Pupal Mortality Research Articles

Characterization, Knockdown and Parental Effect of Hexokinase Gene of Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) Revealed by RNA Interference.

Hexokinase (HK) is a key enzyme in chitin biosynthesis in insects and plays an important role in development and energy regulation. It also performs a crucial role in the synthesis of Glucose-6-phosphate and its putative functions are studied via injection of dsRNA corresponding to the hexokinase gene from Cnaphalocrocis medinalis (CmHK). This study was designed to analyze the characteristics and expression patterns of HK-related genes in various tissues of C. medinalis at different developmental stages. The CmHK ORF is a 1359 bp in length, encoding a protein of 452 amino acids, with homology and cluster analysis showing that CmHK shares an 85.11% sequence similarity with hexokinase from Ostrinia furnacalis. CmHK was highly expressed in the ovary and in the fifth instar larvae. Injection of dsCmHK significantly suppressed mRNA expression (73.6%) 120 h post-dsRNA injection as compared to a control group. The results demonstrated an increased incidence of larval and pupal mortality of 80% and 78%, respectively, with significant variation in the sex ratio between males (68.33%) and females (35%), overt larval deformities, and a reduction in average weight gain observed 120 h post-dsRNA injection. In addition, dsCmHK-injected C. medinalis showed a significant reduction in ovulation per female and larval hatching rate, along with increased larval and pupal mortality and variation in male and female emergence over three generations (G1, G2, and G3). Taken together, the outcomes of the study provide a foundation to study gene function and a new dimension to control C. medinalis by transgenic RNAi technology.

Developmental changes in larvae of the oriental latrine fly, Chrysomya megacephala, exposed to deltamethrin.

The Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) has a worldwide distribution and is considered of medical and veterinary importance. Its synanthropic behavior combined with the visitation of decaying organic matter allows it to mechanically transmit pathogens to human and animals. Pyrethroids are widely used pesticides, effective in low doses against a broad spectrum of insects. Our objective was to evaluate the action of K-Othrine® on the post-embryonic development of C. megacephala. First instar larvae were exposed to different concentrations of K-Othrine® (3.75 × 10-5 g a.i/mL (low), 7.5 × 10-5 g a.i/mL (intermediate low), 1.125 × 10-4 g a.i/mL (intermediate), 1.5 × 10-4 g a.i/mL (intermediate high), and 2.5 × 10-4 g a.i/mL (high)) mixed into artificial diets and a control with no pesticide. We measured weight, time of development, sex ratio, larval and pupal mortality, and esterase patterns. The mean weight values at intermediate low and intermediate concentrations were significantly lower compared with the control; additionally, the development time was delayed compared with the control. The larval and pupal mortality differed among the treatments. The larvae had six esterase regions, which altered its relative activity at 48 h and 72 h after insecticide ingestion. Further studies must investigate the effects of different insecticides on the post-embryonic development of C. megacephala.

Influence of Aquatain™, a monomolecular surface film on surface tension for controlling the filarial vector Culex pipiens (Diptera: Culicidae)

Surface tension is a phenomenon in the liquid media and plays an important part in the development and survival of aquatic animals. Influence of Aquatain™ monomolecular film on surface tension was determined against mosquito larvae and pupae at different temperatures (10, 15, 20, 25, 30 and 35 °C) and Aquatain™ doses (0.5, 1.0 and 2.0 ml/m2). In the laboratory, Aquatain™ showed larvicidal and pupicidal effects against the filarial vector Culex pipiens. Higher mortality was observed in late and more weighted instars/stages than young ones as well as in the pupal stage. The pupal mortality reached 76.2%, 86% and 93.3% after 12 h post-treatment at 0.5, 1.0 and 2.0 ml/m2, respectively, and it was completely eliminated (100%) within 24 h compared to 15.1%, 26.9% and 38.2% for 1st larval instar, respectively. Also, results showed at 0.5 ml/m2 with temperature range: 10, 15, 20, 25, 30 and 35 °C, the mortality reached 4.0, 6.7, 10.8, 17.3, 22.7, 29.3% and 32, 44, 54, 72, 84, 97.3% for 1st and 4th larval instar, respectively, where the surface tension (γ) was 65.6, 62.4, 58.0, 57.0, 54.2 and, 49.6 dyn/cm, while the Aquatain™ was more effective on mosquito larvae and pupae at high doses with the temperature range. On the other hand, without Aquatain™ dose, the mortality value ranged between 0.0 - 1.2%, and the surface tension (γ) was 74.5 dyne/cm, which is considered as an accidental death. Aquatain™ was effective against all aquatic phases of mosquitoes, especially against the last and weighted ones. Not only was the efficacy of Aquatain™ increased by increasing the dose, but it also increased with the increased temperature of the environment. This efficiency of Aquatain™ is due to its ability to reduce the surface tension of the water medium, preventing different stages of mosquitoes from reaching the surface for breathing thereby leading to suffocation and death. Therefore, we recommended Aquatain™ in programmes for mosquito control and other aquatic insects as a safe, cost-effective control agent.

