Fourth Instars Research Articles

Interactions Between Two Invertebrate Pathogens: An Endophytic Fungus and an Externally Applied Bacterium.

The members of family Noctuidae exist in diverse environments and many species from this group are of agriculture importance, particularly Helicoverpa spp. Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a major pest of many legumes and cereal crops. Due to environmental and regulatory concerns, safe alternatives to broad spectrum chemical insecticides are needed for the control of key noctuid pests such as H. armigera. A strain of Beauveria bassiana (Cordycipitaceae: Hypocreales) was evaluated for its ability to colonize endophytically in chickpea plants, and its effectiveness against second (L2) and fourth (L4) larval instars of H. armigera. B. bassiana was inoculated to chickpea plants through injection and endophytic establishment was confirmed by re-isolating the fungi from leaf samples. A detached leaf assay was used to evaluate pathogenicity. Bacillus thuringiensis was also applied to both larval stages through leaf dip method. In a novel approach, combined treatments of bacteria and endophytic fungi were compared with single-pathogen treatments. Relative to the single treatments, the combined pathogen treatments exhibited an increase in larval mortality, and decrease in pupation, adult emergence and egg eclosion. Specifically, synergistic effects on mortality were observed when larvae were exposed to simultaneous application of B. bassiana (1 × 108 conidia ml–1) with B. thuringiensis (0.75 μg ml−1). Both instars exhibited varying level of growth, development, frass production, diet consumption and fecundity when exposed to the chickpea leaves inoculated with endophytic B. bassiana and dipped with sub-lethal doses of B. thuringiensis. These findings indicate that the integrated application of endophytic colonized B. bassiana and B. thuringiensis can be effectively used against H. armigera.

Pathogen‐mediated modulation of host metabolism and trophic interactions in Spodoptera littoralis larvae

AbstractThe success and sustainability of entomopathogens in insect control depend on their stress potential and ability to modulate certain physiological aspects of their insect hosts. In the present study, newly moulted fourth instars of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) were incubated for 24 h with the median lethal dose (LD50) of Steinernema riobrave, Heterorhabditis bacteriophora, or Beauveria bassiana to determine their effects on certain metabolic activities and nutritional physiology compared to those of uninfected (control) larvae. Infection decreased total protein, lipid, and carbohydrate contents. Carbohydrase activity was found to be pathogen and enzyme dependent, with S. riobrave and H. bacteriophora infection increasing amylase, invertase, and trehalase activities. Beauveria bassiana infection decreased amylase and invertase activities but increased that of trehalase. Infection with the three pathogens also enhanced phosphatase activity. All pathogens reduced transaminase activity. Changes in the nutritional indices varied not only with the variation in the candidate entomopathogen and surviving instar but also with the variation in the age of the same instar, with a profound change in late last instars (3‐day‐old sixth instars). The link between the metabolic activities and nutritional indices was discussed. Overall, the entomopathogen‐host interaction appears to be primarily nutritional. The pleiotropic effects of the median lethal infections on the insect pest might eventually help in the biological control potential of the entomopathogens tested.

THE POTENTIAL OF THREE LARVAL PREDATORS AGAINST FALL ARMYWORM SPODOPTERA FRUGIPERDA (LEPIDPTERA: NOCTUIDAE) UNDER THE LABORATORY CONDITION

Most cereal crops are often damaged by lepidopterous insects. Of recent, fall armyworm, S. frugiperda (J.E. Smith) has resulted into yield and economic loss in many African and Asian countries. This reduces farmers’ income drastically and to overcome this damage, pesticides have been used which are not also environmentally friendly. Experiments were set up to collect data on the potential of three larval predators Orius strigicollis, Micromus angulatus, and Podisus maculiventris against S. frugiperda. The consumption of S. frugiperda larvae by three predators had highly significant effects (P≤0.05) on first, fourth, and sixth instars. No significant difference was reported between M. angulatus and O. strigicollis on second, third and fifth larval instars of S. frugiperda. O. strigicollis consumed more first larval instar (6.2±0.71) of S. frugiperda than M. angulatus (4.9±1.07) and P. maculiventris (4.2±0.74). However, P. maculiventris consumed more second to sixth larval instars of S. frugiperda than other two predators (O. strigicollis and M. angulatus). The predator P. maculiventris is recommended for controlling S. frugiperda in their second to sixth larval instars while O. strigicollis in the first larval instar. It can be also concluded that fourth larval instars of S. frugiperda is more suitable for its control using predator P. maculiventris as compared to other larval instars. This study therefore recommends predator Podisus maculiventris to be used in control of S. frugiperda under laboratory conditions.

