Assessment of larvicidal, growth-suppressing, and development-altering bioefficacy of Ageratum houstonianum against Aedes aegypti (L.).

Mosquitoes are significant public health pests and act as a vector of several diseases viz ., malaria, filariasis, Japanese encephalitis, dengue fever and chikungunya, which are transmitted by the three genera of mosquitoes, viz ., Anopheles, Culex and Aedes . Mosquito control strategies have depended primarily on the use of synthetic chemical insecticides but resulted in rebounding vectorial capacity, environmental and human health concerns. Plants may be a source of alternative agents to replace the synthetic insecticides for mosquito control. In the present study, the isolated fractions of Murraya koenigii hexane leaf extracts were evaluated for larvicidal activity against vector mosquitoes viz., Aedes aegypti , Anopheles stephensi and Culex quinquefasciatus . Six fractions viz., A, B, C, D, E and F were obtained from the residue of hexane extract by column chromatography. Standard WHO protocol with minor modifications was adopted for the larvicidal bioassay. Larvicidal activity was evaluated against the isolated fractions at concentrations of 25, 50, 75 and 100 ppm. Larval mortality was observed 24 hours post exposure. Amongst the isolated fractions tested, fraction ‘D’ showed 100.0, 97.6 and 99.2% mortality against third instar larvae of Aedes aegypti , Culex quinquefasciatus and Anopheles stephensi at 100 ppm, respectively and LC50 values were 35.06, 27.20 and 42.51 ppm respectively. Further investigations are needed to explore the larvicidal activity of the isolated fraction ‘D’ of hexane leaf extract of this plant and also the active principle(s) responsible for larvicidal activity.

Larvicidal potential of selected indigenous lichens against three mosquito species–Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi

Mosquitoes are the most important group of insects in terms of public health importance, which transmit serious human diseases. The continuous application of synthetic insecticides to control these mosquitoes causes development of resistance in vector species, and an adverse effect on environmental quality and non-target organisms including human health. Therefore, the use of active toxic agents from plant extracts as alternative mosquito control strategy cannot be over emphasized, as these are non-toxic, easily available at affordable prices, biodegradable and show target - specific activities against different species of vector mosquitoes. The aim of the present study was to evaluate the larvicidal efficacy of the aqueous and methanol leaf extracts of H. suaveolens against the fourth instars larvae of Anopheles species. Standard WHO protocols was adopted for the larvicidal bioassay. Larvicidal activity was evaluated at concentrations of 200, 400, 600, 800 and 1000 mg/L. The larval mortality was observed after 24 and 48hours bioassay. The results are mean of three replicates and the mortalities recorded were subjected to chi-square test and probit analysis to determine median lethal concentrations (LC50). TheGC-MS analysis ofthe methanolic leaf extract of the plantrevealed the presence of twelve compounds on the chromatogram. Among the major compounds areOleic Acid (33.33%), Octadecanoic acid (13.52%), 1,3-Cyclohexadiene-1-methanol,alpha.,2,6,6-(10.42%), 1,3-Cyclopentanediol, trans (9.60%), n-Hexadecanoic acid (9.01%) and 4-Hepten-3-one, 4-methyl (7.0%).The phytochemical screening of the aqueous and methanol leaf extracts of the plant revealed the presence of Tannins, Terpenoids, Flavonoids, Steroids, Carbohydrates, Cardiac glycoside and resins. The LC50 values estimated were 316.22mg/Lfor methanol extract and 323.59 mg/L for aqueous extract. The differences between the two extracts were however not significantly different at P>0.05. The findings also revealed that mortality was concentration dependent and both extracts showed promising larvicidal activity against Anopheles species larvae. Therefore, the crude leaf extract of the plant is recommended to be used as alternative to synthetic larvicides and further research is needed to test the activity of the plant on non-target organisms.

