Conventional Synthetic Insecticides Research Articles

Field Evaluation of Biological and Conventional Insecticides for Managing Multiple Insect Pests in Cotton

Abstract Cotton, Gossypium hirsutum (L.), is an economically important crop in the United States that is plagued by a complex of insect pests. Two key pests of cotton in the midsouthern United States are the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), and bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae). A suite of highly effective synthetic insecticides is typically used for control of these pests. However, it is unclear how the combined management of these two insect pests with biological insecticides impacts the economics of cotton production. To address this shortcoming, we conducted a field experiment in the Mississippi Delta over 2 yr to study the effects of synthetic and biological insecticides for control of the tarnished plant bug and bollworm on cotton yield. The results indicated the control of tarnished plant bug with synthetic insecticides had the most significant impact on cotton yield and net returns. The conventional tarnished plant bug treatment also significantly increased bollworm density and damage, but these increases did not significantly alter yield or net return in non–Bacillus thuringiensis (Bt) or Bt cottons. The economic benefit of a conventional approach to tarnished plant bug control with synthetic insecticides was US$438.07/ha in non-Bt and $700.88/ha in Bt cotton relative to those treated with a biological insecticide. The biological insecticides used for this study were ineffective at significantly altering yield or net return. However, for insect management in cotton to be sustainable, alternatives must be found to complement conventional synthetic insecticides.

Formicidal Potential of Thymol Derivatives: Adverse Effects on the Survival and Behavior of Acromyrmex balzani

Leaf-cutting ants are important pests of agricultural and forest crops. Currently, few insecticides are registered for the control of these insects. Natural bioactive molecules can serve as models for the synthesis of new insecticidal compounds. Such ant killer products must be sustainable and efficient, considering not only lethal effects, but also sublethal effects, which can interfere with behavior and communication between colony members. In this study, we analyzed the toxicity of the monoterpene thymol and its derivatives, as well as the sublethal effects of these compounds on the behavior of the leaf-cutting ant Acromyrmex balzani. These effects were compared with the conventional synthetic insecticide deltamethrin. Although deltamethrin showed higher toxicity (LD50 = 0.87 × 10−5 µg/mg), all other tested compounds increased ant mortality, with thymyl chloroacetate being the most toxic derivative (LD50 = 1.41 µg/mg), followed by thymol (LD50 = 2.23 µg/mg). These three most toxic compounds interfered differentially in the behavior of ants. Thymyl chloroacetate caused increased self-cleaning and reduced allogrooming, which may be related to an attempt to avoid contamination between nestmates. In general, thymol caused greater avoidance among ants, reduced walking speed and caused disorientation in workers. On the other hand, thymyl chloroacetate (LD30) considerably increased the walking speed of the group, without changing the orientation of the individuals. Such changes may interfere with basic activities such as foraging and altering colony cohesion via different mechanisms. Thus, despite the desirable effects of deltamethrin on ant control, this insecticide is highly toxic and should be discontinued soon. Our results show that thymol and its structural modification in thymyl chloroacetate may represent potential ant killers to be used in the management of A. balzani.

