Control Of Mosquito Larvae Research Articles

Prevention of resistance to spinosad by a combination of spinosad and Bacillus thuringiensis subsp. israelensis in Culex quinquefasciatus (Diptera: Culicidae).

Spinosad consists of spinosyn A and spinosyn D that are produced by the soil-dwelling actinomycete Saccharopolyspora spinosa. It has been used to control a wide variety of arthropod pests of economic importance. Formulations of spinosad have been used to control larval mosquitoes since approximately 2010. However, the target site- and metabolism-based resistance to this neurotoxin has been reported since 2000 in agricultural pests The current studies aim to further evaluate resistance risk and develop resistance prevention tactics in the southern house mosquito Culex quinquefasciatus. The first comparison group involved selection at lethal concentration, 75% (LC75) of technical spinosad for 30 generations, resulting in baseline resistance ratios (RRs) of 51.1-fold at LC50 and 45.4-fold at LC90 in Cx. quinquefasciatus. However, under the same conditions, selection by a combination of spinosad and Bacillus thuringiensis subsp. israelensis (B.t.i.), negated resistance development to spinosad, RRs ranging 1.00-1.75-fold at LC50 and 0.83-1.76-fold at LC90. At the same time, the selected population remained susceptible to the combination throughout the selection process, RRs fluctuating 0.74-1.38-fold at LC50 and 0.63-1.23-fold at LC90. Combination of spinosad and B.t.i. negates resistance development to spinosad, as opposed to spinosad alone in Cx. quinquefasciatus. Moreover, the species tested does not develop resistance to this combination upon repeated exposures, implying the potential for further developing this combination as a viable product for larval mosquito control. © 2024 Society of Chemical Industry.

COMPARATIVE LABORATORY ACTIVITY AND SEMI-FIELD EFFICACY OF OMNIPRENE® G AND ALTOSID® PELLETS AGAINST AEDES AEGYPTI.

Mosquito larval control by biorational larvicides plays a crucial role in mosquito and mosquito-borne disease management. However, the availability of larvicides that meet the criteria of efficacy, safety, and quality is limited and conventional pesticides are no longer preferred for larval control. Although efforts are made to research new active ingredients (AIs), it is equally important to innovate new formulations based on currently available AIs such as microbial agents and insect growth regulators. Studies were therefore conducted to compare the laboratory activity and semi-field efficacy of OmniPrene® G and Altosid® Pellets with DR-tech, both containing 4.25% S-methoprene, at 2.8 kg/ha and 11.2 kg/ha against the yellow fever mosquito Aedes aegypti (L.) in outdoor microcosms. Both products performed equally in bioassays against the test species with comparable inhibition of emergence activities. In the semi-field study, the lower dose of Altosid Pellets at 2.8 kg/ha, showed lower efficacy than OmniPrene G during the initial 6 weeks; this difference became negligible on week 7, followed by higher efficacy in Altosid Pellets on weeks 8 and 9. More uniform efficacy was observed at the higher dose of 11.2 kg/ha. Equal performance was revealed during weeks 2 to 6, with the OmniPrene G outperforming the Altosid Pellets in week 1, but the opposite during weeks 7 to 9. Mortality patterns were similar in both products, i.e., majority of mortality occurred before emergence, although more incomplete emergence was noted in lower doses, particularly in Altosid Pellets. Overall, newly available OmniPrene G provided comparable activity and efficacy with Altosid Pellets against the test species, with the advantages of fast initial AI release and even coverage, particularly when applied at low doses.

Extreme resistance to S-methoprene in field-collected Culex pipiens (Diptera: Culicidae) across the Chicago, IL region

Insect growth regulators, like S-methoprene, are heavily relied upon worldwide for larval mosquito chemical control due to their target specificity and long-lasting effects. In this study, susceptibility to S-methoprene was evaluated in Culex pipiens, a globally important vector species. Populations from 14 sites throughout the Chicago area with a long history of S-methoprene use and two sites with minimal use in Wisconsin were examined. Using a bioassay methodology and probit analyses, LC50 and LC90 values were calculated and compared to a susceptible laboratory strain to develop resistance ratios, then categorized for resistance intensity. The resistance ratios observed required the addition of another category, termed ‘extreme’ resistance, indicating resistance ratios greater than 100. ‘Low’ to ‘extreme’ levels of resistance to S-methoprene were detected throughout Illinois populations, with resistance ratios ranging from 2.33 to 1010.52. Resistance was not detected in populations where S-methoprene pressure has been very limited. These 'extreme’ resistance ratios observed have never been documented in a wild vector species mosquito population. The relationships between historical S-methoprene use, resistance detected with laboratory bioassays, and the potential for field product failure remain unclear. However, the profound resistance detected here demonstrates a potential critical threat to protecting public health from mosquito-borne diseases.

