Variations in insecticidal activity and chemical compositions of leaf essential oils from Cryptomeria japonica at different ages

The larvicidal effects of the essential oils extracted from the leaves of Cryptomeria japonica at different ages (58, 42, and 26 years old) against 2 mosquito species, Aedes aegypti and Aedes albopictus, were studied. The analysis of major constituents of these essential oils was also investigated. Results obtained from the larvicidal tests, using essential oil from the leaves of 58-year-old C. japonica was found to be most effective against both A. aegypti and A. albopictus larvae, indicating tree age has significant influence on mosquito larvicidal activity. In addition, the eleven pure constituents from C. japonica leaf essential oil were also tested individually against the two mosquito larvae. Among them, alpha-terpinene, gamma-terpinene, p-cymene, 3-carene, terpinolene, and beta-myrcene shows strong larvicidal effect against the two mosquito larvae. Among these pure constituents, 3-carene exhibits the best larvicidal effect against A. aegypti and terpinolene shows an excellent inhibitory action against A. albopictus larvae. The results of this study show that the leaf essential oil and its effective constituents might be considered as a potent source for the production of fine natural larvicides.     

Insecticidal activities of leaf essential oils from Cinnamomum osmophloeum against three mosquito species

The larvicidal activities of leaf essential oils and their constituents from six chemotypes of indigenous cinnamon (Cinnamomum osmophloeum Kaneh.) trees were evaluated against three mosquito species. Results of larvicidal tests demonstrated that the leaf essential oils of cinnamaldehyde type and cinnamaldehyde/cinnamyl acetate type had an excellent inhibitory effect against Aedes albopictus larvae, and their LC(50) values in 24h were 40.8 microg/ml (LC(90)=81.7 microg/ml) and 46.5 microg/ml (LC(90)=83.3 microg/ml), respectively. Results of the 24-h mosquito larvicidal assays also showed that the effective constituents in leaf essential oils were trans-cinnamaldehyde and benzaldehyde and that the LC(50) values of these constituents against A. albopictus larvae were below 50 mug/ml. In addition, cinnamaldehyde type leaf essential oil and trans-cinnamaldehyde have also exhibited great larvicidal performance against Culex quinquefasciatus and Armigeres subalbatus larvae. Comparisons of mosquito larvicidal activity of trans-cinnamaldehyde congeners revealed that alpha-methyl cinnamaldehyde, benzaldehyde, and trans-cinnamaldehyde exhibited strong mosquito larvicidal activity.     

Insecticidal, repellent and oviposition-deterrent activity of selected essential oils against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus

Essential oils extracted from 10 medicinal plants were evaluated for larvicidal, adulticidal, ovicidal, oviposition-deterrent and repellent activities towards three mosquito species; Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. The essential oils of Juniperus macropoda and Pimpinella anisum were highly effective as both larvicidal and ovicidal. The essential oil of P. anisum showed toxicity against 4th instar larvae of A. stephensi and A. aegypti with equivalent LD95 values of 115.7 microg/ml, whereas it was 149.7 microg/ml against C. quinquefasciatus larvae. Essential oils of Zingiber officinale and Rosmarinus officinalis were found to be ovicidal and repellent, respectively towards the three mosquito species. The essential oil of Cinnamomum zeylanicum resulted into highest repellent (RD95) values of 49.6, 53.9 and 44.2 mg/mat against A. stephensi, A. aegypti and C. quinquefasciatus, respectively apart from oviposition-deterrent potential.     

Bioactivity of selected plant essential oils against the yellow fever mosquito Aedes aegypti larvae

The bioactivity of 14 essential oils from five plants has been studied using the brine shrimp lethality test and the Aedes aegypti larvicidal assay. All essential oils screened had LC50 values smaller than 200 microg/ml, showing significant lethality against brine shrimp. In addition, nine of the 14 essential oils tested showed toxicity against the fourth-instar A. aegypti larvae in 24 h (LC50<100 microg/ml). Of these, the leaf and bark essential oils of Cryptomeria japonica demonstrated high larvicidal activity, the most active being the leaf essential oil of C. japonica, with a LC50=37.6 microg/ml (LC90=71.9 microg/ml), followed by the bark essential oil of C. japonica also showing high activity against A. aegypti larvae, with a LC50=48.1 microg/ml (LC90=130.3 microg/ml). The results obtained from this study suggest that the leaf and bark essential oils of C. japonica are promising as larvicides against A. aegypti larvae and could be useful in the search for new natural larvicidal compounds.     