MANAGEMENT OF RED PUMPKIN BEETLE AND FRUIT FLY IN ASH GOURD USING BIORATIONAL INSECTICIDES

Ash gourd Benincasa hispida Thumb., a cucurbit vegetable, faces frequent infestation of red pumpkin beetle and cucurbit fruit fly. Farmers in Bangladesh mainly apply conventional synthetic insecticides to protect crops from the attack of these pests. The current study was conducted in the experimental field of the Department of Entomology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur during March 2021 to July 2021 to know the effects of five biorational insecticides, namely Biotrin (matrine), Proclaim (emamectin benzoate), Sunmectin (abamectin), Mahogany oil and Neem oil on the abundance and infestation of red pumpkin beetle and fruit fly infesting ash gourd. The insecticides were applied 3 times maintaining 7 days interval. Results showed significant reduction of the insect population compared to untreated control. Sunmectin (1.55±0.34) treated plot showed the lowest abundance of red pumpkin beetle after the 3rd spray with 65% reduction of population compared to untreated control plot. Biotrin (8.59±1.00%) treated plot showed the lowest leaf and flower infestation by red pumpkin beetle after 3rd spray, with the reduction (69% in both) over control. The lowest fruit infestation was found in Sunmectin treated plot (23.01±8.05%). The highest yield of ash gourd (17.9 T/ha) was recorded from Sunmectin treated plot which showed statistical similarity to Proclaim (16.01 T/ha) and Biotrin (15.90 T/ha) treated plots with 3.5, 2.5 and 2.6 benefit cost ratio, respectively. Therefore, it could be concluded that Sunmectin, Proclaim and Biotrin were more effective to control the infestation of red pumpkin beetle and fruit fly of ash gourd than the other tested insecticides.

Safeness and effectiveness of entomopathogenic fungi for use as bioinsecticide: A mini review

Usage of conventional synthetic insecticide to control insect pests has increased to improve crops yield and production to meet the global food demands of a growing population. However, it should not be neglected that synthetic insecticide causes negative impacts on humans, livestock as well as the environment. This review aims to provide data on entomopathogenic fungi species that can be developed into bioinsecticide to control insect pests, in order to reduce the usage of synthetic insecticide. The fungi are discussed based on two criteria, its effectiveness in controlling the targeted pests, and its safety level to humans, non-targeted organisms, and the environment. Relevant data and information on entomopathogenic fungi from various research tools including Google Scholar, NCBI, Science Direct and Researchgate were compiled into tables for comparison and analysed. Six entomopathogenic fungi namely Beauveria bassiana, Metarhizium anisopliae, Verticillium lecanii, Metarhizium (Nomuraea) rileyi, Paecilomyces fumosoroseus and Hirsutella thompsonii are proposed as having the required criteria having potential to control targeted insects by means of producing various toxins or metabolites with insecticidal properties. Five out of the six species, B. bassiana, M. anisopliae, V. lecanii and N. rileyi are safe to humans, non-targeted organisms, and the environment. Furthermore, all these fungi can be mass produced to ensure their availability to be used as a biocontrol agents. However, future studies are required for further justification for harmful metabolites produced and their impact on environment.

Assessment of non-neonicotinoid treatments against aphids on sugar beets

Aphids can cause significant damage to sugar beet crops. Myzus persicae (Sulzer) (Hempitera: Aphididae), also called green peach aphid, is responsible for transmitting yellows (i.e., beet yellows virus, beet mild yellowing virus, beet chlorosis virus, and beet mosaic virus) to sugar beet (Beta vulgaris Linné) that can substantially decrease crop yields and cause significant economic losses.In a context of increasing awareness of environmental health, products containing neonicotinoids were recently banned in several countries, making it necessary to identify new effective means of aphid control. Our study aims to assess the effectiveness of six non-neonicotinoid conventional synthetic insecticides and five biopesticides in reducing the number of aphids on sugar beets. We used data from 35 trials (site-years) managed over five years (from 2018 to 2022) located in France's main sugar beet-producing regions. We fitted a mixed-effect model able to take the variability of treatment effect across site-years into account. The most effective conventional synthetic insecticides were spirotetramat and flonicamid, with a reduction in aphid numbers (compared to the untreated control) of up to 85.6% [95% confidence interval = (80.5; 89.4)] and 79.9% [95% confidence interval = (72.9; 85.2)], respectively, 14 days after their applications at registered rates when combined with oil-based adjuvant. Biopesticides were much less effective, with the best biopesticide (Lecanicillium muscarium R. Zare & W. Gams Ve6) leading to only 40.7% [95% confidence interval = (16.6; 57.9)] reduction in aphid numbers, 14 days after its application, with great uncertainty due to the limited number of trials available for this product. Our results reveal that the most effective alternative treatments to neonicotinoids could reduce aphid abundance by more than 70% in most cases.

