Insecticidal activity of plant essential oils against Pediculus humanus capitis (Anoplura: Pediculidae)

Insecticidal and Repellent Activity of Essential Oils from Copaifera reticulata, Citrus paradisi, Lavandula hybrida and Salvia sclarea Against Immature and Adult Stages of Ctenocephalides felis felis

PURPOSE

The flea Ctenocephalides felis (Siphonaptera: Pulicidae), parasitizes dogs and cats globally, acting as a vector for various pathogens affecting both animals and humans. Growing interest in environmentally friendly, plant-based products prompted this study. The aim of the study was to determine the chemical composition of essential oils (EOs) from Copaifera reticulata, Citrus paradisi, Lavandula hybrida and Salvia sclarea, assessing their insecticidal and repellent properties, determining lethal concentrations (LC50 and LC90), and evaluating residual efficacy in vitro against Ctenocephalides felis felis.

METHODS

Gas Chromatography with Flame Ionization Detector analyzed EO composition. In vitro tests involved preparing EO solutions at various concentrations. Ten specimens from each life stage (egg, larva, pupa, adult) were used for insecticidal activity assessment. Adulticidal activity was assessed using 10 cm2 filter paper strip, each treated with 0.200 mL of the test solution. Immature stages activities were evaluated using 23.76 cm2 discs of the same filter paper, each treated with 0.470 mL of the test solution. Mortality percentage was calculated using (number of dead insects × 100) / number of incubated insects. Probit analysis calculated LC50 values with a 95% confidence interval.

RESULTS

Major EO constituents were β-caryophyllene (EOCR), linalool (EOLH), linalyl acetate (EOSS), and limonene (EOCP). LC50 values were obtained for all stages except for the essential oil of C. paradisi. All oils showed repellent activity at 800 μg/cm2. OECR exhibited greater residual efficacy.

CONCLUSION

Each EO demonstrated superior insecticidal activity against specific C. felis felis stages.

Toxicity of 6-gingerol and Cymbopogon citratus against Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae): Mortality, detoxifying enzymes, and morphological ultrastructure alterations in lice

Pediculus humanus capitis (head louse), which causes pediculosis capitis, remains a global health concern. Plant products are efficient alternative pediculicides for treating the human ectoparasite P. h. capitis which is resistant to permethrin. The study evaluates the toxicity and mechanisms of 6-gingerol and Cymbopogon citratus leaf extract on P. h. capitis. Pediculus humanus capitis adult stages were exposed to three different dosages of 6-gingerol and C. citratus crude leaf extract on filter sheets for 5, 10, and 30 min, respectively. The biochemical approach was used to assess the activity of detoxifying enzymes including acetylcholinesterase (AChE), glutathione S-transferase (GST), and oxidase. Scanning electron microscope (SEM) was used to investigate the ultrastructure of the morphological body of lice. After 30 min, 6-gingerol and C. citratus leaf extract killed P. h. capitis completely. Bioassay periods significantly affected lice mortality (P < 0.05). The LC50 values for 6-gingerol and C. citratus extract were 1.79 μg/cm2 and 25.0 μg/cm2, respectively. 6-Gingerol and C. citratus leaf extract significantly lower AChE and GST activity (P < 0.05). Cymbopogon citratus also caused morphological ultrastructure changes in P. h. capitis, including an irregularly formed head, thorax, abdominal respiratory spiracles, and belly. 6-Gingerol and C. citratus leaf extracts could be used as an alternate pediculicide to decrease P. h. capitis populations.

Current perspectives and difficulties in the design of acaricides and repellents from plant-derived compounds for tick control

Ticks and tick-borne diseases have gained increasing attention in recent years due to their impact on public health and significant losses in livestock production. The use of synthetic compounds for tick control is becoming problematic, mainly due to the resistance to commercially available products as well as their toxicity. Therefore, new alternative control methods are required. For this purpose, plant-derived extracts may be considered as effective repellents and/or acaricides. The present literature review focuses on studies evaluating the acaricidal and repellent activity of plant-derived extracts and plant secondary metabolites. We also noted recent advances in protein-ligand-docking simulation to examine the possible toxic effect of natural chemical compounds on ticks. In conclusion, plant-derived repellents/acaricides can be effective against ticks, especially in rural areas and livestock farms.

Ovicidal and Pediculicidal Activity of Indigofera suffruticosa Mill. Leaf Oil on Pediculus humanus capitis Egg to Adult Stages

PURPOSE

Pediculosis capitis, commonly known as head lice infestation, represents a significant health 26 problem for school children worldwide. Repeated and long-term usages of highly toxic pediculicides have resulted in the development of increased levels of resistance and do not kill louse eggs. Alternative pediculicides, such as herbal products, have recently been proposed for the treatment of head lice infestation, thereby decreasing toxicity.

METHODS

This study analyzed the chemical composition of I. suffruticosa leaf extracts using GC-MS and evaluated the effects of Indigofera suffruticosa Mill. (I. suffruticosa) leaf extract on the mortality of head lice and their eggs.

RESULTS

The major five components of the tested oils identified were as follows: n-hexadecanoic acid, hexadecanoic acid, ethyl ester, oleic acid, (E)-9-octadecenoic acid ethyl ester, and linoleic acid ethyl ester. The effective pediculicide of the I. suffruticosa leaf extracts affected head lice in all stages (egg, nymph, and adults). The concentrations of I. suffruticosa leaf extracts at 500 mg/mL produced the highest effective ovicidal on egg with 96.6% unhatching and pediculicide on nymphs and adults with 96.7 ± 5.7% and 86.7 ± 5.7% mortality, respectively, at 60 min (LT50 value < 10 min). The analysis of the external structure of the adult-stage head lice by SEM examination revealed that dead lice exposed to I. suffruticosa leaf extract displayed damage to the outer smooth architecture and obstructed the respiratory spiracles.

CONCLUSION

We may conclude that the application of I. suffruticosa leaf extract produces an effective herbal pediculicide capable of affecting all stages of head lice.