Efficacy of Antimicrobial and Larvicidal Activities of Green Synthesized Silver Nanoparticles Using Leaf Extract of Plumbago auriculata Lam.

This work reports the synthesis of silver nanoparticles (AgNPs) using aqueous extract of Plumbago auriculata, and evaluates their antibacterial and larvicidal activities. The synthesized silver nanoparticles were characterized by various spectroscopy techniques, such as FTIR, XRD, TEM, EDX, Zeta potential, and DLS. The synthesized AgNPs exhibited significant antibacterial activity against Gram-positive and Gram-negative bacteria, such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae. Furthermore, synthesized nanoparticles inhibited the fourth instars larvae of Aedes aegypti and Culex quinquefasciatus at the concentration of 45.1 and 41.1 µg/mL respectively. Results of dose-dependent studies showed that synthesized nanoparticles were also effective at low concentrations. Molecular docking studies performed with the salivary protein and odorant-binding protein of Aedes aegypti and Culex quinquefasciatus demonstrated that the naphthoquinone compound plumbagin exhibited reliable binding affinity towards the two enzymes. The findings thus reveal that the plant extract and its nanoparticles can be a better alternative to available chemicals to control mosquitos.

Effects of Low Temperature Exposure on Diapause, Development, and Reproductive Fitness of the Emerald Ash Borer (Coleoptera: Buprestidae): Implications for Voltinism and Laboratory Rearing.

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), native to Northeast Asia, is the most destructive invasive ash (Fraxinus spp.) pest in the United States. In the present study, we evaluated the effect of exposure of diapausing mature fourth instars (J-shaped larvae, JL) of EAB to cool temperatures, either 1.7 or 12.8°C for 1-9 mo, on their post-chill development including adult emergence, longevity, and lifetime fecundity under standard rearing conditions (26 ± 0.5°C, 16:8 h L:D). In addition, we determined the effect of different stages of the larvae chilled at 12.8°C for 3 mo on the subsequent post-chill development to EAB adults. Findings from the study revealed that a period (≥2 mo) of chill at 12.8°C is required for the termination of the EAB diapause. However, chill treatment of the larvae at the near zero temperature (1.7°C) does not result in the post-diapause larval development to adults, regardless of the chill time (1-9 mo). In addition, our results showed that chill treatment of immature young larvae (L1-L4 prior to JL) results in little production of EAB adults, indicating that EAB diapause predominantly as JL. Findings of this study may be useful to laboratory rearing of EAB from eggs through continuous generations and help us understand the pest's voltinism resulting from the diapause and post-diapause development under different climatic conditions.

The Granulate Cutworm (Lepidoptera: Noctuidae): Biological Parameters Under Controlled Conditions, Host Plants, and Distribution in the Americas.

Feltia subterranea (Fabricius), commonly known as the granulate cutworm, is a common species of owlet moths (Noctuidae) of major agricultural importance, widely distributed in Nearctic and Neotropical regions. This study was conducted to determine the species biological parameters, gather information about its larval host plants, and assess the agricultural significance of this species in the Americas. The viability of the egg, larval, pupal stages, and prepupal period was 98, 98, and 100%, respectively, under laboratory conditions. The average duration of the egg, larval, pupal stages, and prepupal period was 3, 17, 4, and 13 d, respectively. All laboratory-reared larvae developed through five instars. The growth ratio was 1.93 for females and 1.85 for males. The duration of the larval stage was significantly longer in females than in males from the fourth instar. The duration of the pupal stage was significantly shorter in females than in males. When larval and pupal stage durations were combined, there were no significant differences in total development time as a function of sex. In total, 159 botanical taxa belonging to 41 families were recorded as host species for F. subterranea. The families with the greatest number of host species were Fabaceae (22), Poaceae (19), Asteraceae (16), Brassicaceae (13), Solanaceae (12), Amaranthaceae (7), Cucurbitaceae (7), and Malvaceae (5). It is noteworthy that the large number of native weeds used by F. subterranea as host plants could represent a significant source of infestation of crops in the agricultural landscape.

