Mosquito Control Agent Research Articles

Sublethal exposure to deltamethrin reduces the abilities of giant water bugs to prey upon Aedes aegypti larvae

Freshwater ecosystems provide environmental conditions for many arthropod species, including pests like mosquitoes and beneficial insects. Giant water bugs, Belostoma anurum (Hemiptera: Belostomatidae), are aquatic insects that provide biological control of mosquitoes and small vertebrates in freshwater environments. However, the application of insecticides aiming to control mosquitoes can lead to insecticide exposures of aquatic predators that can result in their death or significant reductions in their behavioral abilities. Here, we assessed the susceptibilities of B. anurum to the pyrethroid insecticide deltamethrin and evaluated whether sublethal exposure to deltamethrin would change the abilities of B. anurum to prey upon larvae of Aedes aegypti (Diptera: Culicidae). Bioassays of predator performance were conducted at three prey densities (i.e., 3, 6 and 9 larvae/100 mL of water) just after insecticide exposure and on the three following days. Our results revealed that B. anurum (LC50 = 90.9 μg a. i./L) was approximately 32-fold less susceptible to deltamethrin than A. aegypti larvae (LC50 = 2.8 μg a. i./L). However, the number of larvae eaten by B. anurum sublethally exposed to deltamethrin (at 13 μg a. i./L for 24 h) was significantly (P < 0.05) smaller than that recorded for unexposed predators. Furthermore, the deltamethrin-mediated behavioral changes were higher at the highest availability of prey and, as expected, just after insecticide exposure. Thus, sublethal exposure to deltamethrin reduces the ability of B. anurum to capture and prey upon A. aegypti larvae, compromising the efficacy of these insects as naturally occurring mosquito control agents.

Characterization of Tolypocladium cylindrosporum (Hypocreales: Ophiocordycipitaceae) and Its Impact Against Aedes aegypti and Aedes albopictus Eggs at Low Temperature.

We examined the growth characteristics of Tolypocladium cylindrosporum IBT 41712 and its potential to infect eggs of Aedes aegypti and Ae. albopictus at a low temperature (15°C). When grown on Sabouraud dextrose agar supplemented with yeast extract, the IBT 41712 formed white colonies turning to a slightly darker, off-white color when mature. The mycelia bore swollen conidiophores producing smooth-walled, oblong to cylindrical conidia with varying sizes, ranging from 1.5 to 3.5 μm long. To determine the optimum temperature for the fungus, we cultured the fungus at eight temperatures (4°C, 12°C, 15°C, 21°C, 28°C, 33°C, 37°C, and 40°C) and measured the diametric growth. The optimum temperature for growth was 28°C since it had the highest diametric growth rate (2.1 ± 0.05 mm/day) and the fastest sporulation period (within 8-10 days of incubation). There was no fungal growth at the 3 highest temperatures (33°C, 37°C, and 40°C) but plates incubated at 33°C, when shifted to optimal temperature (28°C), showed visible growth indicating that following incubation at 33°C, the fungus remained viable. The IBT 41712 successfully infected mosquito eggs at 15°C. Fungal treatment induced egg hatch on moist seed-germination paper and this effect was more pronounced in Ae. aegypti compared to Ae. albopictus. When treated eggs were immersed in dH2O 21 days posttreatment, larval hatch of both Ae. aegypti (control = 91%, 1 × 107 conidia/ml, fungal treatment = 0%) and Ae. albopictus (control = 85%, fungal treatment = 28%) was significantly lower in fungal treatment compared to the controls. The ability of the strain to grow in a wide temperature range, and effectively infect mosquito eggs and induce egg hatch at a low temperature warrants further investigation for its potential as a mosquito control agent targeting eggs that overwinter or undergo long diapause.

Larvicidal and Nematicidal Activities of 3-Acylbarbituric Acid Analogues against Asian Tiger Mosquito, Aedes albopictus, and Pine Wood Nematode, Bursaphelenchus xylophilus.

