Development Of Insect Resistance Research Articles

The Role of Organic Farming in Sustainable Agriculture

Organic farming, as a sustainable alternative to conventional high-input practices reliant on synthetic fertilizers, fungicides, and pesticides, prioritizes the vitality of soil as a living ecosystem. Embracing practices such as crop rotation, animal manures, crop residues, green manures, and biological pest and disease control, organic agriculture aims to uphold soil health and productivity. By meeting present food demands in an environmentally conscientious manner, organic farming also safeguards the needs of future generations, thereby preserving and nurturing our ecosystem. Modern agriculture has detrimentally impacted the environment, leading to issues such as decreased soil fertility, elevated water hardness, insect resistance development, reduced genetic diversity in plants, heightened levels of toxic residues in the food chain and animal feed, contributing to health problems and environmental degradation. In contrast, organic farming nurtures plants with essential macronutrients and micronutrients while simultaneously enhancing soil physical, chemical, and biological characteristics. Guided by the ethos of sustainability, organic farming prioritizes mitigating health risks linked to synthetic inputs and cultivating a healthier ecosystem. The minimal environmental footprint of organic farming positions it as a practical solution for tackling urgent concerns like soil degradation, water pollution, and global ecological well-being. Essentially, organic farming stands out as a beacon of sustainable agriculture, paving the way to reconcile food production with environmental conservation. Moreover, organic farming's low environmental impact presents an opportunity to rehabilitate and enhance degraded agricultural lands.

Laboratory evaluation of a bio-insecticide candidate from tangerine peel extracts against Trialeurodes vaporariorum (Homoptera: Aleyrodidae).

The excessive use of synthetic insecticides in modern agriculture has led to environmental contamination and the development of insect resistance. Also, the prolonged use of chemical insecticides in producing flowers and tomatoes in greenhouses has caused health problems for workers and their offspring. In this study, we analyzed the efficacy of mandarin peel (Citrus reticulata L.) essential oil (EO) as a natural insecticide against greenhouse whitefly (Trieurodes vaporariorum W., Homoptera: Aleyrodidae), a common pest in greenhouse production of different crops. Petroleum ether (PET) and n-hexane (HEX) were used as solvents to extract essential oil (EO) from tangerine peels. The yield of EO was 1.59% and 2.00% (m/m) for PET and HEX, respectively. Additionally, the insect-killing power of EO was tested by checking how many greenhouse whiteflies died at different times. The results showed that PET and HEX extracts of tangerine EO effectively controlled greenhouse whiteflies. Furthermore, with both solvents, a 12.5% (v/v) application was as practical as the commercial insecticide imidacloprid. Further characterization tests with the polarimeter, FTIR, HPLC-RP, and GC-MS showed that the essential oil (EO) contained about 41% (v/v) of d-limonene and that this compound may be responsible for the observed insecticidal properties. Therefore, tangerine peel essential oil is an excellent botanical insecticide candidate for controlling greenhouse whiteflies.

Efficacy of two amorphous silica powders applied to soft red winter wheat against the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

The increased demand for residue-free grains and development of insect resistance to insecticides has led to a surge in the utilization of diatomaceous earths as grain protectants. Diatomaceous earth formulations, effective at lower application rates, are crucial for managing stored product insects without compromising grain quality. In this study, the efficacy of two different amorphous silica powders applied to soft red winter wheat was tested against the lesser grain borer, Rhyzopertha dominica (F.). Twenty adults of R. dominica were exposed to 100 g of organic soft red winter wheat admixed with varying application rates (0 for the untreated control, 0.05, 0.1, 0.15, and 0.20 g/kg) of silica powders 1 and 2. Mortality assessments were made after 14 d of exposure, and data on adult progeny production, insect-damaged kernels, and grain weight loss were determined at 42 d. Exposing R. dominica adults to wheat treated with 0.20 g/kg of silica powder 1 resulted in a mean ± SE of 94.5 ± 5.5% mortality and 1.3 ± 1.3 adult progeny production. Insect-damaged kernels and grain weight loss caused by R. dominica exposed to 0.20 g/kg of silica powder 1 were 0.19 ± 0.19 and 0.1 ± 0.1%, respectively. Exposure of R. dominica adults exposed to wheat mixed with 0.20 g/kg of silica powder 2 resulted in complete mortality, with no observed adult progeny production, insect-damaged kernels, or grain weight loss. Overall, silica powder 2 exhibited greater efficacy than silica powder 1, and this superior performance can be attributed to its higher oil adsorption capability and low pH (<8.5) value.

