3rd Instar Larvae Research Articles

Sustainable use of plastic-derived nanocarbons as a promising larvicidal and growth inhibitor agent towards control of mosquitoes

Nanoscale carbon was obtained from six widely used plastics (PET, HDPE, PVC, LDPE, PP and PP) via thermal degradation (600 °C) under inert atmosphere. The thermally degraded products were processed through bath sonication followed by lyophilisation and the same was characterized through proximate analysis, UV–Vis spectroscopy, Scanning electron micrograph (SEM) with energy dispersive X-ray (EDX) analysis, Transmission electron micrograph (TEM), Dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FTIR). A series of aqueous solution of nanoscale carbon (5–30 mg/L) were prepared and same were used as both mosquito growth inhibitor and larvicidal agent against 3rd and 4th instar larvae of Culex pipiens. The significant percent mortality results were recorded for LDPE (p < 0.007) with average particle size of 3.01 nm and 62.95 W% of carbon and PS (p < 0.002) with average particle size of 12.80 nm and 58.73 W% of carbon against 3rd instar larvae, respectively. Similarly, for 4th instar larvae, both significant pupicidal and adulticidal activity were also recorded for PET (F = 24.0, p < 0.0001 and F = 5.73, p < 0.006), and HDPE (F = 26.0, p < 0.0001) and F = 5.30, p < 0.008). However, significant pupicidal activity were observed for PVC (F = 6.90, p < 0.003), and PS (F = 21.30, p < 0.0001). Histological, bio-chemical and microscopic studies were revealed that nanoscale carbon causes mild to severe damage of external and internal cellular integrity of larvae. However, nanoscale carbon does not exhibit any chromosomal abnormality and anatomical irregularities in Allium cepa and Cicer arietinum, respectively. Similarly, non-significant results with respect to blood cell deformation were also recorded from blood smear of Poecilia reticulata. Therefore, it can be concluded that plastic origin nanoscale carbon could be a viable sustainable nano-weapon towards control of insects.

Chronic exposure to 2,2′-azobis-2-amidinopropane that induces intestinal damage and oxidative stress in larvae of Drosophila melanogaster

Embryonic development is exceptionally susceptible to pathogenic, chemistry and mechanical stressors as they can disrupt homeostasis, causing damage and impacted viability. Oxidative stress has the capacity to induce alterations and reshape the environment. However, the specific impacts of these oxidative stress-induced damages in the gastrointestinal tract of Drosophila melanogaster larvae have been minimally explored. This study used 2,2-azobis (2-amidinopropane) dihydrochloride (AAPH), a free radical generator, to investigate oxidative stress effects on Drosophila embryo development. The results showed that exposing Drosophila eggs to 30 mM AAPH during 1st instar larva, 2nd instar larva and 3rd instar larva stages significantly reduced hatching rates and pupal generation. It increased the activity of antioxidant enzymes and increased oxidative damage to proteins and MDA content, indicating severe oxidative stress. Morphological changes in 3rd individuals included decreased brush borders in enterocytes and reduced lipid vacuoles in trophocytes, essential fat bodies for insect metabolism. Immunostaining revealed elevated cleaved caspase 3, an apoptosis marker. This evidence validates the impact of oxidative stress toxicity and cell apoptosis following exposure, offering insights into comprehending the chemically induced effects of oxidative stress by AAPH on animal development.

Biology of Fall Armyworm Spodoptera frugiperda (J.E. Smith) on Maize under Laboratory Conditions

Maize is a important cereal harvests developed for food, fodder and raw material throughout the country. It is rich source of proteins, carbohydrates and vitamins. Corn production is decreasing day by day due to attack of more than 353 insect species and mites. Among insect pests, Fall armyworm, Spodoptera frugiperda is best destructive pest for corn production. The rearing of Fall armyworm, Spodoptera frugiperda was conducted under laboratory conditions in Department of Entomology, Acharya Narendra Deva University of Agriculture &amp; Technology, Kumarganj, Ayodhya, U. P. during 2023. The complete metamorphosis (egg, larva, pupa and adult) was certified in Spodoptera frugiperda. The average fecundity was 2.59 ± 0.40 days. There were 6th instar larval of Spodoptera frugiperda and total larval period was 15-20 days. The growth period of 1st, 2nd, 3rd, 4th, 5th and 6th larval instar was 2-3, 2.5-3, 2.2-3, 2-2.5, 2.5-3, 4-6 days respectively on corn leaves. The average period of pupa was 10.33 ± 1.07 days. The female was long lived than male. The total evolved period from egg to adult was 45-47 days.