Widespread concern for the occurrence of resistant strains, along with the avoidance of the use of highly toxic insecticides and their wide environmental dispersal, highlights the need for the development of new and safer pest control agents. Natural products provide inspiration for new chemical entities with biological activities, and their analogues are good lead compounds for the development of new pest control agents. For this purpose, we evaluated the larvicidal and nematicidal activities of 48 3-acylbarbituric acid analogues against the Asian tiger mosquito, Aedes albopictus and the pine wood nematode, Bursaphelenchus xylophilus, organisms of increasing global concern. Among the 48 3-acylbarbituric acid analogues, four compounds—10, 14d, 14g and 19b—showed >90% larvicidal activity against Ae. albopictus at 10 μg/mL concentration, and one (compound 10) showed the strongest larvicidal activity against Ae. albopictus, with a LC50 value of 0.22 μg/mL. Only compound 18 showed strong nematicidal activity against pine wood nematode. Most active compounds possessed similar physicochemical properties; thus, actives typically had ClogP values of around 1.40–1.50 and rel-PSA values of 16–17% and these similar cheminformatic characteristics reflect their similar structure. This study indicates that active 3-acylbarbituric acids analogues have potential as lead compounds for developing novel mosquito control agents.

Development of an eco-friendly mosquitocidal agent from Alangium salvifolium against the dengue vector Aedes aegypti and its biosafety on the aquatic predator.

Plant extracts with their enriched chemical constituents have established potential alternative mosquito control agents. In this research, we developed an eco-friendly mosquitocidal agent from Alangium salvifolium leaves against the dengue and Zika virus vector Aedes aegypti and we investigated its biosafety on the mosquito aquatic predator Toxorhynchites splendens. Results showed that the methanolic extract of A. salvifolium leaves was composed by eight main compounds, with major peak area for hexadecenoic acid (21.74%). LC50 and LC90 values calculated on Ae. aegypti fourth instar larvae were 104.80 and 269.15ppm respectively. The methanolic extract tested at 100ppm decreased the α-β carboxylesterase and SOD ratio significantly and upregulated the GST and CYP450 level. The A. salvifolium methanolic extract displayed significant repellent and adulticidal activity at 100 and 400ppm respectively. The treatment with 100ppm of the methanolic extract led to 210min of protection from Ae. aegypti bites. Four hundred parts per million of the extract showed 98% adult mortality within 30min from the treatment. Lastly, biosafety assays on the mosquito aquatic predator Tx. splendens showed that the toxicity of the A. salvifolium extract was significantly lower if compared to the cypermethrin-based treatments. The methanolic extract of A. salvifolium showed a maximum of 47.3% mortality rate at the concentration of 1000ppm, while 0.7ppm of cypermethrin achieved 91.3% mortality rate on Tx. splendens. Overall, our study enhances basic knowledge on how to improve natural larvicidal agents against dengue and Zika virus mosquito vector with harmless responses on non-target aquatic predators.

Larvicidal activity of lignans and alkaloid identified in Zanthoxylum piperitum bark toward insecticide-susceptible and wild Culex pipiens pallens and Aedes aegypti

BackgroundThe yellow fever mosquito, Aedes aegypti, and the common house mosquito, Culex pipiens pallens, transmit dengue fever and West Nile virus diseases, respectively. This study was conducted to determine the toxicity of the three lignans (–)-asarinin, sesamin and (+)-xanthoxylol-γ,γ-dimethylallylether (XDA), and the alkaloid pellitorine from Zanthoxylum piperitum (Rutaceae) bark to third-instar larvae from insecticide-susceptible C. pipiens pallens and Ae. aegypti as well as wild C. pipiens pallens resistant to deltamethrin, cyfluthrin, fenthion, and temephos.MethodsThe toxicities of all isolates were compared with those of mosquito larvicide temephos. LC50 values for each species and their treatments were significantly different from one another when their 95% confidence intervals did not overlap.ResultsXDA was isolated from Z. piperitum as a new larvicidal principle. XDA (LC50, 0.27 and 0.24 mg/l) was 4, 53, and 144 times and 4, 100, and 117 times more toxic than pellitorine, sesamin, and asarinin toward larvae from susceptible C. pipiens pallens and Ae. aegypti, respectively. Overall, all the isolates were less toxic than temephos (LC50, 0.006 and 0.009 mg/l). These constituents did not differ in toxicity to larvae from the two Culex strains. The present finding indicates that the lignans and alkaloid and the insecticides do not share a common mode of larvicidal action or elicit cross-resistance.ConclusionNaturally occurring Z. piperitum bark-derived compounds, particularly XDA, merit further study as potential mosquito larval control agents or as lead compounds for the control of insecticide-resistant mosquito populations.