Native Larvivorous Fishes vs Alien Fishes: A Comparative Study of Biological Control of Mosquito Larvae

Native Larvivorous Fishes vs Alien Fishes: A Comparative Study of Biological Control of Mosquito Larvae

Comparison of yeast microencapsulated fluralaner to commercially available mosquito larval control products, 2023

Comparison of yeast microencapsulated fluralaner to commercially available mosquito larval control products, 2023

Bioactive potential of L. camara and O. gratissimum extracts in the control of mosquito larvae: An ecologically friendly approach

In the present study, the larvicidal efficacy of the extracts of the weeds Lantana camara Linn (L. camara) and Ocimum gratissimum Linn (O. gratissimum) was evaluated against the larvae of the malaria vectors A. aegypti, An. subpictus, and C. quinquefasciatus. The ethanol, n-hexane and diethyl ether crude leaf extracts were evaluated in a preliminary screening for larvicidal activity at 20,40,80,160,320 and 640 mg/l concentrations. 20 larvae of each species were introduced in different sterile Petri dishes in aqueous media under a controlled environment to assess biological activity. The larvicidal activity of both extracts was evaluated at 6 and 12-h post-exposure time points by observing the movement of each larva. The obtained data were subjected to probit analysis to determine the lethal concentrations that kill 50% and 90% (LC50 and LC90) of the treated larvae. The results revealed a noticeable larvicidal activity following 12 h of exposure. The extract of L. camara leaves exhibited an LC50 range between 18.66 and 51.35 mg/l and an LC90 range between 87.78 and 312.21 mg/l. Moreover, for the extract of O. gratissimum leaves, the LC50 range was 52.26 to 59.09 mg/l and the LC90 range was 260.22 to 348.23 mg/l. Taken together, the results indicate that the extracts of L. camara and O. gratissimum leaves may be useful as effective, economical, and eco-friendly larvicidal agents. However, additional studies are needed to explore the bioactive components of the weeds that exhibit larvicidal activity along with their mode of action.

MosChito rafts as a promising biocontrol tool against larvae of the common house mosquito, Culex pipiens

Mosquito control is of paramount importance, in particular, in light of the major environmental alterations associated with human activities, from climate change to the altered distribution of pathogens, including those transmitted by Arthropods. Here, we used the common house mosquito, Culex pipiens to test the efficacy of MosChito raft, a novel tool for mosquito larval control. MosChito raft is a floating hydrogel matrix, composed of chitosan, genipin and yeast cells, as bio-attractants, developed for the delivery of a Bacillus thuringiensis israeliensis (Bti)-based bioinsecticide to mosquito larvae. To this aim, larvae of Cx. pipiens were collected in field in Northern Italy and a novel colony of mosquito species (hereafter: Trescore strain) was established. MosChito rafts, containing the Bti-based formulation, were tested on Cx. pipiens larvae from the Trescore strain to determine the doses to be used in successive experiments. Thus, bioassays with MosChito rafts were carried out under semi-field conditions, both on larvae from the Trescore strain and on pools of larvae collected from the field, at different developmental stages. Our results showed that MosChito raft is effective against Cx. pipiens. In particular, the observed mortality was over 50% after two days exposure of the larvae to MosChito rafts, and over 70–80% at days three to four, in both laboratory and wild larvae. In conclusion, our results point to the MosChito raft as a promising tool for the eco-friendly control of a mosquito species that is not only a nuisance insect but is also an important vector of diseases affecting humans and animals.