Host-instar selection, interspecific competition, and reproductive capacity of extant and novel parasitoids (Hymenoptera: Braconidae) on Egyptian cotton leafworm

Abstract Background Cotesia marginiventris (Cresson) and Microplitis rufiventris Kok. (Hymenoptera: Braconidae) are larval endoparasitoids of Spodoptera frugiperda (Smith) and S. littoralis (Boisd.), respectively. Cotesia marginiventris was introduced in Egypt to control the recent invasive pest, S. frugiperda and local one, S. littoralis. Therefore, competition between the two parasitoid species may occur. Results When single females of C. marginiventris (Exp. 1), single females of M. rufiventris (Exp. 2), and one female each of C. marginiventris and M. rufiventris (Exp. 3) were offered a choice of 60 1st, 60 2nd, and 60 3rd instars, of the tested host species, S. littoralis and different parasitization levels were obtained. In the non-competitive context (Exps. 1, 2), all instars were parasitized, but C. marginiventris and M. rufiventris parasitized primarily 2nd and 3rd instar host larvae, respectively. In the competitive context (Exp. 3), the same preference pattern emerged but the percentage of parasitism was lower than in each of the two non-competitive contexts. Conclusions M. rufiventris appears to be a superior competitor when simultaneously exploiting the host with the other parasitoid species. The knowledge of this work can be used to predict and/or understand possible outcomes of a biological control program using the two biocontrol agents against one or the two pests species, and to gain insight into possible biotic interference between species at the same trophic level exploiting the same host. Graphical abstract

Biocidal Efficacy of a New and Native Species of Entomopathogenic Nematode against Gram Pod Borer, Helicoverpa armigera (Hubner)

Efficacy of new and native species of entomopathogenic nematode (EPN), Heterorhabditis casmirica SKUAST-K 104 was evaluated against gram pod borer, Helicoverpa armigera in laboratory conditions. Larval mortality was directly proportional to time period as well as time period but inversely proportional to larval size. H. casmirica SKUAST-K 104 applied @ 50, 100, 150 and 200 IJs per 2nd instar larva resulted in pest mortality by 0.00, 8.33, 16.66, and 25.00 per cent, respectively at 24 hours and they were statistically significant (p ≤ 0.05) from each other. At 200 IJs inoculum level, 8.33, 16.66, 25.0, 41.66 and 50 per cent mortality of 5th instar larva was recorded at 24, 48, 72, 96 and 120 hours post inoculation, respectively. LC50 values was directly proportional to the size of larva but inversely proportional to size of nematode inoculum level. On the other hand, LT50 values was directly proportional to the size of larva but inversely proportional to size of nematode inoculum level. LC50 values calculated at 24 hours for 2nd, 3rd, 4th and 5th instar larvae was 256.88, 277.24, 326.25 and 384.25, respectively, whereas at 120 hours it was 126.11, 160.22, 184.36 and 219.14, respectively. Similarly, LT50 values calculated at inoculum level of 50 IJs per 2nd, 3rd, 4th and 5th instar larvae were 105.0, 113, 122 and 131 hours, respectively but at highest inoculum level of 200 IJs, it was 75, 89, 94 and 100 hours, respectively. Nematode multiplication rate within the host cadaver was directly proportional to the size of the host. Minimum and maximum number of IJs/ larva was 2.72 x 105 and 1.03 x 105, obtained from 2nd and 5th instar larva, respectively.

Genetic Diversity and Virulence Variation of Metarhizium rileyi from Infected Spodoptera frugiperda in Corn Fields.