Essential Oils in Urban Insect Management-A Review

The allures of city life have culminated in the rise of urban populations resulting in conditions that promote the establishment of certain insect pests. Globally, the public health significance of these urban insect pests is enormous, ranging from billions of dollars to loss of lives. Most chemical insecticides no longer provide the anticipated level of control, and significant insecticide resistance has been reported. Therefore, there has been a spike in interest for alternatives to conventional insecticides. Among them, natural products from plants such as essential oils (EOs) and essential oil components (EOCs) have enjoyed the most attention owing to widespread reports of efficacy and toxicity even against insecticide-resistant urban insects. Yet, there is no comprehensive synthesis on the extent and impact of the management of urban insects using EOs or EOCs. Such a review is highly relevant since it provides a means to assess the extent of progress made, shortfalls, limitations, and prospects. More so, we hope it can be used to make informed decisions and develop relevant policies reliably. We present the ranges of insecticidal effects of EOs, EOCs, and commercially available EO-based products from laboratory and field studies. Finally, we discuss the gaps in our knowledge and prospects for the sustainable use of EOs.

Antiparasitic Activity of Tea Tree Oil (TTO) and Its Components against Medically Important Ectoparasites: A Systematic Review

Ectoparasites are pathogens that can infect the skin and cause immense pain, discomfort, and disease. They are typically managed with insecticides. However, the fast-emerging antimicrobial resistance and the slow rate of development of new bio-actives combined with environmental and health concerns over the continued use of neurotoxic insecticides warrant newer and alternative methods of control. Tea tree oil (TTO), as an alternative agent, has shown remarkable promise against ectoparasites in recent studies. To our knowledge, this is the first systematic review to assess preclinical and clinical studies exploring the antiparasitic activity of TTO and its components against clinically significant ectoparasites, such as Demodex mites, scabies mites, house dust mites, lice, fleas, chiggers, and bed bugs. We systematically searched databases, including PubMed, MEDLINE (EBSCOhost), Embase (Scopus), CENTRAL, Cochrane Library, CINAHL, ScienceDirect, Web of Science, SciELO, and LILACS in any language from inception to 4 April 2022. Studies exploring the therapeutic activity of TTO and its components against the ectoparasites were eligible. We used the ToxRTool (Toxicological data reliability assessment) tool, the Joanna Briggs Institute (JBI) critical appraisal tools, and the Jadad scale to assess the methodological qualities of preclinical (in vitro and in vivo) studies, non-randomised controlled trials (including cohort, case series, and case studies), and randomised controlled trials, respectively. Of 497 identified records, 71 studies were included in this systematic review, and most (66%) had high methodological quality. The findings of this review revealed the promising efficacy of TTO and its components against ectoparasites of medical importance. Most importantly, the compelling in vitro activity of TTO against ectoparasites noted in this review seems to have translated well into the clinical environment. The promising outcomes observed in clinical studies provide enough evidence to justify the use of TTO in the pharmacotherapy of ectoparasitic infections.

Chemical Composition, Antioxidant, Insecticidal Activity, and Comparative Analysis of Essential Oils of Leaves and Fruits of Schinus molle and Schinus terebinthifolius

Schinus terebinthifolius Raddi. and Schinus molle L. are perennial woody plants belonging to the Anacardiaceae family, widely distributed in the United States, Europe, Asia, and Africa, and they are broadly used for many applications such as in traditional medicine as an antipyretic, analgesic, depurative, and in the treatment of diseases of the urogenital system as well as culinary and ornamental species. Our work aims to study and compare the chemical composition and the antioxidant and insecticidal activity of the essential oils of the leaves and fruits of the two species of the genus Schinus. The essential oils were characterized by a very spicy aromatic odor, and by the abundance of hydrocarbon monoterpenes in the leaves and fruits of Schinus molle (49.70% and 42.65%), unlike the EOs of the fruits of Schinus terebinthifolius which have a high content in hydrocarbon sesquiterpenes (40.57%). Usually, these oils have shown relatively low antioxidant activity was expressed in IC₅₀; especially, the essential oil of the fruits of S. terebinthifolius revealed a concentration of 3.292 ± 2.82 mg/mL. The evaluation of the insecticidal activity gave good results in the method of exposure of adults of Sitophilus oryzae to EOs by contact; thus, the fruits of Schinus molle are more active against this species of beetle than the other essential oil.

The Toxicity of Essential Oils From Three Origanum Species Against Head Louse, Pediculus humanus capitis

PURPOSE

Pediculosis caused by human head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae) is a public health problem with a high prevalence, especially among children in school age. Different chemical pediculicides (insecticides) are used against lice but the repeated application of these pediculicides for the treatment of P. humanus capitis infestation in the past decades has resulted in the development of resistance. The plant essential oils have been used as alternative sources of lice treatment agents. Pediculicidal activity of the essential oils of three Origanum species (O. onites, O. majorana and O. minutiflorum) against P. humanus capitis adults was examined in this study.

METHODS

Essential oils from aerial parts of three Origanum species were obtained by hydrodistillation using a Clevenger-type apparatus. P. humanus capitis specimens used were obtained from infested children by combing method at primary schools. Adult lice were exposed to three dilutions (1%, 0.5% and 0.1% w/v) of tested oils for 5 min using the adult immersion test.

RESULTS

According to the results, all Origanum essential oils at 1% concentration have been shown to significantly decrease the rate of limb, bowel and abdomen movements, producing more than 90% mortality after 12 h.

CONCLUSION

Our results indicated that Origanum essential oils can be used for the development of new pediculicides against head louse.

Phytochemical Constituents, Antimalarial Efficacy, and Protective Effect of Eucalyptus camaldulensis Aqueous Leaf Extract in Plasmodium berghei-Infected Mice

This study examined the bioactive components of Eucalyptus camaldulensis aqueous leaf extracts and their protective effects on liver and renal function in a Plasmodium berghei-induced albino mouse model of malarial infection. The results showed that E. camaldulensis extracts are rich in phytochemicals, including flavonoids, phenols, saponin, terpenes, and tannin. Four days after infection with malaria, elevated parasitemia levels in untreated control mice dropped by 4.57%. Administration of E. camaldulensis extracts at doses of 100, 200, and 300 mg/kg significantly decreased parasitemia levels by 17.39, 61.88, and 60.53%, respectively (all P<0.05), relative to untreated control mice; however, standard antimalarial drugs were more efficacious and reduced parasitemia by 86.73%. Treatment with both E. camaldulensis extracts (100∼300 mg/kg) and standard antimalarial drugs significantly decreased malarial-induced physiological imbalances in liver and renal biomarkers, and serum electrolytes in malaria-infected mice compared with controls (P<0.05). The therapeutic effect of E. camaldulensis was greatest at a dose of 200 and 300 mg/kg. These findings indicate that E. camaldulensis aqueous leaf extracts could protect against malarial-induced aberrations in liver and renal function whilst exhibiting anti-malarial effects, and could explain its use as an antimalarial remedy in traditional medicine.

