Significant Insecticidal Activity Research Articles

Metarhizium dianzhongense sp. nov. and New Record of M. bibionidarum (Clavicipitaceae, Hyocreales) Attacking Insects from China

The genus Metarhizium is one of the most significant entomopathogenic fungi with diverse morphological characteristics and host species. Species of Metarhizium have been widely used for pest control as an environmentally safe alternative to chemical pesticides. This study reports a new species of Metarhizium and a new record of M. bibionidarum from China. The taxonomic positions of the two species within Metarhizium were assessed by morphological and multi-gene phylogenetic data. This assessment confirmed that the new species M. dianzhongense on white grubs (Coleoptera) is a sister to M. ellipsoideum on adult leafhoppers (Hemiptera) and represents a distinctive fungus according to the morphological and phylogenetic evidence. The two species, M. dianzhongense and M. bibionidarum, were described and illustrated. Pathogenicity tests by M. bibionidarum and M. dianzhongense were performed on early instar larvae of the significant agricultural pest Spodoptera frugipera (Lepidoptera). The results demonstrated that both M. bibionidarum and M. dianzhongense exhibit significant insecticidal activity against larvae of S. frugipera, providing new fungal resources for the development of an eco-friendly biocontrol agent against this pest.

Studies on the mechanism of the contact toxicity of carvone against Tribolium castaneum

Carvone exhibits significant insecticidal activity against Tribolium castaneum. Whereas, the precise underlying mechanism of carvone's toxicity remains elusive. In this study, we aimed to investigate the contact toxicity mechanism of carvone on T. castaneum through a comprehensive set of experiments. These experiments included observation of poisoning symptoms in T. castaneum, a time-mortality test, analysis of weight measurement and respiration activities, histological assessment, enzymatic assays, and molecular simulation studies. Physiological analyses show that carvone induces excitement, spasms, and a comatose state in T. castaneum, accompanied by darkening of the body surface. Survival rates significantly dropped by 44% after 8–12 h of carvone treatment. Carvone also affects metabolism, increasing CO2 release and body weight loss. Histopathological examination reveals changes in the body wall structure, including wax particle shape alterations, increased gaps, and damaged hair bases. Abdominal tissue examination shows impacts on muscle and fat tissues, leading to dehydration and impaired physiological functions. Key enzymatic assays demonstrate sustained inhibition of acetylcholinesterase and succinate dehydrogenase activity by carvone, with peak inhibition rates reaching 65.15% and 39.90%, respectively. Carvone exhibits a biphasic effect on ATPases and activates glutathione S-transferase while inhibiting carboxylesterase activity. Molecular docking analysis reveals direct interactions between carvone and acetylcholinesterase in T. castaneum, suggesting its inhibition mechanism. This study provides insights into the insecticidal mechanism of carvone on T. castaneum and contributes to the development of plant-based insecticides.

Bioinsecticide PA1b alleviates lipopolysaccharide-induced inflammation and impairment of bovine mammary epithelial cells

Pea Albumin 1, subunit b (PA1b) is a 37 amino acid peptide. It was extracted from pea seeds and showed significant insecticidal activity against certain insects, such as the mosquitoes Culex pipiens and Aedes aegyptii, cereal weevils (genus Sitophilus), and certain species of aphids. Considering that pea seeds are regularly consumed by humans and mammals, PA1b is assumed to be a promising bioinsecticide with no allergenicity or toxicity to hosts. To clarify this aspect, PA1b was applied to bovine mammary epithelial cells challenged with lipopolysaccharide (LPS). The results revealed that LPS induced inflammatory cytokine tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL6) and monocyte chemoattractant protein 1 (MCP-1) secretion, while PA1b depressed these cytokines release via inhibiting NF-κB signaling activation. In addition, PA1b protected mammary epithelial cells from impairment caused by LPS, because it reduced cell membrane permeability and subsequently reconstructed mammary epithelial cell viability. Moreover, it inhibited cell apoptosis accompanied with alleviated oxidative stress. Furthermore, PA1b prevented opening of mitochondrial permeability transition pores, in turn up-regulated mitochondrial membrane potential and ATP production. Therefore, PA1b improved mitochondrial function, which contributed to re-construction of mammary epithelial cell viability. In conclusion, PA1b alleviates LPS-induced inflammation of bovine mammary epithelial cells via inhibiting NF-κB signaling activation and protects bovine mammary epithelial cells by improving mitochondrial function. PA1b is a good therapeutic survival factor for mammary epithelial cells.