A novel pyrazole–pyridine derivative (PPD) targets specific biological pathways in the larval stages of the northern house mosquito Culex pipiens Linnaeus (Diptera: Culicidae)

BackgroundMosquitoes cause a variety of health problems in humans and pets. So, the control of mosquito larvae is one of the best ways to avoid health problems arising from diseases transmitted by these insects. There are various control mechanisms including mechanical, biological and chemical control. The latter, despite the presence of some obstacles associated with its use, is preferred because of its ability to supply rapid management results.ResultA novel laboratory-synthesized chemical compound containing pyrazole and pyridine moieties (pyrazole–pyridine derivatives, PPD) was used to control and address the biological effects on Culex pipiens mosquito second larval instar. A sublethal concentration (LC30) of PPD inhibited larval growth by about 50%. Furthermore, the developmental time of larvae into pupae and the emergence of adults from the pupal stages were increased by about 20% and 17%, respectively. The ultrastructural studies on the midgut cells revealed that treated larvae suffered dramatic degeneration in the gastric caeca and the posterior midgut cells, while the anterior midgut epithelium appeared with an abundance of lysosomal activities. Additionally, treated larvae showed fluctuated activities in the levels of the detoxifying enzymes and increased levels in total antioxidants.ConclusionsThese results clearly show that pyrazole and pyridine moieties containing compounds can be used against larval stages of C. pipiens.

Comparative efficacy of natural aquatic predators for biological control of mosquito larvae: A neglected tool for vector control.

Mosquitoes are a dominant fraction of dipteran fauna, occupying a variety of niches. The most common method deployed for their control is the use of insecticides. Throughout their life cycle they are exposed to a wide range of predators in different habitats, thus biological control of mosquitoes by using aquatic predators has been suggested. Therefore, the present study was carried out to explore the type of natural predators coexisting with the mosquito larvae in still water bodies and to determine their efficacy as predators for mosquito larvae. A coexistence of different predators with mosquito larvae was observed in 27 standing water bodies of Chandigarh, India. The predation efficiency of tadpoles of frog was comparable to Gambusia fish, as 97% of the mosquito larvae of all instars of the medically important mosquito genera Anopheles, Aedes, Culex and Armigeres were preyed. The toad tadpoles were found to be least effective and their predation rate was found to be negligible. Further studies on larval source management by frog tadpoles in combination with insecticides or stand-alone would be worthwhile.

Ecological and Behavioral Factors to Aid in Modelling Environmental Mosquito Control & to Design Larval Robots

Abstract: The anatomical location of human pathogens in mosquitoes ranging from Plasmodium, Wucheriria, flavivirus and other viruses are in salivary glands of the mosquitoes which is important for transmission. Further Dengue virus (DENV) is known to exist from egg stage to adult stage in mosquitoes. The other important fact in mosquito borne transmission is the blood meal that renders them capable of egg laying. Hence hormonal, ecological, behavioral control of mosquitoes with environmental thyroxine, larval behavior pattern, predatory dragonfly larva, air turbulence g-force was studied. Environmental contamination of shallow water bodies with animal urine could introduce thyroxine in water bodies where mosquito larva is breeding. Modeling such an outcome, the results indicated significance influence of thyroxine on mosquito larva resulting in alteration of eclosed mosquito size, weight, sex ratio, antennal hairs. The second mode of ecological control with predatory dragonfly larva in water bodies modeled with introduced coal resulted in excellent mosquito larval control. The third mode of using air turbulence g-force (with home appliances like ceiling fan) induced mosquito control was also found to be effective in reducing the no of hatched larva when the adult mosquitoes are exposed to g-force but it did increase the longevity of male mosquitoes. Further based on mosquito larval behavior pattern, it was observed that mosquito larva does have the tendency to be social and tend to meet each other in water bodies that can be used for mosquito control by design of larval robots that can deliver larvicidal compounds on one-to-one basis.