Prolonged Insecticidal Activity of Clove oil-Loaded Halloysite Nanotubes on Plodia interpunctella Infestation and Application in Industrial-Scale Food Packaging

Previous study reported the development of insect-proof halloysite nanotubes (HNTs) and food packaging; however, the duration of their insecticidal properties remains unclear. Here, we aimed to (1) demonstrate the duration of repellency of clove bud oil (CO) encapsulated by HNTs for more than 30 days, and (2) manufacture insect-proof film containing HNTs for commercial use. Also, the release behavior of CO from insect-resistant HNTs was evaluated and HNTs were applied to food packaging composed of polypropylene and low-density polyethylene films to prevent Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) larva infestation. CO, a natural insecticide, was embedded with HNTs and polyethyleneimine (PEI) via vacuum pulling process to cause a slow and gradual release of CO. The sustained release profile of CO from CO-containing HNTs with a PEI coating [(HNTs/CO/layer-by-layer (LBL)] was verified by gas chromatography analysis. The repellent activity of HNTs/CO/LBL was observed for up to 46 days, whereas CO film and HNTs/CO film exhibited no insecticidal activities during the test period. After 30-day exposure, the HNTs/CO/LBL film exhibited a 7-day extension in the penetration test. To evaluate the insecticidal properties of the insect-proof film (HNTs/CO/LBL scale-up film) manufactured in an industrial facility, the inhibitory effects of HNTs/CO/LBL scale-up film on insect infestation was elucidated in both the segregation and combination tests. As a result, HNTs/CO/LBL alone or gravure-printed film treated with HNTs/CO/LBL were capable of protecting food from insect infestation. PRACTICAL APPLICATION: Halloysite nanotubes containing natural insect repellent were applied to industrial production of food packaging. Commercial cornflake cereal packaging using insect-resistant film successfully inhibited pest infestation. Insect-proof film produced at an industrial facility can be utilized to protect processed food from insect infestation.

The repellency and toxicity effects of essential oils from the Libyan plants Salvadora persica and Rosmarinus officinalis against nymphs of Ixodes ricinus

Essential oils extracted from the leaves of Libyan Rosemary (Rosmarinus officinalis L.), and Miswak (Salvadora persica L.) were evaluated for their acaricidal and repellent effects on Ixodes ricinus L. nymphs (Acari: Ixodidae) using a bioassay based on an 'open filter paper method'. Rosmarinus officinalis leaf essential oil diluted to 0.5 and 1 µl/cm² in acetone exhibited, respectively, 20 and 100% tick mortality after about 5 h of exposure. A total of 50 and 95% of I. ricinus nymphs were killed by direct contact with the oil when exposed to lethal concentrations (LC) of 0.7 µl/cm² (LC₅₀) and 0.95 µl/cm² (LC₉₅), respectively. The LC₅₀ (0.5 µl/cm²) was reached before the end of the first 24 h of exposure time (ET), as tick mortality at 24 h was 60%. Salvadora persica leaf essential oil at 1 µl/cm² showed a significant repellency effect against I. ricinus nymphs at 1.5 h ET. A 95% repellency was observed at a repellent concentration (RC₉₅) of 1 µl/cm² of S. persica, but no significant mortality was recorded at this dose of S. persica oil. Gas chromatography-mass spectrometry analyses showed that the main monoterpenes in both oils were 1,8-cineol, α-pinene, and β-pinene, although in markedly different proportions. These results suggest that essential oils have substantial potential as alternative approaches for I. ricinus tick control.

The Medicinal Use of Essential Oils and Their Components for Treating Lice and Mite Infestations

Recent studies have demonstrated that essential oils, and in particular, pennyroyal, tea tree and anise, have potent insecticidal and acaricidal (mite-killing) activity. The individual components of essential oils are now being investigated in order to give a rational basis to discover which essential oils may prove to be the most effective all-round agents for killing headlice and their eggs, and treating scabies, and for eliminating house dust mites, a major cause of asthma.

Acaricidal properties of ylang-ylang oil and star anise oil against nymphs of Ixodes ricinus (Acari: Ixodidae)

Ylang-ylang oil (YYO) from Cananga odorata (Lam.) Hook.f. & Thomson and star anise oil (SAO) from Illicium verum Hook.f. were tested at four concentrations 0.05, 0.1, 0.2, 0.4 µl/cm². Mortality rates were obtained by counting dead nymphs at 30-min intervals during the first 5 h after the start of exposure and then at 24, 48 and 72 h. Mortality increased with increasing oil concentration and time of exposure. The two highest concentrations of YYO (0.2, 0.4 µl/cm²) gave maximum lethal concentrations (LC) of 50 and 95% mortality after 4.5 h exposure. Mortality of 95% was obtained after 24 h with the next highest dose (0.1 µl/cm²), whereas LC₉₅ required 3 days with the lowest YYO (0.05 µl/cm²). The lethal effect time (LT) was correlated with the duration of exposure, with a significant effect at 0.4 μl YYO/cm² after 3 h' (LT₅₀= 3.2 h, LT₉₅= 4.3 h). In contrast, only the highest concentration of SAO, 0.4 µl SAO/cm², showed increasing mortality with time of exposure. This reached LT₅₀ after 10 h and LT₉₅ after 24 h. However, with the lower concentration (0.2 µl/cm²) 50% mortality was reached after 24 h and 100% at 72 h. At to the lowest concentration of SAO (0.1 µl/cm²), 67% mortality after 48 h. The study indicates that YYO and SAO exhibit strong acaricidal properties against nymphs of I. ricinus and suggest that both YYO and SAO should be evaluated as potentially useful in the control of ticks.

In vitro efficacy of five essential oils against Pediculus humanus capitis

Treatment of head lice has relied mainly on the use of topical insecticides. Today, conventional topical pediculicides have suffered considerable loss of activity worldwide. There is increasing interest in the use of natural products such as essential oils for head louse control, and many of them are now incorporated into various over-the-counter products presented as pediculicides, often without proper evaluation. The aim of the present study was to assess the in vitro efficacy of five essential oils against adults of Pediculus humanus capitis using a contact filter paper toxicity bioassay. The chemical composition of the essential oils from wild bergamot, clove, lavender, tea tree, and Yunnan verbena was analyzed by gas chromatography-mass spectrometry. All treatments and controls were replicated three times on separate occasions over a period of 11 months. In all, 1239 living lice were collected from the scalp of 51 subjects, aged from 1 to 69 years. Clove oil, diluted either in coco oil or sunflower oil, demonstrated the best adulticidal activity, reaching > 90% mortality within 2 h in lice submitted to a 30-min contact. Yunnan verbena oil diluted in coco oil showed also a significant efficacy. Other essential oils showed a lower efficacy. The oil's major component(s) differed according to the tested oils and appeared chemically diverse. In the case of clove oil, the eugenol appeared as the main component. This study confirmed the potential interest of some of the essential oils tested, but not all, as products to include possibly in a pediculicidal formulation.