Predation and reproduction of the generalist predator Nabis pseudoferus preying on Tuta absoluta

AbstractThe damsel bug, Nabis pseudoferus Remane (Hemiptera: Namidae), is a generalist predator of small arthropods, including key insect pests of vegetable crops. In this study, we characterized the predation and development of various N. pseudoferus life stages when preying on the eggs and first‐ and fourth‐instar nymphs of the invasive South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae). These findings were compared to those of the bug’s common prey, cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae). Of the life stages tested, females showed the highest predation rate on all tested prey, due to their high longevity, large body, and great energy requirements for reproduction. The predator’s oviposition rate was clearly influenced by prey type, and was highest when feeding on fourth instars of T. absoluta. Considering the zoophytophagy of most of the life stages of other mirid species of tomato, and the lower propensity of N. pseudoferus to feed on plants, these results show that this species can be considered as a key indigenous natural enemy for sustainable pest control packages against T. absoluta in newly invaded areas.

Regulation of gene expression encoding the digestive α-amylase in the larvae of Colorado potato beetle, Leptinotarsa decemlineata (Say) in response to plant protein extracts

Considering the relevance of insect α-amylases and natural α-amylase inhibitors present in plants to protect against insect damage, we investigated the effect of white bean and rapeseed protein extracts on digestive α-amylase gene expression of the Colorado potato beetle, Leptinotarsa decemlineata (Say). For this purpose, in vitro and in vivo trials were performed to determine the inhibitory activity of seed proteins on the third and fourth instar larvae. In both trials, the significant inhibitory effect of each extracts on the third and fourth instar larval α-amylase activity and considerable mortality in treatments were observed compared to control trials. In the RT-qPCR, expression ratio demonstrated that the α-amylase gene of two different larval stages grown on both proteins treated leaves had significantly differentiated expression and was up-regulated in third instar larvae and down-regulated in fourth instar larvae compared to control. Results suggest that the hyper-production of α-amylase in third instar larvae is elicited to compensate for the enzyme activity inhibition at an earlier stage and also down-regulation suggests the existence of a negative feedback of plant proteins on the last instar larvae via impaired food intake and digestive α-amylase activity in Colorado potato beetle. Therefore, disruption of the insect’s digestive physiology by plant defensive proteins can be considered in the development of innovative controlling methods of this crucial potato pest.

Sublethal Effects of Malathion on Biology and Population Growth of Khapra Beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae)

Khapra beetle, Trogoderma granarium Everts is a serious pest that affects stored grains and oilseeds. The current work was carried out to investigate the effect of malathion sublethal concentrations (LC10 and LC40) exposed to first and fourth larval instars on biological aspects and population growth of T. granarium. Results indicated that exposure of 1-st instar to either LC10 or LC40 had a destructive effect and treated larvae failed to complete their larval stage. While 4-th instar exposed to the same sublethal concentrations completed their life cycle with considerable impacts on biological aspects and life table parameters. Treatments increased the number of instars molting reaching seven or eightinstars. In contrast, larval, pre-adult, and total longevity periods were decreased in treatments compared with control. Concerning life table parameters such as net reproductive rate (R0), intrinsic rates of increase (r), finite rate (λ), fecundity and mean generation time (T) were decreased compared to control. The current study clarified thatsublethal concentrations of malathion induce strong adverse effects and suppress the population growth of T. granarium. Our results would be useful to assess the overall effects of malathion on T. granarium and can contribute effectively in pest management.

The sex ratio of the koinobiont parasitoid Microcharops anticarsiae Gupta remains female-biased on young larvae of velvetbean in the laboratory environment

