Occurrence of Aedes aegypti (L.) and Culex quinquefasciatus Say (Diptera, Culicidae) in houses of different constructions in Phnom Penh, Kampuchea

The relation between the number of mosquito specimens of the most abundant species Aedes aegypti (L.) and Culex quinquefasciatus Say and the construction of houses which they inhabited was studied. The effect of the building materials and of the height at which the floor was situated above the ground were assessed in five and four localities, respectively. It was found that in the localities having the character of a town the mosquitoes were most abundant in houses constructed from corrugated plate and in those the floor of which was situated 2-3.5 m above the ground. In the locality of a village character, the mosquitoes were most numerous in brick houses with the floors at the ground level.     

Susceptibility of adult Aedes aegypti (L.) and Culex quinquefasciatus Say (Diptera; Culicidae) to DDT in Kampuchea.

The susceptibility to 4% DDT was tested in adult Aedes aegypti and Culex quinquefasciatus mosquitoes collected in houses in Phnom Penh (Kampuchea). It was found that in spite of the fact that insecticide treatment had not been performed for many years, the populations of both species as a whole remained resistant. However, there were some differences in the susceptibility between males and females and between engorged and hungry females. Possible causes of these differences are discussed in the present paper.     

Isolation of a Pseudomonas fluorescens metabolite/exotoxin active against both larvae and pupae of vector mosquitoes

A formulation was developed from the metabolite(s) of a novel Pseudomonas fluorescens Migula strain (VCRC B426) and tested against 4th-instar larvae and pupae of three species of vector mosquitoes, Anopheles stephensi Liston, Culex quinquefasciatus Say and Aedes aegypti (L). The larvae and pupae of An. stephensi were the most susceptible to the formulation, followed by those of C. quinquefasciatus and Ae. aegypti, in that order, and the dosage requirement for pupal mortality was less than that required for larval mortality. The LC50 dosage requirements for larvae of these mosquito species were, respectively, 70.4, 511.5 and 757.3 microg protein ml(-1), whereas for pupae they were, respectively, 2.0, 9.4 and 19.2 microg protein ml(-1). The lethal fraction was purified from the culture broth and its molecular mass, as determined by high performance liquid chromatography, was 44kDa. This is the first report of a microbial formulation acting upon mosquito pupae, a non-feeding stage. Its mode of action and efficacy to control mosquitoes under field conditions need to be studied further.     

A survey on indoor resting mosquito species in Phnom Penh, Kampuchea

Indoor resting mosquitoes were collected in 7 localities (250 houses) of Phnom Penh at various periods. The mosquitoes were collected for 8 min in every house by means of an aspirator and net. A total of 16 species of mosquitoes resting in houses were found, one of them for the first time in Kampuchea. Culex quinquefasciatus was the predominant species in 6 of the localities observed; its predominance in houses was more or less evident; Aedes aegypti prevailed in one locality. The percentage of A. aegypti predominance in houses corresponds with the risk of occurrence of dengue haemorrhagic fever. Anopheles vagus was found resting in higher abundance in houses of one locality. This fact is of little epidemiological significance because of the zoophilic character of An. vagus in Kampuchea. On the other hand even uncommon occurrence of Anopheles subpictus found in houses may signalize a possibility of an endemic occurrence of malaria in Phnom Penh.     

三种植物精油对致倦库蚊成蚊的熏蒸活性及其混配增效作用

研究了香樟叶、香樟果实、天竺桂叶的水蒸气蒸馏精油对致倦库蚊Culex pipiens quinquefasciatus成蚊的熏蒸活性及其混配增效作用。结果表明:用香樟叶、香樟果实和天竺桂叶精油对致倦库蚊熏蒸20 min后,其24 h的LC50值分别为7.47、4.92和5.70μg/cm3;在设定的熏蒸剂量下,3种精油的半数击倒时间(KT50值)分别为16.62、15.91和16.98 min。将香樟叶精油与天竺桂叶精油以体积比1∶9、3∶7和5∶5混配,其共毒系数分别为152.09、158.20和152.86;将香樟果实精油与天竺桂叶精油以体积比1∶9、5∶5和7:3混配,其共毒系数分别为145.73、146.30和139.79。表明3种植物精油均对致倦库蚊成蚊具有显著的熏蒸活性,将其以适当比例混配后具有增效作用。     