Design and elucidation of an insecticide from natural compounds targeting mitochondrial proteins of Aedes aegypti

Developing new pesticides poses a significant challenge in designing next-generation natural insecticides that selectively target specific pharmacological sites while ensuring environmental friendliness. In this study, we aimed to address this challenge by formulating novel natural pesticides derived from secondary plant metabolites, which exhibited potent insecticide activity. Additionally, we tested their effect on mitochondrial enzyme activity and the proteomic profile of Ae. aegypti, a mosquito species responsible for transmitting diseases. Initially, 110 key compounds from essential oils were selected that have been reported with insecticidal properties; then, to ensure safety for mammals were performed in silico analyses for toxicity properties, identifying non-toxic candidates for further investigation. Subsequently, in vivo tests were conducted using these non-toxic compounds, focusing on the mosquito's larval stage. Based on the lethal concentration (LC), the most promising compounds as insecticidal were identified as S-limonene (LC50 = 6.4 ppm, LC95 = 17.2 ppm), R-limonene (LC50 = 9.86 ppm, LC95 = 27.7 ppm), citronellal (LC50 = 40.5 ppm, LC95 = 68.6 ppm), R-carvone (LC50 = 61.4 ppm, LC95 = 121 ppm), and S-carvone (LC50 = 62.5 ppm, LC95 = 114 ppm). Furthermore, we formulated a mixture of R-limonene, S-carvone, and citronellal with equal proportions of each compound based on their LC50. This mixture specifically targeted mitochondrial proteins and demonstrated a higher effect that showed by each compound separately, enhancing the insecticidal activity of each compound. Besides, the proteomic profile revealed the alteration in proteins involved in proliferation processes and detoxification mechanisms in Ae. aegypti. In summary, our study presents a formulation strategy for developing next-generation natural insecticides using secondary plant metabolites with the potential for reducing the adverse effects on humans and the development of chemical resistance in insects. Our findings also highlight the proteomic alteration induced by the formulated insecticide, showing insight into the mechanisms of action and potential targets for further exploration in vector control strategies.

Screening and characterization of Bacillus thuringiensis isolates for high production of Vip3A and Cry proteins and high thermostability to control Spodoptera spp

Bacillus thuringiensis (Bt) is an entomopathogenic bacterium that produces crystalline (Cry and Cyt) and soluble (vegetative insecticidal proteins or Vips) proteins during the sporulation and vegetative growth phases, respectively. Combining Cry and Vip proteins could delay insect resistance development and exhibit synergistic activity against various insect pests. This study aims to screen Bt isolates collected from Thailand for high Vip3A and Cry protein production levels and high thermostability to control Spodoptera spp. Among the selected Bt isolates with high target protein synthesis, Bt isolate 506 was found to be safe for further biopesticide formulation due to the absence of non-specific metabolite, as determined by the detection of thermo-stable β-exotoxin I based on biological assays and PCR analysis. Bt isolate 506 showed the presence of Cry1A, Cry2A, and Vip3A-type proteins identified as Cry1Aa45, Cry2Aa22, and Vip3A87, respectively. The insecticidal activity of whole culture extracts containing Vip3A and Cry mixtures and culture supernatants containing secreted Vip3A protein was evaluated against the second-instar larvae of S. exigua and S. frugiperda. The Bt isolate 506 showed high toxicity against both insects, and the insecticidal proteins produced by this isolate retained their activity after heating at 50 °C. This Bt isolate is a promising candidate for further development as a biopesticide against lepidopteran pests.

Laboratory-Induced Bifenthrin, Flonicamid, and Thiamethoxam Resistance and Fitness Costs in Rhopalosiphum padi.

