Inhibition Of Adult Emergence Research Articles

Effect of Moringa oleifera Leaf Powder and Seed Oil on Insect Pests of Stored Maize and Cowpea

The leaf powder of Moringa oleifera was applied as direct admixture at 5g, 10g and 15g while the seed oil was applied at 5ml and 10ml to 100g each of Maize and Cowpea grains respectively, while the control was without insecticide application to test for insect mortality., progeny development and damage caused on stored maize and cowpea (Sitophilus zeamais and Callosobruchus maculatus). The experiment was laid out in a Completely Randomized Design (CRD) and results obtained were subjected to analysis of variance (ANOVA) while means were separated using the Least Significant Difference (LSD). The result showed significantly (P<0.05) progeny reduction of adult Sitophilus zeamais and Callosobruchus maculatus using Moringa oleifera leaf powder at different concentration 0, 5g (23.90, 28.62), 10g and 15g respectively. Control (0) recorded the highest number 68.51 in Callosobruchus maculatus, and 56.85 in Sitophilus zeamais. Mortality test result showed that moringa leaf powder significantly(P<0.05) increased the mortality of adult S. zeamais and C. maculatus with increase in concentration after 96 hours of exposure while moringa seed oil offered 100% mortality after 24 hours of exposure. Germination of maize and cowpea was not affected after treatment with moringa leaf powder and seed oil. Contact toxicity result showed significant adult mortality of S. zeamais and C. maculatus on filter paper with 15% mortality in C. maculatus and 10% in S. zeamais. Damage was significantly reduced in treated grains compared with the untreated control. Moringa seed oil was more toxic to S. zeamais and C. maculatus compared to moringa leaf powder and the untreated control. The protective effect of moringa seed oil against S. zeamais and C. maculatus comes principally through oviposition suppression and reduced or complete inhibition of adult emergence, consequently reducing or eradicating infestation risk, damage and loss of maize and cowpea grains in storage. While the use of plant essential oils against storage insect pest is being advocated, the availability, affordability and the tendency of tainting protected grains should be considered.

Impact of SumiLarv® 2MR on Aedes aegypti larvae: a multicenter study in Brazil

BackgroundAedes aegypti is associated with dengue, Zika, and chikungunya transmission. These arboviruses are responsible for national outbreaks with severe public health implications. Vector control is one of the tools used to prevent mosquito proliferation, and SumiLarv® 2MR is an alternative commercial product based on pyriproxyfen for larval/pupal control. In this study, the residual effectiveness of SumiLarv® 2MR in different regions of Brazil was evaluated in simulated field conditions.MethodsWe conducted a multicenter study across four Brazilian states—Amapá, Pernambuco, Rio de Janeiro, and São Paulo—given the importance to the country’s climatic variances in the north, northeast, and southeast regions and their influence on product efficiency. The populations of Ae. aegypti from each location were held in an insectary. Third-instar larvae (L3) were added every 2 weeks to water containers with SumiLarv® 2MR discs in 250-, 500- and 1000-l containers in Amapá and Rio de Janeiro, and 100-l containers in Pernambuco and São Paulo, using concentrations of 0.04, 0.08, and 0.16 mg/l.ResultsAdult emergence inhibition over 420 days was observed in all tests conducted at a concentration of 0.16 mg/l; inhibition for 308–420 days was observed for 0.08 mg/l, and 224–420 days for 0.04 mg/l.ConclusionsSumilarv® 2MR residual activity demonstrated in this study suggests that this new pyriproxyfen formulation is a promising alternative for Aedes control, regardless of climatic variations and ideal concentration, since the SumiLarv® 2MR showed adult emergence inhibition of over 80% and residual activity greater than 6 months, a period longer than that recommended by the Ministry of Health of Brazil between product re-application in larval breeding sites.Graphical abstract

Efficacy of the insect growth regulator novaluron in the control of dengue vector mosquitoes Aedes aegypti and Ae. albopictus