Discovery of New Botanical Insecticides: Identification and Insecticidal Activity of Saponins from Clematis obscura Maxim and Insights into the Stress Response of Acyrthosiphon pisum Harris.

To discover new botanical products-based insecticide candidates, 14 triterpenoid saponins (1-14) including four new ones, obscurosides A-D (1-4), were isolated from Clematis obscura Maxim as potential agrochemicals against Acyrthosiphon pisum Harris and Plutella xylostella (L.). Compounds 1-3 were characterized by a rare ribose substitution at C-3, and 4 was a bidesmoside glycosylated at the rare C-23 and C-28 positions of the oleanane aglycone. Compounds 10 (median antifeeding concentration, AFC50 = 1.10 mg/mL; half-lethal concentration, LC50 = 1.21 mg/mL) and 13 (AFC50 = 1.09 mg/mL, LC50 = 1.37 mg/mL) showed significant insecticidal activities against third larvae of P. xylostella at 72 h. All saponins displayed antifeedant activities against A. pisum with the deterrence index of 0.20-1.00 at 400 μg/mL. Compound 8 showed optimal oral toxicity (LC50 = 50.09 μg/mL) against A. pisum, followed by compounds 1, 5-7, 9, and 14 (LC50 = 90.21-179.25 μg/mL) at 72 h. The shrinkage of the cuticle and the destruction of intestinal structures of microvilli, nucleus, endoplasmic reticulum, and mitochondria were toxic symptoms of 8-treated A. pisum. The significantly declined Chitinase activity in 8-treated A. pisum with an inhibition rate of 79.1% at LC70 (70% lethal concentration) could be the main reason for its significant oral toxicities. Molecular docking revealed favorable affinities of compounds 1 and 8 with group I Chitinase OfChtI (Group I Chitinase from Ostrinia furnacalis) through conventional hydrogen bonds and alkey/π-alkey interactions by different patterns. These results will provide valuable information for the development of novel botanical pesticides for the management of insect pests, especially against A. pisum.

Bioactivity and Sublethal Effects of Ageratina adenophora (Asteraceae) on Bactrocera dorsalis (Diptera: Tephritidae)

Abstract Local fruit orchards have incurred heavy losses due to invasive insects, including the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), in Guizhou Province, China. In our efforts to manage this invasive pest, a laboratory study was conducted to evaluate the response of adult B. dorsalis to an extract of Ageratina adenophora (Spreng.) R.M. King & H. Rob (Gunneridae: Asteraceae). We evaluated the contact toxicity and oviposition-deterrent activity of the extract on adult B. dorsalis, as well as the sublethal effects on survival and reproduction. We found that the A. adenophora extract has significant insecticidal activity, with the 24-h median lethal concentration (LC50) for adults being 26.014 mg/ml. The extract of A. adenophora also showed oviposition inhibition. A residual deterrent effect (28.16%) was evident up to 5 d after treatment. Exposure to the LC25 concentration of the A. adenophora extract caused significant differences in preoviposition and fecundity, decreased adult longevity in the F0 generation, and decreased egg and pupa survival in the F1 generation. The levels of carboxylesterase enzyme activity in adults treated with the extract were significantly lower than those in the untreated controls at 12 h and 24 h. This latter phenomenon could perhaps be an adaptive response to the extract that might reduce its toxic effects in B. dorsalis.

Diversifying the benzenesulfonamide scaffold for potential V-ATPase inhibitors: synthesis and insecticidal activity evaluation.