The natural parasitic behavior of parasitoids should be known by those in charge of planning strategies for the biological control of pests; therefore, the aim of the present study was to determine the larval instar of Anticarsia gemmatalis Hübner parasitized by Microcharops anticarsiae Gupta in the field and the implication of such parasitic behavior in the sex ratio in the laboratory environment. The length of each larval instar of A. gemmatalis parasitized by M. anticarsiae in the field was determined, and the egg-to-pupa period of the parasitoid and its larval instar lengths were plotted in Gantt charts. According to the chart, A. gemmatalis was parasitized at the first (15%) and second (85%) larval instars in the field, but the length of the first, second and third larval instars of this species was not affected by the parasitism by M. anticarsiae in the field; however, its fourth larval instar was extended and the fifth one was shortened in 2015 but not affected in 2016. The sex ratio of A. gemmatalis larvae parasitized by M. anticarsiae in the field was female-biased, and the sex ratio of early parasitized larvae (3-day old) in the laboratory environment was also female-biased for three cultivated generations. The ‘generation’ factor has affected the egg-to-pupa, pupal and egg-to-adult periods of M. anticarsiae, since females pupated earlier than males in the egg-to-pupa period. Based on the results, M. anticarsiae mostly parasitized the second larval instar of A. gemmatalis in the field, and parasitism in 3-day old larvae in the laboratory environment produced female-biased sex ratio in M. anticarsiae, regardless of the generation.

Insecticide susceptibilities of Hydrometra species (Hemiptera: Hydrometridae), including an endangered species, inhabiting paddy fields in Japan

Freshwater ecosystems tend to have the highest proportion of species threatened with extinction. Paddy fields provide alternative habitats for many species inhabiting wet hinterlands of rivers. This study examined the susceptibilities of three hydrometrid species, Hydrometra procera Horvath (Hemiptera: Hydrometridae), H. albolineata (Scott) (Hemiptera: Hydrometridae), and H. okinawana Drake (Hemiptera: Hydrometridae), inhabiting paddy fields in Japan to seven insecticides that were frequently applied to paddy fields, and evaluated the effect of each insecticide according to the hazard assessment classes by the International Organization for Biological Control and Integrated Control of Noxious Animals and Plants/West Palearctic Regional Section. Etofenprox, imidacloprid, and fenobucarb were found to be seriously harmful to the third instar nymphs of the three hydrometrid species. Buprofezin (an insect growth regulator) was also evaluated as seriously harmful based on the mortality at the third instar of the three species before the completion of molting to the fourth instar. Etofenprox, imidacloprid, and buprofezin were particularly harmful even at low concentrations to H. procera. Some of these insecticides have been heavily used in paddy fields since the 1950s or 1960s. It was around this time when the endangered species, H. albolineata populations began to decline drastically. Our results suggested that heavy use of these insecticides is one of the factors that caused the decline in H. albolineata populations.

Larvicidal Activity of Some Plants Extracts and Their Partitioned Fractions against Culex quinquefasciatus

Aim: The methanol extracts of fifteen plants and their partitioned fractions were screened for larvicidal activity against the fourth instar of larvae Culex quinquefasciatus, the vector of lymphatic filariasis with a view to identifying the active ones.
 Methodology: The plant parts were collected, separately dried and milled. Each powdered material was extracted in methanol at room temperature for 3 days, with agitation. The extract was filtered and concentrated in vacuo. Each extract was tested against the fourth instar larvae of Cx. quinquefasciatus. The methanol extracts were suspended in water and successively partitioned into n-hexane and ethylacetate. Each partitioned fraction was also tested against the fourth instar larvae of Cx. quinquefasciatus.
 Results: About fifty six percent (56.3%) of the tested extracts had moderate larvicidal activity after 48 hours. The fruit extract of Thevetia neriifolia and the leaf extracts of Calotropis procera and Solanum macrocarpon were the most active. After partitioning the methanol extracts, each of the plant extracts had one or two highly active partitioned fractions after 48 hours. The n-hexane fractions of S. macrocarpon (0.78 ± 0.03 mg/mL) and Spondias mombin (0.81 ± 0.03 mg/mL) were the most active.
 Conclusion: The non-polar fractions of S. macrocarpon and S. mombin were the most active. Purification of these highly active fractions could lead to the isolation of potent larvicidal compounds that could be used in the control of Cx. quinquefasciatus mosquito.

Timing the Implementation of Cultural Practices for Spissistilus festinus (Hemiptera: Membracidae) in California Vineyards Using a Stage-Structured Degree-Day Model.