Insecticidal activities of their components derived from the essential oils of Cinnamomum sp. barks and against Ricania sp. (Homoptera: Ricaniidae), a newly recorded pest

BACKGROUND

Insecticidal activities of Cinnamomum cassia and Cinnamomum zeylanicum oils and their components are not known against Ricania sp. Insecticidal activities of major components derived from C. cassia and C. zeylanicum oils were examined in spray and leaf-dipping bioassays against Ricania sp. nymphs and adults.

RESULTS

The LC₅₀ value of C. cassia and C. zeylanicum oils was 37.66 and 72.62 mg L^-1 , respectively, in leaf-dipping bioassays against Ricania sp. nymphs, and 77.38 and 134.86 mg L^-1 in spray bioassays against Ricania sp. adults. The insecticidal activity of C. cassia oil was 1.74-1.93 times greater than that of C. zeylanicum oil. When examined by gas chromatography mass spectrometry, the cinnamaldehyde content of C. cassia and C. zeylanicum oils was 80.20% and 46.32%, respectively. Based on the LC₅₀ values of cinnamaldehyde, hydrocinnamaldehyde and 4-hydroxy-3-methoxycinnamaldehyde against Ricania sp. nymphs and adults, cinnamaldehyde (LC₅₀ , 31.25 and 62.43 mg L^-1 ) demonstrated the most potent insecticidal activity, followed by 4-hydroxy-3-methoxycinnamaldehyde (172.19 and 212.77 mg L^-1 ) and hydrocinnamaldehyde (275.05 and 318.63 mg L^-1 ).

CONCLUSION

The findings revealed that C. cassia oil, C. zeylanicum oil and cinnamaldehyde have potential value in the management of Ricania sp. and could be valuable as effective insecticides. © 2017 Society of Chemical Industry.

In vitro activity of ten essential oils against Sarcoptes scabiei

Background

The development of alternative approaches in ectoparasite management is currently required. Essential oils have been demonstrated to exhibit fumigant and topical toxicity to a number of arthropods. The aim of the present study was to assess the potential efficacy of ten essential oils against Sarcoptes scabiei.

Methods

The major chemical components of the oils were identified by GC-MS analysis. Contact and fumigation bioassays were performed on Sarcoptes mites collected from experimentally infected pigs. For contact bioassays, essential oils were diluted with paraffin to get concentrations at 10, 5, and even 1% for the most efficient ones. The mites were inspected under a stereomicroscope 10, 20, 30, 40, 50, 60, 90, 120, 150, and 180min after contact. For fumigation bioassay, a filter paper was treated with 100 μL of the pure essential oil. The mites were inspected under a stereomicroscope for the first 5min, and then every 5min until 1h.

Results

Using contact bioassays, 1% clove and palmarosa oil killed all the mites within 20 and 50min, respectively. The oils efficacy order was: clove > palmarosa > geranium > tea tree > lavender > manuka > bitter orange > eucalyptus > Japanese cedar. In fumigation bioassays, the efficacy order was: tea tree > clove > eucalyptus > lavender > palmarosa > geranium > Japanese cedar > bitter orange > manuka. In both bioassays, cade oil showed no activity.

Conclusion

Essential oils, especially tea tree, clove, palmarosa, and eucalyptus oils, are potential complementary or alternative products to treat S. scabiei infections in humans or animals, as well as to control the mites in the environment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1889-3) contains supplementary material, which is available to authorized users.

Comparative and synergistic activity of Rosmarinus officinalis L. essential oil constituents against the larvae and an ovarian cell line of the cabbage looper, Trichoplusia ni (Lepidoptera: Noctuidae)

BACKGROUND

Plant essential oils are usually complex mixtures, and many factors can affect their chemical composition. To identify relationships between the composition and bioactivity of the constituents, comparative and synergistic interactions of the major constituents of rosemary essential oil were evaluated against third-instar larvae and an ovarian cell line of the cabbage looper, Trichoplusia ni, via different methods of application.

RESULTS

The major constituents of the rosemary oil we used were 1,8-cineole, (±)-camphor, (+)-α-pinene and camphene. Via topical application to larvae, 1,8-cineole was identified as the major active compound, whereas via fumigation, 1,8-cineole and (±)-camphor, and in a cytotoxicity assay, (+)-α-pinene, were determined to be the major active principles. Several combinations of these constituents exhibited synergistic insecticidal activities when topically applied, particularly among combinations of three major constituents, (±)-camphor, (+)-α-pinene and camphene. A binary mixture of 1,8-cineole and (±)-camphor showed enhanced activity, with a synergy ratio of 1.72.

CONCLUSION

Based on our results, the insecticidal activity of rosemary oil appears to be a consequence of the synergistic interaction between 1,8-cineole and (±)-camphor, and (±)-camphor should be considered a promising synergizing agent.

Laboratory and clinical trials of cocamide diethanolamine lotion against head lice

Context. During the late 1990s, insecticide resistance had rendered a number of treatment products ineffective; some companies saw this as an opportunity to develop alternative types of treatment. We investigated the possibility that a surfactant-based lotion containing 10% cocamide diethanolamine (cocamide DEA) was effective to eliminate head louse infestation.

Settings and Design. Initial in vitro testing of the lotion formulation versus laboratory reared body/clothing lice, followed by two randomised, controlled, community-based, assessor blinded, clinical studies.

Materials and Methods. Preliminary laboratory tests were performed by exposing lice or louse eggs to the product using a method that mimicked the intended use. Clinical Study 1: Children and adults with confirmed head louse infestation were treated by investigators using a single application of aqueous 10% cocamide DEA lotion applied for 60 min followed by shampooing or a single 1% permethrin creme rinse treatment applied to pre-washed hair for 10 min. Clinical Study 2: Compared two treatment regimens using 10% cocamide DEA lotion that was concentrated by hair drying. A single application left on for 8 h/overnight was compared with two applications 7 days apart of 2 h duration, followed by a shampoo wash.