Celangulin V is a natural β-dihydroagarofuran derivative isolated from Celastrus angulatus which shows insecticidal activity in many agricultural pests. Using celangulin V as a molecular probe, we find out a new pesticide target: subunit H of V-ATPase. To explore the potential application of this novel target, lead sulfonamides have been found through virtual screening. Combined with the previous work, 46 sulfonamide derivatives are designed and synthesized. All target compounds are first screened for their insecticidal activities against Mythimna separata. The results of bioassay reveal that most of the designed compounds exhibit significant insecticidal activities against third-instar larvae of M. separata under the concentration of 10mg/mL, and compound 8.4 shows the highest activity with LC50 value of 1.72mg/mL, 15-fold smaller than that of celangulin V (25.89mg/mL). Molecular docking results further indicated that compound 8.4 might serve as a potential inhibitor of the subunit H of V-ATPase. This study provides a potential sulfonamide candidate compound for the M. separata control.

Identification and potential application of key insecticidal metabolites in Tilia amurensis, a low-preference host of Hyphantria cunea

Developing effective insecticidal strategies is an important means of reducing the spread and host plant damage by Hyphantria cunea. In this study, key metabolites with insecticidal activity against H. cunea were screened by targeted metabolomics in Tilia amurensis, a low-preference host plant. Subsequently, the potential of key metabolites that could be used as botanical pesticides was evaluated. The results showed that coumarin was the key insecticidal metabolite of T. amurensis and had a significant insecticidal effect and weight inhibition effect on H. cunea larvae. Coumarin treatment significantly decreased the larval nutrient content and the gene expression of rate-limiting enzymes in the glycolytic pathway and tricarboxylic acid cycle. A significantly enhanced detoxification enzyme activity (CarE and GST), antioxidant oxidase activity (SOD and CAT), non-enzymatic antioxidant levels (GSH), and total antioxidant capacity were observed in coumarin-treated larvae. Coumarin treatment resulted in a significant increase in the expression levels of detoxification enzyme genes (CarE1, CarE2, CarE3, GST2, and GST3) and antioxidant oxidase genes (SOD1, CAT1, and CAT2) in H. cunea larvae. Coumarin treatment significantly increased the levels of MDA and H2O2 in larvae but did not cause pathological changes in the ultrastructure of the larval midgut. Coumarin solution sprayed directly or as a microcapsule suspension formulation with coumarin as the active ingredient had significant insecticidal activity against the H. cunea larvae. Overall, coumarin, a key anti-insect metabolite identified from T. amurensis, can significantly inhibit the growth and survival of H. cunea larvae and has the potential to be developed as a botanical pesticide.

Phytochemical composition and biopesticidal potential of Pinus mugo Turra essential oil

Pinus mugo Turra (sensu lato) is an alpine species distributed at high altitudes in the mountains. The species represents a resource for obtaining essential oil (EO). Pinus essential oils (EOs) show great potential as biopesticides in agriculture. To date, there is no comparative study of the EO from various plant parts of P. mugo across the Bulgarian flora. This study aimed to investigate the phytochemical compositions of P. mugo EOs from different plant parts; leaves, twigs, wood, and cones, and evaluate their bioactivity. The botanical pesticides potential of twigs EO against Sitobion avenae, Rhopalosiphum padi, and seeds of weed species Agrostemma githago L., Anthemis arvensis L., Avena fatua L., and Papaver rhoeas L. were tested in Petri dishes. The statistical analysis results showed different EOs yield in different plant parts (0.10–0.63% in leaves, 0.40–1.00% in tips of twigs, 0.1–0.71% in twigs, 0.2–1.43% in wood of one-two year twigs, 0.21–0.6% in male cones, and 0.17% in female cones). The predominant constituents in P. mugo EO were α-pinene, α-phellandrene, β-phellandrene and β-caryophyllene. These constituents were found in all analyzed shrubs from the six populations but in different amounts, depending on the plant part. The tested twigs EO at concentrations of 5%, 4.5%, 3.5%, 2.5%, 1.5%, and 1% had significant insecticidal activity against two aphid species. The efficacy of all concentrations of the EO was 100% on both aphids 24 h after the treatment. The EO demonstrated repellent activity only in high concentrations of 3.5%, 4.5%, and 5% for S. avenae, and 4.5%, and 5% for Rh. padi, respectively. The germination energy, germination, sprouts length, and root length of A. githago, A. arvensis, A. fatua, and P. rhoeas seeds were completely inhibited by low, and high doses (1 µL, 2 µL, 5 µL, 10 µL, and 20 µL) of P. mugo EO. Furthermore, the botanical pesticide capabilities of EOs against six phytopathogens; Alternaria alternata, Botrytis cinerea, Diaporthe nobilis, Fusarium oxysporum, Rhizoctonia solani, and Phytophthora cryptogea were evaluated. The EOs of all investigated parts of the species had strong antimicrobial effect against Salmonella enterica subsp. enterica, and Escherichia coli. The needles tissues extract of P. mugo contained polyphenolic compounds with pronounced antioxidant activity. The findings of this study provide strong support for considering P. mugo EO as a valuable ingredient in the formulation of diverse biopesticides.