The bird cherry-oat aphid, Rhopalosiphum padi (L.) (Hemiptera: Aphididae) is one of the most economically important pests of wheat crops worldwide. Thiamethoxam, bifenthrin, and flonicamid are extensively used insecticides for controlling this key pest. However, the indiscriminate use of chemical insecticides has led to the development of resistance in insects. In this study, we assessed the development of selection-induced resistance to bifenthrin, flonicamid, and thiamethoxam under controlled laboratory conditions. Additionally, we employed the age-stage, two-sex life table method to examine the fitness of R. padi. After ten generations of selection, bifenthrin-, flonicamid-, and thiamethoxam-resistant strains of R. padi were developed with resistance levels of 34.46, 31.97, and 26.46-fold, respectively. The life table analysis revealed a significant decrease in adult longevity and fecundity in these resistant strains compared to susceptible strain. Furthermore, the key demographic parameters such as net reproductive rate (R0) and reproductive days exhibited a significant reduction in all resistant strains, while the intrinsic rate of increase (r) and finite rate of increase (λ) were decreased only in resistant strains to bifenthrin and thiamethoxam. Taken together, these findings provide a comprehensive understanding of laboratory-induced insecticide resistance evolution and the associated fitness costs in R. padi. This knowledge could help to design resistance management strategies against this particular pest of wheat.

Enthralling genetic regulatory mechanisms meddling insecticide resistance development in insects: role of transcriptional and post-transcriptional events.

Insecticide resistance in insects severely threatens both human health and agriculture, making insecticides less compelling and valuable, leading to frequent pest management failures, rising input costs, lowering crop yields, and disastrous public health. Insecticide resistance results from multiple factors, mainly indiscriminate insecticide usage and mounted selection pressure on insect populations. Insects respond to insecticide stress at the cellular level by modest yet significant genetic propagations. Transcriptional, co-transcriptional, and post-transcriptional regulatory signals of cells in organisms regulate the intricate processes in gene expressions churning the genetic information in transcriptional units into proteins and non-coding transcripts. Upregulation of detoxification enzymes, notably cytochrome P450s (CYPs), glutathione S-transferases (GSTs), esterases [carboxyl choline esterase (CCE), carboxyl esterase (CarE)] and ATP Binding Cassettes (ABC) at the transcriptional level, modification of target sites, decreased penetration, or higher excretion of insecticides are the noted insect physiological responses. The transcriptional regulatory pathways such as AhR/ARNT, Nuclear receptors, CncC/Keap1, MAPK/CREB, and GPCR/cAMP/PKA were found to regulate the detoxification genes at the transcriptional level. Post-transcriptional changes of non-coding RNAs (ncRNAs) such as microRNAs (miRNA), long non-coding RNAs (lncRNA), and epitranscriptomics, including RNA methylation, are reported in resistant insects. Additionally, genetic modifications such as mutations in the target sites and copy number variations (CNV) are also influencing insecticide resistance. Therefore, these cellular intricacies may decrease insecticide sensitivity, altering the concentrations or activities of proteins involved in insecticide interactions or detoxification. The cellular episodes at the transcriptional and post-transcriptional levels pertinent to insecticide resistance responses in insects are extensively covered in this review. An overview of molecular mechanisms underlying these biological rhythms allows for developing alternative pest control methods to focus on insect vulnerabilities, employing reverse genetics approaches like RNA interference (RNAi) technology to silence particular resistance-related genes for sustained insect management.

Cross-resistance and redundant killing of Vip3Aa resistant populations of Helicoverpa zea on purified Bt proteins and pyramided Bt crops.