Association of peanut cultivars and aqueous neem extract in the feeding and development of Spodoptera frugiperda (J. E. Smith)

The current study aimed to test how aqueous neem Azadirachta indica A. Juss. extract affects the attractiveness, feeding and development of Spodoptera frugiperda (J. E. Smith) on different: peanut cultivars. Tests were carried out under laboratory conditions with the cultivars IAC 503 and IAC 147 and aqueous neem extract in concentrations (mass/volume) of 5 and 10%, obtained from seeds and dried in an oven at a temperature of 35 to 38 °C for 15 days, with caterpillars offered a food choice preference test. For this, leaf discs from each treatment were placed in Petri dishes into which three first instar caterpillars were released. To assess resistance biology, single newly-hatched caterpillars were transferred to individual Petri dishes, where the following biological parameters were measured: larval mortality after 1, 3, 5, 7 and 10 days; pupal mortality; total mortality; weight of 10-day-old caterpillars; pupal weight at 24 hours; and adult longevity. The main conclusions of the work, include: cultivar IAC 147 was less attractive and consumed less; cultivar IAC 503 plus 10% neem extract reduced leaf consumption; cultivar type did not affect caterpillar biological development, and 10% neem extract caused 100% mortality in S. frugiperda.

Fall Armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) Biological Aspects as A New Alien Invasive Pest in Egypt

The present study may be the first attempt in Egypt which devoted to studying the biological aspects of fall armyworm, Spodoptera frugiperda (J.E. Smith). The study was conducted under laboratory conditions (26 ±1°C and 65 % R.H.) at the Department of Zoology, Faculty of Science, South Vally University, Qena Governorate, Egypt. The results included both hatchability (%) and incubation period (days) for egg stage; larval duration (days), pupation %, larval mortality %, malformed larvae %, and normal larvae % for the larval stage. While, the pupal duration, normal pupae %, malformed pupae %, pupal weight (gm), malformed pupae %, pupal mortality %, and emergence % for the pupal stage. Adult malformation %, sex ratio %, adult longevity (days), male longevity, female longevity, pre- oviposition period, oviposition period, post -oviposition period, fecundity (No. eggs/ ♂) and fertility % for the adult stage. The study of the biological aspects of the fall armyworm as a new invasive pest came to Egypt from the of South Africa countries is very important in order to determine the stages of life history to contribute to the planning IPM strategies for this dangerous pest in the absence of any local information about it

Ovicidal and Latent Effects of Pulicaria jaubertii (Asteraceae) Leaf Extracts on Aedes aegypti.

The control of Aedes aegypti with synthetic pesticides may result in adverse effects on wildlife and the environment. Bioactive plant extracts have been proposed as one of the alternatives to chemical pesticides used against mosquitoes. Here, we report on the ovicidal and latent effects of ethanolic, petroleum ether, and chloroform leaf extracts of Pulicaria jaubertii at 25 to 150 ppm each against the life stages of laboratory stain of Ae. aegypti. At 150 ppm, the ethanolic leaf extract resulted in 100% ovicidal activity, followed by petroleum ether extract (74%), and chloroform extract about 7% mortality. The ethanolic extract produced 100% larval and pupal mortality at both 75 and 50 ppm, while the petroleum ether extract produced 76.5 and 58.3%, respectively. The ethanolic extract recorded the highest percentage of adult mortality (72.7%) at the lowest concentration (25 ppm). At 25 and 50 ppm, the ethanolic extract resulted in 62.2 and 85.2% sterility index of Ae. aegypti females, respectively, as compared with the 0.1 and 3.5% sterility index caused by the chloroform extract at the same concentrations. In conclusion, P. jaubertii appears to have potential to be further evaluated as a mosquito control agent. Additional studies are needed on its mode of action, synergism with other products, and efficacy under actual field conditions.