Metarhizium rileyi is an entomopathogenic fungus that naturally infects the larvae of Spodoptera frugiperda, and has biocontrol potential. To explore more natural entomopathogenic fungi resources, a total of 31 strains were isolated from 13 prefectures in Yunnan Province. All the strains were identified using morphology and molecular biology. The genetic diversity of the 31 isolates of M. rileyi was analyzed using inter-simple sequence repeat (ISSR) techniques. Seven primers with good polymorphism were selected, and fifty-four distinct amplification sites were obtained by polymerase chain reaction amplification. Among them, 50 were polymorphic sites, and the percentage of polymorphic sites was 94.44%. The thirty-one strains were divided into eight subpopulations according to the regions. The Nei's gene diversity was 0.2945, and the Shannon information index was 0.4574, indicating that M. rileyi had rich genetic diversity. The average total genetic diversity of the subpopulations in the different regions was 0.2962, the gene diversity within the populations was 0.1931, the genetic differentiation coefficient was 0.3482 (>0.25), and the gene flow was 0.9360 (<1). The individual cluster analysis showed that there was no obvious correlation between the genetic diversity of the strains and their geographical origin, which also indicated that the virulence of the strains was not related to their phylogeny. Thus, the genetic distance of the different populations of M. rileyi in Yunnan Province was not related to the geographical distance. The virulence of those 32 strains against the 3rd-instar larvae of S. frugiperda were varied with the differences in geographical locations. On the 10th day of inoculation, seventeen strains had an insect mortality rate of 70.0%, and seven strains had an insect mortality rate of 100%. The half-lethal times of the M. rileyi SZCY201010, XSBN200920, and MDXZ200803 strains against the S. frugiperda larvae were less than 4 d. Thus, they have the potential to be developed into fungal insecticidal agents.

Toxicity of Ocimum basilicum L. leaf extract against Spodoptera exigua Hübner (Lepidoptera: Noctuidae)

The beet armyworm Spodoptera exigua Hübner (Lepidoptera: Noctuidae) is one of the most significant shallot pests worldwide, which affects agricultural production by approximately 100% in Indonesia. The growing awareness of sustainable agriculture encourages the search for natural alternatives to synthetic pesticides that promote resistance and contaminate the environment. Therefore, this study aims to evaluate the efficacy of basil (Ocimum basilicum L) leaf extract against the 2nd and 3rd instar larvae of S. exigua. The extracts were prepared using maceration and hydrodistillation and the pathogenicity was carried out against the 2nd and 3rd instar of S. exigua using three replicates with several doses of extract ranging from 0- 2.0%. The extracts were applied to the larvae using contact and topical methods. The results showed that maceration extraction yields a greater extract with different types compared to those of the hydrodistillation method. Maceration extract of basil leaves with the contact application method to 2nd instar showed better results than the topical application with the highest mortality rate of 75% (F=24.464; P&lt; 0.001) and LC50 of 0.007%. This indicated that basil leaf extract with the contact application method has great potential to be developed as a botanical insecticide to control S. exigua in the field as part of Integrated Pest Management (IPM).

Insecticidal activity and possible modes of action of secondary metabolites of some fungal strains and wild plants as natural pesticides against Spodoptera frugiperda

BackgroundThe fall armyworm (FAW), Spodoptera frugiperda, is an invasive and destructive pest to certain strategic crops, especially maize in Egypt. This research was conducted mainly to obtain secondary metabolites from some wild plants and fungal strains, use them in controlling FAW, and investigate their mode of action.ResultsThe ethyl acetate extracts of Cladosporium cladosporioides and Verticillium lecanii, as well as the alkaloid extracts of Ricinus communis and Nicotiana glauca, were extracted to obtain their secondary metabolites. The secondary metabolite contents were identified by gas chromatography mass spectrometry and NMR. The toxicity of all extracts against the 3rd-instar larvae of FAW was evaluated. The possible mode of action of the extracts was studied via their effects on larval enzyme activities and larval tissue. The toxicity results illustrated that, the extract of C. cladosporioides was more effective with LC50 229 ppm, followed by the extract of V. lecanii with LC50 341 ppm and N. glauca with LC50 404 ppm, while the least effective extract was R. communis with LC50 1110 ppm after 72 h of treatment. While, the results of larval enzyme activities showed that C. cladosporioides, V. lecanii, and R. communis extracts led to significant activity of AST, ALT, ACP, and ALP enzymes, but GST and AchE were inhibited in treated larvae compared with control. While N. glauca alkaloid extract caused significant inhibition of AST, ALT, ACP, AchE, and GST enzymes, ALP was activated in the treated larvae compared with control. The results of larval tissue slides indicated that the most affected tissues were the cuticle layer and the membrane lining of the midgut, in addition to the fatty bodies.ConclusionThus, natural pesticides would have a promising role in terms of controlling the FAW and according to this study, it was recommended that, alkaloid extracts of tested wild plants and ethyl acetate extracts of fungal strains be used as natural pesticides to control the fall armyworm, S. frugiperda.