Chemical compositions and antimicrobial activities of three lemon odor essential oils of Cupressus macrocarpa, Cymbopogon citratus. and Citrus limon

ABSTRACT Infectious diseases caused by bacteria, fungi and viruses are globally of major concern. Plant essential oils produced by various differentiated structures possess varied properties as significant antiseptic, antibacterial, antifungal, antiviral, antioxidant, anti-parasitic and insecticidal activities. The essential oil of three lemon odor plants; Cupressus macrocarpa, Cymbopogon citratus and Citrus limon were isolated and evaluated for their antimicrobial activities. The analysis of essential oil components of C. macrocarpa by GC-MS revealed D-limonene (38.00%) as the major component followed by citral (9.72%), carveol (6.86%) and citronellal (5.35%). Analyses of the essential oil of C. citratus resulted in the identification of pseudolimonene (19.2%) as the most abundant component followed by D-limonene (12.34%), Ɣ-terpinene (10.89%), citronellol (9.58%), sabinene hydrate (9.24%), (+)-2-bornanone (8.29%) and α-terpinolene (5.53%). Also, GC-MS detected neral dimethyl acetal (41.56%) was the main component of C. limon EO with carveol (12.39%) and citral (11.21%). A study of the antimicrobial activity of the three essential oils against E. coli, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus. and Candida albicans has been evaluated and revealed that C. citratus EO had antibacterial activity against gram-positive organisms and C. limon EO exhibited the strongest antifungal activity against Candida albicans.

Insecticidal Activity of Selected Essential Oils against Drosophila suzukii (Diptera: Drosophilidae).

The spotted wing drosophila (SWD), Drosophila suzukii Matsumura (Diptera: Drosophilidae), is an invasive polyphagous pest of soft-skinned fruit that has started to threaten small fruit production in Europe since 2008. High reproductive capacity, short generation time, and difficulties in visualizing early damage contribute to its rapid spread. Currently, the control strategy against D. suzukii mostly relies on treatment with synthetic insecticides. Keeping in mind that this pest causes the greatest damage during the harvesting period, control using chemicals is not recommended due to the increased risk of high pesticide residue levels in the fruit. With the aim of reducing the use of insecticides, there is a need for developing an environmentally safer way of control. Alternative solutions could rely on the use of essential oils (EOs), which can be used in conventional and organic production systems. Four essential oils, geranium (Pelargonium graveolens), dill (Anethum graveolens), Scots pine (Pinus sylvestris), and bergamot (Citrus bergamia), were assessed for their insecticidal effects using four different tests (contact toxicity, fumigant-contact toxicity, repellent effect, and multiple-choice tests). The EOs applied were dissolved in acetone at three different concentrations. The most promising one was the geranium essential oil, which had the best effect in all conducted tests, even at the lowest applied concentration. Geranium oil caused very high mortality (95%), even at the lowest concentration applied, after 24 h in the fumigant-contact test, and it caused a mortality of over 85% in the contact test. It was also noticed that geranium demonstrated a deterrent effect by repelling females from laying eggs for four days after at the lowest applied concentration. Scots pine and dill EOs have moderate to strong effects in most tests. The mortality of 100% was achieved for the highest applied concentration in the fumigant-contact and contact tests. Bergamot EO did not have any significant insecticidal activity. Geranium, Scots pine, and dill have great potential to be used as an environmentally friendly way of controlling D. suzukii as they exhibit deterrent, repellent, and insecticidal effects.