ADULTICIDAL ACTIVITY OF BOTANICAL OILS BY IMPREGNATED PAPER ASSAY AGAINST CULEX QUINQUEFASCIATUS SAY

Objective: The present study was undertaken with the aim of finding out the efficacy of essential oils (EOs) as anti-mosquito agents for commercial purposes. Plant source insecticides as an alternative to chemical insecticide, this study were evaluated to assess the knock-down and adulticidal prospective of the essential oils against Culex quinquefasciatus. The plant essential oil is largely cultivated throughout India and in all Tropical countries.Methods: The selected botanical essential oils were procured from commercial producers of plant essential oils and aromatic substances were used in this study. Knock-down and Adulticidal bioassay was performed according to WHO protocol. A single dose of the essential oils was used in the preliminary screening. 20 adult mosquitoes (3-5 d old glucose fed mosquitoes) were exposed on treated paper for one hour and knocked down and live mosquitoes were counted at 5 minute intervals.Results: Among the twenty three oils tested, 100% knock-down and adult mortality was recorded at 10%/cm2dose of calamus, camphor, cinnamon, citronella, clove, eucalyptus, lemongrass, pine, thyme and tulsi oils respectively. At 10 % concentration, clove oil (KT50 =1.8 and KT90 = 2.03 min) was found to be the most potential treatment. After 15 min exposure period clove oil registered the lowest knock-down dosewhich was calculated as (KD50 =1.8 %/cm2and KD90 =11.2 %/cm2). The lower and upper 95 % confidence limits for clove oil were calculated as 0.2 and 4.2 min respectively.Conclusion: From the results it can be concluded that the adult of the Cx. quinquefasciatus were susceptible to the essential oils. Such findings would be useful in promoting research aiming at the development of new agent for mosquito control on basis of chemical compounds from indigenous plant sources as an alternative to chemicals.

Experimental evolution to increase the efficacy of the entomopathogenic fungus Beauveria bassiana against malaria mosquitoes: Effects on mycelial growth and virulence

Entomopathogenic fungi such as Beauveria bassiana are currently considered as a potential control agent for malaria mosquitoes. The success of such strategies depends among others on the efficacy of the fungus to kill its hosts. As B. bassiana can use various resources for growth and reproduction, increasing the dependency on mosquitoes as a nutritional source may be instrumental for reaching this goal. Passage of entomopathogenic fungi through an insect host has been shown to increase its virulence. We evaluated the virulence, fungal outgrowth, mycelial growth rate, and sporulation rate of two B. bassiana isolates (Bb1520 and Bb8028) that underwent 10 consecutive selection cycles through malaria mosquitoes (Anopheles coluzzii) using an experimental evolution approach. This cycling resulted in an altered capacity of evolved B. Bassiana lineages to grow on different substrates while maintaining the ability to kill insects. Notably, however, there were no significant changes in virulence or speed of outgrowth when comparing the evolved lineages against their unevolved ancestors. These results suggest that fungal growth and sporulation evolved through successive and exclusive use of an insect host as a nutritional resource. We discuss the results in light of biocontrol and provide suggestions to increase fungal virulence.