Molecular characterization of the camel nasal botfly, Cephalopina titillator (Diptera: Oestridae)

BackgroundLarval stages of the camel nasal botfly, Cephalopina titillator (Diptera: Oestridae), rank among the top obligate endoparasites causing nasopharyngeal myiasis. Such infestations have adverse effects on camel health, reducing their economic value. The current study’s objective is to assess the applicability of PCR using partial regions of the COI mtDNA and 28S rRNA gene sequences to identify, classify, and reveal the phylogenesis of C. titillator.ResultsLarvae of the 2nd and 3rd instars of C. titillator were collected from the El-Bassatin abattoir in Egypt, extracted from the nasopharyngeal passage of the Arabian camel (Camelus dromedarius) during postmortem inspection. Genomic DNA was successfully isolated from 10 samples of 3rd instar larvae of C. titillator and amplified using primer pairs targeting partial mitochondrial COI (916 bp) and ribosomal 28S rRNA (830 bp) gene fragments. Nucleotide sequences from five samples have been sequenced and submitted to GenBank under accession numbers OP482168 to OP482172 for the COI gene and OP482160 to OP482164 for the 28S rRNA gene fragments. The COI gene exhibited 97.3% nucleotide identity across all specimens, while the 28S rRNA gene displayed 99.74% identical nucleotides. Maximum likelihood trees were constructed based on the generalized time-reversible (GTR) model. The resulting COI phylogenetic tree demonstrated that the subfamily Oestrinae does not exhibit monophyly. Additionally, it revealed that C. titillator is a sister group to the subfamily Gasterophilinae. Despite the scarcity of data available for the 28S rRNA gene, the phylogenetic analysis utilizing 28S rRNA revealed one distinct lineage for the Egyptian camel nasal bot fly.ConclusionsMolecular phylogenetic analysis was conducted using molecular markers of distinct origins (both mitochondrial and nuclear) to elucidate the evolutionary relationships within the family Oestridae. This analysis is particularly significant following the inclusion of C. titillator, a first-time discovery in Egypt.

Gut microbiota variation across generations regarding the diet and life stage in Harmonia axyridis (Coleoptera: Coccinellidae).

We attempt to determine the effect of the dietary switch from a native to non-native prey on the gut microbiota in the predaceous ladybird Harmonia axyridis larvae and adults and examine how the dietary effect may vary across generations. We fed H. axyridis with different diets, native aphid Megoura japonica (Matsumura) versus non-native mealybug Phenacoccus solenopsis (Tinsley), for 5 generations and sequenced microbes in the gut of the 3rd instar larvae and adults of the 1st, 3rd, and 5th generations. In addition, we identified microbes in M. japonica and P. solenopsis. The 2 prey species differed in microbial community as measured by abundances of prevalent microbial genera and diversity. In H. axyridis, abundances of some prevalent microbial genera differed between the 2 diets in the 1st and 3rd generations, but the difference disappeared in the 5th generation; this tendency is more obvious in adults than in larvae. Overall, gut microbial assemblages became gradually cohesive over generations. Microbial diversity differed between diets in the 1st and 3rd generations but became similar in the 5th generation. Major prevalent gut microbial genera are predicted to be associated with metabolic functions of H. axyridis and associated genera are more abundant for consuming the mealybug than the aphid. Our findings from this study suggest that the gut microbiota in H. axyridis is flexible in response to the dietary switch, but tends toward homogeneity in microbial composition over generations.