Results. The initial laboratory tests showed a pediculicidal effect for a 60 min application but limited ovicidal effect. A longer application time of 8 h or overnight was found capable of killing all eggs but this differed between batches of test material. Clinical Study 1: Both treatments performed badly with only 3/23 (13%) successful treatments using cocamide DEA and 5/25 (23.8%) using permethrin. Clinical Study 2: The single overnight application of cocamide DEA concentrated by hair drying gave 10/56 (17.9%) successes compared with 19/56 (33.9%) for the 2 h application regimen repeated after 1 week. Intention to treat analysis showed no significant difference (p = 0.0523) between the treatments. Over the two studies, there were 18 adverse events possibly or probably associated with treatment, most of which were increased pruritus after treatment.

Conclusions. Cocamide DEA 10% lotion, even when concentrated by hair drying, showed limited activity to eliminate head louse infestation.

Control of the chewing louse Bovicola (Werneckiella) ocellatus in donkeys, using essential oils

Infestations by lice can be a significant clinical and welfare issue in the management of large animals. The limited range of commercial pediculicides available and the development of resistance have led to the need to explore alternative louse management approaches. The results of in vitro and in vivo trials undertaken to control populations of the donkey chewing louse, Bovicola ocellatus (Piaget) (Phthiraptera: Trichodectidae) using the essential oils of tea tree (Melaleuca alternifolia) and lavender (Lavandula angustifolia) are reported here. Results of contact and vapour bioassays showed that 5% (v/v) tea tree and lavender oils resulted in > 80% louse mortality after 2 h of exposure. On farms, separate groups of 10 donkeys sprayed with 5% (v/v) tea tree and lavender oil as part of their usual grooming regime showed significant reductions in louse numbers compared with a control group (0.2% polysorbate 80 in water). These findings indicate that tea tree and lavender essential oils can provide clinically useful levels of control of B. ocellatus when used as part of a grooming routine and suggest that with further development could form the basis of an easy to apply and valuable component of a louse management programme for donkeys.

Prevention of vector transmitted diseases with clove oil insect repellent

Vector repellent is one element in the prevention of vector-borne diseases. Families that neglect protecting their children against vectors risk their children contracting illnesses such as West Nile virus, eastern equine encephalitis, Lyme disease, malaria, dengue hemorrhagic fever, yellow fever, babesiosis, Crimean-Congo hemorrhagic fever, Rocky Mountain spotted fever, Southern tick-associated rash illness, ehrlichiosis, tick-borne relapsing fever, tularemia, and other insect and arthropod related diseases (CDC, 2011). Identification of families at risk includes screening of the underlying basis for reluctance to apply insect repellent. Nurses and physicians can participate in a positive role by assisting families to determine the proper prophylaxis by recommending insect repellent choices that are economical, safe, and easy to use. A holistic alternative might include the suggestion of clove oil in cases where families might have trepidations regarding the use of DEET on children. This article will explore the safety and effectiveness of clove oil and its use as an insect repellent.

An evidence-based systematic review of rosemary (Rosmarinus officinalis) by the Natural Standard Research Collaboration

An evidence-based systematic review of rosemary (Rosmarinus officinalis), including written and statistical analysis of scientific literature, expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology, and dosing.

Pediculosis capitis: new insights into epidemiology, diagnosis and treatment

Pediculosis capitis is a ubiquitous parasitic skin disease caused by Pediculus humanus capitis. Head lice are highly specialised parasites which can propagate only on human scalp and hair. Transmission occurs by direct head-to-head contact. Head lice are vectors of important bacterial pathogens. Pediculosis capitis usually occurs in small epidemics in play groups, kindergartens and schools. Population-based studies in European countries show highly diverging prevalences, ranging from 1% to 20%. The diagnosis of head lice infestation is made through the visual inspection of hair and scalp or dry/wet combing. The optimal method for the diagnosis of active head lice infestation is dry/wet combing. Topical application of a pediculicide is the most common treatment. Compounds with a neurotoxic mode of action are widely used but are becoming less effective due to resistant parasite populations. Besides, their use is restricted by safety concerns. Dimeticones, silicone oils with a low surface tension and the propensity to perfectly coat surfaces, have a purely physical mode of action. This group of compounds is highly effective and safe, and there is no risk that head lice become resistant. The control of epidemics requires active contact tracing and synchronised treatment with an effective and safe pediculicide.

Composition and biological activity of essential oils from Labiatae against Nezara viridula (Hemiptera: Pentatomidae) soybean pest

BACKGROUND

Plant essential oils have been recognised as an important natural source of insecticide. This study analysed the chemical constituents and bioactivity of essential oils that were isolated via hydrodistillation from Origanum vulgare L. (oregano) and Thymus vulgaris L. (thyme) against eggs, second instar and adults of Nezara viridula (L.).

RESULTS

The major component of oregano was p-cymene, and, for thyme, thymol. The ovicidal activity was tested by topical application; the essential oil from thyme was more effective. The fumigant activity was evaluated in an enclosed chamber; the LC50 values for oregano were 26.8 and 285.6 µg mL(-1) for nymphs and adults respectively; for thyme they were 8.9 µg mL(-1) for nymphs and 219.2 µg mL(-1) for adults. To evaluate contact activity, a glass vial bioassay was used; the LC50 values for oregano were 1.7 and 169.2 µg cm(-2) for nymphs and adults respectively; for thyme they were 3.5 and 48.8 µg cm(-2) respectively. The LT50 analyses for contact and fumigant bioassays indicated that thyme was more toxic for nymphs and adults than oregano. Both oils produced repellency on nymphs and adults.

CONCLUSION

These results showed that the essential oils from O. vulgare and T. vulgaris could be applicable to the management of N. viridula.