SUSCEPTIBILITY OF Elasmopalpus lignosellus PUPAE TO ENTOMOPATHOGENIC NEMATODES IN MAIZE

Virulence and concentration of entomopathogenic nematodes (NEPs)in Elasmopalpus lignosellus pupae were evaluated. In the laboratory, the virulence of the isolates Heterorhabditis amazonensis MC01, H. amazonensis JPM3, H. amazonensis GL, Steinernema carpocapsae All and Heterorhabditis sp. Nepet 11 was evaluated and, subsequently, H. amazonensis GL was applied at concentrations of 8; 16; 24 and 32 IJ cm-2. The EPNs were applied to Petri dishes containing ten pupae with five replications. Mortality was assessed every 24 hours for three days. In a greenhouse, H. amazonensis GL was tested at concentrations 24, 25, 26 and 27 IJ cm-2. The IJs were applied in pots containing a 20-cm high ‘BM 3061’ maize plant, besides six pupae with four replications. Knowing that the efficiency of EPNss is directly related to the ability to search and penetrate the host, it was found that H. amazonensis GL is highly virulent to E. lignosellus, presenting an LC50 of 6.49 IJ cm-2 after 48 hours, 5.61 IJ cm-2 in 72 hours and LC90 of 39.70 IJ cm-2 in 48 and 27.73 IJ cm-2 in 72 hours under laboratory conditions. In the soil, pupal mortality was lower and a concentration of 25 IJ cm-2 was responsible for the death of 50% of the population, since environmental variability influences the dynamics of IJ infection and insect defense.

Comparison of efficacy of nitric oxide fumigation under nitrogen and carbon dioxide atmospheres in controlling granary weevil (Sitophilus granaries) and confused flour beetle (Tribolium confusum)

Nitric oxide (NO) was a recently discovered fumigant for postharvest pest control. Because NO reacts with oxygen (O2) spontaneously to form nitrogen dioxide (NO2), NO fumigation must be conducted under ultralow oxygen (ULO) atmospheres to preserve NO and nitrogen (N2) has been used to establish ULO atmospheres in NO fumigation studies in the past. However, carbon dioxide (CO2) can also be used to ULO atmospheres and CO2 fumigation was also reported to be effective in controlling certain insect pests and enhancing toxicity of some fumigants. In the present study, NO fumigations under ULO conditions established with N2 and CO2 were compared for effects against granary weevil, Sitophilus granaries, and confused flour beetle, Tribolium confusum. All life stages of the two insects were subjected to 12 h fumigation treatments with 0.5–1.0% NO at 25 °C under ULO established with CO2 (NO–CO2 treatments) and N2 (NO–N2 treatments). The most tolerant life stage for each species in each fumigation treatment was then fumigated with NO for 24 h fumigation at 25 °C to determine an effective treatment. There were no significant differences in mortalities of adults, larvae, and pupae at all NO concentrations between ULO conditions established with CO2 and N2 for either insect. NO–CO2 was, however, significantly less effective than NO–N2 against eggs of both species. Granary weevil pupae and confused flour beetle eggs were the most tolerant stages for each respective species to NO fumigation: >99% mortality of granary weevil pupae and confused flour beetle eggs were, however, achieved in the 24 h fumigation with 2% and 1% NO, respectively. This study showed that CO2 can be used to establish ULO atmospheres for NO fumigation, but did not significantly contribute to insect mortality.

First report on the entomopathogenicity and virulence of Akanthomyces muscarius LY 72.14, a Yungas native fungal isolate, for Anastrepha fraterculus control