Casearia tomentosa fruit extracts exposed larvicidal activity and morphological alterations in Culex quinquefasciatus and Aedes albopictus under in vitro and semi field conditions

Mosquitoes are notorious insects that transmit a wide range of infectious diseases, including zika, malaria, chikungunya, filariasis, and dengue. The overuse and incorrect application of synthetic pesticides to control mosquitoes has resulted in resistance development and environmental contamination, both of which have had a negative impact on human health. To address this issue, the larvicidal and pupicidal potential of acetone extract from Casearia tomentosa fruits was investigated. The extract was evaluated in a lab setting against all larval instars and pupa of Culex quinquefasciatus and Aedes albopictus, as well as against third instar larvae in a semi-field condition. Purified compounds through TLC were also tested against 3rd instar larvae of both mosquito and non-target organisms. The FT-IR and GC-MS analyses were used to characterise the extract. Morphological aberration caused by the acetone extract was observed using FESEM. The anal gills and respiratory siphon of both mosquitoes showed significant deformation from their normal state. 100 ppm was found to cause 100% larval mortality at 24 h of exposure in case of Cx. quinquefasciatus and at 72 h of exposure in Ae. albopictus larvae. After 72 h of exposure under in vitro conditions, the extract demonstrated considerable larvicidal activity with LC50 values of 38.33 and 47.56 against 3rd instar larvae of Culex quinquefasciatus and Aedes albopictus, respectively. The acetone extract can be considered as a highly effective mosquito larvicidal agent that is safe for the environment.Graphical abstract

Sprayable RNAi for silencing of important genes to manage red palm weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae).

The red palm weevil, Rhynchophorus ferrugineus (Oliver, 1970) (Coleoptera: Dryophthoridae) is the most devastating insect-pest of palm trees worldwide. Synthetic insecticides are the most preferred tool for the management of RPW. Alternatively, RNA interference (RNAi) mediated silencing of crucial genes provides reasonable control of insect pests. Recently, we have targeted four important genes; ecdysone receptor (EcR), serine carboxypeptidase (SCP), actin and chitin-binding peritrophin (CBP) in the 3rd and 5th instar larvae RPW. The results from 20 days trial showed that the survival rate of 3rd instar larvae fed on SCP and actin dsRNAs exhibited the lowest survival (12-68%). While, in the 5th instar larvae, the lowest survival rate (24%) was recorded for SCP after 20 days of incubation. Similarly, the weight of the 3rd and 5th instar larvae treated with SCP and actin was significantly reduced to 2.30-2.36 g and 4.64-4.78 g after 6 days of dsRNA exposure. The larval duration was also decreased significantly in the larvae treated with all the dsRNA treatments. The qRT-PCR results confirmed a significant suppression of the targeted genes as 90-97% and 85-93% in the 3rd and 5th instar larvae, respectively. The results suggest that the SCP and the actin genes can be promising targets to mediate RNAi-based control of RPW.

Entomopathogenic bacteria and fungi as eco-safe substitutes to chemical insecticides against leaf eating caterpillars of Spodoptera litura