Adult Diaphorina citri Biocontrol Using Hirsutella citriformis Strains and Gum Formulations.

Hirsutella citriformis Speare is the only entomopathogenic fungus that has been applied to control the hemipteran Diaphorina citri Kuwayama. However, the use of available commercial products under field conditions is limited due to conidia's shelf life and short environmental persistence. We have previously reported the citrus psyllid D. citri adults' biocontrol potential using H. citriformis strains. The aim of the present study was to evaluate different formulations based on H. citriformis (OP-Hir-3, OP-Hir-10, and OP-Hir-12 strains) conidia and gums as additives to improve D. citri adults' biocontrol, under laboratory, greenhouse, and field conditions, using Hirsutella gums as conidia stabilizers to improve their viability under environmental drought conditions and as insecticide. Laboratory bioassay results showed that the highest (p < 0.05) D. citri mortality was achieved using FOP-Hir-10GH (63.5%), followed by the Hirsutella gum control (42.2%). Under greenhouse conditions, adults' mortality reached up to 84.6% with FOP-Hir-12 and 49.0% with Hirsutella gum. In addition, we applied H. citriformis formulations under field conditions in a commercial citrus grove located in Tecomán, Colima, México, at 21.5 °C and 73.3% relative humidity (RH) in March and 25.7 °C and 72.5% RH in October 2022 and observed 67.3% and 94.0% mortality of D. citri adults, respectively. Hirsutella gum alone showed significant insecticidal activity against D. citri adults. In conclusion, this study demonstrated that Hirsutella gum functioned as additive to H. citriformis conidia formulations, improving D. citri adults' mortality and showing potential for this pest biocontrol in citrus orchards.

Research progress on chemical constituents and pharmacological activities of halogenated sesquiterpenes from natural sources

Halogenated sesquiterpenes are important derivatives of sesquiterpenes, referring to chemical components of sesquiterpenes that contain halogens such as chlorine, bromine, and iodine. Halogenated sesquiterpenes have attracted attention from researchers in China and abroad because of their diverse structures, unique halogen elements, and extensive pharmacological activities. Studies have shown that halogenated sesquiterpenes exhibit significant antimicrobial, anti-inflammatory, anticancer, insecticidal, hypoglycemic, and enzyme inhibitory activities. In order to better explore the potential pharmaceutical value of halogenated sesquiterpenes, this paper reviewed the structural characteristics and pharmacological activities of halogenated sesquiterpenes in the past two decades, aiming to provide references for further research and development of this class of compounds.

Insecticidal potential of a Consolida ajacis extract and its major compound (ethyl linoleate) against the diamondback moth, Plutella xylostella

The diamondback moth (Plutella xylostella) is one of the most destructive lepidopteran pests of cruciferous vegetables. However, DBM has developed resistance to current chemical and biological insecticides used for its control, indicating the necessity for finding new insecticides against it. Bio-insecticides derived from plant extracts are eco-friendly alternatives to synthetic pesticides. The aims of this study were to evaluate the insecticidal activity of Consolida ajacis seed extracts against DBM, the underlying mechanism of the control effect of promising extracts, and the identification of the main insecticidal compounds of these extracts. The results showed that ethyl acetate extract of C. ajacis seed exhibited strong contact toxicity (LC50: 5.05 mg/mL), ingestion toxicity, antifeedant, and oviposition deterrent activities against DBM, among the extracts evaluated. At 72 h, glutathiase, acetylcholinesterase, carboxylesterase, peroxidase, and superoxide dismutase activities were inhibited, but catalase activity was activated. The main compound identified from the extract was ethyl linoleate, which had the most significant insecticidal activity on the diamondback moths. This study's findings provide a better understanding of the insecticidal activity of ethyl acetate extract obtained from C. ajacis and its main component (ethyl linoleate). This will help in the development of new insecticides to control DBM.