Screening of Different Extracts of Marine Macro Green Algae for Larvicidal Activity against Dengue Fever Mosquito, &lt;i&gt;Aedes aegypti&lt;/i&gt; (Diptera: Culiadae)

The present study larvicidal activities of hexane, chloroform, ethyl acetate, acetone and methanol extracts of Halimeda macroloba, Decsne, Caulerpa racemosa (Frosk) Weber-Van-Bosses and Ulva lactuca Lin, (Chlorophyceae) against Aedes aegypti. The marine macro green algae extracts were tested against early 4th instar larvae of A. aegypti using WHO protocol and concentrations of 200, 400, 600, 800 and 1000 ppm. The observed mortality was made 24 and 48 h after treatment, data was subjected to probit analysis to determine the lethal concentration (LC50 and LC90) of the treated larvae of the tested species.Among the tested extracts the maximum efficicacy was observed in the ethyl acetate extracts. The ethyl acetate extracts of the seaweeds showed the presence of terpenoids, tannins and phenolic compounds stronger than the other extracts. The results revealed that all the extracts showed varied levels of larvicidal activity against A. aegypti tested. However, the ethyl acetate extract of C. racemosa showed remarkable larvicidal activity against A. aegypti (LC50=579.9 and LC90=1255.4 ppm values at 24 h and LC50 =495.4 and LC90 =1073.9 ppm at 48 h) followed by U. lactuca (LC50=588.1 and LC90=1290.7 ppm values at 24 h, and LC50= 530.8 and LC90= 1160.0 ppm at 48 h), respectively. The lowest larval mortality was observed with hexane extract of H. macroloba against A. aegypti with values of LC50=1116.8 and LC90= 1824.5 ppm (after 24 h) and LC50=1059.9 and LC90=1768.3 ppm (after 24 h). The present studies indicate that the larvicidal activity and phytochemicals derived from the ethyl acetate extract of C. racemosa have the potential to be used as an ideal eco-friendly approach and effective mosquito vector control agent.

Screening of Different Extracts of Marine Macro Green Algae for Larvicidal Activity against Dengue Fever Mosquito, &lt;i&gt;Aedes aegypti&lt;/i&gt; (Diptera: Culiadae)

The present study larvicidal activities of hexane, chloroform, ethyl acetate, acetone and methanol extracts ofHalimeda macroloba,Decsne,Caulerpa racemosa(Frosk) Weber-Van-Bosses andUlva lactucaLin, (Chlorophyceae) againstAedes aegypti.The marine macro green algae extracts were tested against early 4thinstar larvae ofA. aegyptiusing WHO protocol and concentrations of 200, 400, 600, 800 and 1000 ppm. The observed mortality was made 24 and 48 h after treatment, data was subjected to probit analysis to determine the lethal concentration (LC50and LC90) of the treated larvae of the tested species.Among the tested extracts the maximum efficicacy was observed in the ethyl acetate extracts. The ethyl acetate extracts of the seaweeds showed the presence of terpenoids, tannins and phenolic compounds stronger than the other extracts. The results revealed that all the extracts showed varied levels of larvicidal activity againstA. aegyptitested. However, the ethyl acetate extract ofC. racemosashowed remarkable larvicidal activity againstA. aegypti(LC50=579.9 and LC90=1255.4 ppm values at 24 h and LC50=495.4 and LC90=1073.9 ppm at 48 h) followed byU. lactuca(LC50=588.1 and LC90=1290.7 ppm values at 24 h, and LC50=530.8and LC90= 1160.0 ppm at 48 h), respectively. The lowest larval mortality was observed with hexane extract ofH. macrolobaagainstA. aegyptiwith values of LC50=1116.8 and LC90= 1824.5 ppm (after 24 h) and LC50=1059.9 and LC90=1768.3 ppm (after 24 h). The present studies indicate that the larvicidal activity and phytochemicals derived from the ethyl acetate extract ofC. racemosahave the potential to be used as an ideal eco-friendly approach and effective mosquito vector control agent.

Effects of Organic Amendments on Microbiota Associated with the Culex nigripalpus Mosquito Vector of the Saint Louis Encephalitis and West Nile Viruses.