The present study was carried out in laboratory conditions (25 ± 10°C and 70% humidity) for studying the bioefficacy of entomopathogenic fungi and Bacillus thuringiensis against Spodoptera litura using the leaf dip method. The insecticidal attributes of three different commercial bioinsecticides (Bacillus thuringiensis 0.5% W.P., Beauveria bassiana 1.0% W.P., and Metarhizium anisopliae 1.0% W.P.) at different concentrations (0.5, 1.0, and 1.5%) were evaluated against the 3rd and 4th larval instars of S. litura. The analysis of variance results revealed that the highest concentration (1.5% concentration) of B. thuringiensis against the 3rd instar larvae of S. litura caused a maximum 80 ± 0.28% larval mortality, followed by B. bassiana and M. anisopliae, which caused 72 ± 0.21 and 64 ± 0.20% larval mortality after 120 h exposure. The calculated median lethal concentration in probit analysis demonstrated the lowest median lethal concentration of 1.22/10 larvae (95% fiducial limit 4.71–11.45) in the 3rd instar larvae after 72 h. Similarly, in 4th instar larvae of S. litura, the highest concentration (1.5% concentration) of B. thuringiensis caused maximum 76 ± 0.23% larval mortality, followed by B. bassiana and M. anisopliae, causing 70 ± 0.21% and 64 ± 0.20% larval mortality after 120 h. The calculated median lethal concentration in probit analysis demonstrated the lowest LC50 = 1.59/10 larvae (95% FL: 1.08–2.36) in the 4th instar larvae after 72 h. Based on these studies, it was revealed that B. thuringiensis and B. bassiana showed maximum efficacy against S. litura larvae. Although M. anisopliae also exhibits insecticidal properties, all of these bioinsecticides can be used to manage the population of S. litura. These bioinsecticides can be included in integrated pest management programs as they do not pose any toxic hazards to the environment.

Functional response estimations of Chrysoperla carnea to different densities of Aphis craccivora and Gynaikothrips ficorum nymphs.

The functional responses of Chrysoperla carnea larvae were evaluated at different seven densities of the 3rd instar nymphs of Aphis craccivora and Gynaikothrips ficorum in order to find out the relationship between predator densities and its prey by the, and also to find out their capability for biological control of aphids and thrips. Results revealed that all tested larval instars of Ch. carnea exhibited a type II response in relation to the prey. Moreover, the coefficients of attack rate (a) and handling time (Th) was differed among various growing instars of predator and for the prey species. The 3rd instar larvae of Ch. carnea manifested the highest attacking rate (1.23 and 1.22) on the 3rd instar nymphs of A. craccivora and G. ficorum, respectively. In addition it exhibited the highest maximum predation (Na max) (50.00 and 52.63) on A. craccivora and G. ficorum nymphs, respectively as compared with the other treatments. Accordingly, Ch. carnea could be considered as a promising bio-control agent for A. craccivora and G. ficorum management.

Evaluation of Insect Growth Regulators (IGRs) as biological pesticides for control of Aedes aegypti mosquitoes

Background &amp; objectives: Insect growth regulators (IGRs) are biological hormone analogue or mimics used as pesticides to inhibit the growth of larva during their molting and skin shedding. This study aimed to test the effect of IGRs on the eggs hatching and post-hatching inhibition of Aedes mosquitoes and understanding its effect in the mosquito breeding habitats for reduction in adult emergence. Methods: Experiments on the evaluation of three insect growth regulators (IGRs) for the control of different stages of Aedes aegypti was carried out during 2020-21. Each experiment consisted of four treatments viz., Pyriproxyfen, Novaluron, and Larvicol at 1.0 ppm and distilled water as a control. All experiments were carried out in completely randomized design (CRD) except eggs which were carried out in factorial design each with three replications. Results: All tested IGRs performed better in affecting eggs, larval and pupal stages of Ae. aegypti. Highest eggs hatching inhibition (80%) of fresh eggs occurred in Pyriproxyfen followed by Novaluron (66%) and lowest in Larvicol (62%). Eggs hatch inhibition of embryonated eggs was lower than fresh eggs. Pyriproxyfen caused 69%, Novaluron 59% and Larvicol 39% eggs hatch inhibition of embryonated eggs. Both Pyriproxyfen and Novaluron performed better in causing 98–100% larval mortality followed by Larvicol (39%). Larval development to pupal stage was completely prevented by both Pyriproxyfen and Novaluron. Although Larvicol resulted in lowest eggs hatch and larval inhibition but prevented pupae to emerge as adults. Results further showed 70–89% mortality of 3rd instar larvae of Ae. aegypti when exposed to Pyriproxyfen and Novaluron solutions after 30 days storage at lab. temperature (27±2°C), RH 70±5. Interpretation &amp; conclusion: None of the IGRs was more effective at the pupal stage but showed carry-on activity of growth inhibition and mortality of the successive stages of development when used against eggs stages. Therefore, we recommend early application of IGRs at mosquito habitats during the beginning and onset of the season when very early stages of mosquitoes are available in the field.