Insecticide resistance status of Aedes aegypti (L.) from Colombia

BACKGROUND: To evaluate the insecticide susceptibility status of Aedes aegypti (L.) in Colombia, and as part of the National Network of Insecticide Resistance Surveillance, 12 mosquito populations were assessed for resistance to pyrethroids, organophosphates and DDT. Bioassays were performed using WHO and CDC methodologies. The underlying resistance mechanisms were investigated through biochemical assays and RT‐PCR. RESULTS: All mosquito populations were susceptible to malathion, deltamethrin and cyfluthrin, and highly resistant to DDT and etofenprox. Resistance to lambda‐cyhalothrin, permethrin and fenitrothion ranged from moderate to high in some populations from Chocó and Putumayo states. In Antioquia state, the Santa Fe population was resistant to fenitrothion. Biochemical assays showed high levels of both cytochrome P450 monooxygenases (CYP) and non‐specific esterases (NSE) in some of the fenitrothion‐ and pyrethroid‐resistant populations. All populations showed high levels of glutathione‐S‐transferase (GST) activity. GSTe2 gene was found overexpressed in DDT‐resistant populations compared with Rockefeller susceptible strain. CONCLUSIONS: Differences in insecticide resistance status were observed between insecticides and localities. Although the biochemical assay results suggest that CYP and NSE could play an important role in the pyrethroid and fenitrothion resistance detected, other mechanisms remain to be investigated, including knockdown resistance. Resistance to DDT was high in all populations, and GST activity is probably the main enzymatic mechanism associated with this resistance. The results of this study provide baseline data on insecticide resistance in Colombian A. aegypti populations, and will allow comparison of changes in susceptibility status in this vector over time. Copyright © 2011 Society of Chemical Industry     

Contribution of host plant resistance and geographic distance to the structure of Potato virus Y (PVY) populations in pepper in northern Tunisia

The genetic structure of Potato virus Y (PVY) populations was investigated in naturally-infected pepper ( Capsicum annuum ) fields, collected at eight different localities in northern Tunisia, where 23% of the sampled plants were homozygous for the pvr2¹ recessive resistance allele, while the other plants carried the dominant susceptibility allele pvr2⁺ . Restriction fragment length polymorphism analysis at three PVY genome segments revealed a high level of viral diversity, with a majority of cases showing co-infection of individual plants by several PVY haplotypes and a strong genetic differentiation of viral populations collected in the different localities. Geographic distances affected the differentiation of PVY populations and isolation by distance among these populations was significant. However, the occurrence of the pvr2¹ resistance allele did not contribute to the structure of viral populations, suggesting that the virulence properties of the virus did not significantly affect its fitness. Consequently, greater deployment of the pvr2¹ gene would probably not be a suitable strategy to control PVY, and other resistance genes should be preferred.     

Larvicidal and oviposition‐altering activity of monoterpenoids,trans‐anithole and rosemary oil to the yellow fever mosquito Aedes aegypti (Diptera: Culicidae)

BACKGROUND: Aedes aegypti L. is the major vector of dengue fever and dengue hemorrhagic fever. In an effort to find effective tools for control programs to reduce mosquito populations, the authors assessed the acute toxicities of 14 monoterpenoids, trans‐anithole and the essential oil of rosemary against different larval stages of Ae. aegypti. The potential for piperonyl butoxide (PBO) to act as a synergist for these compounds to increase larvicidal activity was also examined, and the oviposition response of gravid Ae. aegypti females to substrates containing these compounds was evaluated in behavioral bioassays. RESULTS: Pulegone, thymol, eugenol, trans‐anithole, rosemary oil and citronellal showed high larvicidal activity against all larval stages of Ae. aegypti (LC₅₀ values 10.3–40.8 mg L^?1). The addition of PBO significantly increased the larvicidal activity of all test compounds (3–250‐fold). Eugenol, citronellal, thymol, pulegone, rosemary oil and cymene showed oviposition deterrent and/or repellent activities, while the presence of borneol, camphor and β‐pinene increased the number of eggs laid in test containers. CONCLUSIONS: This study quantified the lethal and sublethal effects of several phytochemical compounds against all larval stages of Aedes aegypti, providing information that ultimately may have potential in mosquito control programs through acute toxicity and/or the ability to alter reproductive behaviors. Copyright © 2008 Society of Chemical Industry     