New Control Methods Against the Cabbage Stem Flea Beetle in Oilseed Rape Crops

Cabbage stem flea beetle (CSFB) is one of the most damaging pests of oilseed rape (OSR) grown in the UK. An intensive research effort is underway in the UK and throughout OSR growing regions of continental Europe to develop new control methods for this pest. In the first article of a series of three, we review this research and consider approaches to this pest problem that may be available immediately and in the short-term. Agronomic practices (sowing date, seed rate, crop defoliation, companion crops, etc) are being investigated and several of these approaches are already being used on farm. The use of physically acting biopesticides such as fatty acids, while not yet being used may also provide an effective solution and could be available in the short-term. Each of these approaches has the potential to form part of future Integrated Pest Management (IPM) programmes but importantly none should be seen as simple replacements for conventional synthetic insecticides. Solutions that may be available in the medium and longer-term will be discussed in the next articles. The cabbage stem flea beetle (CSFB), Psylliodes chrysocephala (Coleoptera: Chrysomelidae) is one of the most important pests of winter OSR crops in central and northern European countries. The adult beetle causes 'shot holing' feeding damage on cotyledons and true leaves of young winter OSR plants in late summer-early autumn. The larvae feed inside petioles and stems of the plants, causing additional damage. The focus on making food production more environmentally friendly means reduced chemical inputs, protecting nontarget species and overall biodiversity. This led to the withdrawal of systemic synthetic neonicotinoid pesticide seed treatments in many crops (oilseed rape included) in 2013. Since the withdrawal of neonicotinoid seed treatments, there has been a reliance on pyrethroid insecticides. This has been seen with a shift in the use of insecticides in oilseed rape, with CSFB the target for 28% of insecticide applications in 2012 (before neonicotinoid seed treatments were withdrawn) to 75% in 2020. The result of this shift has been the development of resistance to this group of insecticides in CSFB population. This situation has become so severe that some UK populations of CSFB are now 100% resistant to the pyrethroid insecticide lambda-cyhalothrin. These changes have led to the area of oilseed rape grown in the UK being halved (756,000 hectares in 2012 versus 307,000 hectares in 2021), with growers citing CSFB as one of the main reasons for this decrease. At the same time, the number of insecticide spray rounds has increased from two to three between 2012 and 2020, with these applications dominated by the use of pyrethroids. The most widely used pyrethroid insecticide, lambda-cyhalothrin, has also increased as a proportion of the insecticide-treated area from 32% in 2012 to 76% in 2020. Additional surveys by Fera, completed as part of the CropMonitor information service, between 2009 and 2020 show that the number of CSFB larvae per plant increased from an average of 0.5 larvae per plant in the years before the withdrawal of neonicotinoids, to more than 2 larvae per plant the following year in 2014 in East England, and almost 5 larvae per plant in 2019 in the South West of England. Here we present solutions that are currently available or that could be made available in the short-term. We consider how each of these approaches could be used in Integrated Pest Management (IPM) programmes.

Vine Weevil, Otiorhynchus sulcatus (Coleoptera: Curculionidae), Management: Current State and Future Perspectives.

Vine weevil, also known as black vine weevil, Otiorhynchus sulcatus, has been one of the most economically important pest species of global horticultural crops for the past five decades. This period has seen many changes in crop protection practices, including wide-scale adoption of biological controls such as entomopathogenic nematodes and fungi in place of conventional synthetic insecticides. Despite the experimental efficacy of these controls, growers continue to report significant crop losses associated with vine weevil infestation. We argue that simply switching from synthetic insecticides to biological controls, rather than using these controls as part of an integrated management program, is a key factor in the continued importance of this pest. An improved understanding of vine weevil biology and ecology is at the center of the development of truly integrated pest management programs. To this end, we identify opportunities created through recent vine weevil research and highlight key knowledge gaps in which further research may contribute to improved future management approaches.

Lethal Effects of Commercial Kaolin Dust and Silica Aerogel Dust With and Without Botanical Compounds on Horn Fly Eggs, Larvae, Pupae, and Adults in the Laboratory.