Bio-efficacies of different solvent extracts of Cosmos sulphureus on 3rd instar larvae of Aedes aegypti

Bio-efficacies of different solvent extracts of Cosmos sulphureus on 3rd instar larvae of Aedes aegypti

Efficacy of Different Pesticides against Fall Armyworm (Spodoptera frugiperda (J.E. Smith) Lepidoptera: Noctuidae) under Laboratory Conditions in Rupandehi, Nepal

The fall armyworm (FAW), Spodoptera frugiperda, is a highly destructive pest recently reported in various Asian countries and originated in the subtropical regions of America. It was first recorded in Nepal on May 9, 2019. This invasive species poses a significant threat to maize production because it can undergo multiple generations, migrate, and feed on a wide range of host plants. A laboratory study was conducted with 3 categories of pesticides: conventional, newer, and bio‐rational. The study focused on evaluating the efficacy of these pesticides on the third‐instar larvae of S. frugiperda. The treatments included (1) newer chemical pesticides: spinosad 45% suspension concentrate (SC) (Tracer 1 ml/3 L of water), spinetoram 11.7% SC (Delegate 0.5 ml/L of water), chlorantraniliprole 18.5% SC (Allcora 1 ml/2.5 L of water), emamectin benzoate 5.7% water dispersible granules (WDG) (top killer 1 g/2.5 L), (2) conventional pesticide: chlorpyrifos 50% EC (Predator 2 ml/L), and (3) bio‐rational pesticides: Bacillus thuringiensis var kurstaki 0.5% wettable powder (WP) (Maharashtra 2gm/L), Metarhizium anisopliae 1.0% WP (Kalichakra 5 ml/L), Beauveria bassiana 2% AS (DamanL 5 ml/L), Azadirachta indica 4.5% (Neemix 5 ml/L), Syzygium aromaticum 100% v/v (Kanti herbal Clove oil 3 ml/L), and spinosad 45% SC (Tracer 0.3 ml/L). Fresh maize leaves were treated using the leaf dip method and then fed to 3rd instar larvae of FAW. The results revealed that spinetoram and spinosad caused 100% larval mortality within the first 24 hours after treatment. Similarly, spinosad (99.99%) and clove oil (76.64%) were the most effective bio‐rational pesticides followed by B. bassiana and B. thuringiensis. The newer and bio‐rational pesticides that showed high efficacy could be suggested for further study in farmers’ fields. They could be recommended for testing as a component of integrated pest management for effective management of FAW in Nepal.

A chromogenic diarylethene-based probe for the detection of Cu2+ in aqueous medium in Drosophila for early diagnosis of Alzheimer

A diarylethene-based probe (Z)-N'-((2-amino-5-chlorophenyl)(phenyl)methylene)-2-hydroxy benzohydrazide (KBH) has been proficiently developed and its structure has been confirmed by single crystal X-ray diffraction technique. It displays a selective and sensitive colorimetric sensing of Cu2+ ions in aqueous medium with a naked eye colour change from colourless to yellow. It exhibits a significantly low limit of detection as 1.5 nM. A plausible binding mechanism has been proposed using Job's plot, FT-IR, 1H NMR titration, HRMS and DFT studies. The chemosensor is effectively reversible and reusable with EDTA. Test strip kit and real water sample analysis have been shown to establish its practical applicability. Further, the potential of KBH for the early diagnosis of Cu2+ ion-induced amyloid toxicity has been investigated in eye imaginal disc of Alzheimer's disease model of Drosophila 3rd instar larvae. The in-vivo interaction of KBH with Cu2+ in gut tissues of Drosophila larvae establishes its sensing capability in biological system. Interestingly, the in-vivo detection of Cu2+ has been done using bright field imaging which eliminates the necessity of a fluorescent label, hence making the method highly economical.

Investigating postsynaptic effects of a Drosophila neuropeptide on muscle contraction.