Pollution from nutrients in aquatic habitats has been linked to increases in disease vectors, including mosquitoes and other pestiferous insects. One possibility is that changes in mosquito microbiomes are impacted by nutrient enrichments and that these changes affect various traits, including larval development, susceptibility to larval control agents, and susceptibility of the adult mosquitoes to pathogens. We tested this hypothesis using field mesocosms supplemented with low- and high-organic-nutrient regimens and then sampled microbial communities associated with the naturally colonizing Culex nigripalpus mosquito vector. By high-throughput sequencing of 16S rRNA gene sequences, we found no significant differences in overall microbial communities associated with sampled mosquitoes, despite detecting discernible differences in environmental variables, including pH, dissolved oxygen, and nutrient amendments. Nevertheless, indicator species analysis revealed that members of the Clostridiales were significantly associated with mosquitoes that originated from high-nutrient enrichments. In contrast, members of the Burkholderiales were associated with mosquitoes from the low-nutrient enrichment. High bacterial variability associated with the life stages of the C.nigripalpus was largely unaffected by levels of nutrient enrichments that impacted larval microbial resources, including bacteria, ciliates, and flagellates in the larval environments. IMPORTANCE Mosquito microbiota provide important physiological and ecological attributes to mosquitoes, including an impact on their susceptibility to pathogens, fitness, and sensitivity to mosquito control agents. Culex nigripalpus mosquito populations transmit various pathogens, including the Saint Louis and West Nile viruses, and proliferate in nutrient-rich environments, such as in wastewater treatment wetlands. Our study examined whether increases in nutrients within larval mosquito developmental habitats impact microbial communities associated with C.nigripalpus mosquitoes. We characterized the effects of organic enrichments on microbiomes associated with C.nigripalpus mosquitoes and identified potential bacterial microbiota that will be further investigated for whether they alter mosquito life history traits and for their potential role in the development of microbial-based control strategies.

Observations on the predatory potential of Lutzia fuscana on Aedes aegypti larvae: implications for biological control (Diptera: Culicidae)

Among the natural predators, larval stages of the mosquito &lt;em&gt;Lutzia fuscana (&lt;/em&gt;Wiedemann, 1820) (Diptera: Culicidae) bear potential as a biological control agent of mosquitoes. An estimation of the predatory potential of the larva of &lt;em&gt;L. fuscana&lt;/em&gt; against the larva of the dengue vector &lt;em&gt;Aedes aegypti&lt;/em&gt; (Linnaeus, 1762) (Diptera: Culicidae) was made to highlight its use in vector management. Laboratory experiments revealed that the larva of&lt;em&gt; L&lt;/em&gt;. &lt;em&gt;fuscana&lt;/em&gt; consumes 19 to 24 &lt;em&gt;A. aegypti&lt;/em&gt; larvae per day, during its tenure as IV instar larva. The consumption of &lt;em&gt;A. aegypti&lt;/em&gt; larvae was proportionate to the body length (BL) and body weight (BW) of the predatory larva&lt;em&gt; L. fuscana&lt;/em&gt; as depicted through the logistic regressions: y = 1 / (1 + exp(-(-2.09 + 0.35*BL))) and y = 1 / (1 + exp(-(0.4+ 0.06*BW))). While the prey consumption remained comparable among the days, the net weight gained by the &lt;em&gt;L&lt;/em&gt;. &lt;em&gt;fuscana&lt;/em&gt; larva showed a decreasing trend with the age. On the basis of the results, it is apparent that the larva of the mosquito &lt;em&gt;L. fuscana&lt;/em&gt; can be used in the regulation of the mosquito &lt;em&gt;A. aegypti&lt;/em&gt; through augmentative release, particularly, in the smaller mosquito larval habitats.

Towards green oviposition deterrents? Effectiveness of Syzygium lanceolatum (Myrtaceae) essential oil against six mosquito vectors and impact on four aquatic biological control agents.