Contact and fumigant toxicity of hexane flower bud extract of Syzygium aromaticum and its compounds against Pediculus humanus capitis (Phthiraptera: Pediculidae)

The head lice, Pediculus humanus capitis De Geer is an obligate ectoparasite of humans that causes pediculosis capitis, a nuisance for millions of people worldwide, with high prevalence in children. P. humanus capitis has been treated by methods that include the physical remotion of lice, various domestic treatments, and conventional insecticides. None of these methods render complete protection, and there is clear evidence for the evolution of resistance and cross-resistance to conventional insecticides. Non-toxic alternative options are hence needed for head lice treatment and/or prevention, and natural products from plants are good candidates for safer control agents that may provide good anti-lice activity. The plant extracts are good and safe alternatives due to their low toxicity to mammals and easy biodegradability. The present study carried out the pediculocidal activity using the hexane flower bud extract of Syzygium aromaticum (Myrtaceae) against P. humanus capitis examined by direct contact and fumigant toxicity (closed- and open-container methods) bioassay. The chemical composition of S. aromaticum flower bud hexane extract was analyzed by gas chromatography-mass spectrometry. The major chemical constituent (58.79%) of flower bud hexane extract S. aromaticum was identified as chavibetol (5-allyl-2-methoxyphenol) by comparison of mass spectral data and retention times. The hexane extract of S. aromaticum was subjected to gas chromatography analysis, and totally 47 compounds were detected, of which chavibetol was predominantly present. The other major constituents present in the hexane extract were eugenol acetate (phenol,2-methoxy-4-(2-propenyl)-,acetate (15.09%), caryophyllene-(I1) (2,6,10,10-tetramethyl bicyclo [7.2.0] undeca-1,6-diene (13.75%), caryophyllene oxide (3.04%), 2,6,6,9-tetramethyl-1,4,8-cycloundecatriene (1.67%), and copaene (1.33%). The filter paper contact bioassay study showed pronounced pediculicidal activity in the flower bud hexane extract of S. aromaticum. The toxic effect was determined for every five in an 80-min treatment. The result showed percent mortality of 40, 82, and 100 at 5, 10, and 20 min, and the median lethal time (LT(50)) value was 5.83 (0.5 mg/cm(2)); 28, 82, and 100 at 5, 10, and 30 min. (LT(50) = 6.54; 0.25 mg/cm(2)); and 13, 22, 42, 80, and 100 at 5, 10, 20, 40, and 80 min (LT(50) = 18.68; 0.125 mg/cm(2)), respectively. The vapor phase toxicity was tested at 0.25 mg/cm(2). There was a significant difference in pediculicidal activity of S. aromaticum extract against P. humanus capitis between closed- and open-container methods. Adult mortalities were determined for every five in 60 min (closed method) and for every ten in 180 min (open method). The closed method showed the percent mortality was 45, 88, and 100 at 5, 10, and 15 min (LT(50) = 5.39), respectively. In the open-container method, the percent mortality was observed 5, 20, 47, 84, and 100 at 10, 20, 60, 120, and 180 min (LT(50) = 47.91), respectively. The mortality was more effective in the closed containers than in open ones, indicating that the effect of hexane extract was largely a result of action in the vapor phase exhibited fumigant toxicity. Studies of anti-lice activity of extract provide the basis for preliminary conclusions of structure activity relationships; although no clear patterns can yet be drawn. We here attempt to provide a concise compilation of the available information on anti-lice activity of plant extracts and plant-derived compounds.

Control of the myiasis-producing fly, Lucilia sericata, with Egyptian essential oils

BACKGROUND

Myiasis caused by Lucilia sericata (Diptera: Calliphoridae) is widely distributed throughout the world and affects both humans and animals. In addition, L. sericata larvae and adults may play a role in spreading causal agents of mycobacterial infections. Therefore, it is important to establish new and safe alternative methods of controlling this blowfly.

METHODS

The insecticidal effectiveness of four commercially available essential oils [lettuce (Lactuca sativa), chamomile (Matricaria chamomilla), anise (Pimpinella anisum), rosemary (Rosmarinus officinalis)] against third larval instars of L. sericata was evaluated. The effects of sublethal concentrations of these oils on pupation rates, adult emergences, sex ratios, and morphological anomalies were also determined.

RESULTS

The oils were highly toxic to L. sericata larvae, with median lethal concentrations (LC(50) ) of 0.57%, 0.85%, 2.74%, and 6.77% for lettuce, chamomile, anise, and rosemary oils, respectively. Pupation rates were markedly decreased after treatment with 8% lettuce oil, and adult emergence was suppressed by 2% lettuce and chamomile oils. Morphological abnormalities were recorded after treatment with all tested oils, and lettuce was the major cause of deformation. There was a predominance of males over females (4 : 1) after treatment with lower concentrations of chamomile and rosemary; such a skew toward males would lead to a population decline.

CONCLUSIONS

The four tested oils are inexpensive and may represent new botanical insecticides for controlling blowflies.

Fumigant toxicity of essential oils to the German cockroach (Dictyoptera: Blattellidae)

The fumigant toxicity of 12 essential oil components [carvacrol, 1,8-cineole, trans-cinnamaldehyde, citronellic acid, eugenol, geraniol, S-(-)-limonene, (-)-linalool, (-)-menthone, (+)-alpha-pinene, (-)-beta-pinene, and thymol] to adult male, adult female, gravid female, and large, medium, and small nymphs of the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae), was determined. 1,8-Cineole was the most toxic essential oil component to adult males and females, gravid females, and large nymphs, with LC50 values of 6.8, 8.4, 5.3, and 11.4 mg/liter air at 24 h, respectively. (-)-Menthone and carvacrol were the most toxic essential oil components to medium and small nymphs, with LC50 values of 9.0 and 3.6 mg/liter air at 24 h, respectively. Citronellic acid was the least toxic essential oil component to all stages of the German cockroach. There was not a consistent relationship between body mass and toxicity; the susceptibility of the stages differed for each oil. LC50 values of all stages were correlated negatively with vapor pressure and positively with molecular weight of the essential oil components. The most toxic essential oil components to the majority of cockroach stages were cyclic aliphatic hydrocarbons [1,8-cineole, (-)-menthone, (+)-alpha-pinene, (-)-beta-pinene, and S-(-)-limonene]. Ring size and the presence of a carbonyl functional group also may have contributed to the toxicity of the compounds. Citronellic acid had no effect on ootheca hatch (100% hatch), whereas (-)-menthone had the greatest effect on ootheca hatch (73% hatch). Percentage of hatched oothecae decreased linearly with increasing concentration for (-)-menthone, S-(-)-limonene, (+)-alpha-pinene, and (-)-beta-pinene. No essential oil component prevented ootheca hatch, suggesting that multiple treatments would be required in the field to eliminate infestations.