Background: Papaya is a kind of plats which has the medicinal effect. Papaya’s sap (latex) contains papain, cimopapain and lysozim as protein destructor enzyme. Satrija guess that these enzymes has an anthelmintical activity. The research aim was to know the influence of papaya’s sap (latex) as a larvacide in several kind of doses (concentration). Methods: This research was true experimental design with posttest only control group design. Papaya’s sap was made as powder, afterward it was used for the research to know influence of Papaya’s sap in several kinds of doses (consentration) related to larval cumulative mortality rate of Aedes aegypti. Larvicidal activity was calculated based on larval mortality after 24 hours of exposure that was taken notes for each treated group. Data processing used SPSS program version 11,0 with significance 95% that contains data normality test, varians homogeneity test, One Way Anova, and Scheffe Post Hoc Test to know difference in larval cumulative mortality rate. Results: The result from Anova test shown a significant result in cause larval cumulative mortality rate of Aedes aegypti (p-value < 0.05) in comparison with negative gontrol group. Treated group with Papaya’s sap 1% shown higest larvacidal activity. Conclusion: Papaya’s sap has larvacidal activity at the concentration of 0,16%; 0,3%; 0,5%; and 1%. At concentration of 1%, papaya’s sap shown higest larvacidal activity and shown a significant result. Keywords: papaya, larvacide, larvae of Aedes aegypti

The present study focused on comparing virulence of two entomopathogenic nematodes, Steinernema abbasi and S. carpocapsae, to the mosquito, Aedes aegypti. The results showed that the first instar larvae and pupae of Ae. aegypti were not susceptible to both nematodes. The cumulative mortalities inoculated with 300 infective juveniles (IJs) per larva of S. abbasi against second to fourth instar larvae of Ae. aegypti were 21.1, 30.0, and 97.8%, respectively, whereas those inoculated with S. carpocapsae were 45.6, 94.4, and 97.8%, respectively. The LT50 values of older instar larvae inoculated with both nematodes were shorter than those of younger instars. The LD50 values of fourth instar larvae inoculated with S. abbasi and S. carpocapsae were 122.6 and 44.5 IJs/larva at 48 h after inoculation. Encapsulated nematodes were calculated from dead third or fourth instar larvae of Ae. aepypti inoculated with 200 IJs/larva of S. abbasi or S. carpocapsae. Numbers of encapsulated S. abbasi in third and fourth instar larvae were 1-4, and 0-10, respectively, whereas those of S. carpocapsae in third and furth instar larvae were 0-9, and 0-8, respectively. However, the larvae with one nematode encapsulated were mostly observed. The cumulative mortalities of fourth instar larvae inoculated with S. abbasi and S. carpocapsae at 25°C were 93.3 and 95.6%, respectively, while those incubated at 20°C were lowest at only 20.0 and 76.7%, respectively. The mortalities of fourth instar larvae when inoculated with both nematodes immersed previously in four different depths of water were not significantly different. The cumulative mortalities of fourth instar larvae inoculated with both S. abbasi and S. carpocapsae which had been placed in water in a longer diameter of round plate were lower than those in a shorter diameter. The LT50 value of fourth instar larvae inoculated with S. carpocapsae in a longer diameter of round plate was longer than that in a shorter one. The mortalities of fourth larvae inoculated with both S. abbasi and S. carpocapsae, which had been kept in water for 10 or 20 days, were 33.3-48.9 and 80.0-85.6%, respectively, being not significantly different between treatments within the same species. However, the mortalities resulted from inoculations with those nematodes kept in water for 30 days were significantly lower than those for 10 and 20 days. In addition, the LT50 value of fourth instar larvae inoculated with S. carpocapsae kept for 20 days was longer than that for 10 days. Therefore, our experimental data provide information for further studies on potential application of the entomopathogenic nematodes as biological control agents against mosquitoes.

