LC50 Values Research Articles

Toxicity Assessment of Four Commonly Used Insecticides to the Corn-Infesting Rice Weevil (Coleoptera: Curculionidae)1

Abstract Rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), is one of the most significant pests of corn (Zea mays L.) and other stored grains. Historically, synthetic insecticides have been widely used to control pest populations due to their effectiveness, convenience of storage and application, and persistent activity. This study aimed to assess the toxicity profiles of four commonly used insecticides, including pirimiphos-methyl, deltamethrin, deltamethrin plus (S)-methoprene, and malathion, to rice weevil adults. The weevils were exposed to a range of concentrations of each insecticide to generate concentration–mortality response curves and median lethal concentrations (LC50) of each insecticide. Pirimiphos-methyl exhibited the highest toxicity to the adult weevils, with an LC50 of 0.74 ppm (95% confidence limit [CL], 0.57–0.92). Based on nonoverlapping 95% CLs, we determined that the LC50 of pirimiphos-methyl was significantly lower than the LC50 of malathion (7.08 ppm [95% CL, 5.44–9.01]), deltamethrin (9.11 ppm [95% CL, 6.89–12.6]), and deltamethrin plus (S)-methoprene (13.94 ppm [95% CL, 9.71–18.60]). Thus, the relative toxicity of these four insecticides to adult rice weevils was pirimiphos-methyl > malathion > deltamethrin > deltamethrin plus (S)-methoprene. We subsequently compared the LC50 value of each insecticide with that of the label-recommended application rate and found that only malathion aligned with the recommended label rate. These findings could prove useful in refining application rates for the effective control of rice weevils infesting stored grains.

Insecticidal potential of botanical extracts for management of, the oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae)

BackgroundBactrocera dorsalis (Hendel) poses a significant threat to global fruit production and quality, including in Pakistan, where it causes substantial losses. Traditional control methods have heavily relied on the indiscriminate and imprudent use of insecticides, leading to challenges such as insecticide resistance, environmental pollution, fruit contamination, and health risks. This study explores the insecticidal potential of seven selected botanicals: Artemisia vulgaris L., Capparis spinosa L., Mentha longifolia, Mentha piperita, Peganum harmala, Eucalyptus globulus, and Callistemon viminalis, each at three different concentrations (10mL, 20mL, and 30mL), against Bactrocera dorsalis (B. dorsalis). Two in vitro experiments involving the application of plant extracts mixed with protein bait and direct spray were conducted.ResultsBoth experimental results demonstrated a direct correlation between the concentration of plant extract and the mortality of B. dorsalis. In the plant extract mixed with protein bait, results recorded after 96 h at 10 mL ranged from 8.667 ± 1.52–47.000 ± 3.00, at 20 mL from 18.667 ± 1.52–53.667 ± 6.02, and 30 mL from 26.000 ± 5.29- 67.667 ± 2.08. Meanwhile, for direct spray, mortality ranged from 2.333 ± 1.15–32.333 ± 6.80 at 10 mL, 1.000 ± 1.00–42.667 ± 7.02 at 20 mL, and 9.667 ± 2.30–61.333 ± 8.50 at 30 mL, respectively. The plant species exhibiting the highest toxic potential against the respective pests was C. viminalis, followed by A. vulgaris L. In contrast, the least toxic effect was observed in Eucalyptus globulus at all concentrations. The highest mean mortality and repellence % were recorded in C. viminalis and E. globulus in both experimental trials. The results revealed the highest efficacy of C. viminalis with an LC50 value of 9685.15 and 19,909.11 ppm, for the extract mixed with protein bait and sprayed, was obtained, respectively, the most toxic to the pest followed by the extracts E. globulus and C. spinosa L.ConclusionBased on our experimental results, it is concluded that C. viminalis and A. vulgaris L. are an effective alternative for the management of B. dorsalis.

Rhodium complex [RhLI2]I: a novel anticancer agent inducing tumor inhibition and apoptosis

Numerous chemotherapeutic agents are currently employed in cancer treatment, but many are associated with significant side effects. This study aims to identify a novel anticancer drug that minimizes or eliminates these adverse effects. The anticancer activity of the Rhodium (III) complex cis-[RhLI2]I was evaluated through both in vivo and in vitro functional assays. Apoptosis in cancer cells post-treatment was assessed using microscopy and gene expression analysis. In cytotoxicity screening via the brine shrimp lethality bioassay, the compound exhibited an LC50 value of 25.90 µg/mL (P < 0.001). It also achieved an 88.96% inhibition of cell growth (P < 0.001), an 82.39% increase in lifespan (P < 0.001), and a significant reduction in tumor weight at a dosage of 200 µg/kg in Ehrlich ascites carcinoma (EAC)-bearing Swiss albino mice. Restoration of hematological parameters, such as RBC, WBC, and hemoglobin levels, was observed in treated tumor-bearing mice compared to untreated EAC-bearing mice. The compound inhibited the growth and proliferation of breast cancer (MCF7) cells in a dose-dependent manner, achieving a maximum inhibition of 88.9% at 200 µg/mL. Apoptotic induction in MCF7 cells occurred through the upregulation of p53, Bax, caspase-3, -8, and -9, alongside the downregulation of the anti-apoptotic protein Bcl-2. No long-term adverse effects on hematological or biochemical parameters or tissue levels were observed in the mice. Given these findings, this compound demonstrates significant cytotoxic effects and has the potential to serve as a promising chemotherapeutic agent, warranting further investigation at more advanced stages.

Novel Meta-Diamide Derivatives Bearing Triazole: Design, Synthesis, and Bioactivity.