Insect Growth Regulator (IGR) novaluron is an alternative to synthetic neuro-inhibitory insecticides. Present study was designed to assess appropriate dosages of novaluron for dengue vector control. Larvae of Aedes aegypti and Ae. albopictus were exposed to a concentration series of novaluron (Rimon EC10) for two fixed exposure periods of 7-days and 14-days to determined LC50 and LC99 values. Inhibition of adult emergence (IE50 and IE99) was determined by a 14-day exposure. Semi-field experiments were conducted by exposing cohorts of Ae. aegypti larvae to IE99, 2 × IE99 and 10 × IE99 novaluron concentrations in water storage buckets (10 L) and plastic barrels (200 L). For the 7-day exposure, LC50 values were 0.047–0.049 ppm and LC99 were 0.144–0.151 ppm. For 14-day exposure, these values were 0.002–0.005 ppm and 0.006–0.01 ppm respectively. For both species, IE99 was 0.001 ppb under semi-field conditions, and was effective for nearly 2 months. Novaluron concentration 0.01 ppb was effective up to 3 months, with an IE of 89–95%. Authorities should critically review a reduction of the presently recommended field dosage of 200 ppm novaluron by × 100 or more. This would provide the same efficacy but mitigate environmental pollution, development of vector resistance, and financial losses.

Current and future opportunities of autodissemination of pyriproxyfen approach for malaria vector control in urban and rural Africa

Despite the progress made in reducing malaria burden, new ways to address the increasing challenges of insecticide resistance and the invasion and spread of exotic malaria vectors such as Anopheles stephensi in Africa are urgently needed. While African countries are adopting larviciding as a complementary intervention for malaria vector control, the autodissemination technology has the potential to overcome barriers associated with the identification and treatment of prolific habitats that impede conventional larviciding approaches in rural settings. The autodissemination technology as a “lure and release” strategy works by exploiting the resting behavior of gravid mosquitoes to transfer lethal concentration of biological or chemical insecticide such as pyriproxyfen (PPF), an insect growth regulator (IGRs) to their oviposition sites and result in adult emergence inhibition. Despite the evidence of the autodissemination approach to control other mosquito-borne diseases, there is growing and promising evidence for its use in controlling malaria vectors in Africa, which highlights the momentous research that needs to be sustained. This article reviews the evidence for efficacy of the autodissemination approach using PPF and discusses its potential as efficient and affordable complementary malaria vector control intervention in Africa. In the previous studies that were done in controlled semi-field environments, autodissemination with PPF demonstrated its potential in reducing densities of captive population of malaria vectors such as Anopheles gambiae and Anopheles arabiensis. Of importance, empirical evidence and biology-informed mathematical models to demonstrate the utility of the autodissemination approach to control wild populations of malaria vectors under field environment either alone or in combination with other tools are underway. Among others, the key determining factors for future introduction of this approach at scale is having scalable autodissemination devices, optimized PPF formulations, assess its integration/complementarity to existing conventional larviciding, and community perception and acceptance of the autodissemination approach.

Sterilized Anopheles funestus can autodisseminate sufficient pyriproxyfen to the breeding habitat under semi-field settings

BackgroundAnopheles funestus, the main malaria vector, prefer to oviposit in permanent and/or semi-permanent breeding habitats located far from human dwellings. Difficulties in identifying and accessing these habitats jeopardize the feasibility of conventional larviciding. In this way, a semi-field study was conducted to assess the potential of autodissemination of pyriproxyfen (PPF) by An. funestus for its control.MethodsThe study was conducted inside a semi-field system (SFS). Therein, two identical separate chambers, the treatment chamber with a PPF-treated clay pot (0.25 g AI), and the control chamber with an untreated clay pot. In both chambers, one artificial breeding habitat made of a plastic basin with one litre of water was provided. Three hundred blood-fed female An. funestus aged 5–9 days were held inside untreated and treated clay pots for 30 min and 48 h before being released for oviposition. The impact of PPF on adult emergence, fecundity, and fertility through autodissemination and sterilization effects were assessed by comparing the treatment with its appropriate control group.ResultsMean (95% CI) percentage of adult emergence was 15.5% (14.9–16.1%) and 70.3% (69–71%) in the PPF and control chamber for females exposed for 30 min (p < 0.001); and 19% (12–28%) and 95% (88–98%) in the PPF and control chamber for females exposed for 48 h (p < 0.001) respectively. Eggs laid by exposed mosquitoes and their hatch rate were significantly reduced compared to unexposed mosquitoes (p < 0.001). Approximately, 90% of females exposed for 48 h retained abnormal ovarian follicles and only 42% in females exposed for 30 min.ConclusionThe study demonstrated sterilization and adult emergence inhibition via autodissemination of PPF by An. funestus. Also, it offers proof that sterilized An. funestus can transfer PPF to prevent adult emergence at breeding habitats. These findings warrant further assessment of the autodissemination of PPF in controlling wild population of An. funestus, and highlights its potential for complementing long-lasting insecticidal nets.