BackgroundThe cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae), is an economic pest on various crops worldwide. Farmers generally used to apply chemical pesticides to control the pest. The bio-control potential of the entomopathogenic nematodes (EPNs) as alternatives to harmful synthetic pesticides was examined in this study. The study aimed to determine the efficacy of EPNs isolates against the different stages of larvae of the cotton leafworm S. littoralis and the effect of time on mortality rate under laboratory conditions.ResultsEPNs isolates were tested at 4 different concentrations (0, 250, 500 and 1000 IJs/ml) in 150 ml plastic containers on last instar larvae (sixth instar) of S. litorallis. Experiments for third, fourth and fifth instar larvae of S. litorallis were carried out in petri dishes at different concentrations (0, 50, 100 and 200 IJs/ml) at 25 °C temperature. Mortality rates of larvae were calculated at 3 different times (48, 72, 96 h) after inoculation. The high mortality rate of last instar larvae (98.81%) of S. littoralis was caused by Steinernema feltiae (Tokat-Emir), followed by S. carpocapsae (Tokat-Bakışlı05) (95.24%) and then H. bacteriophora (11 KG) with (90.47%) at the highest concentration (1000 IJ/ml). The highest mortality rate of fifth instar larvae was caused by S. feltiae (Tokat-Bakışlı05) and S. carpocapsae (Tokat-Emir) with (100%) and (92.12%). In addition, the highest mortality rate of the 4th instar larvae was determined S. feltiae (Tokat-Bakışlı05) and S. carpocapsae (Tokat-Emir) isolates (98.87%) and (97.74%), respectively. Additionally, the highest larval mortality rate in the third stage by S. feltiae (Tokat-Bakışlı05) and S. carpocapsae (Tokat-Emir) was (100%) and (97.74%) at the highest concentration. Mortality rates of larvae were calculated at 3 different times after inoculation. The highest mortality rate counted in all isolates was determined 96 and 72 h after inoculation of EPNs.ConclusionsAll indigenous EPN isolates were found to be effective at different rates against S. littoralis. The results showed that these nematode species could be used against S. littoralis biological control programs.

The crude leaf extracts of Abutilon indicum were evaluated for larvicidal, pupal deformities and adult emergence inhibition activity against vector mosquitoes viz., Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. Larvicidal activity was carried out using WHO protocol. Hexane extract with LC50 value of 261.31 ppm after a period of 24 hr was found to be effective against Aedes aegypti larvae. Larval and pupal development was arrested resulting in decreased pupal transformation and adult emergence. Larval and pupal periods were prolonged with appearance of larval–pupal and pupal–adult intermediates, with an overall increase in the developmental period. Hatching was delayed and its rate was reduced compared to control. Disrupted egg shells and dechitinized body walls were observed, indicating clearly the anti-juvenile potential of the extract. The growth index was considerably reduced. These results suggest the leaf extracts of Abutilon indicum as a promising adult emergence inhibitor against vector mosquitoes and might be used in small volume aquatic habitats or breeding sites of limited size in and around human dwellings.