Essential Oils of Distichochlamys benenica: Chemical Constituents, Mosquito Larvicidal and Antimicrobial Activities

In recent years, essential oils (EOs) have gained popularity for their potential as natural antimicrobial agents and mosquito larvae control. This study aimed to explore the chemical composition of EOs extracted from the leaves and rhizomes of Distichochlamys benenica Q.B. Nguyen & Škorničk, and to evaluate their mosquito larvicidal and antimicrobial activities. The EOs were obtained using hydrodistillation and subjected to gas chromatography (GC) and GC-mass spectrometry to determine their chemical constituents. The main components identified in the leaf EO were β-pinene (47.7%), cis-β-elemene (8.5%), and α-pinene (7.8%), while the rhizome EO mainly consisted of geranyl acetate (25.7%), geranial (23.3%), neral (16.6%), and geraniol (8.4%). The mosquito larvicidal activity of the EOs was evaluated using larvae of Aedes aegypti and Culex quinquefasciatus during 24 and 48 h of treatment. The results demonstrated that these EOs effectively inhibited the mosquito larvae, with LC50 values ranging from 31.15 to 71.53 μg/mL and LC90 values ranging from 46.28 to 148.66 μg/mL. Additionally, the minimum inhibitory concentration (MIC) and half-maximal inhibitory concentration (IC50) values were used to evaluate the antimicrobial efficacy of EOs. Both EOs exhibited potent antimicrobial effects against Enterococcus faecalis ATCC 299212, Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 14579, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10231, with MIC values ranging from 16 to 64 μg/mL and IC50 values ranging from 4.67 to 45.67 μg/mL. Overall, the mosquito larvicidal and antimicrobial activities of D. benenica EOs highlight their potential as natural alternatives for combating mosquito-borne diseases and microbial infections.

Fatty acid methyl esters (FAMEs) obtained from edible vegetable oils: Larvicidal activity and melanization process in Aedes aegypti larvae

Larval control of mosquitoes using chemical insecticides has promoted the formation of resistant strains of these insects. In the search for more efficient active substances on the different species of invertebrates, the use of compounds of vegetal origin is a potential alternative. The objective of this work was to evaluate the activity of different fatty acid methyl esters (FAMEs) on Aedes aegypti larvae. The main unsaturated methyl esters present in the FAMEs tested were methyl oleate and methyl linoleate. The most active samples on A. aegypti larvae were FAMEs 2, 3, 4, 5 and 6, with LC50 values of 15.55, 5.92, 5.13, 3.35 and 8.01 μg/mL. All FAMEs triggered the melanization response in the larvae, which varied in relation to the time for the appearance of the pigment granules, intensity and number. FAMEs can be considered a source of new natural bioinsecticides for the control of mosquito larvae.

Observation and Simulation of Mosquito Breeding Site Water Temperature for Malaria Transmission at Kaita Local Governmet Township of Katsina State, Nigeria

Studies showed that transmission of malaria is influenced by environmental factors such as temperature. This work is aimed at finding the impact of mosquito's breeding site water temperature on mosquito's larva development time. An artificial mosquito's breeding habitat was created. The water temperature of the habitat was measured at an hourly interval, then it is averaged into daily time scale. Weather variables of the experimental site were inpu into the the energy balance model to simulate the breeding habit water temperature. The mosquito's larva development time was then predicted by inputting both the observed water and simulated water temperature into the vector borne disease community model (VECTRI) .The daily maximum, and minimum observed water temperatures were 27.9°C, 32.6°C and 21.7°C, respectively. The daily mean, maximum, and minimum simulated water temperatures were 29.8°C, 35.6°C, and 23.5°C respectively. These temperatures are within the temperature range that supports mosquito’s larva development. Mosquito's larva development was predicted using the VECTRI model. According to this study larva development reached completion in 7.1 days using the observed water temperature, 6.03 days using the simulated water temperature and 8.01days using the observed air temperature. This energy balance model is an improved water temperature scheme over the assumption that air temperature is equal to air temperature. This work shows the importance of water temperature and the value of degree day required for emergence of an adult mosquito in the simulation of aquatic stage development. Both the observed water and simulated water temperatures are higher than the on observed air temperature, thus air temperature cannot be used as the water temperature in the simulation of the mosquito’s larva development time. The finding of the work can be used as source toward mosquito's larval control through water temperature. It is however clear from the finding that could be as result of temperature due to shorter time predicted for mosquito's larval development.