Larvicidal activity of tectoquinone isolated from red heartwood-type Cryptomeria japonica against two mosquito species

Mosquito larvicidal activities of methanolic extracts from different plant parts of red heartwood-type Cryptomeria japonica D. Don against the fourth-instar larvae of Aedes aegypti and Aedes albopictus were examined. Results of mosquito larvicidal tests demonstrated that the n-hexane fraction of C. japonica sapwood methanolic extract had an excellent inhibitory effect against the larvae of A. aegypti and A. albopictus and its LC50 values were 2.4 and 3.3 microg/ml, respectively, in 24h. Following the bioactivity-guided fractionation procedure, the active constituent isolated from C. japonica sapwood was characterized as tectoquinone by spectroscopic analyses. The LC50 values of tectoquinone against A. aegypti and A. albopictus in 24h were 3.3 and 5.4 microg/ml, respectively. In addition, comparisons of mosquito larvicidal activity of anthraquinone congeners demonstrated that anthraquinone skeleton with a methyl group at C-2 position, such as tectoquinone, exhibited the strongest mosquito larvicidal activity. Results of this study show that the methanolic extract of C. japonica sapwood may be considered as a potent source and tectoquinone as a new natural mosquito larvicidal agent.     

Larvicidal activity of essential oils from Brazilian plants against Aedes aegypti L

Aedes aegypti L. is the major vector of dengue fever, an endemic disease in Brazil. In an effort to find effective and affordable ways to control this mosquito, the larvicidal activities of essential oils from nine plants widely found in the Northeast of Brazil were analyzed by measurement of their LC50. The essential oils were extracted by steam distillation and their chemical composition determined by GL-chromatography coupled to mass spectroscopy. The essential oils from Cymbopogon citratus and Lippia sidoides, reported in the literature to have larvicidal properties against A. aegypti, were used for activity comparison. The results show that Ocimum americanum and Ocimum gratissimum have LC50 of 67 ppm and 60 ppm respectively, compared to 63 ppm for L. sidoides and 69 ppm for C. citratus. These results suggest a potential utilization of the essential oil of these two Ocimum species for the control of A. aegypti.     

Larvicidal activity of the essential oil from Lippia sidoides Cham. Against Aedes aegypti linn

The aim of this work was to study the larvicidal activity of Lippia sidoides essential oil against Aedes aegypti larvae. The essential oil and its hydrolate (saturated solution of essential oil in water) were obtained by vapor extraction and their chemical composition determined by GL-chromatography coupled to mass spectroscopy. Bioassays were run with the essential oil, pure and diluted hydrolate and with their main constituents thymol and carvacrol. The results obtained showed that L. sidoides essential oil and its hydrolate have larvicidal action against the mosquito A. aegypti, causing an almost instantaneous mortality. Thymol, an alkylated phenol derivative and one of the major components of L. sidoides essential oil, was identified as the active principle responsible for the larvicidal action, causing 100% larval mortality at the lowest tested concentration of 0.017% (w/v). These results suggest that the essential oil of L. sidoides is promising as larvicide against A. aegypti and could be useful in the search of newer, more selective, and biodegradable larvicidal natural compounds to be used in official combat programs and at home.     

Chemical composition and anti-mosquito potential of rhizome extract and volatile oil derived from Curcuma aromatica against Aedes aegypti (Diptera: Culicidae).

Crude rhizome extracts and volatile oils of Curcuma aromatica were evaluated for chemical composition and anti-mosquito potential, including larvicidal, adulticidal, and repellent activities against the Aedes aegypti mosquito. Chemical identification achieved by GC/MS analysis revealed that xanthorrhizol, 1H-3a, 7-methanoazulene and curcumene at 35.08 and 13.65%, 21.81 and 30.02%, and 13.75 and 25.71%, were the main constituents in hexane extracts and volatile oils, respectively. Volatile oil of Cu. aromatica possessed a significantly higher larvicidal activity against the 4th instar larvae of Ae. aegypti than that of hexane extracts, with LC50 values of 36.30 and 57.15 ppm, respectively. In testing for adulticidal activity, on the other hand, hexane-extracted Cu. aromatica (LC50: 1.60 microg/mg female) was found to be slightly more effective against female Ae. aegypti than volatile oil (LC50: 2.86 microg/mg female). However, the repellency of these two products against Ae. aegypti adult females differed significantly. The hexane-extracted Cu. aromatica, with a median complete protection time of 1 h (range = 1-1.5 h) when applied at a concentration of 25%, appeared to have significantly higher repellency than that of distillate oil (0.5 h, range = 0-0.5 h). The different results obtained from both products of Cu. aromatica were probably due to variety in quantity and type of active ingredients as well as the biological and physiological characteristics that differed between both developmental stages of mosquitoes, larvae, and adults.     