Ovipositional nonpreference and larval development of stalk-borer, Chilo partellus Swin., on leaf-whorl and stem of 70 sorghums comprising of released varieties and hybrids, experimental high-yielding varieties, lines selected for stalk-borer resistance and local cultivars were studied in the laboratory. Data on oviposition of egg-masses as well as on number of eggs, larval duration, larval mortality and pupal weight on leaf-whorl and stem of individual variety were separately recorded. These characters were also correlated with number of holes, number of tunnels and per cent tunnelling observed in the field. The egg-masses per seedling ranged from 0.32 to 2.25, while eggs per seedling varied from 2.25 to 20.80 on different varieties. These were highly correlated (0.92**) characters. The varieties SPV nos 35, 101, 110, 232, 257, 289, 291, 309 and 311, E 302, E 701, CSV nos 3, 6 and 8R and Aispuri were relatively less preferred for oviposition. Larval development took 17–32 days on leaf-whorl and 33–62 days on stem of the various varieties. The larval duration on leaf-whorl as well as on stem were more than average on SPV nos 35, 103, 107, 110 and 310, E 302, E 701, CSV-8R, IS 2312 and Aispuri The larval mortality ranged from 1.7 to 95.0% on leaf-whorl and 13 to 95% on stem. Significantly higher larval mortality on leaf-whorl of SPV nos 35, 101, 292 and 311, E 302, CSV nos 3, 6 and 8R was recorded. It was 11.5 and 29.6% higher on SPV-35 and CSV-8R respectively than the most resistant variety, IS 2312. Larval mortality on leaf-whorl of early maturing varieties was 8.1% more than late varieties. The mean pupal weight was 65.55 ± 3.82 mg on leaf-whorl and 51.65 ± 4.93 mg on stem. The pupal weights were 47–75 mg on leaf-whorl and 33.5–47.7 mg on stem of local varieties. Larval duration was positively correlated with larval mortality on both leaf-whorl and stem and negatively with pupal weight on leaf-whorl. Larval duration and mortality on leaf-whorl were negatively correlated with per cent ’dead hearts’, and number of tunnels per plant. Larval duration and mortality on stem were also negatively and significantly correlated with holes per peduncle and per cent tunnelling. The magnitude of correlations of larval duration and mortality with tunnelling parameters were higher than that of oviposition. Though ovipositional nonpreference and antibiosis act together to determine the degree of resistance, antibiosis has a greater effect on Chilo resistance than the effect of ovipositional nonpreference. The antibiosis factor(s) affecting larval development exists in leaf or in stem or in both the plant parts. Short peduncle varieties were less preferred for oviposition.

Several diseases are associated to the mosquito-human interaction. Mosquitoes are the carriers of severe and well-known illnesses such as malaria, arboviral encephalitis, dengue fever, chikungunya fever, West Nile virus and yellow fever. These diseases produce significant morbidity and mortality in humans and livestock around the world. The present investigation was undertaken to study the ovicidal, larvicidal and adulticidal activities of crude hexane, ethyl acetate, benzene, chloroform and methanol extracts of root of Asparagus racemosus were assayed for their toxicity against three important vector mosquitoes, viz., Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi (Diptera: Culicidae). The mean percent hatchability of the eggs was observed after 48 h post-treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. All the five solvent extracts showed moderate ovicidal activity; however, the methanol extract showed the highest ovicidal activity. The methanol extract of Asparagus racemosus against Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi exerted 100% mortality (zero hatchability) at 375, 300 and 225 ppm, respectively. Control eggs showed 99-100% hatchability. The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest larval mortality was found in methanol extract of root of Asparagus racemosus against the larvae of Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi with the LC50 and LC90 values were 115.13, 97.71 and 90.97 ppm and 210.96, 179.92, and 168.82 ppm, respectively. The adult mortality was observed after 24 h recovery period. The plant crude extracts showed dose-dependent mortality. At higher concentrations, the adult showed restless movement for some times with abnormal wagging and then died. Among the extracts tested, the highest adulticidal activity was observed in methanol extract against Anopheles stephensi followed by Aedes aegypti and Culex quinquefasciatus with the LD50 and LD90 values were 120.44, 135.60, and 157.71 ppm and 214.65, 248.35, and 290.95 ppm, respectively. No mortality was recorded in the control. The finding of the present investigation revealed that the root extract of Asparagus racemosus possess remarkable ovicidal, larvicidal and adulticidal activity against medically important vector mosquitoes and this is the low cost and ideal eco-friendly approach for the control of mosquitoes. This is the first report on the mosquito ovicidal, larvicidal and adulticidal activities of the reported Asparagus racemosus root.