Chemical composition and bioactivity of essential oils from Piper nigrum L. and Piper retrofractum Vahl. against Callosobruchus maculatus (F.)

Plants containing substances with insecticidal properties can be used for pest control. Essential oils of Piper nigrum L. and Piper retrofractum Vah. from dried seeds and fresh leaves extracted by hydrodistillation was determined using Gas Chromatography-Mass Spectrometry (GC-MS). The fumigation toxicity and bioactivity bioassay were investigated using vapor-phase test. Experiment was performed under completely randomized design (CRD) with 4 replications. Adult mortality, number of eggs and adult emergence of F1 progeny of C. maculatus were recorded. Chemical compounds of essential oils from dried seeds and fresh leaves of P. nigrum and P. retrofractum were determined at 22-27 components (90.34-93.27%). Major compounds in dried seeds and fresh leaves of P. nigrum and P. retrofractum were alpha-bergamotene, caryophyllene, beta-selinene, germacrene D, naphthalene, undecane, 5-octadecene, cyclohexene, limonene and 2-beta-pinene. Both essential oils contained limonene, linalool, caryophyllene and naphthalene in seeds and leaves. These four components showed insecticidal properties. Essential oils at concentrations of 5 µL/L air P. nigrum and 10 µL/L air P. retrofractum extracted from dried seeds were more effective in oviposition inhibition and adult emergence of C. maculatus than essential oils extracted from fresh leaves. P. nigrum essential oil from dried seeds at a concentration of 5 µL/L air was the highest efficiency of oviposition inhibition with 55.17% and adult emergence inhibition of 71.09% of C. maculatus. This suggested that P. nigrum essential oil extracted from dried seeds could be used for protection on C. maculatus in stored grain.

Spent Coffee Grounds and Novaluron Are Toxic to Aedes aegypti (Diptera: Culicidae) Larvae.

Aedes aegypti (Diptera: Culicidae) is a vector for mosquito-borne diseases worldwide. Insecticide resistance is a major concern in controlling this mosquito. We investigated the chemical compounds in wet and dry spent coffee grounds (wSCGs and dSCGs) and evaluated the efficacy of dSCGs, wSCGs, and novaluron on the mortality and adult emergence inhibition of Ae. aegypti. We found higher concentrations of chemical compounds in wSCGs than in dSCGs. The wSCGs and dSCGs both contained total phenolic compounds, total flavonoid compounds, caffeic acid, coumaric acid, protocatechuic acid, and vanillic acid. Complete mortality was observed after 48 h of exposure to 50 g/L wSCGs, while similar mortality was found after 120 h of exposure to 10 µg/L of novaluron. The sublethal dose was a concentration of wSCGs (5 g/L) and novaluron (0.01, 0.1, and 1 µg/L) combined that resulted in a larval mortality lower than twenty percent (at 72 h) to determine their synergistic effects. The death rate of larvae exposed in sublethal combination of wSCGs and novaluron was significantly higher than that of its stand-alone. The findings indicate that the combination of wSCGs and novaluron at sublethal concentrations had synergistic effects on the mortality of Ae. aegypti larvae and could be applied as an alternative control measure.

Studies on Efficacy of Botanical Oils and Leaf Powders Against Lesser Grain Borer, &lt;i&gt;Rhyzopertha dominica&lt;/i&gt; (F.) in Stored Wheat

The experiment on biological activity of botanical oils and leaf powders against R. dominica was conducted under laboratory condition. The results revealed that among the botanical oils and leaf powder, the castor oil 2.0% and neem leaf powder 1% achieved maximum adult mortality at 72 hr after treatment (91.67% and 81.67%) and revealed as the best grain protectants with least seed damage (4.33% and 3.67%), weight loss (2.01% and 1.04%), F1 adult emergence (3.67 and 4.33) and high inhibition rate (97.25% and 97.34%). This is due to their high viscosity of oils and asphyxiation effect by leaf powders. The finding also revealed that the botanical oils and leaf powders do not affect the germination of wheat seed.