Essential oils (EOs) from plants may be alternative sources of molecules toxic against mosquito vectors of public health relevance. Most of researches in this field focused on EOs as larvicides or ovicides, while limited efforts focused on the exploitation of EOs as oviposition deterrents. In the present study, the larvicidal and oviposition deterrent activity of Syzygium lanceolatum leaf EO was evaluated against six mosquito species, Anopheles stephensi, An. subpictus, Aedes aegypti, Ae. albopictus, Culex quinquefasciatus, and Cx. tritaeniorhynchus. The chemical composition of the S. lanceolatum EO was analyzed by GC-MS analysis, showing the presence of phenyl propanal, β-caryophyllene, α-humulene, and caryophyllene oxide as major constituents. S. lanceolatum EO showed high acute toxicity on An. stephensi (LC50=51.20μg/ml), Ae. aegypti (LC50=55.11μg/ml), Cx. quinquefasciatus (LC50=60.01μg/ml), An. subpictus (LC50=61.34μg/ml), Ae. albopictus (LC50=66.71μg/ml), and Cx. tritaeniorhynchus (LC50=72.24μg/ml) larvae. Furthermore, the EO was effective as oviposition deterrent against the six tested mosquito species, with OAI on An. stephensi, An. subpictus, Ae. aegypti, Ae. albopictus, Cx. quinquefasciatus, and Cx. tritaeniorhynchus reaching -0.83, -0.81, -0.84, -0.83, -0.84, and -0.86, respectively. The toxicity of S. lanceolatum EO against several biological control agents of mosquitoes, including water bugs (Anisops bouvieri and Diplonychus indicus) and fishes (Gambusia affinis and Poecilia reticulata), was extremely low, with LC50 ranging between 4148 and 15,762μg/ml. Overall, our results pointed out the promising potential of the S. lanceolatum leaf EO as a source of environmental-friendly oviposition deterrents and larvicides effective against a wide number of mosquito species of importance for parasitology.

Comparative genomics of Beauveria bassiana: uncovering signatures of virulence against mosquitoes.

BackgroundEntomopathogenic fungi such as Beauveria bassiana are promising biological agents for control of malaria mosquitoes. Indeed, infection with B. bassiana reduces the lifespan of mosquitoes in the laboratory and in the field. Natural isolates of B. bassiana show up to 10-fold differences in virulence between the most and the least virulent isolate. In this study, we sequenced the genomes of five isolates representing the extremes of low/high virulence and three RNA libraries, and applied a genome comparison approach to uncover genetic mechanisms underpinning virulence.ResultsA high-quality, near-complete genome assembly was achieved for the highly virulent isolate Bb8028, which was compared to the assemblies of the four other isolates. Whole genome analysis showed a high level of genetic diversity between the five isolates (2.85–16.8 SNPs/kb), which grouped into two distinct phylogenetic clusters. Mating type gene analysis revealed the presence of either the MAT1–1–1 or the MAT1–2–1 gene. Moreover, a putative new MAT gene (MAT1-2–8) was detected in the MAT1–2 locus. Comparative genome analysis revealed that Bb8028 contains 163 genes exclusive for this isolate. These unique genes have a tendency to cluster in the genome and to be often located near the telomeres. Among the genes unique to Bb8028 are a Non-Ribosomal Peptide Synthetase (NRPS) secondary metabolite gene cluster, a polyketide synthase (PKS) gene, and five genes with homology to bacterial toxins. A survey of candidate virulence genes for B. bassiana is presented.ConclusionsOur results indicate several genes and molecular processes that may underpin virulence towards mosquitoes. Thus, the genome sequences of five isolates of B. bassiana provide a better understanding of the natural variation in virulence and will offer a major resource for future research on this important biological control agent.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3339-1) contains supplementary material, which is available to authorized users.

Acetylcholinesterase inhibitory activity of stigmasterol & hexacosanol is responsible for larvicidal and repellent properties of Chromolaena odorata