Pyramiding Bt proteins is a key strategy to delay insect resistance development. However, the durability of pyramided Bt crops for controlling insect pests is threatened by cross-resistance among Bt proteins, which can ultimately contribute to resistance development. The corn earworm, Helicoverpa zea, is a major agricultural pest of pyramided Bt crops. Previous studies have examined cross-resistance and redundant killing of Cry resistance in H. zea, but such information is lacking for Vip3Aa resistance in this pest. Here, we evaluated cross-resistance and redundant killing of Vip3Aa-resistant H. zea to purified Bt proteins, as well as Bt corn and Bt cotton. Diet bioassays demonstrated high susceptibility of Vip3Aa-resistant H. zea to Cry1Ac, Cry1A.105, and Cry2Ab2 purified proteins. No Vip3Aa-susceptible, -heterozygous, or -resistant H. zea could survive on pyramided Bt corn containing Cry1 and/or Cry2 proteins. Complete redundant killing was observed in pyramided Bt corn containing Cry1 and/or Cry2 proteins against Vip3Aa resistance in H. zea. Vip3Aa-susceptible, -heterozygous, and -resistant H. zea exhibited survival rates ranging from 0.0% to 22.5% on pyramided Bt cotton with Cry1 and/or Cry2 proteins. Incomplete to complete redundant killing was observed for Vip3Aa-resistant H. zea on pyramided Bt cotton containing Cry1 and/or Cry2 proteins. Our findings indicate that Vip3Aa-resistant H. zea does not exhibit positive cross-resistance to Cry1 or Cry2 proteins. In addition, most pyramided Bt crops showed complete or nearly complete redundant killing of Vip3Aa-resistant H. zea. These results indicate that a pyramiding strategy would often be effective for managing Vip3Aa resistance in regions of the United States where H. zea has not evolved resistance to Cry1 and Cry2 toxins. © 2023 Society of Chemical Industry.

Bacillus thuringiensis pesticidal toxins: A global analysis based on a scientometric study (1980–2021)

Several studies have been conducted on Bacillus thuringiensis (Bt) pesticidal toxins due to their successful environmentally friendly biopesticide activity against various insect pest orders, protozoa, mites, and nematodes. However, no existing study has systematically examined the trends and evolution of research on Bt pesticidal toxins from a scientometric perspective. This study aimed to analyze the trends and hotspots of global research in this field. 5757 publications on Bt pesticidal toxins were extracted from the Web of Science Core Collection (WoS) from 1980 to 2021. Statistical and scientometric analyses were performed using Excel, CiteSpace, and VOSviewer visualization tools to evaluate research evolution, journal contribution and subject categories, contributing countries and institutions, highly influential references, and most used author keywords. The 5757 publications featured in 917 journals spanning 116 subject categories. The top 5 subject categories ranked as Entomology, Biotechnology & Applied Microbiology, Microbiology, Biochemistry & Molecular Biology, and Agriculture. Out of these publications, the USA contributed the most, with 1562 publications, 72,754 citations, and 46.58 average citations per paper (ACPP); however, Belgium had the highest (106.43) ACPP among the top 20 contributing countries. The Chinese Academy of Agricultural Sciences is the leading institution with 298 publications and 21.20 ACPP. The Pasteur Institute is ranked first (90.04) in terms of ACPP. Keywords analyses revealed that recent studies are inclined toward the evolution of insect resistance against Bt toxins. In future, studies related to the development of resistance mechanisms by insects against Bt pesticidal toxins and ways to overcome them will likely receive more attention. This study highlights the past and current situations and prospective directions of Bt pesticidal toxins-related research.

Appraisal of some granular insecticides against yellow-stem borer and Crop Water Productivity of Rice under two irrigation regimes