Insecticidal activity of menthol derivatives against mosquitoes

BACKGROUND: The insecticidal activity of essential oil of Mentha piperita L. emend. Huds. against local mosquitoes as disease vectors was recognized and found to be due to the presence of menthol, which is the major aroma compound of the oil. The minor compounds of the oil, i.e. menthone, beta-caryophyllene, menthyl acetate, limonene, alpha-pinene and pulegone, showed either less or no activity against the mosquitoes tested. L-Menthol derivatives were synthesized and their knockdown effect and mortality were evaluated against local mosquitoes of Culex quinquefasciatus Say, Aedes aegypti L. and Anopheles tessellatus Theobald as disease vectors. This is the first report of mosquitocidal activity of menthol and its derivatives against Cx. quinquefasciatus, Ae. aegypti and An. tessellatus. RESULTS: Derivative synthesis followed by structure-activity relationship studies identified several derivatives, i.e. menthyl chloroacetate, menthyl dichloroacetate, menthyl cinnamate, menthone glyceryl acetal, thymol, alpha-terpineol and mugetanol, with enhanced mosquitocidal activity against Cx. quinquefasciatus, Ae. aegypti and An. tessellatus relative to the parent compound L-menthone. CONCLUSION: In ester derivatives of L-menthol the optimum activity is dependent on the size and shape of the ester group and the presence of chlorine atoms in the ester group. In structurally related derivatives of L-menthol the optimum activity is dependent on the aromaticity, the degree of unsaturation, the position of the hydroxy group and the type of functional group.     

四种植物精油对蚊虫的熏杀活性及酯酶活性的影响

为了筛选高效、环保、低抗性的植物源灭蚊剂,揭示植物精油熏杀蚊虫的作用机理,测试了湖南香薷Elsholtziahunanensis、藿香Agastacherugosus、八角Illiciumverum和剑叶金鸡菊Coreopsislanceolata精油对白纹伊蚊Aedesalbopictus和致倦库蚊Culexpipiensquinquefasciatus成蚊的熏杀活性及对2种蚊虫体内乙酰胆碱酯酶（AChE）和非特异性酯酶（NSE）活性的影响。结果表明,4种植物精油对蚊虫的熏杀效果显著,但同种植物精油对2种蚊虫的熏杀活性有差异。藿香精油对白纹伊蚊的熏杀效果最好（LC50值为26．12μg．cm-3）,八角精油对致倦库蚊的熏杀活性最强（Lc50值为29-31μg·cm-3）。4种植物精油对白纹伊蚊和致倦库蚊体内AChE活性起诱导作用;对致倦库蚊体内NSE活性均有抑制作用,其中八角精油的酶活性抑制率最高（19．79％）。湖南香薷和八角精油对白纹伊蚊NSE活性有抑制作用,酶活性抑制率分别为34．90％和25．26％;藿香和剑叶金鸡菊精油对白纹伊蚊NSE活性有促进作用,酶活性增长率分别为25．66％和66．35％。综合分析4种植物精油对蚊虫的熏杀活性及对酯酶活性的影响,湖南香薷和藿香精油更适宜作为植物源灭蚊产品的备选材料。     

甘肃省白银市保护地蔬菜根结线虫病病原鉴定

2012年5月-7月在甘肃省白银市采集了番茄、黄瓜、豇豆等几种保护地蔬菜的25个根结线虫群体.直接解剖获得雌虫,通过雌虫会阴花纹观察,结合酯酶和苹果酸脱氢酶(MDH-EST)测定,鉴定出所收集的25个群体中有16个为南方根结线虫[Meloidogyne incognita (Kofoid&White)],9个为爪哇根结线虫[M.javanica (Treub)].南方根结线虫为优势种群,本次试验也是首次在甘肃省发现爪哇根结线虫.     

福建柏精油对蚊虫的生物活性

为筛选环保型植物源灭蚊剂,从福建柏Fokienia hodginsii叶中提取精油,采用浸液法测试了该精油对白纹伊蚊Aedes albopictus和致倦库蚊Culex pipiens quinquefasciatus IV龄幼虫和蛹的毒杀作用,采用密闭圆筒法研究了该精油对2种蚊虫成蚊的熏蒸活性,并用气相色谱-质谱联用法对其化学成分进行了检测。结果表明:福建柏精油对白纹伊蚊IV龄幼虫和蛹的LC50值分别为53.21和144.34μg/mL,对致倦库蚊分别为55.85和147.68μg/mL;在4.36μg/cm3熏蒸剂量下,该精油对白纹伊蚊和致倦库蚊成蚊的KT50值分别为14.63和14.90 min,24 h校正死亡率均为90.00%。从福建柏精油中共检测出16种主要化学成分:其中相对含量最高的为α-蒎烯(α-pinene),为29.25%;其次是马鞭烯醇(bicyclo[2.2.1]hept-3-en-2-ol)10.88%和氧化石竹烯(caryophyllene oxide)9.64%等。研究结果表明,福建柏精油对2种供试蚊虫具有显著的杀虫活性。     

