepel in the aquatic environment. It was thus determined that Bayrepel undergoes rapid primary aerobic biodegradation, yielding a more stable metabolite, Bayrepel-acid (1-piperidinecarboxylic acid, 1-methylpropyl ester, 2-acetic acid). In order to study the biodegradation and investigate the fate of this metabolite, Bayrepel-acid was synthesized and characterized. Various chromatographic and mass spectrometric techniques, such as gas chromatography–mass spectrometry (MS) after derivatization, liquid chromatography (LC)–electrospray ionization (ESI) MS and LC–ESI time-of-flight MS were applied.

Effect of selected pesticides and their ozonation by-products on gap junctional intercellular communication using rat liver epithelial cell lines

The non-genotoxic effects of two commonly used pesticides, 1,1- bis ( p-chlorophenyl)-2,2,2-trichloroethane (DDT) and malathion, and one widely used commercial insect repellent N,N-diethy- m-toluamide (DEET) on gap junction intercellular communication (GJIC) were determined using a rat liver epithelial cell line. Malathion and DDT reversibly inhibited GJIC in a treatment time- and dose-dependent manner at non-cytotoxic doses, whereas, DEET did not inhibit GJIC. Malathion was very reactive with ozone, while DEET and DDT did not react to any appreciable extent with ozone. The mixtures of ozonation products from malathion and DEET did not inhibit GJIC. The mixtures of ozonation by-products formed from DDT inhibited GJIC, but to a lesser extent than did DDT, itself. These results suggest that ozone can effectively remove malathion from solution without forming GJIC-toxic products, but is less effective in eliminating DEET and DDT from solution.