Insect pests are serious threat to agricultural crops. Recurrent use of similar chemicals has resulted in many problems like resistance development in insects and hazardous effects on environments. The present research work was executed to probe out the comparative efficacy of some newer granular insecticidal formulations against yellow stem borer of rice, Scirpophaga incertulus (Walker). Recommended dose rates of the selected insecticides were used against the targeted insect pest. Results of incidence of S. incertulus larvae on paddy tillers showed that highest mean number population (22.40 larvae) were noted in experimental plots under flood irrigation compared with AWD irrigated plots (12.36 larvae). Data regarding dead-hearts revealed that maximum (8.5 dead-hearts /plot) were recorded in control followed by Cartap Hydrochloride (4.2 dead-hearts/plot) while lowest (2.21 dead-hearts/plot) by S. incertulus infestation were noted in chlorantraniliprol + Thiamethoxam plots under AWD irrigation. However, all the tested treatments were found superior over control. Results of white earheads showed that maximum (12.1 white earheads/plot) were recorded in case of control plot followed by Cartap Hydrochloride@ 22 kg/ha (4.16 white earheads/plot), Fipronil @20.0 kg/ha (3.78 white earheads/plot) whereas lowest (2.96 white earheads/plot) were recorded in chlorantraniliprol + Thiamethoxam treated plots. Crop water productivity of paddy plots under AWD irrigation was 0.29 kg/m3 comparatively greater than plots under flood irrigation i.e., 0.12 kg/m3. Use of new granular formulation of insecticide together with improved irrigation can be helpful for Integrated Management of yell stem borer of rice.

Using Sentinel Plots to Monitor for Changes in Thrips Susceptibility to MON 88702 Cotton Containing the Cry51Aa2.834_16 Bt Protein.

Transgenic Bt crops are important tools for growers to manage insect pests, but their durability is threatened by the evolution of insect resistance. Implementing a resistance monitoring program is essential to detect and mitigate resistance. For non-high-dose Bt crops, resistance monitoring is challenging, because insect control is not complete, so targeted insects and insect damage will be present even without resistance. Given these challenges, sentinel plots have been used to monitor for insect resistance to non-high-dose crops by assessing changes in the efficacy of a Bt crop over time relative to a non-Bt control. We optimized a sentinel plot resistance monitoring approach for MON 88702 ThryvOn™ cotton, a new non-high-dose Bt product targeting two sucking pest taxa-Lygus (L. lineolaris and L. hesperus) and thrips (Frankliniella fusca and F. occidentalis)-and report here on the thrips monitoring methods and results. Quantifying thrips immatures was the best metric to characterize the impact of the trait, with at least a 40-60% average reduction of thrips immatures on ThryvOn relative to the control cotton at all sites with higher thrips densities. These data can be used within a ThryvOn resistance monitoring program and represent a case study for establishing a resistance monitoring approach for a non-high-dose trait product.

Encapsulation of Rosmarinus officinalis essential oil and of its main components in cyclodextrin: application to the control of the date moth Ectomyelois ceratoniae (Pyralidae).

Synthetic insecticides are the most useful tools for preventing losses caused by insect pest's infestation during storage. However, the use of pesticides should be limited because of the development of insect resistance and their adverse effects on human health and environment. In the last decades, natural insecticidal products, principally essential oils (EOs) and their active components, exhibited potential alternatives for pest control. Nevertheless, due to their volatile nature, encapsulation could be considered as the most appropriate solution. Therefore, this work aims to investigate the fumigant ability of inclusion complexes of Rosmarinus officinalis EO and its major constituents (1,8-cineole, α-pinene and camphor) with 2-hydroxypropyl-beta-cyclodextrin (HP-β-CD) against Ectomyelois ceratoniae (Pyralidae) larvae. The encapsulation within HP-β-CD reduced greatly the release rate of the encapsulated molecules. Therefore, free compounds were more toxic than those encapsulated. Moreover, results revealed that encapsulated volatiles exhibited interesting insecticidal toxicity towards E. ceratoniae larvae. In fact, after 30 days mortality rates were 53.85, 94.23, 3.85 and 42.31% for α-pinene, 1,8-cineole, camphor and EO, respectively, encapsulated within HP-β-CD. In addition, results showed also that 1,8-cineole free and encapsulated was more effective toward E. ceratoniae larvae than the other tested volatiles. Additionally, the HP-β-CD/volatiles complexes exhibited best persistence compared to the volatiles components. The half-life of the encapsulated α-pinene, 1,8-cineole, camphor and EO (7.83, 8.75, 6.87 and 11.20 days) was significantly longer than that of the free ones (3.46, 5.02, 3.38 and 5.58 days). These results sustain the utility of R. officinalis EO and its main components encapsulated in CDs as treatment to stored-date commodities. © 2023 Society of Chemical Industry.