广西平果县岩溶石山飞机草种群的生殖配置研究

对广西岩溶石山3个典型群落——飞机草优势群落（优势群落）、黄荆条-飞机草混合群落（混合群落）和类芦-蔓生莠竹群落（伴生群落）中飞机草种群的生殖配置进行了研究。结果表明：（1）3个群落中飞机草的营养构件（根、茎和叶）生物量占总生物量的百分比均达90%以上,在构件生物量分配比率方面表现出基本一致的规律,即茎〉根〉叶〉花果;（2）3个群落中飞机草的生殖配置平均为6.1%。优势群落中飞机草的生殖配置与伴生群落有显著差异（P=0.009）,而混合群落中飞机草的生殖配置与优势群落和伴生群落均无显著差异;（3）3个群落中飞机草的生殖配置与株高均存在显著的正相关关系,而与分枝数和总生物量相关性不显著。     

Resistance in the mosquito, Culex quinquefasciatus, and possible mechanisms for resistance

Two mosquito strains of Culex quinquefasciatus (Say), MAmCq(G0) and HAmCq(G0), were collected from Mobile and Huntsville, Alabama, respectively. MAmCq(G0) and HAmCq(G0) were further selected in the laboratory with permethrin for one and three generations, respectively. The levels of resistance to permethrin in MAmCq(G1) (after one-generation selection) and HAmCq(G3) (after three-generation selection) increased rapidly. Resistance to permethrin in MAmCq(G1) and HAmCq(G3) was partially suppressed by piperonyl butoxide (PBO), S,S,S-tributylphosphorotrithioate (DEF) and diethyl maleate (DEM), inhibitors of cytochrome P450 monooxygenases, hydrolases and glutathione S-transferases (GST), respectively, suggesting these three enzyme families are important in conferring permethrin resistance in both strains. A substitution of leucine to phenylalanine (L to F) resulting from a single nucleotide polymorphism (SNP), termed the kdr mutation, in the para-homologous sodium channel gene has been reported as a very common mutation associated with pyrethroid resistance of insects. A 341-bp sodium channel gene fragment, where the kdr mutation resides, was generated by PCR from genomic DNAs of Cx. quinquefasciatus strains. We found that the kdr mutation was present in both permethrin-selected and unselected HAmCq and MAmCq mosquito populations, suggesting that the kdr mutation plays the role in permethrin resistance. There was no significant change in the frequency and heterozygosity of the A to T SNP for the kdr allele between permethrin-selected and unselected MAmCq and HAmCq mosquitoes, indicating that other mechanisms are involved in the evolution of resistance in mosquitoes selected by permethrin in the laboratory.     

流行性乙型脑炎与三带喙库蚊的防控

流行性乙型脑炎(乙脑)在我国广泛流行。三带喙库蚊是主要媒介,依据如下:(1)三带喙库蚊是乙脑流行区的优势蚊种;(2)该种蚊的季节消长与乙脑的季节分布相一致;(3)该种蚊有乙脑病毒的自然感染,带菌率高;(4)该种蚊能叮刺和经卵传递乙脑病毒。防控方法:(1)环境治理;(2)管理宿主动物(猪等);(3)灭蚊降低密度;(4)做好个人防护;(5)接种疫苗。     

斜纹夜蛾成虫在不同寄主上的繁殖行为日节律

为摸清斜纹夜蛾成虫在不同寄主上的行为节律变化,在室内分别用烟草和白菜饲养3代,建立烟草种群和白菜种群,比较分析了成虫的羽化、交配、产卵等行为节律。结果表明:烟草种群雌虫有2个羽化高峰期,分别在熄灯前2 h和熄灯后1 h,雄虫只有1个高峰期,出现在熄灯后2 h;白菜种群雌、雄虫均有2个高峰期,主、次高峰期分别在熄灯前后1 h内和熄灯后4~5 h。2种群均有2个交配高峰期,烟草种群第1高峰期在熄灯后2 h,而白菜种群在熄灯后5 h,第2高峰期均在开灯前2 h;烟草种群和白菜种群一生的交配持续时间分别为54.78±3.09 min和60.00±2.58 min,差异不显著;烟草种群一生交配1~3次,而白菜种群只交配1次,差异极显著;2种群均只有1个产卵高峰期,烟草种群在熄灯后4 h,白菜种群则在熄灯后5 h。表明斜纹夜蛾取食烟草和白菜2种不同寄主其成虫繁殖节律会发生较大的改变。     