Bioatividade de extratos aquosos de folhas de plantas na biologia de Spodoptera frugiperda (J.E.Smith, 1797) (Lepidoptera: Noctuidae)

The armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), is a key pest of corn, as it causes defoliation to plants throughout the year, causing significant economic losses. The most common method for its control is chemical, but the indiscriminate use of pesticides, in addition to causing adverse effects to humans and the environment due to the toxicity of the products, favors the development of resistant individuals, thus causing the insect in question is difficult to control. Plants popularly known as myrtle (Murraya paniculata), guaco (Mikania glomerata), são Caetano melon (Momordica charantia) and lemon balm (Melissa officinalis) have demonstrated pharmacological potential, presenting repellent or toxic effects to insects. Thus, the objective of this work was to analyze in the laboratory the insecticidal activity of M. paniculata, M. glomerata, M.charantia and M. officinalis on the biological parameters of S. frugiperda, through the incorporation of extracts in artificial diets. Based on the results obtained, a significant insecticidal activity of the myrtle leaf extract (Murraya paniculata) was observed on S. frugiperda, as it caused a significant reduction in larval and pupal viability.

Synthesis and Reactions of Fused Pyrazolo[3,4-b]Pyridine Derivatives: Insecticidal Activity and Digestive Dysfunction against Mosquito Larvae

Abstract: 5-Amino-4-formyl pyrazole 1 was used as a precursor for the synthesis of 6- aminopyrazolo[3,4-b]pyridine-5-carbonitrile 2, and 6-aminopyrazolo[3,4-b]pyridine-5- carboxamides 3 and 4. Pyrazolo[3,4-b]pyridines 2, 3, and 4 were treated with different reagents leading to structurally confirmed heterocycles. Mosquito adult females carry and transmit the causatives of many diseases to humans and other domestic animals. Therefore, their management has become a necessity. Ten of the synthesized compounds were tested for larvicidal activity against second-stage C. pipiens larvae. : IR spectra were recorded on Shimadzu-408 infrared spectrophotometer. The NMR spectra were performed on a Bruker AV-400 spectrometer and JEOL ECA II 500 MHz. Mass spectrometry was provided on a Varian MAT 312 instrument in EI mode (70 eV). Lethal concentrations were calculated based on probit analysis. Biochemical enzymes were analyzed using analysis of variance ANOVA with Graph Pad Prism 5. Mean comparisons were analyzed using Tukey's test. : Five compounds, 1, 2, 4, 5 and 11 exhibited detectable insecticidal activity as these compounds recorded 154.4, 5.6x103, 8.4, 135.1 and 697.2 ppm, respectively. Moreover, the effect of these insecticidal compounds on lipids and carbohydrates digestive pathways in the larvae was evaluated by comparing the activities of amylase and lipase digestive enzymes in both control and treated larvae. Compounds 1, 4 and 5 showed an inhibitory effect on both lipase and amylase enzymes. Compound 2 inhibited lipase activity, while compound 11 didn’t affect both enzymes compared with the control. : Results showed that the incorporation of pyridine and pyrazole induced significant insecticidal activity against larval mosquitoes. Furthermore, insertion of amino or carbonyl groups into the synthesized compounds enhanced the insecticidal activity. Our findings showed that development of such novel compounds is promising in enhancing the agricultural productivity and management of diseases transmitted by insects.