Nano-Encapsulation Of Neem Based Pesticide Formulations

Neem based pesticide formulations are reported to control plant parasitic fungi, bacteria, virus, nematodes, insects and mites. Despite its many promising properties, low stability under field conditions, mainly due to a high rate of photo-degradation, as well as a short residence time and slow killing rates, compared to conventional pesticides hinder effective large-scale use of Neem. Although when two lines of Myzus persicae Were exposed to pure azadirachtin and refined Neem seed extract at the same concentration, it was found that after forty generations, the line treated with azadirachtin had developed ninefold greater resistance compared to a control line, whereas the line treated with the extract did not show resistance. To overcome these limitations, nanotechnology has emerged as a novel tool for agricultural sustainability. Many studies have shown that the encapsulation of agrochemicals in nanoparticulate systems can enhance the efficacy of the active ingredient, decrease toxicity toward the environment and humans, and reduce losses due to volatilization, leaching, and photobleaching. Thus, the use of nanoparticles provides an effective means of protecting neem oil against premature degradation, resulting in prolongation of its effect on the target pest. Due to nano encapsulation sustained release of the active component is achieved. Furthermore, the number of applications of neem oil can be reduced, bringing substantial economic benefits. Therefore, nano-encapsulation of neem oil may enable the production of more stable formulations for control of diseases and pests. Further, the use of nanotechnology is an excellent way to combat development of resistance in insects and pathogens due to indiscriminate use of neem oil.

RNAi-based knockdown of candidate gut receptor genes altered the susceptibility of Spodoptera frugiperda and S. litura larvae to a chimeric toxin Cry1AcF.

A multitude of Cry toxins (secreted by Bacillus thuringiensis or Bt) has been deployed globally either via transgenic mean or bio-pesticidal formulations in order to manage insect pests. However, Bt resistance development in insects is emerging as a major concern. To avoid this problem, multiple gene pyramiding or protein-engineered chimeric toxin-based strategy has been analyzed. In the present study, one such chimeric toxin Cry1AcF (contain the swapped domains of Cry1Ac and Cry1F) was used to investigate its in vivo pathogenesis process in lepidopteran pests Spodoptera frugiperda and S. litura. A number of biochemical and molecular analysis were performed. Oral ingestion of Cry1AcF caused greater toxicity in S. frugiperda than S. litura with larvae displaying increased hemolymph melanization. Histopathology of the midgut transverse sections exhibited Cry1AcF-induced extensive gut damage in both the test insects followed by cytotoxicity in terms of reduced hemocyte numbers and viability. Elevated hemolymph phenoloxidase activity indicated the immune-stimulatory nature of Cry1AcF. In order to analyze the role of gut receptor proteins in Cry1AcF intoxication in test insects, we performed RNAi-mediated silencing using bacterially-expressed dsRNAs of individual receptor-encoding genes including CAD, ABCC2, ALP1 and APN. Target-specific induced downregulation of receptor mRNAs differentially altered the insect susceptibility to Cry1AcF toxin in our study. The susceptibility of ALP1 and APN dsRNA pre-treated S. frugiperda was considerably decreased when treated with Cry1AcF in LD50 and LD90 doses, whereas susceptibility of CAD and ABCC2 dsRNA pre-treated S. litura was significantly reduced when ingested with Cry1AcF in different doses. CAD/ABCC2-silenced S. frugiperda and ALP1/APN-silenced S. litura were vulnerable to Cry1AcF alike of control larvae. In conclusion, our results indicate ALP1/APN and CAD/ABCC2 as the functional receptor for Cry1AcF toxicity in S. frugiperda and S. litura, respectively.

Epigenetic regulations as drivers of insecticide resistance and resilience to climate change in arthropod pests.