ABSTRACT In this work, we report the entomopathogenic potential of Akanthomyces muscarius LY72.14, a fungus isolated from a soil sample collected in the Southernmost sector of Las Yungas (Tucumán, Argentina) subtropical rainforest. The isolated fungus exhibited both pathogenicity and virulence in larvae, pupae and adults of the pestiferous fruit fly Anastrepha fraterculus, ability that could then be applicable for fruit pest biocontrol. Groups of 120 late-third-instar larvae were inoculated by immersion with four different conidial concentrations of A. muscarius LY 72.14 ranging from 105 to 108 conidia mL−1. Mycosis was subsequently verified through different time lapses for larva (1–2 days), pupa (14 days) and adults (13 days). Results revealed adult stage as the most susceptible to fungal infection, with a mortality percentage of 29.4 ± 3.2%, whilst pupal mortality reached 7.8 ± 1.2%. On the other hand, larval mortality was similar to the non-infected control (5.9 ± 1.4%). When 108 conidia mL−1 fungal inocula were used, the total host mortality (involving the three fly developmental stages) reached 53%. Virulence against fly adults was significantly dependent on high conidial concentrations, achieving a LC50 value of 8.4 × 107 conidia mL−1, with a similar killing effectiveness pattern (43–45%) among 107 and 108 conidial concentrations. The promising herein demonstrated biocontrol potential of A. muscarius LY 72.14 to effectively infect and kill A. fraterculus under lab-condition assays, makes relevant to evaluate this native fungal isolate under field-cage and open-field conditions to weight the possibilities for biocontrol massive usage and its tentative application for integrated plague management.

Effect of Plant-growing Media on Western Flower Thrips, Frankliniella occidentalis, Pupae and Fungus Gnat, Bradysia sp. nr. coprophila, Larvae under Laboratory Conditions

Western flower thrips, Frankliniella occidentalis, and fungus gnats (Bradysia spp.) are major insect pests of greenhouse production systems. Both insect pests have life stages that reside in the soil or plant-growing medium: prepupae and pupae of western flower thrips and fungus gnat larvae. There are unsubstantiated allegations made by a manufacturer that certain plant-growing media that contain a bacterium, Bacillus pumilus, and arbuscular mycorrhizal fungus, Glomus intraradices, negatively affect the survival of western flower thrips pupae and fungus gnat larvae. Therefore, we conducted a study involving laboratory experiments replicated over time (2019 and 2020) to investigate the influence of the plant-growing media Pro-Mix BX + Mycorrhizae and Pro-Mix BX + Biofungicide + Mycorrhizae on western flower thrips pupae and fungus gnat larvae. All experiments involved placing western flower thrips pupae or fungus gnat larvae (second and third instar) into 473-mL deli containers with the different treatments (plant-growing media). A 5 × 4-cm section of a yellow sticky card was affixed to the lid of each deli container. After 21 days, the number of western flower thrips or fungus gnat adults that emerged from the growing media and were captured on the yellow sticky cards was recorded. The use of the yellow sticky card was an indirect assessment of western flower thrips pupal or fungus gnat larval mortality. We found none of the plant-growing media tested that contained a bacterium and/or arbuscular mycorrhizal fungus affected the survival of western flower thrips pupae or fungus gnat larvae. Therefore, greenhouse producers should be leery of information provided by manufacturers that does not contain valid, scientifically based data.

Green synthesis of silver nanoparticle using Leonotis nepetifolia and their toxicity against vector mosquitoes of Aedes aegypti and Culex quinquefasciatus and agricultural pests of Spodoptera litura and Helicoverpa armigera.

Pest insects causing damage to cultivable crops and food products by feeding, fecundity, and parasitizing livestock, also being a nuisance to human health. In consideration with human health, the World Health Organization reports that more than 50% of the world's population is presently at risk from mosquito-borne diseases. Mosquitoes are primary vectors for major dreadful diseases such as yellow fever, malaria, and dengue fever, which infect millions of human beings all over the world and kill millions of peoples every year. The present research work was carried out to evaluate the antifeedant, larvicidal, pupicidal, larval, and pupal duration activity of Leonotis nepetifolia-mediated silver nanoparticles (AgNPs) against Spodoptera litura, Helicoverpa armigera, Aedes aegypti, and Culex quinquefasciatus. Biosynthesized AgNPs were characterized through various techniques such as UV-Vis spectrometer, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential analysis. The AgNPs showed potential antifeedant activity of 78.77% and 82.16% against the larvae of S. litura and H. armigera, respectively. The maximum larval mortality rate (78.49% and 72.70%) and maximum pupal mortality rate (84.66% and 77.44%) were observed against S. litura and H. armigera. Mosquito larvae were tested with biosynthesized AgNPs, and recorded LC50 values were 47.44ppm and 35.48ppm on A. aegypti and C. quinquefasciatus, respectively. The histological examinations showed that the acceleration of the nanomaterial caused severe tissue damage in the epithelial and goblet cells in the larval midgut region of S. litura, H. armigera, A. aegypti, and C. quinquefasciatus. Biosynthesis of silver nanoparticles using L. nepetifolia is an ideal eco-friendly approach for the management of insect pests. Graphical abstract.