BackgroundChromolaena odorata, has been traditionally known for its insect repellent property. Aim of this study was to determine larvicidal tendency of C. odorata on Culex quinquefasciatus and isolate compounds responsible for this activity and to determine the mechanism of action of these compounds. MethodsC. odorata plant extract was screened for mosquito larvicidal activity. The extract was fractionated using chromatography and the bioactive fraction showing larvicidal activity was identified. The chemical nature of the compounds in the bioactive fraction was determined using NMR and Mass spectrometry. ResultsWe identified phytosterols and alkanols to be the compounds regulating larvicidal activity in the bioactive fraction of the plant extract. Stigmasterol and 1-hexacosanol were identified to be the chief orchestrators of larvicidal activity and their mode of action has been observed to be neurotoxicity. At a molecular level both stigmasterol and 1-hexacosanol were found to be inhibiting acetylcholinesterase activity in C. quinquefasciatus & A. aegypti. The acetylcholinesterase inhibitory effect was validated in vitro using recombinant acetylcholinesterase and ex vivo in larval homogenates of Culex and Aedes. Electrophysiological studies using electroantennography have shown enhanced neural response to these compounds. ConclusionsNeurotoxic effect of C. odorata derived stigmasterol and 1-hexacosanol, exerted through acetylcholinesterase inhibition was responsible for the mortality of C. quinquefasciatus, A. aegypti &Chironomus riparius. EAG studies pointed out hyper-excitability of the olfactory system by these compounds. General significanceThese compounds are natural agents for mosquito control that can be used in vector control as larvicidal compounds, pending further investigations.

Comparative Studies on in- vitro Phytochemicals Analysis and Larvicidal Efficacy of Medicinal Plant Extracts against Culex quinquefasciatus

Comparative Studies on in- vitro Phytochemicals Analysis and Larvicidal Efficacy of Medicinal Plant Extracts against Culex quinquefasciatus

Dimefluthrin: A new pyrethroid insecticide and innovative mosquito control agent

Dimefluthrin: A new pyrethroid insecticide and innovative mosquito control agent

New data on the taxonomic status and distribution of Gambusia sp. in Croatia and Bosnia and Herzegovina

Background and Purpose: In the early 20th century, two native North American poeciliid species Gambusia holbrooki and Gambusia affinis were introduced to Europe as a mosquito control agent. The first introduction to Istria from Italy in 1924 was followed by several independent introductions and massive translocations. Presently, the distribution of these two species in Croatia and Bosnia and Herzegovina (Bosnia and Herzegovina) is still largely unknown and they are often confused. The purpose of this study was to determine the taxonomic status of individual Gambusia populations and to shed more light on the distribution and phylogeographic patterns of these invasive species in Croatia and Bosnia and Herzegovina. Materials and Methods: All new and literature data were plotted together to obtain the overall distribution of Gambusia sp. in Croatia and Bosnia and Herzegovina. The samples collected across this range were analysed meristically and by means of mitochondrial cytochrome b (cytb) gene sequence analysis to ascertain the true taxonomic status of the populations. For phylogeographic analysis, the cytb sequences from this study were combined with previously published data. Results and Conclusions: The methods only confirmed the presence of G. holbrooki. G. holbrooki is continuously distributed across the entire Mediterranean biogeographical region in Croatia and Bosnia and Herzegovina. Two different mitochondrial cytb haplotypes were found: the widely spread Hol1 haplotype and haplotype Hol5 that in Europe was previously found only in France and Greece. This suggests that G. holbrooki populations in the region originated from different stocks.

Mosquitocidal Activity of Extracts from &amp;lt;i&amp;gt;Ammi visnaga &amp;lt;/i&amp;gt;(Apiaceae) Seeds

Aedes aegypti mosquitoes are responsible for transmission of many viral diseases, such as Zika fever, dengue fever, yellow fever, and chikungunya. Emergence of resistance to currently used pesticides among mosquitoes has increased the importance for the search for novel mosquito control agents. Natural products, particularly plant and microbe derived secondary metabolites, are good sources in the search for such compounds. Ammi visnaga (Lam.) Lamarck is a plant in the Apiaceae family native to North Africa, Europe, and Asia. In the search for environmentally benign and effective insecticides as part of an ongoing joint effort between the USDA (US Department of Agriculture) and the DWFP (Deployed War Fighter Protection) program sponsored by the Department of Defense, we have investigated ethyl acetate extract of A. visnaga seeds. Two furanochromones, khellin and visnagin that exhibited larvicide activity against Aedes aegypti mosquito larvae were isolated from the ethyl acetate extract of the seeds by bioassay-guided fractionation. This is the first report of mosquito larvicidal activity of khellin and visnagin.