The horn fly, Haematobia irritans irritans (L.) (Diptera: Muscidae), is an important bloodsucking ectoparasite of cattle throughout much of the world. The fly is mostly controlled using conventional synthetic insecticides but as concerns about resistance increase, alternative tactics have come under heightened scrutiny. Four desiccant dust products: Surround WP, a kaolin clay-based wettable powder; CimeXa, comprised of silica aerogel; Drione, silica aerogel + pyrethrins; and EcoVia, silica aerogel + thyme oil, were assessed for their lethal effects against horn fly eggs, larvae, pupae, and adults, under laboratory conditions. Although Surround WP and CimeXa did not prevent egg hatching and (when mixed with manure substrate) pupal development, the two products were associated with moderate reductions of emerged adults, and with complete adult contact mortality within 6 hr and 24 hr, respectively. Drione and EcoVia eliminated egg hatching, pupal development, and adults within 15 min to 1 hr, respectively, whether the flies were exposed to treated filter paper substrate or exposed by immersion in the dusts. Implications for horn fly control and advantages of inert desiccant dust formulations are discussed.

Insecticidal activity of bis(methylthio)methane based volatile extract of Olax zeylanica (L.) against Sitophilus zeamais (L.) and Corcyra cephalonica (Stainton)

Sri Lankan natives traditionally introduce pungently odorized Olax zeylanica (L.) leaves into their grain storages aiming at the efficient control of insect pests associated with stored grains. The headspace components of O. zeylanica leaves were analyzed by GC–MS, subsequently isolated the major compound being responsible for the plant’s protective effect and laboratory bioassays were conducted to test its lethal activities against Sitophilus zeamais (L.) (Coleoptera: Curculionidae) and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae). A total of 2 headspace sulfur-containing constituents were found consisting the volatilome of O. zeylanica leaves wherein bis(methylthio)methane (BMTM) was identified as the major organosulfur constituent (75.3 %). BMTM provided strong and immediate control against 3–7 days old S. zeamais adults, 1 day old eggs, 15–17 days old larvae and 1 day old adults of C. cephalonica within 24 h of post treatment. In contact and fumigation assays, S. zeamais (LC50(contact) = 0.16 v/v% and LC50(fumigation) = 0.17 v/v%) was more susceptible to BMTM than C. cephalonica (LC50(contact) = 0.19 v/v% and LC50(fumigation) = 0.22 v/v%) in their adult stages. In contact grain assays, adulticidal effects persisted for 84 h. The degree of susceptibility of different C. cephalonica life stages to BMTM was arranged in the order of eggs (LC50 = 0.18 v/v%) > adults (LC50 = 0.19 v/v%) > larvae (LC50 = 0.29 v/v%) producing > 95 % lethal effects at the respective time points of 9, 12, and 24 h. Additionally, it was evidenced that the grain viability and germination were not affected by the uptake of BMTM. BMTM caused substantial toxicities in S. zeamais and C. cephalonica inferring the favorable use of natural BMTM in the successful control of stored grain insect pests, thereby obviating the necessity in sole relying on conventional synthetic insecticides in storage systems.

SCREENING OF VEGETABLE POWDERS USED AS A BIO-INSECTICIDE AGAINST CALLOSOBRUCHUS MACULATUS F. (CHRYSOMELIDAE: BRUCHINAE)