The three-cornered alfalfa hopper, Spissistilus festinus (Say), was shown to transmit Grapevine red blotch virus (GRBV), the causative agent for Grapevine red blotch disease, in a greenhouse study on grapes. GRBV is a major concern of wine grape growers due to its economic impact on wine quality. Plants in the family Fabaceae are preferred hosts of S. festinus and are commonly planted as cover crops or present in a vineyard's native vegetation. In late winter, during grapevine dormancy, S. festinus migrate into vineyards to feed and reproduce on these cover crop and weed hosts. Tilling vineyard floor vegetation provides growers an opportunity to disrupt the life cycle of early instars that are relatively immobile, reducing the S. festinus first-generation population. Nymphal presence is difficult to detect. First through third instars were not detected in sweep net samples in a 2-yr weekly sampling study, whereas fourth and fifth instars were first found on the same sample date as emerging adults. A degree-day model was developed and successfully predicted when early S. festinus instars are present in the vineyard to aid in exploiting the time period when S. festinus is most susceptible to cultural control measures.

The Inability of Spotted Lanternfly (Lycorma delicatula) to Vector a Plant Pathogen between its Preferred Host, Ailanthus altissima, in a Laboratory Setting.

Simple SummaryThe invasive and accidently introduced insect, the spotted lanternfly, is spreading rapidly and becoming abundant in the mid-Atlantic region of the USA. Though this insect prefers to feed on the also invasive tree-of-heaven, its ability to feed on other native and crop plant species is concerning, and therefore eradication and control efforts are underway. These efforts include targeting the difficult to control tree-of-heaven for removal. Recently, researchers have found that a naturally occurring fungus effectively kills the tree-of-heaven and work towards making this fungus publically available is ongoing. Therefore, we tested whether the spotted lanternfly is capable of spreading the pathogen between symptomatic fungus-inoculated tree-of-heaven seedlings or plant material to healthy tree-of-heaven seedlings in a controlled laboratory setting. In these conditions, we found no evidence that this transmission occurred. This included monitoring the seedlings for symptoms and sampling the seedlings and the insects for the fungus. This lack of transmission may indicate that the spotted lanternfly cannot help spread this fungus to other tree-of-heaven.With the recent introduction of the non-native spotted lanternfly (Lycorma delicatula) to the USA, research and concern regarding this insect is increasing. Though L. delicatula is able to feed on many different plant species, its preference for the invasive tree-of-heaven (Ailanthus altissima) is apparent, especially during its later life stage. Therefore, management focused on A. altissima control to help limit L. delicatula establishment and population growth has become popular. Unfortunately, the control of A. altissima is difficult. Verticillium nonalfalfae, a naturally occurring vascular-wilt pathogen, has recently received attention as a potential biological control agent. Therefore, we studied if L. delicatula fourth instars or adults could vector V. nonalfalfae from infected A. altissima material to healthy A. altissima seedlings in a laboratory setting. We were unable to re-isolate V. nonalfalfae from the 45 A. altissima seedlings or from the 225 L. delicatula utilized in this experiment. We therefore, found no support that L. delicatula could effectively vector this pathogen between A. altissima in laboratory conditions. Since L. delicatula’s ability to vector V. nonalfalfae has implications for the dissemination of both this beneficial biological control and other similar unwanted plant pathogens, future research is needed to confirm these findings in a field setting.

Seasonal Development, Cumulative Growing Degree-Days, and Population Density of Spotted Lanternfly (Hemiptera: Fulgoridae) on Selected Hosts and Substrates.

Seasonal development, cumulative growing degree-days (CUMDD10), and population density of Lycorma delicatula (White) were studied through weekly sampling of 30 plants (5 plants/species, 3 common plus 3 site-specific species per site) at six sites in Pennsylvania in 2019. In total, 24,159 L. delicatula (1,987 egg masses, 1,068 first instars, 239 second instars, 153 third instars, 410 fourth instars, and 20,302 adults) were recorded in 28 wk. Seasonal development followed similar pattern at all sites despite differences in starting, peaking, and ending time for specific life stages. The average CUMDD10 requirement for the onset of the first instars, second instars, third instars, fourth instars, adults, and eggs was 270, 465, 645, 825, 1,112, and 1,825, respectively. Population density ranged from 0 to 207.4, 0-298.9, and 0-9.6/m2 for nymphs, adults, and egg masses, respectively. Significant difference in population density was found between sites, hosts/substrates, and sampling weeks. Favored oviposition substrates included tree-of-heaven and black birch despite egg masses being laid on many other surfaces. Nymphs fed on different hosts in early stages but preferred American beech, tree-of-heaven, black birch, and multiflora rose. Adults were predominately found on tree-of-heaven with preoviposition surge on black birch and red maple. Sizable nymph and adult populations persisted on summer grape throughout the season. Tree-of-heaven played an irreplaceable role in the seasonal development and life history of L. delicatula in the field. Survey and detection activities should focus on tree-of-heaven with management efforts directed to aggregating adults for maximum efficacy.