Effects of essential oils on Aedes aegypti larvae: alternatives to environmentally safe insecticides

The essential oils from leaves of Hyptis fruticosa (Lamiaceae) Salzm., H. pectinata (Lamiaceae) Poit., and Lippia gracilis (Verbenaceae) HBK were investigated for their larvicidal activity against Aedes aegypti and analyzed by GC/MS. Fifty-nine compounds, representing 91.28-98.39% of the essential oils, have been identified. A standard solution was used to make 20 mL solutions ranging from 30 to 2000 ppm. Twenty larvae between third and fourth stages were added to the essential oil solution. A mortality count was conducted 24 h after treatment. Essential oils LC50 and their confidence limits at 95% probability were calculated by the methods of Reed-Muench and Pizzi, respectively. The essential oil of Lippia gracilis showed potent insecticidal effect against Aedes aegypti larvae, the vector of dengue fever. Carvacrol and caryophyllene oxide were the main responsible for the activity of L. gracilis and H. pectinata. Minor compounds are probably acting synergistically to achieve H. fruticosa activity.     

Composition and larvicidal activity of leaves and stem essential oils of Chloroxylon swietenia DC against Aedes aegypti and Anopheles stephensi

The laboratory bioassay of the essential oil and the isolated compounds from Chloroxylon swietenia against Aedes aegypti and Anopheles stephensi was carried out to evaluate the larvicidal activity. LC50 value estimated for A. aegypti and An. stephensi were 16.5 and 14.9 microg/ml and 20.2 and 19 microg/ml for leaf and stem oils, respectively. The three sesquiterpenes pregeijerene, geijerene and germacrene D were isolated and their Larvicidal activity was evaluated. Pregeijerene and geijerene were observed for the first time in the volatile constituents of C. swietenia, however, leaves contained higher amount of geijerene compared to stems.     

三种桉叶油化学成分研究

通过水蒸汽蒸油试验,发现已贮藏半年多的风干桉叶,仍有较高的含油量。云南省弥勒产的直杆桉(Eucalyptus maidenii)得油率为4.14％,蓝桉(E.globulus)为3.5％,福建省惠安产的窿缘桉(E.exserta)为1.2％,桉叶油生产厂也可以通过贮藏的风干桉叶生产桉叶油。通过气相色谱和质谱分析,从直杆桉叶油中鉴定出44个组份,蓝桉叶油中鉴定出35个组份,窿缘桉叶油中鉴定出26个组份。三种桉叶油单萜部分的组份基本一致,只是相对含量各有不同。桉油素含量,以直杆桉最高为68.02％,其次是蓝桉为67.54％,窿缘桉最低为34.33％。直杆桉、蓝桉可以怍材、油两用树种,窿缘桉不宜作油用树种。     

Repellent effect of plant essential oils against Aedes albopictus.

Six essential oils: asteraceae oil, rutaceae oil, mentha piperta oil, carvacryl oil, citronella oil, and eucalyptus oil were tested for evaluation of their repellent effects against Aedes albopictus mosquitoes under laboratory conditions. Only citronella oil and eucalyptus oil were tested with human beings. There was considerable protection for mice. Carvacryl oil (7%) provided 100% protection for mice after 7 h. Eucalyptus oil (15%) gave protection to humans for least 3 h; the protection time was prolonged to 5 h after adding 5% vanillin. The mixture could be developed into a practical product after the field evaluation.     