Biological Control of Pectinophora Gossypiella (Saunders) Using Spores and Supernatants of some Entomopathogenic Fungi

The spores and supernatants of some fungal isolates; Paecilomyces violacea, Trichoderma harzianum andBeauveria bassiana;were evaluated to control the pink bollworm, Pectinophora gossypiella biologically at Plant Protection Research Institute, Sharkia branch, (ARC).All fungi were isolated from soil and dead pink bollworm larvae. B. bassiana was the most active isolate caused the greatest larval and pupal mortality, also the highest deformed adult, also, the lowest numbers of eggs and hatchability percentage. Protease and chitinase produced from B. bassiana. strain had high effects on percent of larval mortality, comparing with control. Identification ofBeauvaria sp. was assured by using 18s rRNA with accession number MT644472.1.

Effects of zinc acquired through the plant-aphid-ladybug food chain on the growth, development and fertility of Harmonia axyridis

Heavy metal pollution is an increasingly serious problem in agricultural ecosystems. Zinc accumulation in the food chain may harm the physiological functions of organisms, including herbivorous and predatory insects. Its effects on development and reproduction in Harmonia axyridis are largely unknown. In this study, five Zn solutions (25, 50, 100, and 150 mg/kg) plus control (0 mg/kg) were used to treat broad beans and to water the resulting seedlings. Aphids fed on these seedlings were eaten by H. axyridis ladybugs. Zn accumulation was found at all three trophic levels. Compared with the control group, ladybugs in the 25, 50, and 100 mg/kg groups had significantly reduced weight gain from the 4th instar to adulthood. Pupae and larvae (instars 1–4) in the 150 mg/kg group had the lowest survival of any group; pupal mortality in the 100 mg/kg group was significantly higher than that in the control group. Under Zn stress, female adults had inhibited expression of Vg1, Vg2 and VgR, reducing egg production and hatchability. Zn thus negatively affected their fertility. These results provide a theoretical basis for future exploration of soil heavy metal pollution impacts in ecosystems.

Novel treatment of gelatin-copper bio-nanoparticles as a management method against the spiny bollworm, Earias insulana, (Boisd.) (Lepidoptera: Noctuidae) in comparison studies with the uncoated nanoparticles

Spiny bollworm, Earias insulana causes drastic damages in cotton crop. A new safe strategy rather than insecticide is urgent for its control. Copper nanoparticles (CuNPs) and gelatin-copper nanoparticles (G-CuNPs) were biosynthesized safely using fungal filtrates of Aspergillus wentii, Aspergillus mottae and enecillium expansum. The biosynthesized nanoparticles were confirmed by UV–visible spectroscopy, Transmission electron microscope, Dynamic Light Scattering and Fourier Transform Infrared. G-CuNPs were smaller in size and had strong inhibitory activity against E. insulana than CuNPs at all experimental conditions. The treatment with G-CuNPs synthesized by A. wentii released lowest values of LC50 and LC90 and caused the highest value of larval and pupal mortality, pupal mortality and pupation of the insect. There was highly significant decrease in the percentage of hatchability and egg numbers in the case of treatment with all types of experimental nanoparticles, where G-CuNPs was the best at all. G-CuNPs can be used safely in a management program against Earias insulana.

Behavioral aspects of Sphenophorus levis (Coleoptera: Curculionidae), damage to sugarcane and its natural infection by Steinernema carpocapsae (Nematoda: Rhabditidae)