CONTROL OF HUMAN FILARIAL VECTOR, CULEX QUINQUEFASCIATUS (DIPTERA: CULICIDAE) THROUGH COMBINATION OF THE ENTOMOPATHOGENIC FUNGUS, METARHIZIUM ANISOPLIAE AND NANOPARTICLES OF ZINC OXIDE AND ALUMINUM OXIDE

Culex quinquefasciatus (Diptera: Culicidae) is a vector of many pathogens and parasites of humans,as well as domestic and wild animals. Its eradication or control is regarded as one of the important alternativeavailable in preventing and controlling such diseases. Thus, there is an urgent need to checkthe proliferation of the population of vector mosquitoes in order to reduce vector-borne diseases byappropriate control methods. This study investigated the effect of the entomopathogenic fungus, Metarhiziumanisopliae against Cx. quinquefasciatus larvae, as well as its effect when combined withzinc oxide (ZnO) and aluminum oxide (Al2O3) nanoparticles (NPs). Larvae were exposed to differentconcentrations of fungus, M. anisopliae (1.42×105, 1.42×106, 1.42×107, 1.42×108 spore/ml). Mortalityrates of fourth instars ranged from 100% for the highest spore concentration to 80% for lowest sporeconcentration tested. Larvae exposed to different concentrations of ZnO & Al2O3 (5, 10, & 30mg/ l)combined individually with low concentration of fungus, M. anisopliae, showed significantly highrates of mortality reaching 100% and 96.25% for ZnO & Al2O3, respectively after 4 days of treatment.SEM micrographs confirmed the attachment and penetration of the fungus M. anisopliae into the larvalcuticle in different body parts. The combination of NPs and fungus had a synergistic effect on larvaemortality. This study showed that addition of the synthesized nano-metal oxides to M. anisopliae havegreater efficacy on control of Cx. quinquefasciatus larvae.

CONTROL OF HUMAN FILARIAL VECTOR, CULEX QUINQUEFASCIATUS (DIPTERA: CULICIDAE) THROUGH COMBINATION OF THE ENTOMOPATHOGENIC FUNGUS, METARHIZIUM ANISOPLIAE AND NANOPARTICLES OF ZINC OXIDE AND ALUMINUM OXIDE

Culex quinquefasciatus (Diptera: Culicidae) is a vector of many pathogens and parasites of humans,as well as domestic and wild animals. Its eradication or control is regarded as one of the important alternativeavailable in preventing and controlling such diseases. Thus, there is an urgent need to checkthe proliferation of the population of vector mosquitoes in order to reduce vector-borne diseases byappropriate control methods. This study investigated the effect of the entomopathogenic fungus, Metarhiziumanisopliae against Cx. quinquefasciatus larvae, as well as its effect when combined withzinc oxide (ZnO) and aluminum oxide (Al2O3) nanoparticles (NPs). Larvae were exposed to differentconcentrations of fungus, M. anisopliae (1.42×105, 1.42×106, 1.42×107, 1.42×108 spore/ml). Mortalityrates of fourth instars ranged from 100% for the highest spore concentration to 80% for lowest sporeconcentration tested. Larvae exposed to different concentrations of ZnO & Al2O3 (5, 10, & 30mg/ l)combined individually with low concentration of fungus, M. anisopliae, showed significantly highrates of mortality reaching 100% and 96.25% for ZnO & Al2O3, respectively after 4 days of treatment.SEM micrographs confirmed the attachment and penetration of the fungus M. anisopliae into the larvalcuticle in different body parts. The combination of NPs and fungus had a synergistic effect on larvaemortality. This study showed that addition of the synthesized nano-metal oxides to M. anisopliae havegreater efficacy on control of Cx. quinquefasciatus larvae.