Chemical Composition and Use of &amp;lt;i&amp;gt;Momordica charantia&amp;lt;/i&amp;gt; L. and &amp;lt;i&amp;gt;Hyptis spicigera&amp;lt;/i&amp;gt; Lam. Extracts as Mosquito Larvicides and Insect Growth Regulators against Malarial Vector, &amp;lt;i&amp;gt;Anopheles gambiae&amp;lt;/i&amp;gt; Giles

Background: Mosquitoes are responsible of numerous vector-borne diseases and among these diseases is malaria which takes away lives of thousands of people, especially children of under five, particularly in Africa. To reduce the mortality and economic burdens of this deadly disease, synthetic insecticide has been of use to control its main vector, Anopheles gambiae. Due to adverse effects caused by these conventional products on non-target organisms and the environment, plants have been of first choice as they proved their effectiveness against mosquitoes and are said to be eco-friendly and relatively safer. Therefore, the aim of this study was to screen the phytochemicals and determine the larvicidal and adult emergence exhibitory activities of Momordica charantia and Hyptis spicigera leaves extracts against Anopheles gambiae larvae. Methods: The WHO standard protocol for larvicidal activity and IGRs was followed up and concentrations from 500 - 2000 ppm for larvicidal and 500 - 1500 ppm for IGRs were set up. Results: There was the presence of alkaloids, flavonoids, tannins, phenols, steroids, terpenoids and oils in Momordica charantia against alkaloids, taponins, tannins, phenols, steroids, terpenoids and oils in Hyptis spicigera. Methanol crude extract registered the lowest LC50 value of 270.6 ppm followed by ethyl acetate and hexane fractions recorded the LC50 of 742.1 and 756 ppm, respectively for larvicidal activity of Momordica charantia against LC50 of 760 and 867.5 ppm for hexane fraction and methanol crude extract, respectively for Hyptis spicigera. Methanol crude extract and hexane fraction of both plants as well as the ethyl acetate fraction of M. charantia registered greater emergence inhibition with IE50 values of 590.2, 842.3 and 982 ppm for methanol crude extract, hexane and ethyl acetate fractions of M. charantia, respectively against 901.7 and 873.2 for methanol crude extract and hexane fraction of H. spicigera, respectively. Conclusion: The toxicity and adult emergence inhibition may be associated with constituents in both plants that interfere with the normal neuronal, respiratory and endocrine systems functions.

Chemical Composition, Larvicidal and Adult Emergence Inhibition Activities of &amp;lt;i&amp;gt;Balanites aegyptiaca&amp;lt;/i&amp;gt; Del. Seed and &amp;lt;i&amp;gt;Aristolochia albida&amp;lt;/i&amp;gt; Duch. Root Extracts against Malaria Vector, &amp;lt;i&amp;gt;Anopheles gambiae&amp;lt;/i&amp;gt; Giles

Background: Anopheles gambiae is enemy number one of mankind in Africa and particularly in Cameroon due to its ability of transmitting malaria which is the deadliest disease in this part of the world. Synthetic insecticides have been used to control malaria vectors but they have negative effects on non-target organisms and are environmentally unfriendly. Control of mosquitoes at larval stages using phytochemicals is currently the leading tool to reduce the mosquito population and so the reduction of malaria transmission rates. Therefore, the present study was to evaluate the phytochemical contents, larvicidal and adult emergence inhibition activities of Balanites aegyptiaca seed and Aristolochia albida root solvents extracts against Anopheles gambiae larvae. Methods: The World Health Organization standard protocols were followed for the different bioassays. Concentrations ranging from 500 - 2000 ppm for larvicidal and 500 - 1500 ppm for IGRs were used. Results: Both plants showed the presence of alkaloids, flavonoids, saponins, tannins, phenols, terpenoids and oils except the absence of phenols in Aristolochia albida. The larvicidal activity of Aristolochia albida extracts showed that hexane and methanol fractions were the most active killing relatively all exposed larvae with the LC50 values of 420.1 and 453 ppm, respectively. The same observation was made in hexane fraction from Balanites aegyptiaca (LC50 = 588 ppm). The insect growth inhibitory activity of Aristolochia albida extracts proved that hexane and methanol fractions relatively caused a 100% inhibition in the mosquito development, recording the EI50 values of 482.4 and 555.6 ppm, respectively. The same trend was observed with Balanites aegyptiaca hexane fraction registering better EI50 of 623.9 ppm. Conclusions: Our findings demonstrate that Balanites aegyptiaca seed and Aristolochia albida seed extracts are rich in phytochemicals capable of killing mosquito larvae and disrupting mosquito larval development. This could contribute to the control of mosquito populations and improved management of malaria.