In Brazil, the sugarcane billbug Sphenophorus levis (Coleoptera: Curculionidae) bores sugarcane rhizomes in its larval stage, causing high losses to the crop. Entomopathogenic nematodes (EPNs) of the genera Heterorhabditis and Steinernema (Nematoda: Rhabditidae) could be applied in the sugarcane fields to control the larvae and pupae of S. levis inside rhizomes. However, it is not clear whether this insect leaves an opening in the rhizome that would allow EPNs to enter and reach the insects in their immature stages. In addition, there is still no record of the natural occurrence of EPNs in the immature stages of S. levis or on the losses this insect can cause to sugarcane crops. This work aimed to investigate aspects of S. levis behavior on sugarcane plants and to determine the cane damage and crop loss percentage it causes through observations and regular evaluations of plants in the field; as well as to assess the natural occurrence of EPNs in the insect population found inside the cane rhizomes. For every 1% increase in its damage to the rhizomes, S. levis caused a 1% loss in the cane crop due to reductions of 0.318% in the weight of the stems and of 0.68% in the number of shoots generated by the rhizomes. The insect leaves openings that link the tunnels inside the root to the outside; these openings are made by adults during oviposition or by last-instar larva to allow the adults to exit. Almost 90% of the openings were made below the ground, allowing EPNs to enter the tunnels to reach the insect life stages inside the root. Steinernema carpocapsae was found to cause natural infection in S. levis inside the root, providing up to 60% pupal mortality. This information may help to establish the level of economic damage caused by S. levis and highlights EPNs as a potential alternative for S. levis control; their application just after cane harvesting is suggested in order to reduce the S. levis population in the next plant generation.

Lethal and sub-lethal effects of bio-and chemical insecticides on the tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

The tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a destructive pest affecting the tomato crop causing a loss of 60–100% of the tomato crop production. In the present study, the lethal and sub-lethal effects of Bacillus thuringiensis (Bt), spinosad, and emamectin benzoate as bio-insecticides comparing with 2 synthetic insecticides: chlorpyrifos and indoxacarb against T. absoluta under laboratory conditions were evaluated. Take in consideration, life tables and reproductive parameters of treated larvae with LC30 for each pesticide (bio- and chemical insecticides) by using leaf dipping technique were calculated. The results showed that Lepinox formulation of Bt was the most effective one against the early 2nd instar larvae with 0.01 × 10−2 mg/l (ppm), followed by spinosad with 0.07 × 10−2 ppm comparing to indoxacarb and chlorpyrifos (0.01 and 11.44 μg/ml, respectively). Sub-lethal effect of the Bt formulations significantly increased pupal mortality by 29.77, 33.30, and 26.94% for Lepinox, Dipel 2×, and Protecto, respectively. In addition to their efficiency, Bt formulations and emamectin benzoate increased larval developmental period and reduced adult emergency percentage to 70.28, 66.70, 73.06, and 75.55% for Lepinox, Dipel 2×, Protecto, and emamectin benzoate, respectively. All bio-insecticides including Bt, spinosad, and emamectin benzoate caused abnormalities in different life stages. The results suggest these bio-insecticides are promising alternatives to synthetic insecticides for T. absoluta management.

Control of the Banded Fruit Weevil, Phlyctinus callosus (Schönherr) (Coleoptera: Curculionidae), Using Entomopathogenic Fungi

Phlyctinus callosus (Schönherr) (Coleoptera: Curculionidae), the banded fruit weevil (BFW), is a sporadic pest, causing damage to fruits, leaves and roots of deciduous fruits and grapevines in the Western Cape Province. Using trunk barriers to prevent the flightless weevils from reaching the leaves and fruits is labour-intensive. Entomopathogenic fungi (EPF) are effective biocontrol agents for the control of soil-borne and above-ground insect pests. Different EPF isolates were screened at 1 × 106 conidia/ml for virulence against different life stages (larvae, pupae and adults) of the BFW. The results indicated that unformulated, laboratory-cultured Beauveria bassiana 1 (Broadband®) and Metarhizium anisopliae 1 (Meta 69®) resulted in significantly higher BFW larval mortality of 97 % and 93 %, respectively, than B. bassiana 2 (Eco-Bb®) with 58 % mortality. Beauveria bassiana 1 (92 %) resulted in significantly higher pupal mortality than B. bassiana 2 (68 %) and M. anisopliae 1 (66 %). Beauveria bassiana 1 caused 90 % adult BFW mortality, which differed significantly from that obtained with B. bassiana 2 (69 %) and M. anisopliae 1 (65 %). A local EPF isolate (EA2) was compared with the commercial EPF isolates, and B. bassiana 1 (92 %) again caused significantly higher mortality of BFW adults compared to B. bassiana 2 (65 %), M. anisopliae 1 (60 %) and M. anisopliae isolate EA2 (64 %). In a sand bioassay using final instar BFW larvae, B. bassiana 1 (85 %) resulted in higher mortality than both B. bassiana 2 (55 %) and M. anisopliae 1 (70 %). The results indicated that all the commercial EPF isolates were effective against the immature and adult stages of the BFW, but with clear differences between isolates. Beauveria bassiana 1 consistently caused the highest BFW mortality under laboratory conditions. Large-scale field trials with the formulated commercial products are recommended to further demonstrate the potential use of this biocontrol agent in integrated pest management programmes.