The beetle Callosobruchus maculatus (F. 1775) (Chrysomelidae: Bruchinae) is a destructive pest of stored chickpea seeds. Bio-pesticides are pesticides of animal, plant and bacterial origin. Plant products are among the best known substances tested against insects. These products have an insecticidal and repellent effect on insects and can also affect certain biological parameters such as fecundity, life span and reproduction. In search of plant bio-pesticides to control Callosobruchus maculatus main pest of stored chickpea seeds, 18 plants traditionally used in Morocco to control insect pests have been tested in the laboratory, for their toxic effects against this beetle. A conventional synthetic insecticide was included as a positive control, while untreated seed was used as a control. The toxicity of the powders was assessed by measuring the parameters of the life cycle in a situation of non-choice maintained at a climatic chamber with a temperature of 25 ±1 degrees Celsius, a relative humidity of 75% and a photoperiod of 14h (light) / 10h (darkness) for several successive generations. The powders of Mentha pulegium and Syzygium aromaticum have completely wiped out the population of the bruches (% IR=100%) 2%, 1% and 0.5% p/p. Similarly, the powders of the two plants retained the weights of the seeds, which remain significantly different (P < 0.01) at the weight of the control. Also Origanum compactum , Mentha officinalis, Allium sativum Zingiber officinale, Urtica doica and Calamintha officinalis have significantly reduced (P < - 0.01) the population of bruches, the percentage reduction reached (97.5, 89.32, 72.84, 50.3, 46.52 and 39.24% by the highest 2%). The other plants show no significant difference from the control. The results therefore suggest that Syzygium aromaticum powder and Mentha pulegium have an insecticide potential similar to those of conventional insecticides and could be a biotechnological alternative against C. maculatus infestations and damag

Bioactivity of two marine algae extracts and their synthesized silver nanoparticles as safe controls against Musca domestica housefly

AbstractIn this study, two marine algae, Avrainvillea amadelpha and Codium edule, and their synthesized silver nanoparticles were evaluated against the second larval instars of the housefly Musca domestica. The marine algae‐fabricated silver nanoparticles (AgNPs) were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X‐ray diffraction analysis (XRD). The precolored aqueous silver solution changed from pale yellow to brown by mixing the algae extracts, revealing Ag nanocomposite production. There was a maximum UV–vis absorption at 400 nm for A. amadelpha and 420 nm for C. edule. SEM results showed that the A. amadelpha‐ and C. edule‐fabricated AgNPs were spherical and irregular in shape. A. amadelpha extract alone gave higher effective mortalities against M. domestica larvae, which were 22.1–98.3% in the tested concentrations (62.5–1,000 ppm), while a highly significant increased mortality (36.9–99.7%) was obtained from concentrations ranging from 6.3–100 ppm when A. amadelpha extract was mixed with silver nanoparticles. C. edule extract alone gave moderate effective control with 15.9–90.3% mortality using the above concentrations, whereas the mortality significantly increased (21.8–95.8%) with concentrations ranging from 6.3–100 ppm when C. edule extract was mixed with silver nanoparticles. According to the LC50 values, A. amadelpha with silver nanoparticles (LC50 9.66 ppm) provided more effective control against larval stages of M. domestica than A. amadelpha alone (LC50 133.08 ppm) by a factor of 13.776. Additionally, C. edule alone provided moderately effective control (LC50 300.37 ppm), while when mixed with silver nanoparticles, it provided highly effective control (LC50 21.34 ppm) by a factor of 14.075. Some algae extracts that synthesize silver nanoparticles offer a promising role in housefly integrated pest management (IPM) and may be an effective alternative to conventional synthetic insecticides.

Seed preservatives properties of Secamone afzelii (Schult) K. Schum extracts on wheat grains damage and germination capability

BackgroundBotanical pesticides may be a possible solution to the post-harvest loss of stored grains faced by farmers and food processors. In this study, seed preservatives properties of Secamone afzelii leaves extracts at 50, 100, 150, 200 µl concentrations were investigated against lesser grain borer Rhyzopertha dominica (Fabricus) infestation on wheat grains weight loss and seed germination capability arranged in a Completely Randomized Design (CRD) and replicated thrice under ambient laboratory conditions.ResultsThe outcomes of the study showed that S. afzelii leaves extracts exhibited significant effect (p < 0.05) in suppressing R. dominica adult emergence and weight loss of wheat grains than untreated. The increase in the concentrations led to significant decrease in adult emergence and weight loss with different extracts. Secamone afzelii ethyl acetate and hexane extracts significantly subdued adult emergence in contact toxicity (6.69% and 8.49%) and fumigant toxicity (8.85 and 8.87); a similar trend was observed in weight loss in both contact (2.33% and 5.13%) and fumigant (1.50% and 1.03%) toxicities at 200 µl, respectively. None of the extracts hinder the germination of treated grains, while germination percentage ranged between 88.69% and 93.40%.ConclusionThe results clearly indicated that S. afzelii extracts, in general, ethyl acetate and hexane extracts of S. afzelii in particular were the best seed preservative for stored wheat. Thus S. afzelii leaves extracts could be utilized as grain protectant substitute for conventional synthetic insecticides and fumigants in the control of insect infestation and conservation of stored grain quality and germination capability. Further study is required to identify the bioactive chemicals responsible for the S. afzelii extracts insecticidal activity and stored grains quality preservation.