Competition and resistance to starvation in larvae of container-inhabiting Aedes mosquitoes

Abstract. 1. Hypotheses about declining populations of container-inhabiting Aedes mosquitoes following the invasion by additional species were tested.
2. The larval competition hypothesis was studied experimentally in pure and mixed cultures of Aedes aegypti (L.), A.albopictus (Skuse) and A.triseriatus (Say). The experiments used decomposing leaf litter in the laboratory, as opposed to most previous research which used non-natural food.
3. Resistance to starvation is introduced as a new measure of larval performance and competitiveness. The hypothesis is that more successful larvae store larger energy reserves and resist the lack of food longer.
4. Contrary to previous research showing better performance of A.aegypti in mixed cultures, A.albopictus developed faster and had greater survival when natural food was used.
5. Resistance to starvation was greater in the better performing species (i.e. A.aegypti with non-natural food and A.albopictus with leaf litter). Oxygen consumption by starved larvae was similar in the three container species, and in the ground-water mosquito, A.taeniorhynchus (Wied.), whose resistance to starvation was comparatively very low.     

Comparison of the insecticide susceptibilities of laboratory strains of Aedes aegypti and Aedes albopictus

A susceptible strain of Aedes albopictus derived from the Gainesville strain (Florida, USA) was established in our laboratory. The larvicidal efficacies of the neurotoxic insecticides temephos, permethrin and the pure cis and trans-permethrin isomers and the microbial insecticide Bacillus thuringiensis israelensis (Bti) against Ae. albopictus were estimated and compared to a susceptible strain of Aedes aegypti. The larvicidal effect of insect growth regulator pyriproxyfen was also evaluated in both mosquito strains. The median lethal concentration/median emergency inhibition values for Ae. aegypti and Ae. albopictus, respectively, were: temephos, 3.058 and 6.632 ppb, permethrin, 3.143 and 4.933 ppb, cis-permethrin, 4.457 and 10.068 ppb, trans-permethrin, 1.510 and 3.883 ppb, Bti, 0.655 and 0.880 ppb and pyriproxyfen, 0.00774 and 0.01642 ppb. Ae. albopictus was more tolerant than Ae. aegypti to all six larvicides evaluated. The order of susceptibility for Ae. aegypti was pyriproxyfen > Bti > trans-permethrin > temephos > permethrin > cis-permethrin and for Ae. albopictus was pyriproxyfen > Bti > trans-permethrin > permethrin > temephos > cis-permethrin. Because both species can be found together in common urban, suburban and rural breeding sites, the results of this work provide baseline data on the susceptibility of Ae. albopictus to insecticides commonly used for controlling Ae. aegypti in the field.     

市售长叶松油和锡兰肉桂油对登革热媒蚊埃及伊蚊的灭幼效果(英文)

松油和桂皮油由于具有芳香性气味, 因而成为良好的成虫驱避剂, 但是关于它们对蚊虫的杀幼虫作用研究不多。为揭示市售的长叶松Pinus longifolia油和锡兰肉桂Cinnamomum zeylanicum油对来源于印度德里的埃及伊蚊Aedes aegypti 4龄幼虫的毒杀潜力, 我们进行了室内研究, 以幼虫死亡率及行为改变和形态改变等指标评估其杀幼虫潜力。结果表明： 两种油对埃及伊蚊4龄幼虫均具有毒杀作用, 且松油的灭幼效果优于桂皮油。松油的LC₅₀和LC₇₀ 值分别为0.33093 mg/L 和0.54476 mg/L, 而桂皮油的LC₅₀和LC₇₀ 值分别为0.63159 mg/L和0.77736。进一步观察发现, LC₉₀剂量下桂皮油的杀幼虫潜力强于松油, 其LC₉₀为1.11879 mg/L, 而松油的LC₉₀为 1.04915 mg/L。在处理的幼虫中观察到行为改变, 如兴奋、 坐立不安、 颤抖、 痉挛然后瘫痪, 说明这两种油可能对其神经肌肉系统产生了影响。显微观察处理幼虫的形态改变发现, 与对照相比, 大多数器官的外观正常, 只是肛鳃略为内收缩而引起结构畸形, 提示肛腮可能是这两种油的作用位点, 腮的功能异常引起了幼虫死亡。这两种油品可开发用作防治蚊虫的新型杀幼虫药剂。     

The first report of Aedes (Stegomyia) albopictus in Haiti

Aedes albopictus was found in six of the 10 departments of Haiti and in 14 of the 35 communes surveyed. The survey found the larvae of Ae. albopictus in 13 different types of containers. Used tires and tins were by far the most common breeding sites used by this mosquito species. At the breeding sites, Ae. albopictus was associated with other mosquito species, such as Aedes aegypti, Culex nigripalpus and Aedes mediovittatus. The highest proportion of association was with Ae. aegypti. This study represents the first report of Ae. albopictus in Haiti.     