Role of CYP6MS subfamily enzymes in detoxification of Sitophilus zeamais after exposure to terpinen-4-ol and limonene

Food security is an important basis and guarantee to national safety, the loss caused by storage pests was a serious problem which affects the food security widely. Frequent application of chemical pesticides caused several critical crises including the development of resistance, pesticide residues, environmental pollution, and exposure risk to human or non-target organisms. The utilization of volatile components acts as a natural alternative for controlling storage pests has aroused extensive interest in recent years. It has been reported that terpinene-4-ol and limonene showed significant insecticidal activity against Sitophilus zeamais in our previous studies, which was evaluated to have strong influences to CYP450 genes. To determine the links and roles of related genes, we identified the SzCYP6MS subfamily genes which encoded a putative protein of 493 or 494 amino acids. Then, the expression of four CYP6MS subfamily genes were increased significantly under the fumigation stress by terpinen-4-ol and limonene, which was determined by the RT-qPCR analysis compared with non-fumigated colonies. In addition, we determined that RNAi-mediated CYP6MS genes knockdown significantly increased the sensitivity of S. zeamais to terpinen-4-ol and limonene, the mortality rates of insects with knocked down CYP6MS1, CYP6MS5, CYP6MS6, CYP6MS8, and CYP6MS9 genes increased by 25%, 25%, 16%, 17%, and 4% in terpinen-4-ol treatment groups and by 29%, 25%, 15%, 22%, and 3% in limonene treatment groups compared with that in the control groups, respectively. Finally, it was validated that CYP6MS5 exhibited the most stable binding with terpinen-4-ol that was similar to the result between CYP6MS8 and limonene which were verified by molecular docking analysis. In together, this study demonstrates the potential of terpinen-4-ol and limonene used as novel botanical pesticides to control storage pests, thereby reducing application of chemical pesticides and postponing resistance development.

Group h Chitinase: A Molecular Target for the Development of Lepidopteran-Specific Insecticides.

Sustainable agriculture requires insecticides that are selective between insects and mammals and even between harmful and beneficial insects. Lepidoptera includes the largest number of insect pests that threaten crops, and Hymenoptera contains the natural enemies for these pests. Discovery of lepidopteran-specific molecular targets is one route to develop such selective pesticides. Group h chitinase (Chi-h) is an ideal target for lepidopteran-specific insecticides because it is only distributed in Lepidoptera and is critical to their molting processes. This minireview focuses on the latest progress in developing Chi-h as a lepidopteran-specific insecticide target. We describe the biological function, crystal structure, and small-molecule inhibitors of the enzyme. Notably, two unique pockets were discovered in the crystal structure of Chi-h for the binding of the selective inhibitors, phlegmacin B1 and lynamicin B. Moreover, lynamicin B was found to exhibit significant insecticidal activity toward lepidopteran pests but is harmless toward their natural enemies. These findings are advancing the development of selective insecticides to meet the needs of sustainable agriculture.

Cloning and expression of the mitochondrial cytochrome c oxidase subunit II gene in Sitophilus zeamais and interaction mechanism with allyl isothiocyanate

In the United States, allyl isothiocyanate (AITC) has been registered as an insecticide, bactericide, and nematicide. And it has been confirmed that AITC has significant insecticidal activities against four stored product pests including Sitophilus zeamais Mostchulky (Coleoptera: Curculionidae). This study aimed to verify the mechanism of action of AITC on cytochrome c oxidase core subunits II in S. zeamais. Enzyme - catalyzed reactions and Fourier transform infrared spectrometer (FTIR) analysis revealed that the expressed COX II proteins could competitively bind and inhibit the activity of COX II. Furthermore, molecular docking results showed that a sulfur atom of AITC could form a 2.9 Å hydrogen bond with Ile-30, having a binding energy of −2.46 kcal/mol.

Essential Oil Composition of Seven Bulgarian Hypericum Species and Its Potential as a Biopesticide.