The Drosophila neuropeptide, DPKQDFMRFamide, was previously shown to enhance excitatory junctional potentials (EJPs) and muscle contraction by both presynaptic and postsynaptic actions. Since the peptide acts on both sides of the synaptic cleft, it has been difficult to examine postsynaptic modulatory mechanisms, particularly when contractions are elicited by nerve stimulation. Here, postsynaptic actions are examined in 3rd instar larvae by applying peptide and the excitatory neurotransmitter, l-glutamate, in the bathing solution to elicit contractions after silencing motor output by removing the central nervous system (CNS). DPKQDFMRFamide enhanced glutamate-evoked contractions at low concentrations (EC50 1.3 nM), consistent with its role as a neurohormone, and the combined effect of both substances was supra-additive. Glutamate-evoked contractions were also enhanced when transmitter release was blocked in temperature-sensitive (Shibire) mutants, confirming the peptide's postsynaptic action. The peptide increased membrane depolarization in muscle when co-applied with glutamate, and its effects were blocked by nifedipine, an L-type channel blocker, indicating effects at the plasma membrane involving calcium influx. DPKQDFMRFamide also enhanced contractions induced by caffeine in the absence of extracellular calcium, suggesting increased calcium release from the sarcoplasmic reticulum (SR) or effects downstream of calcium release from the SR. The peptide's effects do not appear to involve calcium/calmodulin-dependent protein kinase II (CaMKII), previously shown to mediate presynaptic effects. The approach used here might be useful for examining postsynaptic effects of neurohormones and cotransmitters in other systems.NEW & NOTEWORTHY Distinguishing presynaptic and postsynaptic effects of neurohormones is a long-standing challenge in many model organisms. Here, postsynaptic actions of DPKQDFMRFamide are demonstrated by assessing its ability to potentiate contractions elicited by direct application of the neurotransmitter, glutamate, when axons are silent and when transmitter release is blocked. The peptide acts at multiple sites to increase contraction, increasing glutamate-induced depolarization at the cell membrane, acting on L-type channels, and acting downstream of calcium release from the sarcoplasmic reticulum.

Biocontrol potential of entomopathogenic nematode, Heterorhabditis indica against pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae)

BackgroundThe emergence of pink bollworm (PBW), Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), in cotton due to Bt resistance and concealed feeding habit has created a need for alternative, eco-friendly, and cost-effective control methods. This study aimed to evaluate the bio-efficacy and reproductive potential of two native strains of entomopathogenic nematodes (EPNs), Heterorhabditis indica, namely CICR-HI-CL and CICR-HI-MN, against PBW larvae and pupae under in-vitro conditions.ResultsThe larval assay revealed that strain CICR-HI-CL exhibited higher potency than strain CICR-HI-MN against 2nd, 3rd, and 4th instar larvae, with median lethal dose (LD50) values of 5.45, 4.45, and 4.60 infective juveniles (IJs) per larva, respectively. In case of pupal bioassay, both EPN strains demonstrated greater virulence when applied directly (LD50 values: 29.65 and 73.88 IJs per pupa for strains CICR-HI-CL and CICR-HI-MN, respectively) compared to soil application (147.84 and 272.38 IJs per pupa). Both EPN strains successfully penetrated and reproduced on 4th instar larvae, resulting in maximum production of 19.28 and 20.85 lakh IJs per larva in the next generation when inoculated at 30 IJs per larva.ConclusionThe present study has generated useful information on the virulence and reproductive potential of two strains of EPN H. indica (CICR-HI-CL and CICR-HI-MN) against PBW, a dreaded pest of cotton. Higher virulence and reproductive potential of EPN strains demonstrated their ability to multiply, sustain and perpetuate on larval and pupal stages of PBW. The knowledge generated will help formulate effective management strategies for PBW with the inclusion of EPN as a potential biological control candidate. The soil-dwelling life stages viz., last instar hibernating larvae and pupae of PBW can be the ideal weak links to make a successful use of H. indica for sustainable management of PBW in the cotton ecosystem. However, before taking these EPN strains to field for managing PBW, detailed studies investigating their biocontrol potential against PBW under field conditions are needed.