Development and Application of Biopesticides for the Management of Disease Vectors and Pests of Public Health Importance

The development and practical use of natural products occurred in the late 1970s when a spore-forming bacterium producing enterotoxins was discovered. This organism was designated as Bacillus thuringiensis ssp. israelensis (Bti). By 1985, large quantities of Bti formulations were employed in mosquito and black fly control programs globally. As research efforts in this area continued, a second bacterium Bacillus sphaericus (Bsph) was isolated and found to be highly effective against most mosquito species. This entomopathogen found its way into mosquito control around 1997. Today, both these (Bti and Bsph) microbial control agents are produced by large-scale fermentation processes in many countries. Recent advances in formulation technology of both bacteria have increased their usefulness in vector control programs. Another soil bacterium known as Saccharopolyspora spinosa (Actinomycetes), was discovered, producing bioactive components known as spinosyn A and spinosyn D. Large-scale fermentation technology has been developed and the product known as spinosad was produced and developed in agriculture, and recently for use in public health. However, spinosad has not been used to any great extent in public health as yet. All three microbial control agents have a good margin of safety for mammals, birds, and wildlife and are environmentally friendly. Considerable efforts were directed toward developing plant extracts for vector control, especially mosquitoes. In this context, plant-based extracts were formulated for the control of larval and adult mosquitoes. Some of the plant parts were used in manufacturing mosquito coils which number into the billions on a worldwide basis; however, only a small proportion of coils are manufactured with plant-derived products. A major area for the development of plant-based products is the use of plant essential oils which are formulated in various ways for personal protection from the attack of hematophagous insects. A number of such insect-repellent products are commercialized in many countries. The public has the perception that plant-based and other natural products are environmentally friendly and safer to use for vector control or apply to human skin as personal protectants than synthetic chemicals. In this paper, we will dwell upon the research and development efforts leading to the development, production, and application of microbial control agents, and phytochemicals for the control of adult and preimaginal stages of disease vectors, as well as the development and use of plant essential oils for personal protection from anthropophilic insects.

Larvicidal Efficacy of Azadirachta indica, Ocimum gratissimum and Cymbopogon citratus Ethanolic Extracts against Culex quinquefasciatus Larvae

Background: Effective and repeated control use of synthetic insecticides has led to the development of resistance development in mosquitoes. This problem has resulted in the need for the development of new strategies for selective mosquito larval control. The present work investigated the larvicidal efficacy of Azadirachta indica, Ocimum gratissimum, and Cymbopogon citratus ethanolic extracts against Culex quinquefasciatus mosquitoes. Methods: Extracts of A. indica, O. gratissimum, and C. citratus were obtained using 80% ethanol after their leaves had been previously air-dried for about 3-4 weeks. Thereafter, the solvent was evaporated with a rota-ry evaporator to eliminate any solvents still present. Twenty-five samples (in four replicates) of 2nd-3rd in-star larvae of C. quinquefasciatus were exposed to various concentrations (20 mg/L, 40 mg/L, 60 mg/L, 80 mg/L, and 100 mg/L) of each leaf extracts using WHO standard procedures. Data obtained were analyzed using the Statistical Package for Social Sciences (SPSS) for Windows, version 14, and statistical differences among mortalities induced by the different concentrations were obtained using Analysis of Variance (ANOVA) at a 95% confidence level (P= 0.05) with the aid of GraphPad prism 8. Results: There was an increase in the mortality rates of C. quinquefasciatus larvae as the concentration of each of the three leaf extracts increased over 24 hours. Eighty mg/L ethanolic extract of A. indica gave a mortality rate of 96.10% (24±0.1) after 24 hours of exposure, 100 mg/L of the same extract of A. indica gave a mortality rate of 100% (25.0. ±0.0) which is significantly (P < 0.05) higher than 96.1% (24±0.1) and 80.0 % (20.0±0.5) at the same conditions in C. citratus and O. gratissimum respectively. Eighty mg/L and 100 mg/L of ethanolic extract of C. citratus gave 51% (12.5±0.7) and 96.1% (24±0.1) mortality rates after 24 hours. However, ethanolic extract of O. gratissimum resulted in the least 80.0 % (20.0±0.5) motility rate of C. quinquefasciatus larvae with exposure to 100 mg/L concentration after a 24-hour duration of exposure. Conclusion: The study concluded that the ethanolic extract of A. indica was the most active, followed by that of C. citratus and then O. gratissimum. The extracts of A. indica, C. citratus, and O. gratissimum hold great larvicidal potential, and they are important tools that can be integrated into the Culex mosquito vector control programme

Bacillus thuringiensis Cyt Proteins as Enablers of Activity of Cry and Tpp Toxins against Aedes albopictus.