Hypericum species and especially H. perforatum L. are well known for their therapeutic applications. The present study assessed the essential oil (EO) composition, and antifungal and aphid suppression activity of seven Bulgarian Hypericum species. The EOs were analyzed by GC-MS-FID. Two experiments were conducted. In the first experiment, H. perforatum, H. maculatum, and H. hirsutum were used. Additionally, the EO composition of H. perforatum extracted via hydrodistillation (ClevA) and via commercial steam distillation (Com) were compared. The second experiment compared the EOs of H. perforatum, H. cerastoides, H. rumeliacum, H. montbretii, and H. calycinum (flowers and leaves) extracted via hydrodistillation and collected with n-hexane. Overall, the EO constituents belonged to four classes, namely alkanes, monoterpenes, sesquiterpenes, and fatty acids. The main class for compounds in H. maculatum and H. perforatum (section Hypericum) were sesquiterpenes for both experiments except for H. perforatum (Com). Hypericum montbretii (section Drosocarpium) EO had monoterpenes (38.09%) and sesquiterpenes (37.09%) as major groups, while H. hirsutum EO (section Taeniocarpium) contained predominately alkanes (67.19%). Hypericum hirsutum EO contained cedrol (5.04%), found for the first time in Hypericum species. Fatty acids were the main compounds in H. cerastoides (section Campylopus), while monoterpenes were the most abundant class in H. rumeliacum and H. calycinum EOs. α-Pinene and germacrene D were the major EO constituents of all analyzed Hypericum species except for H. hirsutum and H. cerastoides. Hypericum perforatum EO (Com) had significant repellent and insecticidal activity against two aphid species, Rhopalosiphum padi (Bird Cherry-oat aphid) and Sitobion avenae (English grain aphid) at concentrations of 0%, 1%, 2.5%, 3.5%, 4.5%, and 5%. The tested EOs did not show significant activity against selected economically important agricultural fungal pathogens Fusarium spp., Botrytis cinerea, Colletotrichum spp., Rhizoctonia solani, and Aspergillus sp. The EO of the Hypericum species found in the Bulgarian flora could be utilized for the development of new biopesticides for aphid control.

Variation in chemical composition, insecticidal and antioxidant activities of essential oils from the leaves, stem barks, and roots of Blighia unijugata (Baker) and B. sapida (K. D. Koenig)

Blighia unijugata (Baker) and B. sapida (K.D. Koenig) (Sapindaceae) are forest trees widespread in Tropical Africa. They are used in folk medicine for the treatment of rheumatism, cardiovascular diseases, yellow fever, dysentery, and epilepsy. The essential oils of the air-dried leaves, stem bark, and roots of the plants were extracted using the hydrodistillation method and were analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). The antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical method using α-tocopherol and ascorbic acid as standards. The insecticidal activity of the oils was investigated by determining the percentage mortality of the grain insects (Sitophilus zeamaise). Results showed that the yield of the colorless oils (% w/w) from the leaves, stem bark, and roots of the plants were 0.91%, 0.42%, and 0.34% for B. unijugata and 0.67%, 0.32%, and 0.48% for B. sapida, respectively. The most abundant compounds in B. unijugata leaves were pentadecanoic acid (14-methyl-, methyl ester) (38.34%), carbonic acid, propyl-en-2-yl undecylpropyl ester (36.79%), and 9-octadecanoic acid (Z)-methyl ester (24.86%). The stem bark was rich in 1,3-dimethoxybenzene (79.01%) while the root contained limonene (20.51%), trans-13-octadecanoic acid (16.74 %), and cis-vaccenic acid (9.50%). The leaf essential oil of B. sapida had hexahydrofarnesyl acetone (21.43%), phytol (20.45%), geosmin (16.258%), and α-ionone (8.271%) as the major constituents. The stem bark had cholesterol (38.66%) as the major constituent while the root contained nonanal (18.09%) and 4-cyclopropyl carbonyl tetradecane (11.6%). The antioxidant analysis revealed that B. unijugata root had 83.96% inhibition at 100 mg/ml, while B. sapida stem had 79.73% inhibition, better than α-tocopherol. No significant insecticidal activity was observed in the essential oils of the plants against S. zeamaise except for B. sapida stem which showed 50% toxicity to the maize weevils. However, the two plants can be the source of antioxidant agents against oxidative stress and related diseases.