Population Surveillance of Poecilia reticulata in Kolkata, India: Implications in Mosquito Regulation

Background: The guppy, Poecilia reticulata (Cyprinodontiformes: Poeciliidae) is promoted as a biological control agent of mosquitoes. Augmentative release of guppy has led to the elimination of the mosquitoes at a local scale, though resurgence is possible in absence of adequate population of guppy in the larval habitats. Surveillance of the guppy population in the introduced habitats is therefore required to support the use and enhance the success of biological control. Objective: Monitoring of the guppy population in the sewage drain larval habitats where P. reticulata have been released to justify the colonization and establishment in the habitat. Assessment of the aquatic community that can sustain the population in absence of the target prey will substantiate the vector management strategy employing guppy as a bio control agent. Method: Random sampling of guppy with associated local fauna during every season from different sampling sites of Kolkata and adjoining areas in consecutive three years was carried out. The population of guppy was categorized in terms of the size groups and temperature regimen. Analysis of the relative density of mosquito and guppy was made to highlight the effects of guppy in the sewage drains. Results: The population of guppy varied significantly with reference to the samples and the size classes constituting the population. Variations in the population size classes corresponded significantly to the ambient water temperature explaining ~70% variation of the data observed on the population abundance of guppy. Significant differences in the composition of the macro invertebrates (prospective prey) and the guppy population was observed, that could be represented through a Principal component analysis which explained for more than 60% variations of the data obtained on the relative abundance of the representative members of the aquatic community. A negative correlation was observed for the relative abundance of mosquito immature and guppy in situations where both the groups were present. Overall, the relative abundance suggested the colonization and establishment of the guppy and the local elimination of the mosquito immature in the sewage drains sampled. Inference: From the results it is apparent that the guppy population colonized and established in the sewage drain habitats following the augmentative release to regulate mosquito. The heterogeneity in the size class of guppy population was evident in the sewage drain habitats. Alternative prey population in the sewage drain ensures the sustenance of the guppy in the long run. A negative correlation between mosquito immature and the guppy suggests that the availability of the guppy in the habitats reduces availability of mosquito both as a direct predatory impact as well as indirect effect on the oviposition. The observations indicate that guppy can colonize and sustain in the sewage drain habitats for long time period and reduce the possible colonization of the mosquito in the sewage drain habitats.

Insecticidal Activity and Insect Repellency of Four Species of Sea Lily (Comatulida: Comatulidae) From Taiwan

The methanol and ethyl acetate (EA) extracts of four species of sea lily (Himerometra magnipinna, Comaster multifidus, Comanthina sp., and Comatella maculata) were evaluated for their insecticidal activity against Yellow-fever mosquito larvae (Aedes aegypti) and their repellency against adult Asian Tiger mosquitoes (Aedes albopictus). The 24-hr minimum inhibition concentration (MIC) data revealed that the extracts from H. magnipinna and the C. maculata were the most active, killing mosquito larvae at 12.5 ppm. The toxicity of the extracts from these four sea lilies in descending order was H. magnipinna (12.5 ppm), C. maculata (12.5 ppm), C. multifidus (100 ppm), and Comanthina sp. (200 ppm). Furthermore, no significant difference in toxicity was found using either EA or methanol as the extraction solvent. The MIC at 12.5 ppm is promising as an insecticide lead. The repellency study results show that EA is a better solvent for one species (H. magnipinna), but the methanol is a better solvent overall. The repellency of these sea lily extracts in descending order was Comanthina sp. MeOH (ED50 at 0.32%), followed by H. magnipinna EA (ED50 at 0.38%), C. multifidus MeOH (ED50 at 0.57%), C. maculata MeOH (ED50 at 0.76%), C. multifidus EA (ED50 at 1.25%), and H. magnipinna MeOH (ED50 at 1.67%). A compound with ED50 <0.5% is considered to be a promising repellant. Among the studied sea lilies, both Comanthina sp. and H. magnipinna have potential to be further developed as mosquito control agents due to their favorable toxicity and repellency.