Arthropod pests are remarkably capable of rapidly adapting to novel forms of environmental stress, including insecticides and climate change. The dynamic interplay between epigenetics and genetics explains the largely unexplored reality underlying rapid climatic adaptation and the development of insecticide resistance in insects. Epigenetic regulation modulates gene expression by methylating DNA and acetylating histones that play an essential role in governing insecticide resistance and adaptation to climate change. This review summarises and discusses the significance of recent advances in epigenetic regulation that facilitate phenotypic plasticity in insects and their symbiotic microbes to cope with selection pressure implied by extensive insecticide applications and climate change. We also discuss how epigenetic changes are passed on to multiple generations through sexual recombination, which remains enigmatic. Finally, we explain how these epigenetic signatures can be utilized to manage insecticide resistance and pest resilience to climate change in Anthropocene.

Development and evaluation of clove and cinnamon oil-based nanoemulsions against adult fleas (Xenopsyllacheopis)

Adult fleas is one of the important vector borne insects which transmitting many diseases to mammals (cats, dogs, rodents, and humans) and birds worldwide. Because of the impact of climatic changes, the distribution of transmitted vector-borne pathogens may change, as well as the host ranges and the spread of diseases. Rat flea, Xenopsylla cheopis, can transmit Plague, a dangerous infectious disease caused by the bacterium Yersinia pestis. As the widespread use of synthetic insecticides to control fleas for a long time led to the development of insect resistance, and adverse health effects on humans, animals, and the ecosystem. This is the first work for formulating and evaluating clove and cinnamon oil nanoemulsions and studying their effect on adult flea. Clove and cinnamon nanoformulations were prepared and subjected to physicochemical and stability studies. Results showed that the small droplet size of nanoformulations was 158.4 nm and 282.5 nm of clove and cinnamon oils at a ratio of 1:2 of oil: tween 80 with 15 min as the sonication time. Cinnamon nanoemulsions have high insecticidal activity against flea compared to clove nanoemulsions. The LC50 account for 14.50 μg/ml and 26.42 μg/ml with a 39.90% increase in cinnamon nanoemulsion activity compared to clove nanoemulsion, respectively. Cinnamon nanoformulation is solvent-free and did not have any toxic effects on experimental animals and EC50 more than 100 mg/l (EC50 > 100 mg/l) on Vibrio fischeri bacteria. Therefore, it considers an eco-friendly green nano-insecticide for controlling Xenopsylla cheopis flea.

Molecular features and functional studies of transcription factor, Cap ‘n’ collar C, in the brown planthopper, Nilaparvata lugens Stål (Hemiptera Delphacidae)

• Molecular features of Cap ‘n’ Collar C of Nilaparvata lugens was firstly described. • Knockdown of NlCncC cause lethality in N. lugens. • NlCncC mediate resistance of N. lugens to imidacloprid by affecting transcript level of P450 genes. Cap ‘n’ collar C ( CncC ), a transcription factor, plays a vital role in the development of insect resistance by regulating the expression of multiple detoxifying genes. Clarifying the molecular characteristics of CncC and its pathway regulating insecticide resistance will aid the development of integrated pest control strategies. Here we cloned and identified the molecular feature of CncC genes from the brown planthopper (BPH), Nilaparvata lugens (Stål), (Hemiptera: Delphacidae). The full-length open reading frame of NlCncC was 3015 nucleotides with 1005 amino acids. The deduced amino acid sequence has a high similarity with other insect homologs and contains the characteristic Cnc/bZip domain architecture. Functional studies showed that silencing NlCncC by RNA interference (RNAi) could downregulate the transcript expression of NlCYP6ER1 , NlCYP6CW1, and NlCYP6AY1, which increase the susceptibility to imidacloprid in N. lugens . The identification of molecular characteristics of NlCncC and functional studies in this paper will contribute to designing effective control strategies for N. lugens .

Larvicidal, antioxidant and biotoxicity assessment of (2-(((2-ethyl-2 methylhexyl)oxy)carbonyl)benzoic acid isolated from Bacillus pumilus against Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus.