Plastic pollution and infectious diseases

The number of documented dengue cases has increased dramatically in recent years due to transmission through the Aedes aegypti mosquito bite. Vector control remains the most effective measure to protect against this and other arboviral diseases including Zika, chikungunya and (urban) yellow fever, with an established vaccine only available for yellow fever. Although the quinone class shows potential as leading compounds for larvicide development, limited information restricts the development of optimized structures and/or formulations. Thus, in this contribution we investigated the larvicidal and pupicidal activity of three quinone compounds isolated from a Connarus suberosus root wood ethyl acetate extract together with 28 quinones from other sources. Eight quinones demonstrated larvicidal activity, of which tectoquinone (4) proved to be the most active (LC50 1.1 µg/mL). The essential residual effect parameter of four of these quinones was evaluated in laboratory trials, with tectoquinone (4) and 2-ethylanthraquinone (7) presenting the most prolonged activity. In small-scale field residual tests, tectoquinone (4) caused 100% larvae mortality over 5 days, supporting its selection for formulation trials to develop a prototype larvicide to control Ae. aegypti.

Vector-borne diseases such as malaria, filariasis, yellow fever, dengue, and Japanese encephalitis are major illnesses in in tropical countries. The main objective of this study was to investigate the larvicidal activity of synthesized silver nanoparticles (AgNPs) utilizing aqueous leaf extract of Ocimum sanctum against fourth instar larvae of Aedes aegypti and Anopheles stephensi. The present study was carried out to establish the larvicidal activity of synthesized silver nanoparticles (AgNPs) using leaf aqueous extract of Ocimum sanctum against fourth instar larvae of dengue and malaria vector. The larval mortality was observed after different time of exposures. Further, characterization such as XRD and SEM analysis were carried out for the synthesized silver nanoparticles. The mortality values were obtained using the probit analysis. The larvae of Aedes aegypti and Anopheles stephensi were found to be highly susceptible for the silver nanoparticles. The larvae have shown 100% mortality against the silver nanoparticles, whereas fourth instar larvae have shown efficacy (LC50) after 24 and 48 hr. The characterization studies of synthesized AgNPs by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), of silver nanoparticles along with stability. In conclusions, the findings revealed that synthesized AgNPs possess excellent mosquito larvicidal activity. These results suggest that the green synthesis of AgNPs have the potential to be used as an ideal eco-friendly approach for the control of head lice and vectors.&#x0D;

Physical influence on larvicidal and pupicidal activity of the silicone-based monomolecular film

Effect of Moringa oleifera lectin on development and mortality of Aedes aegypti larvae

Resistance to insecticides is spreading among populations of Aedes aegypti, the primary vector of important human arboviruses. The escalating insecticide resistance poses a significant threat to dengue vector control, with an expanding number of countries affected by the disease. To gain a deeper insight into the evolution of insecticide resistance, it is essential to have longitudinal surveillance results, which are currently lacking, particularly from African Ae. aegypti populations. Here we report on three-years of surveillance of Ae. aegypti susceptibility to insecticide resistance phenotypes and associated kdr mutations in Burkina Faso, a country with regular dengue outbreaks. Ae. aegypti susceptibility to insecticides and the V410L, V1016I, and F1534C kdr target site mutations linked to pyrethroid insecticide resistance were monitored in Ouagadougou from 2016 to 2018. Larvae were collected from artificial containers at two sites and reared to adulthood in an insectary. Bioassays were conducted on female adults, along with a laboratory-susceptible strain, following standard WHO protocols. Allele-specific PCR genotyping assays were utilized to identify the V410L, V1016I, and F1534C kdr pyrethroid target site mutations. Bioassays revealed a high level of resistance to permethrin and deltamethrin that progressively increased over the three-year period in both localities. The 1534C mutation was nearly fixed throughout the three years at each locality, and while the closely-related 410L and 1016I mutations did not vary between localities, their frequency notably increased from 2016 to 2018. Interestingly, Ae. aegypti populations in both areas remained susceptible to bendiocarb, fenitrothion, and malathion. Modelling the mortality data further confirmed the escalating resistance trend over the years and emphasized the significant role played by the three kdr mutations in conferring resistance to pyrethroids. Mortality rates indicate that Ae. aegypti populations from Ouagadougou are becoming increasingly resistant to pyrethroid insecticides, likely due to an increase in the frequencies of the 410L and 1016I kdr mutations. Organophosphate insecticides are likely to be better alternative options for control.