Pesticide resistance in glasshouse whitefly (Trialeurodes vaporariorum west

A survey in SE England showed that seven out of 17 populations of glasshouse whitefly were resistant to DDT. Resistance to malathion occurred in 15 populations and to resmethrin in eight. Mecarbam and methiocarb gave good kills in screening tests but some insect growth regulators gave variable results. The synthetic pyrethroid permethrin was slightly more effective against a population of whitefly resistant to both DDT and malathion than against a susceptible population. Parthenogenetic females from a population susceptible to DDT and malathion produced almost entirely male progeny. An unsuccessful attempt was made to lower the resistance level of a DDT/malathion resistant strain by introducing these males to resistant females.     

野胡萝卜果实精油对蚊幼虫的毒杀活性

采用浸液法研究了野胡萝卜Daucus carota果实精油对白纹伊蚊Aedes albopictus和致倦库蚊Culexpipiens quinquefasciatus幼虫的毒杀活性;利用气相色谱-质谱联用（GC-MS）对精油的主要成分进行了定性、定量分析。结果发现,野胡萝卜果实精油毒杀白纹伊蚊和致倦库蚊4龄幼虫的24h LC50值分别为67.87μg.mL-1和34.12μg.mL-1;精油中共含有34种化合物,相对含量最高的是α-蒎烯（54.72%）,其次为β-红没药烯（11.35%）和β-细辛脑（10.14%）;对6种活性化合物进行定量分析,含量最高的是α-蒎烯（577.46mg.mL-1）,其次是月桂烯（80.26mg.mL-1）、柠檬烯（28.95mg.mL-1）、β-石竹烯（24.38mg.mL-1）、β-蒎烯（11.59mg.mL-1）和γ-萜品烯（2.33mg.mL-1）。研究结果表明,野胡萝卜果实精油对蚊幼虫的毒杀效果强于以往文献报道的多种植物精油,是开发高效环保蚊虫杀幼剂的好材料。     

Effects of natural pyrethrum and synthetic pyrethroids on the tiger mosquito,Aedes albopictus (skuse) and non-target flower-visiting insects in urban green areas of Padua,Italy

Abstract

The tiger mosquito is a key vector of several human diseases and is considered a public health concern worldwide. The implementation of strategies aimed at maximizing mosquito control without affecting non-target insect groups is of major importance. In a field trial, we tested the efficiency of a natural pyrethrum-based vs. a synthetic pyrethroid-based insecticide in reducing tiger mosquito population and how they affect the diversity of non-target flower-visiting insects in green urban areas. Only the pyrethroid insecticide was effective in reducing mosquito abundance, although its effects disappeared nine days after application. The two adulticides did not significantly affect the diversity of flower-visiting insects, probably because of their large body size and the difference in flying and foraging activity. To effectively control mosquito populations while preventing intoxication of non-target flower-visiting insects, adulticide applications should be applied early in the morning and only on bushes and trees. Results from our small-scale applications cannot be extrapolate when larger areas are treated.     

Life cycle and epizootiology of Amblyospora ferocis (Microspora: Amblyosporidae) in the mosquito Psorophora ferox (Diptera: Culicidae)

A natural population of Psorophora ferox (Humbold, 1820) infected with the microsporidium Amblyospora ferocis Garcia et Becnel, 1994 was sampled weekly during a seven-month survey in Punta Lara, Buenos Aires Province, Argentina. The sequence of development of A. ferocis in larvae of P. ferox leading to the formation of meiospores followed the developmental pathway previously reported for various species of Amblyospora. The natural prevalence of A. ferocis in the larval population of P. ferox ranged from 0.4% to 13.8%. Spores were detected in the ovaries of field-collected females of P. ferox and were shown to be responsible for transovarial transmission of A. ferocis to the next generation of mosquito larvae in laboratory tests. These spores were binucleate and slightly pyriform in shape. The prevalence of A. ferocis in the adult population ranged from 2.7% to 13.9%. Data on effects of the infection on female fecundity showed that infected field-collected adults of P. ferox laid an average of 47.6 +/- 6.5 eggs of which 35.8% +/- 4.1% hatched. Uninfected field-collected adults of P. ferox laid 82.8 +/- 6.8 eggs of which 64.1% +/- 5.5% hatched. Six species of copepods living together with P. ferox were fed meiospores from field-infected larvae but none became infected. Horizontal transmission of A. ferocis to P. ferox larvae remains unknown.