Encapsulation, release and insecticidal activity of Pongamia pinnata (L.) seed oil

Pongamia pinnata (L.) seed oil is effective for its insecticidal and larvicidal activities. However, its low aqueous solubility, high photosensitivity, and high volatility restrict its application for the control of agricultural pests. Encapsulation can be an effective technique to overcome such hindrances. Therefore, P. pinnata oil (PO) was extracted from its seeds and analyzed for karanjin content (3.18%) by GC-MS/MS as the marker compound. Micro-encapsulation (MC) of PO was prepared by interfacial polymerization between isocyanates and polyamine and tested for insecticidal and larvicidal activities. Bioassay of the developed formulations was tested in-vitro against 2nd instar larvae of Bombyx mori (Bivoltine hybrid) and in-vivo insecticidal bio-efficacy was tested against aubergine aphid (Aphis gossypii G.) and whitefly (Bemisia tabaci G.). Various properties of micro-capsules viz., stability, size, oil content and release kinetics were examined. Average diameter of capsules (1 μm) with Zeta potential (-16 mV) was indicated by the Dynamic Light Scattering (DLS) instrument. Existence of PO in the microcapsules was confirmed by an optical microscopic study. Spectroscopic analysis revealed 87.4% of PO was encapsulated in polyurea shell. The shelf-life (T10), half-life (T50), and expiry-life (T90) of polyurea coated capsules were 11.4, 75.3 and 250.0 h, respectively. Polyurea coated PO capsule formulation showed evidence of in-vitro toxicity against 2nd instar larvae of B. mori (LC50= 1.1%; LC90 = 5.9%). The PO formulation also exhibited 67.0–71.8% and 62.4–74.8% control of aphid and whitefly population in aubergine at 4.0% dose following 7–14 days after application. The study unveiled its significance in developing controlled release herbal formulations of P. pinnata as an alternative to harmful conventional synthetic insecticides for crop protection.

Can Mushrooms and Their Derivatives Be Efficient Bioalternatives to Conventional Synthetic Insecticides? (Review)

Annual losses in both agricultural and economic sectors have increased dramatically because of insect pests; hence, the effects of these pests pose a major global threat. In addition, some control methods currently used to combat insect pests are no longer as effective due to the continuous evolution in resistance and to the serious damage of these control approaches on the ecological system. Therefore, there is an urgent need to find new avenues that are more effective and environmentally friendly. In the search for novel, effective, and natural insecticides, many mushroom species are substantial sources of biologically active compounds, including those that possess insecticidal activities. This review illustrates the potential role of mushrooms as promising and powerful bioinsecticidal agents.

Karyomorphological effects of two new oil formulations on Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae).

The cotton bollworm Helicoverpa armigera is a serious pest of many economically important crops. Since this pest has become resistant to the conventional synthetic insecticides, newer compounds and formulations are being developed against this insect pest. Many natural compounds isolated from the plants were tested against this pest. Among them Hyptis suaveolens and Melochia corchorifolia showed insecticidal properties against H. arnigera. Based on bioefficacy studies, caryophyllene and β-sitosterol were isolated from H. suaveolens and M. corchorifolia respectively. The isolated natural compounds were further developed as formulations in various combinations with neem (Azadirachta indica) and karanj (Pongamia pinnata) oils. The present study indicated that the formulations influenced the karyomorphology of H. armigera.