Mosquitoes are a vector for many dreadful diseases known for their public health concern. The continued use of synthetic insecticides against vector control has led to serious environmental impacts, human health problems, and the development of insect resistance. Hence, alternative mosquito control methods are needed to protect the environment and human health. In the present study, the bioefficacy of (2-(((2-ethyl-2 methylhexyl)oxy)carbonyl) benzoic acid isolated from Bacillus pumilus were tested against Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi. The isolated bioactive compound was characterized through thin layer chromatography (TLC), UV-visible spectroscopy (UV), Fourier-transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and gas chromatography-mass spectrometry analysis. The pure compound caused a high percent mortality rate in a dose-dependent manner, the obtained values were 96, 82, 69, 50 and 34%; 86, 72, 56, 43, and 44%; 100, 90, 83, 70 and 56% against Ae. aegypti, Cx. quinquefasciatus, and An. stephensi respectively. The effective lethal concentration values (LC50) were 13.65, 14.90 and 9.64ppm against Ae. aegypti, Cx. quinquefasciatus, An. Stephensi, respectively. The effect of (2-(((2-ethyl-2 methylhexyl)oxy)carbonyl) benzoic acid significantly increased the superoxide dismutase, catalase, α, β esterase and Glutathione-S-transferase level after 24h of the treatment period. The comet assay confirmed that isolated compound causes DNA damage in all tested insects. Histopathological examinations of treated larvae showed shrunken body posture, damaged epithelial cells and microvillus as compared to control organisms. The biosafety of the isolated compound was assessed against G. affinis and did not produce mortality which confirmed that the activity of the isolated compound is species specific. The current study concludes that the critical success factors of new insecticidal agent development are based on the eco-compatibility and alternative tools for the pesticide producing industry.

Virtual Evaluation of Insecticidal Potential of Fused Vip3Aa and Garlic Lectin against Fall Armyworm (Spodoptera frugiperda)

The use of transgenic crops to combat insect infestation has been proven to be an effective and environment-friendly approach. However, insecticidal proteins with a single mode of action are prone to the development of insect resistance. Researchers are now interested in combining insecticidal proteins to acquire multiple modes of action to address that problem. Here, we have performed a virtual evaluation of a fusion protein that was in silico constructed by combining the vegetative insecticidal protein (Vip3Aa) of Bacillus thurengensis and the garlic leaf lectin of Allium sativum (ASAL) with a fl exible peptide linker (GGGGS)3. Two fusion modes were conducted, one with ASAL as the N-terminus (AV) and the other where Vip3Aa is the N-terminus (VA) of the fusion construct. Molecular dynamics simulation of the fusion constructs (AV and VA) revealed their differences in conformational changes and compactness, with VA being more stable and favorable. Protein-protein docking studies against the fall armyworm aminopeptidase-N of S. frugiperda resulted in the identifi cation of interacting residues at the interface. A novel fusion protein proposed in this study would be valuable for rational design of potent insecticidal proteins with multiple modes of action.

RNAi Mediated Gene Silencing of Detoxification Related Genes in the Ectropis oblique.

Ectropis oblique is one of the main pests that feed on tea leaves. At present, the main control method is chemical control, but the long-term use of insecticides has been related to the development of insect resistance. One of the resistance mechanisms is the upregulation of relevant detoxification enzymes for defense. In this study, four genes with increased expression were screened from the gene sequences annotated from the transcriptome data of deltamethrin-treated larvae of E. oblique, which are acid phosphatase EoACP138, and cytochrome P450 EoCYP316, carboxylesterase EoCarE592 and acetylcholine esterase EoAchE989, respectively. The fourth instar larvae of E. oblique were stimulated by deltamethrin, chlorpyrifos and fenpropathrin respectively, and the expression levels of the genes were detected by qRT-PCR. The result showed that all four genes’ expression had significantly increased under the stimulation of three insecticides. RNAi technology was used to silence the expression of genes of EoACP138, EoCYP316, EoCarE592 and EoAchE989 in the fourth instar larvae of E. oblique. The change in the expression levels of the above genes in the larvae treated with dsRNA and stimulated with pesticides was determined by qRT-PCR. The target genes have been effectively silenced after feeding on dsRNA and higher sensitivity with higher mortality to pesticides was observed in the larvae interfered with dsRNA. The above genes are related to the detoxification and metabolism of resistance of E. oblique, which lays a foundation for further study on the mechanism of insecticide resistance in E. oblique.