Efficacy of the Horse Chestnut, Aesculus hippocastanum Seeds Extract on some Biological Activities of Culex pipiens and the Detection of its Phytochemical Constituents

In the present study, mosquito larvicidal and repellent activity and phytochemical screening of the horse chestnut, Aesculus hippocastanum seeds extract have been evaluated against Culex pipiens mosquito. The obtained results indicated that there was a positive correlation between the concentration of Aesculus hippocastanum seeds extract and the total larval and pupal mortality percent, the recorded LC50 was 122 and 76 ppm for larvae and pupae, respectively. In addition, a remarkable reduction in both the pupation and adult emergence percent were obtained. Also, the extract showed prolonged activity on both larval and pupal duration. Moreover, various degrees of morphogenic abnormalities were observed in the immature and adult stages. The antifeedant and repellent activity of the present plant extract was investigated, it exhibits the highest protection (100%) from the bites of starved females at the dose of 3mg/cm2. the major bioactive chemical constituents in Aesculus hippocastanum seeds extract were identified using HPLC and FT-IR analysis.These results suggested the Aesculus hippocastanum seeds extract as a promising adult emergence inhibitor and repellent agent against the vector mosquitoes and might be used in small volume aquatic habitats or other breeding sites of mosquitoes.

Ultrasonic Technology Applied against Mosquito Larvae

The effective management of mosquito vectors is a timely challenge for medical and veterinary entomology. In this study, we evaluated the acoustic Larvasonic device to control young instars of the mosquito Aedes aegypti in diverse freshwater environments. Under laboratory conditions, we investigated the effect of exposure time and distance from the transducer on the mortality of larvae and pupae of Ae. aegypti. Furthermore, we evaluated the effectiveness of the ultrasound window of the electromagnetic spectrum under different field conditions. Results showed that first and second instar larvae were more sensitive to the frequency range of 18–30 kHz of the Larvasonic device. Ultrasonic waves applied for 180 s at a frequency from 18 to 30 kHz caused 100% larval mortality at a distance of 60 cm from the transducer. No mortality was observed in the non-target copepod Megacyclops formosanus. The exposure to the soundwaves produced by the acoustic larvicidal device over different distances effectively damaged Ae. aegypti through destruction of the larval dorsal tracheal trunk, thorax and abdomen. Overall, results indicated that the Larvasonic device tested can provide an alternative tool to reduce young instar populations of Ae. aegypti, without any effects on non-target aquatic invertebrates like copepods. It turned out to be a useful device for mosquito biocontrol. This technology has a relevant potential to fight the spread of mosquito-borne diseases.

Uncertainty and sensitivity analyses of extinction probabilities suggest that adult female mortality is the weakest link for populations of tsetse (Glossina spp).

BackgroundA relatively simple life history allows us to derive an expression for the extinction probability of populations of tsetse, vectors of African sleeping sickness. We present the uncertainty and sensitivity analysis of the extinction probability, to offer key insights into factors affecting the control or eradication of tsetse populations.MethodsWe represent tsetse population growth as a branching process, and derive closed form estimates of population extinction from that model. Statistical and mathematical techniques are used to analyse the uncertainties in estimating extinction probability, and the sensitivity of the extinction probability to changes in input parameters representing the natural life history and vital dynamics of tsetse populations.ResultsFor fixed values of input parameters, the sensitivity of extinction probability depends on the baseline parameter values. Extinction probability is most sensitive to the probability that a female is inseminated by a fertile male when daily pupal mortality is low, whereas the extinction probability is most sensitive to daily mortality rate for adult females when daily pupal mortality, and extinction probabilities, are high. Global uncertainty and sensitivity analysis show that daily mortality rate for adult females has the highest impact on the extinction probability.ConclusionsThe high correlation between extinction probability and daily female adult mortality gives a strong argument that control techniques which increase daily female adult mortality may be the single most effective means of ensuring eradication of tsetse population.