Evaluation of semiochemical toxicity to Aedes aegypti, Ae. albopictus and Anopheles quadrimaculatus (Diptera: Culicidae)

BACKGROUND

Mosquitoes are the most important vectors of human pathogens. Wide-scale use of pesticides has led to the development of resistance to most common insecticide groups. The need to develop novel products that have a low impact on human health and the environment is well established. The toxicity of selected semiochemicals with molecular structures indicative of insecticidal activity was determined against adult Aedes aegypti (L.) and Anopheles quadrimaculatus (Say). The two most active insecticides against Ae. aegypti were also evaluated against Ae. albopictus (Skuse).

RESULTS

Fifteen semiochemicals classified as terpenoid alcohols, ketones or carboxylic esters showed toxicity to both mosquito species. Geranyl acetone (LC(50) = 38.51 microg cm(-2)) followed by citronellol (LC(50) = 48.55 microg cm(-2)) were the most toxic compounds to Ae. aegypti, while geraniol and lavonax, with LC(50) values of 31.88 and 43.40 microg cm(-2), showed the highest toxicity to An. quadrimaculatus. Both geranyl acetone and citronellol were highly toxic to Ae. albopioctus. No semiochemical showed fumigation activity against either species. All semiochemicals persisted for less than 24 h when tested on filter paper.

CONCLUSION

Quantification of LC(50) values of several semiochemicals against Ae. Aegypti, An. quadrimaculatus and Ae. albopioctus showed that semiochemicals not only modify insect behaviors but also hold potential as potent insecticides for mosquito control programs.

Acaricidal Activity against Tetranychus urticae and Chemical Composition of Peel Essential Oils of Three Citrus Species Cultivated in NE Brazil

The repellency and fumigant toxicities of the peel essential oils of Citrus sinensis var. pêra (LP), C. sinensis var. mimo ( LM), and C. aurantium ( LL) cultivated in northeast Brazil were evaluated against Tetranychus urticae. Analysis of the oils by GC and GC/MS led to the identification of twenty-eight components, which represented 99.9%, 99.7% and 99.3% of the total constituents of the LP, LM and LL oils, respectively. Limonene was the main component found in all three oils. Other main components were α-pinene (1.5% in LP; 1.4% in LM), myrcene (5.7% in LP; 5.9% in LM and 5.6% in LL) and linalool (2.4% in LP; 2.3% in LM and 3.9% in LL). The best repellency action was observed for LM at 2.0%, followed by LL oil and eugenol, both of them at 2.5%. The Citrus oils were less active than eugenol (LC50 = 0.004 μL/L air) and phosphine, which revealed 100% mortality at 2×10−3g/L (66.7% of the recommended dose). However, the most potent fumigant toxicity was found with LL oil, with an LC50 value of 1.63 μL/L air, followed by the oils from LM and LP with LC50 values of 2.22 μL/L air and 4.63 μL/L air, respectively. The associated fumigant and repellent properties of these Citrus peel oils, particularly those of C. aurantium and C. senensis var. mimo, could be used to advantage for the control of T. urticae.

In vitro screening of anti-lice activity of Pongamia pinnata leaves

Growing patterns of pediculocidal drug resistance towards head louse laid the foundation for research in exploring novel anti-lice agents from medicinal plants. In the present study, various extracts of Pongamia pinnata leaves were tested against the head louse Pediculus humanus capitis. A filter paper diffusion method was conducted for determining the potential pediculocidal and ovicidal activity of chloroform, petroleum ether, methanol, and water extracts of P. pinnata leaves. The findings revealed that petroleum ether extracts possess excellent anti-lice activity with values ranging between 50.3% and 100% where as chloroform and methanol extracts showed moderate pediculocidal effects. The chloroform and methanol extracts were also successful in inhibiting nymph emergence and the petroleum ether extract was the most effective with a complete inhibition of emergence. Water extract was devoid of both pediculocidal and ovicidal activities. All the results were well comparable with benzoyl benzoate (25% w/v). These results showed the prospect of using P. pinnata leave extracts against P. humanus capitis in difficult situations of emergence of resistance to synthetic anti-lice agents.

Lousicidal, ovicidal and repellent efficacy of some essential oils against lice and flies infesting water buffaloes in Egypt

The lousicidal and repellent effects of five essential oils were investigated for the first time against the buffalo louse, Haematopinus tuberculatus, and flies infesting water buffaloes in Qalyubia Governorate, Egypt. For the in vitro studies, filter paper contact bioassays were used to test the oils and their lethal activities were compared with that of d-phenothrin. Four minutes post-treatment, the median lethal concentration, LC50, values were 2.74, 7.28, 12.35, 18.67 and 22.79% for camphor (Cinnamomum camphora), onion (Allium cepa), peppermint (Mentha piperita), chamomile (Matricaria chamomilla) and rosemary oils (Rosmarinus officinalis), respectively, whereas for d-phenothrin, it was 1.17%. The lethal time (50) (LT50) values were 0.89, 2.75, 15.39, 21.32, 11.60 and 1.94 min after treatment with 7.5% camphor, onion, peppermint, chamomile, rosemary and d-phenothrin, respectively. All the materials used except rosemary, which was not applied, were ovicidal to the eggs of H. tuberculatus. Despite the results of the in vitro assays, the in vivo treatments revealed that the pediculicidal activity was more pronounced with oils. All treated lice were killed after 0.5-2 min, whereas with d-phenothrin, 100% mortality was reached only after 120 min. The number of lice infesting buffaloes was significantly reduced 3, 6, 4, 6 and 9 days after treatment with camphor, peppermint, chamomile, onion, and d-phenothrin, respectively. Moreover, the oils and d-phenothrin significantly repelled flies, Musca domestica, Stomoxys calcitrans, Haematobia irritans and Hippobosca equina, for 6 and 3 days post-treatment, respectively. No adverse effects were noted on either animals or pour-on operators after exposure to the applied materials. Consequently, some Egyptian essential oils show potential for the development of new, speedy and safe lousicides and insect repellents for controlling lice and flies which infest water buffaloes.

Variation in chemical composition and acaricidal activity against Dermanyssus gallinae of four eucalyptus essential oils

The results of this study suggest that certain eucalyptus essential oils may be of use as an alternative to synthetic acaricides in the management of the poultry red mite, Dermanyssus gallinae. At a level of 0.21 mg/cm(2), the essential oil from Eucalyptus citriodora achieved 85% mortality in D. gallinae over a 24 h exposure period in contact toxicity tests. A further two essential oils from different eucalyptus species, namely E. globulus and E. radiata, provided significantly (P < 0.05) lower mite mortality (11 and 19%, respectively). Notable differences were found between the eucalyptus essential oils regarding their chemical compositions. There appeared to be a trend whereby the essential oils that were composed of the fewer chemical components were the least lethal to D. gallinae. It may therefore be the case that the complexity of an essential oil's chemical make up plays an important role in dictating the toxicity of that oil to pests such as D. gallinae.