Mosquitocidal activities of Chenopodium botrys whole plant n-hexane extract against Culex quinquefasciatus.

This research aimed to investigate various mosquitocidal activities of Chenopodium botrys whole- plant n-hexane extract against Culex quinquefasciatus. The extract showed remarkable larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus. During the larvicidal and pupicidal activities, the 24-hour lethal concentration (LC50) of extract against 2nd instar larvae, 4th instar larvae and pupae were 324.6, 495.6 and 950.8 ppm, respectively. During the CDC (Centers for Disease Control and Prevention) bottle bioassay for adulticidal activity, the median knockdown times (KDT50) at 1.25% concentration was 123.4 minutes. During the filter paper impregnation bioassay for adulticidal activity, the KDT50 value at 0.138 mg/cm2 concentration was 48.6 minutes. The extract was fractionated into 14 fractions through silica gel column chromatography which were then combined into six fractions on the basis of similar retention factor (Rf) value. These fractions were screened for adulticidal activity by applying CDC bottle bioassay. The fraction obtained through 60:40 to 50:50% n-hexanes-chloroform mobile phase with 0.5 Rf value showed 100% adulticidal activity at 0.2% concentration. During oviposition deterrent activity, the highest concentration (1000 ppm) showed 71.3 ± 4.4% effective repellence and 0.6 ± 0.1 oviposition activity index. During adult emergence inhibition activity, the median emergence inhibition (EI50) value was 312.3 ppm. From the outcome of the present investigation, it is concluded that the n-hexane extract of C. botrys whole- plant possesses strong larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus.

Ingestion and effects of green synthesized cadmium sulphide nanoparticle on Spodoptera Litura as an insecticidal and their antimicrobial and anticancer activities

The current study investigated the multifunctional properties of Cadmium Sulphide Nanoparticles synthesized using a green synthesis method (CdS NPs) using a green feedstock, Nopal Cactus fruit extract. The biological activities of the CdS NPs were thoroughly investigated, including their insecticidal, antibacterial, and anticancer activities. The different concentrations (0.005–0.04%) of CdS NPs were fed to the larvae of Spodoptera litura, and their ingestion effects were observed on the different biological, biochemical, and oxidative stress markers. There are significant dose-dependent changes in the biochemical parameters like superoxide dismutase (SOD), Catalase (CAT), Glutathione-S-transferase (GST), and MDA level as a marker of lipid peroxidation in the treated larvae were studied. In the highest concentration (0.04%), significant larval mortality (46.66%), malformation (pupae and adult) (27.78%), inhibition of adult emergence (43.87%), as well as reduced fecundity (25.28%), and fertility (22.74%) as compared to control was observed. CdS NPs have been investigated for antibacterial activity against Pseudomonas aeruginosa and Staphylococcus aureus bacterial strains. In vitro anticancer activities were carried out to decrease the viability of the Pancreatic cancer cell line. The cells showed 18% and 12% viability at a 200 μg/ml concentration when incubated with CdS NPs for 24 and 48 h, respectively, confirming its potent anticancer property. The lack of cytotoxicity against the (RBC) endorses the biocompatible nature of synthesized CdS NPs. It was observed that green synthesized CdS NPs could be used as a promising insecticidal, antibacterial, and anticancer agent.

Evaluation on the Activity and Efficacy of Omniprene™ WSP and XWSP Against the Southern House Mosquito Culex quinquefasciatus in Simulated Catch Basins.