Larvicidal activity of major essential oils from stems of Allium monanthum Maxim. against Aedes aegypti L

The stems of Allium monanthum were extracted, and the major essential oil composition and larvicidal effects were studied. The analyses were conducted by gas chromatography and mass spectroscopy revealed that the essential oils of A. monanthum stems. The A. monanthum essential oil yield was 4.25%, and gas chromatography and mass spectroscopy analysis revealed that its major constituents were dimethyl trisulfide (23.21%), dimethyl tetrasulfide (11.24%) and methlyl propyl trisulfide (8.21%). The essential oil had a significant toxic effect against early fourth-stage larvae of Aedes aegypti L with an LC(50) value of 23.14 ppm and an LC(90) value of 36.31 ppm. Also, dimethyl trisulfide (≥95.0%), dimethyl tetrasulfide (≥95.0%) and methlyl propyl trisulfide (≥95.0%) were tested against the F(21) laboratory strain of A. aegypti. Methlyl propyl trisulfide (≥95.0%) has good activity with an LC(50) value of 19.38 ppm. Also, the above indicates that other major compounds may play a more important role in the toxicity of essential oil.     

竹叶花椒果实精油对两种蚊虫的毒杀活性研究

采用浸液法测试了竹叶花椒果实的水蒸汽蒸馏精油对白纹伊蚊和致倦库蚊幼虫的毒杀效果,并用三角瓶密闭熏蒸法研究了精油对这两种成蚊的熏杀活性;此外,采用GC-MS分析了该精油的化学成分。研究结果:(1)精油对白纹伊蚊和致倦库蚊的Ⅰ、Ⅱ、Ⅲ、Ⅳ龄期幼虫及蛹的LC50值分别为25.634/61.472、31.763/76.431、52.356/110.172、258.497/121.884和198.263/162.048mg.L-1;(2)精油对白纹伊蚊和致倦库蚊成蚊的LC50值分别为24.957和29.517μg.cm-3;(3)在147.52μg.cm-3熏杀剂量下,精油对白纹伊蚊和致倦库蚊成蚊的KT50值分别为3.493和2.993min,24h致死率均为100%;(4)共鉴定出18种化合物,其中萜烯类10种,占精油总量的67.122%,为竹叶花椒果实精油的主要成分。竹叶花椒果实精油对白纹伊蚊和致倦库蚊均有明显的致死作用,且作用速度快,具有开发为植物源杀蚊剂的潜力。     

Interspecific hybridization of Eucalyptus as a potential tool to improve the bioactivity of essential oils against permethrin-resistant head lice from Argentina

The essential oils extracted from Eucalyptus grandis, Eucalyptus camaldulensis, Eucalyptus tereticornis, and the hybrids E. grandisxE. camaldulensis, and E. grandisxE. tereticornis were analyzed by GC-MS, and evaluated for their fumigant and repellent effects on permethrin-resistant head lice. Fumigant activity of both hybrids was higher than that for pure species. E. grandisxE. tereticornis and E. grandisxE. camaldulensis showed KT50 values of 12.99 and 13.63min, respectively. E. grandis, E. camaldulensis, and E. tereticornis showed KT50 values of 25.57, 35.01, and 31.31, respectively. A simple regression analysis revealed a significant correlation between KT50 data and % of 1,8-cineole in these essential oils. Repellency varied from 47.80+/-16% to 80.69+/-6% for the five Eucalyptus essential oils tested. Interspecific hybridization improves the pediculicidal activity of Eucalyptus essential oils.     

Genetic determinants of host ranges of Bacillus sphaericus mosquito larvicidal toxins.

The 51.4-kDa-41.9-kDa binary toxin produced by different strains of Bacillus sphaericus shows differential activity toward Culex quinquefasciatus, Aedes atropalpus, and Aedes aegypti mosquito larvae. The patterns of larvicidal activity toward all three mosquito species and growth retardation in A. aegypti have been shown to be due to the 41.9-kDa protein. By using mutant toxins expressed in Escherichia coli, insecticidal activity and growth retardation correlated with amino acids centered around position 100 of the 41.9-kDa protein. In its response to these toxins, A. atropalpus resembled C. quinquefasciatus rather than its congener, A. aegypti.