Ovicidal and adulticidal activities of Origanum majorana essential oil constituents against insecticide-susceptible and pyrethroid/malathion-resistant Pediculus humanus capitis (Anoplura: Pediculidae)

The toxicity of essential oil constituents from marjoram, Origanum majorana, to eggs and adult females of the susceptible KR-HL and dual malathion- and permethrin-resistant BR-HL strains of human head louse, Pediculus humanus capitis, was examined using contact + fumigant mortality bioassay. Results were compared with those following treatment with two pyrethroid pediculicides, d-phenothrin or pyrethrum. As judged by the lethal time to 50% mortality (LT(50)) values at the exposure rate of 0.25 mg/cm(2), 1,8-cineole (14.1 min) was the most toxic compound, followed by linalool (15.4 min) to KR-HL females. These compounds were faster acting than either d-phenothrin (24.1 min) or pyrethrum (33.4 min). Based on the lethal concentration causing 50% mortality (LC(50)) values, (-)-camphor (0.022 mg/cm(2)) was the most toxic compound, followed by linalool (0.035 mg/cm(2)), (-)-terpinen-4-ol (0.040 mg/cm(2)), alpha-terpineol (0.045 mg/cm(2)), and 1,8-cineole (0.068 mg/cm(2)) against KR-HL females. These monoterpenoids were less toxic than either d-phenothrin (LC(50), 0.0015 mg/cm(2)) or pyrethrum (0.0013 mg/cm(2)). However, the toxicities of these monoterpenoids were almost identical against females from either of the two strains, even though the BR-HL females exhibited high levels of resistance to d-phenothrin [resistance ratio (RR), 667] and pyrethrum (RR, 754). After a 24 h exposure to linalool, BR-HL egg hatch was inhibited 100 and 84% at 0.25 or 0.125 mg/cm(2), respectively, while (-)-terpinen-4-ol caused 94 and 69% inhibition of egg hatch at 0.25 and 0.125 mg/cm(2). alpha-Terpineol caused 88 and 76% inhibition of egg hatch at 0.5 and 0.25 mg/cm(2), respectively. Thus, certain monoterpenoids from O. majorana essential oil, particularly linalool, (-)-terpinen-4-ol and alpha-terpineol, merit further study as potential pediculicides and ovicides for the control of insecticide-resistant P. h. capitis populations as fumigants with contact action.

In vitro efficacy of over-the-counter botanical pediculicides against the head louse Pediculus humanus var capitis based on a stringent standard for mortality assessment

Infestation of the head louse Pediculus humanus var capitis DeGeer (Phthiraptera: Pediculidae) is an important public health problem in Australia, with up to a third of children infested in some primary schools. Insecticide resistance and inadequate attention to the application instructions of topical pediculicides are common reasons for treatment failure. This study evaluated six popular Australian over-the-counter products against head lice, primarily comprised of different botanical extracts, and compared them with permethrin 1% (Quellada) and a non-treatment control in order to assess their in vitro efficacy. We also assessed commonly used criteria for evaluating pediculicide efficacy in vitro. All tested products failed to demonstrate high levels of efficacy with the exception of Tea Tree Gel((R)), which outperformed 1% permethrin. Permethrin had a high level of efficacy, but using stringent criteria 18% of lice were not dead at 3 h, indicating some resistance to Quellada. Commonly used less stringent criteria were shown to overestimate mortality of head lice as a result of the protective phenomenon of stasis or sham death observed in exposed lice that may recover after some time. Using two different levels of stringency resulted in different rankings of efficacy for most products, with the exception of the first ranked product, Tea Tree Gel. Rankings of efficacy also varied over time, even within the different assessment criteria. Government regulatory agencies should require standard in vitro tests using stringent mortality criteria, with an observation period of >or= 6 h, to determine the efficacy of new pediculicides, and only products that cause a minimum mortality rate (e.g. 80%) in head lice collected from the target population should be licensed for sale.

Biological effects of essential oils--a review

Since the middle ages, essential oils have been widely used for bactericidal, virucidal, fungicidal, antiparasitical, insecticidal, medicinal and cosmetic applications, especially nowadays in pharmaceutical, sanitary, cosmetic, agricultural and food industries. Because of the mode of extraction, mostly by distillation from aromatic plants, they contain a variety of volatile molecules such as terpenes and terpenoids, phenol-derived aromatic components and aliphatic components. In vitro physicochemical assays characterise most of them as antioxidants. However, recent work shows that in eukaryotic cells, essential oils can act as prooxidants affecting inner cell membranes and organelles such as mitochondria. Depending on type and concentration, they exhibit cytotoxic effects on living cells but are usually non-genotoxic. In some cases, changes in intracellular redox potential and mitochondrial dysfunction induced by essential oils can be associated with their capacity to exert antigenotoxic effects. These findings suggest that, at least in part, the encountered beneficial effects of essential oils are due to prooxidant effects on the cellular level.

Laboratory determination of efficacy of a Santalum spicatum extract for mosquito control

The activity of QN50, a sequiterpene alcohol derived from Australian sandalwood (Santalum spicatum), was tested for its effectiveness against larvae of 2 mosquito species (Culex molestus and Aedes camptorhynchus [Diptera: Culicidael), nymphs of 2 species of water boatmen (Micronecta robusta and Agraptocorixa [Hemiptera: Corixidae]), immature Daphnia sp. (Crustacea), and mosquito eggs (Cx. molestus). In a series of laboratory bioassays, field-collected mosquito larvae, eggs, and immature corixids and daphnids were placed in beakers with either QN50, methoprene or source water only (control). The mosquito larvae exposed to QN50 had reduced survivorship and average longevity relative to the control and to methoprene at most concentrations used in this study. The hatching rate of mosquito eggs was unaffected by methoprene or QN50. Corixid nymphs and daphnids experienced high mortality in both methoprene and QN50 relative to the control, but there was no difference in the effect between the compounds. The results of this preliminary study suggest that further research into the mode of action and efficacy of QN50 as a potential alternative to methoprene for mosquito abatement is warranted.