Mosquitoes and mosquito-borne diseases remain one of the major public health burdens. In most cases, vector control is the main or the only intervention to mitigate these problems. We are facing the challenges of traditional, emerging, or resurging vectors and diseases, yet the availability and affordability of safe and effective mosquito control products are at a historical low. Development of new active ingredients (AI) and novel formulations based on currently available AI are demanded by mosquito control operations. This paper validated the bioactivity in the laboratory and evaluated the semi-field efficacy for 2 newly registered controlled-release products based on juvenile hormone analog S-methoprene: OmniPrene™ water-soluble pouch (WSP) and extended water-soluble pouch (XWSP). Along with technical S-methoprene, these 2 formulations showed high inhibition of adult emergence in laboratory bioassays against Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus that are commonly found in catch basins. High initial and long-term residual efficacy were demonstrated in simulated catch basins against Cx. quinquefasciatus, where the OmniPrene WSP consistently provided over 90% control for 15 wk (105 days) and OmniPrene XWSP did the same for 38 wk (266 days). Considering the need for reliable mosquito control products, combined with commonly encountered product performance issues in catch basins, OmniPrene WSP and XWSP can be viable tools to combat mosquito species of public health concern that are associated with urban drainage systems.

The impact of insect growth regulators on adult emergence inhibition and the fitness of Aedes aegypti field populations in Thailand

BackgroundThe frequent use of insecticides in vector control causes the development of insecticide resistance. Insect growth regulators (IGRs), which effect insect development, are used as a promising alternative to control resistant insect vectors. This study aimed to develop novel effective tools for Aedes aegypti control by evaluating the efficacy of different IGRs on larval development, blood feeding capacity, fecundity, and fertility in females and sperm productivity in males across geographical regions of Thailand. MethodsThe efficacy of 16 technical grade IGRs were evaluated against laboratory strain Ae. aegypti larvae in order to determine their emergence inhibition (EI) at 50% and 95% under laboratory conditions. Six IGRs were selected for fecundity, fertility, and sperm productivity studies using feed-through treatments at EI95 concentration levels against adult Ae. aegypti field strains. ResultsThe results from larval bioassay tests indicate that juvenile hormone mimics (EI50 = 0.010–0.229 ppb; EI95 = 0.066–1.118 ppb) and chitin synthesis inhibitors affecting CHS1 (EI50 = 0.240–2.412 ppb; EI95 = 0.444–4.040 ppb) groups effectively inhibited adult Ae. aegypti emergence. Methoprene and fenoxycarb significantly reduced blood feeding capacity. Egg production was comparable among strains while methoprene, pyriproxyfen and diflubenzuron induced egg production. Egg retention was detected in females fed on diflubenzuron. Methoprene, fenoxycarb, diflubenzuron, and teflubenzuron reduced egg hatching rates in mosquito field strains compared to laboratory strain. Male mosquitoes fed on fenoxycarb showed significantly lower sperm production compared to other treatments. ConclusionJuvenile hormone analogues and chitin synthesis inhibitors affecting CHS1 groups showed excellent results in adult emergence inhibition in this study. They also disrupted reproductive systems in both adult males and females. This study suggested that they can be used as an alternative larvicide in mosquito control programs.

Effect of pyriproxyfen on development and survival of Anopheles gambiae sensu stricto under forested and deforested areas