Aedes albopictus is a species of mosquito, originally from Southeast Asia, that belongs to the Culicidae family and the Dipteran insect order. The distribution of this vector has rapidly changed over the past decade, making most of the temperate territories in the world vulnerable to important human vector-borne diseases such as dengue, yellow fever, zika or chikungunya. Bacillus thuringiensis var. israeliensis (Bti)-based insecticides represent a realistic alternative to the most common synthetic insecticides for the control of mosquito larvae. However, several studies have revealed emerging resistances to the major Bti Crystal proteins such as Cry4Aa, Cry4Ba and Cry11Aa, making the finding of new toxins necessary to diminish the exposure to the same toxicity factors overtime. Here, we characterized the individual activity of Cyt1Aa, Cry4Aa, Cry4Ba and Cry11Aa against A. albopictus and found a new protein, Cyt1A-like, that increases the activity of Cry11Aa more than 20-fold. Additionally, we demonstrated that Cyt1A-like facilitates the activity three new Bti toxins: Cry53-like, Cry56A-like and Tpp36-like. All in all, these results provide alternatives to the currently available Bti products for the control of mosquito populations and position Cyt proteins as enablers of activity for otherwise non-active crystal proteins.

Toxicity Evaluation and Genetic Improvement of Bacillus thuringiensis Isolated from Different Regions in Assiut, Egypt against Mosquito Larvae

This study aims to evaluate the toxicity and genetic improvement of Bacillus thuringiensis isolates. Isolates were obtained from soil, insect and water samples from different regions of Assiut, Egypt for biological control of mosquito larvae. B. thuringiensis colonies were identified based on morphological and then by PCR which detect the Cry toxic genes in the isolates. Bioassays were performed to evaluate the toxicity of different strains of B. thuringiensis against mosquito larvae such as (Culex spp). In general, 36 B. thuringiensis isolates were obtained (31 from soil, 4 from insects, and 1 from water). And they were all toxic to mosquito larvae with different mortality percentages from 7 to 97% after 48 hours. Isolate Am2 recorded the highest mortality percentage 97% and Mn3 lowest mortality percentage 7%. PCR revealed that Am2 isolate which caused the highest mortality encodes three different types of Cry toxins, Cyt1AA, Cry1Ac and Cry2Aa. This isolate Am2 was examined by scanning electron microscopy to observe the shape of the Cry proteins. The results showed that the Am2 isolate contained of spherical and cuboidal toxic proteins. Then UV-mutagenesis was performed on the Am2 isolate to improve its toxicity. Out of 30 obtained UV-mutants, only one mutant showed improvement in the mortality of mosquito larvae since it caused a mortality rate of 100%. The results of the present study revealed the larvicidal efficacy of B. thuringiensis (Am2) isolate found in the soil of Assiut, could be used in biological control program of mosquito larvae.

Assessment of the Knowledge, Prevalence, and Control Strategies of Malaria Among Households in Sunyani Municipality, Bono Region, Ghana.

Malaria remains a global public health concern for centuries. The study assessed the knowledge, prevalence and control strategies of malaria among households in the Sunyani Municipality, Bono Region, Ghana. A simple random sampling method was used to administer semi-structured questionnaires to the respondents (n = 422). STATA version 14.0 was used to analyse the data and the results were presented in charts, graphs, and tables. The study shows that the knowledge level of malaria, its vector of transmission and mosquitoes breeding sites among the respondents was quite high. Among the respondents, 43% reported to have been infected by malaria once in a year and 94% indicated that, their relatives have been infected with malaria parasites previously. Also, majority, 65% of the respondents selected environmental management and sanitation (EMS), followed by settlement (building houses) away from wetlands, 20.0% as alternative vector control methods to be employed to supplement the core vector control methods in the Municipality. Further, majority, 69% of the respondents indicated that enforcement of environmental sanitation bye-laws will compel residents to clean their environment, and this is likely to eliminate most mosquito breeding sites, whiles 46% called on Government to support, and employ more Environmental Health Officers and Sanitary Labourers, and adequately resource them to work effectively. Health authorities in the Sunyani Municipality must intensified education on malaria at all levels with the aim to influence the attitudes of households towards its prevention and control. Central and Local Government must employ more Environmental Health Officers, and empower and adequately resourced them to strictly enforce the environmental sanitation bye-laws. Malaria control authorities in the study area must consider employing environmental management and sanitation (EMS) and application of larvicides for mosquito larval control as alternative/supplementary malaria prevention and control methods to compliments the current core vector control methods.