Toxicity, repellent and oviposition deterrent effects of select essential oils against the house fly Musca domestica

• Bio-efficacy of selected essential oils were evaluated against Musca domestica. • Oils of A. indica , T. peruviana and E. camaldulensis were the most potent oils. • These oils can be used to develop environment-friendly insecticides. Essential oils from plants may provide environment-friendly alternatives to conventional synthetic insecticides. Here, toxic, repellent, and oviposition deterrent effects of essential oils of six plants: Allium sativum L. (Alliaceae), Azadirachta indica A. Juss. (Meliaceae), Cinnamomum cassia (L.) (Lauraceae), Eucalyptus camaldulensis Dehnh. (Myrtaceae), Piper nigrum L. (Piperaceae), and Thevetia peruviana (Pers.) (Apocynaceae), were evaluated against different life stages of Musca domestica . Bioassays revealed that the essential oils of A. indica , T. peruviana and E. camaldulensis exhibited: a) the highest toxicity on larvae (LC 50 = 169.72, 182.23 and 277.01 ppm, respectively), pupae (LC 50 = 150.56, 164.84 and 164.87 ppm, respectively) and adults (LC 50 = 166.69, 139.15 and 302.75 ppm, respectively) of M. domestica ; b) the highest repellency (91.44, 72.19 and 72.80%, respectively) and oviposition deterrent (90.36, 88.82 and 89.13%, respectively) effects on adults of M. domestica , as compared to the other essential oils. Moreover, the speed of mortality caused by essential oils of A. indica (LT 50 = 16.85 and 17.06 h for larvae and adults, respectively) and T. peruviana (LT 50 = 16.46 and 18.58 h for larvae and adults, respectively) was faster than the rest of the essential oils. On the whole, it might be expected that the essential oils of A. indica , T. peruviana and E. camaldulensis could be developed into a new type of environment-friendly insecticides and/or repellents for the management of M. domestica .

Polymer-Coated Hydroxyapatite Nanocarrier for Double-Stranded RNA Delivery.

Conventional synthetic insecticides have limited success due to insect resistance and negative effects on off-target biota and the environment. Although RNA interference (RNAi) is a tool that is becoming more widely utilized in pest control products, naked dsRNA has limited success in most taxa. Nanocarriers have shown promising results in enhancing the efficacy of this tool. In this study, we used a layer-by-layer electrostatic assembly where we synthesized poly(acrylic acid) (PAA)-coated hydroxyapatite (HA) nanoparticles (PAA-HA NPs) as inorganic nanocarriers, which were then coated with a layer of a cationic poly(amino acid), 10 kDa poly-l-arginine (PLR10), to allow for binding of a layer of negatively charged dsRNA. Binding of PLR10-PAA-HA NPs to dsRNA was found to increase as the mass ratio of NPs to dsRNA increased. In vitro studies with transgenic SF9 cells (from Spodoptera frugiperda) expressing the firefly luciferase gene showed a significant gene silencing (35% decrease) at a 5:1 NP-to-dsRNA ratio, while naked dsRNA was ineffective at gene silencing. There was a significant concentration-response relationship in knockdown; however, cytotoxicity was observed at higher concentrations. Confocal microscopy studies showed that dsRNA from PLR10-PAA-HA NPs was not localized within endosomes, while naked dsRNA appeared to be entrapped within the endosomes. Overall, polymer-functionalized HA nanocarriers enabled dsRNA to elicit gene knockdown in cells, whereas naked dsRNA was not effective in causing gene knockdown.