BackgroundThe land cover changes in the form of deforestation are known for their impact on enhancing Anopheline life-history traits. In most cases, these traits depend on environmental parameters such as temperature and light. Pyriproxyfen is an insect growth regulator juvenile hormone (JH) designed to inhibit adult mosquito emergence. It is an effective biolarvicide in controlling immature stages of malaria vectors and many other insects. Despite the known efficiency of pyriproxyfen in malaria vector control, but the understanding of its performance under deforested or afforested areas is not clear. The present study aimed at evaluating the impact of pyriproxyfen on development and survivorship of Anopheles gambiae s.s. in forested and deforested areas. Tests of two dosages (0.03 ppm.ai. and 0.3 ppm.ai.) of pyriproxyfen were done in standardized semi-field conditions under ambient temperature and light in netting screened environment. The plastic artificial microcosms containing 1 kg of soil and 2000 mL of dechlorinated water were used. First instars larvae were distributed in densities of 20, 40, and 60 in six replicates each, to form a total of 18 microcosms per each land cover type. Larvae mortality, development, and survival time were monitored and recorded after every 24 h until pupation. Emerging adults from pupa were recorded, and their sexes were identified.ResultsPyriproxyfen increased Anopheles gambiae larvae mortality rates and larvae developmental time of first instar larvae to pupal at densities of 20, 40 and 60 larvae in forested area (p < 0.05). Also, the larvae survival time was found to be longer in forested area compared to deforested area (p < 0.05) except at the density of 20 larvae. Pyriproxyfen reduced larvae pupation rates by 88% in forested area and it had 100% adult emergence inhibition regardless of land cover type and pyriproxyfen concentration, except at the density of 60 larvae exposed to 0.03 ppm, where adult emergence rate of 6.7% was detected.ConclusionThese findings suggest that, the efficacy of pyriproxyfen against Anopheles gambiae s.s. larvae and pupae is dependent on land cover types and its larvicidal effect can be increased by presence of trees canopy covers. Therefore, reviving forestry schemes and community afforestation programmes could have a positive impact on mosquito larval control by using larvicides. Also, increasing land canopy cover can be opted as a way to discourage the development and survival of potential malaria vectors.

Developmental inhibitory effect of the Syzygium aromaticum essential oil on the postembryonic stages of a polyphagous pest, Pericallia ricini (Lepidoptera: Arctiidae)

ABSTRACT The chemical composition of Syzygium aromaticum essential oil (EO), and its efficacy on the development and metamorphosis of polyphagous pest, Pericallia ricini was assessed. The chemical composition of the S. aromaticum EO was analysed by gas chromatography and mass spectrometry method. The major volatile components present in the EO were eugenol, β-caryophyllene, caryophyllenyl alcohol, α-humulene, clovene, globulol, and eugenyl acetate. For topical bioassay, EO was tested against the sixth (penultimate) and seventh (ultimate) larval instars of P. ricini resulted in the disruption of normal moulting and metamorphosis, leading to various developmental aberrations. The results comprised larval mortality, delayed larval-larval, and larval-pupal ecdysis duration, ecdysial failure, formation of non-viable intermediates, emergence of abnormal adults, reduced pupation, and inhibition of total adult emergence. This study also reports about the juvenoid nature of clove oil for the first time. Our finding demonstrates that S. aromaticum EO has significant negative effects on P. ricini, and suggests that it can be implemented for the successful control of this economically important insect.

Toxicity of Ulva lactuca and green fabricated silver nanoparticles against mosquito vectors and their impact on the genomic DNA of the dengue vector Aedes aegypti.

Marine seaweeds are known to have a potential role against microbial and pesticidal activities. Ulva lactuca, a green macroalgae extract analysed through gas chromatography mass spectrometry reveals 31 compounds. Resistance of mosquito vectors to synthetic insecticides remains a major problem. Discovering and applying natural agents to act against disease vectors is challenging. The activities of the extract and nano‐fabricated green synthesised silver nanoparticles were checked for use against Aedes aegypti and Culex pipiens. The crude extract and synthesised silver nanoparticles exhibited a notable larvicidal effect, and very effective inhibition of pupal and adult emergence. Inhibition of adult emergence of Ae.aegypti was 97.7% and in Cu.pipiens, it was 93.3%. Our genotypic study of Deoxyribonucleic acid from treated larvae utilising random primers MA‐09, MA‐12 and MA‐26 revealed damaged nucleotide sequences when compared with the controls. The antimicrobial activity of both the extract and green synthesised nanomaterials showed prominent activity against pathogenic drug resistant bacteria. Our results contribute to further development of eco‐friendly insecticides with lower cost of preparation. This could further contribute to further research helping future generations to be free from these deadly disease‐causing vectors and pathogenic microbes.