Knowledge, attitudes, and practices towards mosquito control and used vehicle tire dumping by median household income, in metropolitan New Orleans, Louisiana.

Discarded vehicle tires are an important artificial habitat for the larvae of many container-breeding mosquito species worldwide, including in the United States. Unmanaged discarded vehicle tires create health, environmental and social costs, and with budget and staffing constraints, effective management of discarded used vehicle tires a mosquito larval habitat depends in part on the knowledge, attitude, and practices (KAP) of community residents. This study aims to examine the knowledge, attitude and practices of New Orleans, Louisiana residents toward illegally discarded vehicle tires, and larval mosquito control. A descriptive cross-sectional design study was used where 422 households were selected using a two-stage cluster random sampling procedure in New Orleans, Louisiana. Heads of households or a person aged 18 years or older self-administered the survey. The questionnaire comprised five parts: screening, tire sightings, preferred communication method, knowledge, attitude and precautionary measures against mosquito control, disease risk and illegal discarding. We then statistically compared above and below median income household responses to identify likely causes of detected differences. The data were analyzed using ordinal regression models via IBM SPSS statistics V.26.0. Statistical significance was set at p<0.05. Out of 290 responding households, 95.5% strongly agree or agree that mosquitoes can spread serious diseases like West Nile, Zika or Dengue. Only 2.3% of the sample had high knowledge of illegally discarded tires dumping and mosquito larval control. Those employed were 1.0 times more likely to possess good knowledge than the unemployed (p<0.001). Despite low knowledge levels regarding mosquito breeding and polluted water in discarded tires, 29.9% of respondents had positive attitude and 20.5% reported sufficient practices. Among the socio-demographic variables, only home ownership and being employed were predictors of knowledge and attitude towards mosquito breeding in illegally discarded tires (p<0.05). Despite the observed increasing number of illegally discarded vehicle tires in New Orleans, the knowledge of people about illegal tire dumping and their associated risk factors as suitable larval habitants was low. Therefore, there is a need for developing community-based and place-based tailored sensitization campaigns to prevent illegal used tire dumping, and larval control.

Long-term storage does not affect the infectivity of entomopathogenic nematodes on insect hosts.

Entomopathogenic nematodes (EPNs) are effective biopesticides used in insect control. There are several formulations of entomopathogenic nematodes which are commercially available, but their popularity is low because the requirement of periodic release of stored entomopathogenic nematodes in field has reduced infectivity and is a constraint in large-scale repeated application of entomopathogenic nematodes in field. So, in order to overcome this impediment, the current study focuses on storage of entomopathogenic nematodes for a longer period of time using encapsulating beads. In this study, three EPNs, namely, Steinernema carpocapsae, Steinernema monticolum, and Rhabditis blumi, were encapsulated with Arabic gum and sodium alginate gel beads at different concentrations. Bio-efficacy of stored EPNs at different concentrations (50, 100, 200, 500, and 1000 infective juveniles (IJs)) in varying time intervals of 3, 6, 9, and 12weeks were tested against Culex quinquefasciatus larvae. The results show that, after 3weeks of storage, these entomopathogenic nematode species showed survival up to 96%, and in 12-week storage, survival rate was 50%. The virulence of the progeny that emerged from these stored entomopathogenic nematodes was similar to the fresh infective juveniles. The results of the present study show that Arabic gum-sodium alginate combination is a promising approach toward storing entomopathogenic nematodes. Furthermore, semi-field trials showed 70-90% larval mortality at a concentration of 3000 IJs (encapsulated and stored entomopathogenic nematodes in S. monticolum, S. carpocapsae, and R. blumi) on C. quinquefasciatus larvae. KEY POINTS: • Increased survival of stored EPNs (S. carpocapsae, S. monticolum, and R. blumi) in encapsulated gel using Arabic gum, sodium alginate, and yeast cells was assessed. • The efficacy was greater in stored EPNs at different concentrations from 3 to 12 weeks. • Semi-field trials of stored encapsulated EPNs are efficient in mosquito larval control.