Effectiveness of Beauveria bassiana against Piezodorus guildinii (Hemiptera: Pentatomidae), a key pest of soybeans in the neotropics

ABSTRACTRedbanded stink bug, Piezodorus guildinii (Westwood), is a neotropical pest of soybean in the southern United States and the Neotropical Americas. Two strains of Beauveria bassiana (Bals.-Criv) Vuill. (Hypocreales: Cordycipitaceae) were evaluated for potential control of redbanded stink bug. Four concentrations (104, 105, 106, and 107 spores/mL) of both a Mississippi Delta native strain (NI8) and a commercially available formulation (GHA) were tested against field-collected redbanded stink bug adults in the laboratory and evaluated at four time points (3, 5, 10, and 15 days after application). Application methods simulated field sprays and were similar to those previously used to screen several other pests and beneficial insects. Both isolates of B. bassiana tested were pathogenic to redbanded stink bug adults. A significant overall difference between strains (regardless of the concentration) was observed at 3 days after treatment, while differences among concentrations were observed at 10, and 15 days after treatment. The lethal concentration (LC50) and lethal sporulation (LS50) were not significantly different between strains at either 10 or 15 days after treatment. However, higher mortality was observed in cohorts sprayed with GHA at lower concentrations than those sprayed with NI8. Unlike other control options, B. bassiana has a short re-entry interval and no harvest interval, making it a potentially attractive and environmentally benign alternative to conventional synthetic insecticides for control of redbanded stink bug in soybeans. Further testing on juvenile life stages and field testing is needed to evaluate the potential for in-field control.

Insecticidal Activity and Chemical Composition of Moringa oleifera Extract Against The Leguminous Aphid, Aphis craccivora Koch on Broad Bean Plants

In this study, Moringa oleifera leaves were extracted by ethanol 70% and the contents of total phenolic and total flavonoids were estimated by using spectrophotometer methods and HPLC analysis. The content of total phenolic in the ethanolic extract of M. oleifera leaves was 11.66 g GAE/100 g ethanolic extract. The content of total flavonoids in the ethanolic extract of M. oleifera leaves was 4.52 g IQE/100g extract. Twenty five components were represented in the tested sample by HPLC. The study also aimed to evaluate the M. oleifera extract (ethanolic extract) prepared from M. oleifera leaves, as a natural insecticide and thiamethoxam (80 g / fed.) as a comparative insecticide against aphid, Aphis craccivora on broad bean (Vicia faba L.) plants in Faculty of Agriculture farm, Sharkia Governorate, Egypt during the 2017 season. A series of concentrations were prepared from M. oleifera extract, concentrations 1, 2, 4 and 8%. The results obtained that the reduction percentage in the population of aphid insect increases with increasing concentration of M. oleifera extract (1% - 8%). The concentrations of 2 and 4% of M. oleifera extract caused 48.66 and 58.95 % mortality, respectively. The results also revealed that there is no significant differences between thiamethoxam and 8% M. oleifera leaf extract, there are recorded the highest values in reducing the population of the insect tested compared with the control treatment. The results indicate that biomaterials derived from M. oleifera leaves can be used for integrated pest management, which is a good alternative to conventional synthetic insecticides.

Evidence Based Efficacy of Selected Herbal Extracts Against Culex quinquefasciatus (Say) Larvae.

Chemical insecticides have some limitations in vectors control such as the emergence of resistance in vector mosquitoes to conventional synthetic insecticides. It aimed to evaluate the larvicidal efficacy and phytochemical potential of Azadirachta indica, Cymbopogon citratus and Allium sativum L. against ulex quinquefasciatus fourth instar larvae. The plants were screened and evaluated for their phytochemical composition and larvicidal effects on . quinquefasciatus larvae. The bioassay results showed that the effects were dependent on time and concentration of the extract used. Results showed the least lethal dose value for ethanolic extract of . citrates (72 h exposure) and the highest value for aqueous extract of A. indica (24 h exposure). Chi-square values were significant at p<0.05. Phytochemical analysis showed phytochemicals such as alkaloids, flavonoids, cardiac glycosides and resins in all the three plants. However, tannins were absent in A. indica and A. sativum, while balsam was only present in A. indica. Saponins, balsam and phenols were not found in A. sativum. Phenols were also absent in . citratus. Terpenes, steroids and resins were absent A. indica. Findings of this study revealed that these herbal extracts constitute an effective eco-friendly approach for the control of . quinquefasciatus larvae.