Low Doses Gamma Irradiation as Quarantine Treatment for Controlling Bactrocera zonata (Saund, 1841) and Its Impact on Guava Fruits Quality

The current laboratory study investigates the effect of low doses of gamma irradiation range of (5-50 Gy) cesium cell- 137 on the different developmental stages eggs, 1st, 2nd , 3rd instars larvae and pupae of peach fruit fly, Bactrocera zonata. In addition to that the evaluation of phytosanitary irradiation dose on 3rd instar larvae and their effects on the biochemical quality of guava fruits were proven. The findings indicate that irradiation of eggs with dose 25Gy prevents adult emergence, while the dose 45Gy prevents pupation and the dose 50Gy prevents the hatchability of eggs. Moreover, exposure of larvae with the dose 50 Gy resulted in 98.5, 91 and 86 % mortality for the 1st, 2nd and 3rd instars larvae, respectively. No adult emergence was reported in 1st, 2nd and 3rd instars at the dose level 30, 35 and 45 Gy, respectively. The 3rd instar larvae appeared to be the most tolerant stage to radiation treatment than the 2nd and 1st larval instars. When adult emergence was used as a criterion for determination of the effective irradiation dose, 50 Gy was adopted for phytosanitary irradiation dose for B. zonata. Large scale confirmatory tests were applied to 25,000 3rd instar larvae of B. zonata in guava fruits resulting in non- F1 adults’ production with a confidence level of 91.8%. In conclusion, the irradiation dose of 50 Gy induces the inhibition of adult emergence of 3rd instar larvae and is suggested as a possible minimum dose for phytosanitary treatment of B. zonata fruit fly without causing significant effect (p ≤ 0.05) on some biochemical characteristics of guava fruits.

Novel pyriproxyfen based treatment for Aedes breeding control through a long-lasting formulation: Laboratory and field trials in Western Maharashtra, India.

There is a need to evaluate novel techniques for dengue control in India. Several formulations of pyriproxyfen have been assessed for efficacy and duration of action. Pyriproxyfen is also used as a microencapsulated ready-to-use formulation against the Aedes vector. We evaluated a novel pyriproxyfen-based microencapsulated formulation. This slow-release, ready-to-use aqueous spray is a larvicidal formulation, and we assessed its efficacy and residual action through laboratory and semi-field trials against Aedes immature stages. The study was carried out as per the guidelines for laboratory and field/small-scale field testing of mosquito larvicides by the World Health Organization. The evaluation was conducted in laboratory and semi-field conditions from August to December 2018. We tested the novel formulation on three materials (plastic, ceramic, and enamel) in the laboratory for its action as an antilarval. Four containers of each kind were sprayed with the formulation and kept as replicates. Four controls were used in the laboratory trials - 120 larvae (third instar) were introduced in the replicates and the controls each. Readings were taken daily till complete adult emergence or larval and pupal mortality. In the semi-field trials, we applied this formulation to the inside of desert coolers and observed larvicidal and pupicidal activity over five months. Data is presented in numbers and percentages, along with mean and standard deviation. Adult emergence and Emergence Inhibition was calculated. There was 100% adult emergence inhibition amongst the exposed larvae in the treated containers in the laboratory trials. In the untreated controls, adult emergence ranged from 80-95% in all types of containers. In the semifield trials, Inhibition Emergence was 100% in the treated desert coolers during the five months of the study period. This advancement in insecticide formulation technology promises to make dengue control more effective and efficient.

FUNCTIONAL RESPONSE, HOST STAGE PREFERENCE AND DEVELOPMENT OF RHYNOCORIS FUSCIPES (FAB.) (HETEROPTERA: REDUVIIDAE) FOR TWO COTTON PESTS

The rice weevil, Sitophilus oryzae is a major stored grain insect pest that causes both quantitative and qualitative damage to cereals. Hence, the study was conducted to evaluate the insecticidal efficacy of Clerodendrum multiflorum, Clerodendrum viscosum, Vitex negundo, Argemone mexicana and Withania somnifera leaves essential oil against S. oryzae in laboratory conditions. The essential oil isolated from V. negundo and A. mexicana at 2.0 μL/gm of wheat was found to be toxic, causing 100% mortality as compared to other plant essential oils. The percentage of oviposition deterrence increased from 20% to 90% by increasing the concentrations of essential oils. Interestingly, all plant essential oils were inhibited F1 adult emergence at lower dose. Essential oils of V. negundo and A. mexicana revealed significant toxicity, oviposition deterrence and inhibition of F1 adult emergence of S. oryzae at lower concentrations. Thus, these plant essential oils may be suggested as admixtures in the integrated management of rice weevil during the storage of grains.