Larvicidal and antibacterial activity of aqueous leaf extract of Peepal (Ficus religiosa) synthesized nanoparticles

In this study, the zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO2 NPs) were synthesized using the aqueous leaf extract of Ficus religiosa (Peepal tree). The synthesized nanoparticles were tested as larvicides against the larvae of Anopheles stephensi. Further, the synthesized nanoparticles were tested as antibacterial agents against the Escherichia coli (gram negative) and Staphylococcus aureus (gram positive) bacteria. The synthesized nanoparticles were characterized with UV-visible spectroscopy, X-rays powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The larvicidal mortality was observed after 24 h and 48 h by probit analysis. The antibacterial activity was evaluated using the well diffusion method. The synthesized nanoparticles were irregular shape and varied size. The larvae of An. stephensi were found highly susceptible against the ZnO NPs than the TiO2 NPs and aqueous leaves extract. The highest mortality was observed in synthesized ZnO NPs against first to third instars of (LC50 50, 75, and 5 ppm) and 100% mortality in fourth instars of An. stephensi. The higher zone of inhibition was occurred against the E. coli. This report of present investigation revealed that the rapid biological synthesis of ZnO NPs and TiO2 NPs using aqueous leaf extract of F. religiosa would be effective potential larvicides for mosquito control as well as antimicrobial agents with eco-friendly approach

Insecticidal Efficacy of Three Nanoparticles for the Control of Khapra Beetle (Trogoderma granarium) on Different Grains

The khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is an important pest of stored wheat worldwide. Nanoparticles have become one of the most promising new tools for insect pest management in recent years. This laboratory study was conducted to evaluate the insecticidal efficacy of three commercially available nanoparticles [silicon oxide (SNPs), aluminium oxide (ANPs) and zinc oxide (ZNPs)] against T. granarium at 50, 100 and 200 mg kg–1. The efficacy of SNPs, ANPs and ZNPs on wheat, barley, rice, white maize and yellow maize was assessed after 1, 3, 5 and 7 d of exposure. Corrected mortality of T. granarium was significantly affected by nanoparticle types, application rates, grain types, and the insect developmental stages. SNPs and ANPs were more effective than ZNPs, where 100% mortality of second instars was obtained at the highest concentration. Mortality of second instars on wheat treated with SNPs, ANPs or ZNPs at the rate of 200 mg kg–1 was significantly higher than other concentrations. Insecticidal efficacy of all nanoparticles at the rate of 200 mg kg–1 against second instars was significantly higher on barley and wheat than those on rice and maize. First, second and third instars exposed to all nanoparticle types at the rate of 200 mg kg–1 were more susceptible than fourth and fifth instars and adults. Female adults exposed to wheat treated with all nanoparticles at the rate of 200 mg kg–1 stopped reproduction completely. The results demonstrate that commercially available SNPs and ANPs can be used as eco-friendly management strategy of T. granarium; however, further studies under commercial storage conditions are required.

Evaluation of Nuclear Polyhedrosis Virus (NPV) and Emamectin Benzoate against Spodoptera litura (F.) (Lepidoptera: Noctuidae)

The Oriental leaf worm moth, Spodoptera litura (F.) (Lepidoptera: Noctuidae), is among the most voracious insect pests in a variety of economically important crops, particularly cotton. It has developed resistance against conventional chemical insecticides. Therefore, it is vital to evaluate an integrated application of bio- and synthetic pesticide against this pest. Nuclear polyhedrosis virus (NPV) can be a potent alternative to control this pest. The present study was conducted to evaluate the efficacy of NPV and emamectin benzoate (Proclaim® 19EC) against three geographically distinct populations of S. litura in vitro conditions. Second and fourth larval instars were treated by three different concentrations of NPV (NPV-1 2 × 109, NPV-2 3 × 109, and NPV-3 4 × 109 POB ml−1) and emamectin benzoate (EB 0.1 ppm) alone and in combination. The results showed that the highest mortality rate (83.28%) was recorded for NPV-3 + EB, followed by NPV-2 + EB, NPV-1 + EB, EB, NPV-3, NPV-2, and NPV-3 at all the tests. Moreover, Faisalabad (FSD) population was found more susceptible, followed by Layyah (LY) and Multan (ML) populations. Reduction in pupation, adult emergence and egg eclosion was found directly related to the pathogenicity of the applied pathogens. The results of this study revealed that biorational control of S. litura with combined application of NPV + emamectin benzoate was an effective tool.