In searching for novel insecticide lead, 20 new meta-diamide compounds containing triazole were designed and synthesized regarding cyproflanilide as lead compound. All the compounds were characterized by 1H NMR, 13C NMR, and High-resolution mass spectra (HR MS). In preliminary bioassay, we found that one of the compounds: N-(cyclopropylmethyl)-N-(5-((2,6-dibromo-4-(1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl)phenyl)carbamoyl)-2-(1H-1,2,4-triazol-1-yl)phenyl)-6-(trifluoromethyl) nicotinamide (16a) had high activity against the target organism Plutella xylostella at 1mg/L and against the target organism Mythimna separata at 2mg/L. It is obviously superior to the known compounds Ia and Ib, and it is equivalent to cyproflanilide, and the LC50 values of the compound against P. xylostella and M. separata were 0.90mg/L and 0.64mg/L, respectively. It is providing important clues for subsequent structure-activity relationship (SAR) studies. From this, we explored the SAR of these compounds. Through comprehensive analysis of their structural characteristics and insecticidal activity data, we found that different halogen substituents on benzene ring and different aromatic substituents on amino group in the compound had significant effects on insecticidal activity. This has certain guiding significance for further structural optimization and activity enhancement.

Abstract A003: In vitro anticancer activities of some organoplatinum (IV) derivatives

Abstract Recent investigations into organoplatinum (IV) complexes as potential anticancer agents have shown considerable promise. Unlike cisplatin, these compounds are more stable in physiological environments and generally exhibit fewer side effects. Additionally, chelating aromatic ancillary ligands have been found to enhance the intercalation of metal-based agents into tumor DNA. This study aimed to synthesize novel organoplatinum (IV) complexes with chelating aromatic ligands and evaluate their anticancer efficacy through in vitro assays. Five complexes were synthesized: [Pt(CH3)2X2{2,2’-bipyridine-4,4’-R2}] (X = Br, I; R = H, CO2H) and [{Pt(CH3)3}2(μ-I)2(μ-adenine)]. These were characterized by single crystal X-ray diffraction and assessed for anticancer activity. The MTT assays indicated that the [Pt(CH3)2X2{2,2’-bipyridine}] complexes were more cytotoxic to the ZR-75-1 human breast cancer cell line than cisplatin, with LC50 values of 6.1 µM for X = I, 11.5 µM for X = Br, compared to 16.4 µM for cisplatin. Furthermore, the sulforhodamine B assays conducted by the National Cancer Institute's Developmental Therapeutics Program revealed that [Pt(CH3)3}2(μ-I)2(μ-adenine)] was highly effective against various cancer cell lines. Notably, it showed an LC50 value of 5.20 µM against the glioblastoma multiforme SF-539 cell line, whereas cisplatin and temozolomide had LC50 values exceeding 100 µM. Similarly, [Pt(CH3)3}2(μ-I)2(μ-adenine)] had an LC50 value of 5.99 µM against the renal carcinoma RXF-393 cell line, with cisplatin and cabozantinib showing LC50 values above 100 µM. While these results highlight the superior cytotoxicity of the tested organoplatinum (IV) complexes, further research and development are required before these compounds can be considered for commercial use as chemotherapy drugs. Citation Format: William A. Howard. In vitro anticancer activities of some organoplatinum (IV) derivatives [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Optimizing Therapeutic Efficacy and Tolerability through Cancer Chemistry; 2024 Dec 9-11; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(12_Suppl):Abstract nr A003

Active Components of 16 Essential Oils and Their Fumigation Effects on Galleria mellonella (Lepidoptera: Pyralidae)

The greater wax moth (GWM, Galleria mellonella) is a prevalent pest of the honeybee and a significant risk to both honeybee populations and honeycomb storage. Research on the toxicity of essential oils (EOs) to GWM larvae has provided promising results, although their ovicidal effects and active ingredients require further study. Identifying effective plant compounds is essential for developing insecticides for GWM control. This study assessed the fumigation efficacy of 16 EOs on GWM eggs and fifth instar larvae and determined the effectiveness of these EOs and their primary components for fumigating fifth larvae. Wintergreen, star anise, and clove oils demonstrated significant insecticidal effects on GWM eggs and fifth instar larvae, resulting in a mortality rate exceeding 80% within 48 h. Gas chromatography-mass spectrometry analysis identified methyl salicylate (93.26%), trans-anethole (87.75%), and eugenol (77.75%) as the primary compounds in wintergreen, star anise, and clove oils, respectively. Further toxicity testing confirmed that these compounds were responsible for the observed insecticidal properties of the EOs. Notably, trans-anethole exhibited the lowest LC50 value (25.22 μL/L) against the fifth instar larvae of GWM and significant toxicity against GWM eggs and fifth instar larvae, suggesting its potential as a viable option for the future control of GWM populations.

Toxicological Effects of Pendimethalin: Behavioral Changes and LC50 Analysis in Cyprinus carpio

The pre-emergent herbicide pendimethalin is a selective dinitroaniline compound that interferes with the production of microtubules, potentially contaminating groundwater. The current investigation sought to ascertain the acute toxicity levels and behavioral effects of pendimethalin (30% EC) on Cyprinus carpio. Finney's probit bioassay method estimated the lethal toxicity LC50 values for commercial-grade herbicide pendimethalin on C. carpio. This method entails fitting the data collected from experiments to a probit model, which converts the results obtained (such as mortality rates) into a normal distribution scale. It is a useful tool in toxicological research since it enables more precise estimations of the LC50. The lethal toxicity (LC50) values of pendimethalin to C. carpio exposed to 24, 48, 72 and 96-hr were determined to be 2.83µL/L, 2.59µL/L, 2.39µL/L and 2.20µL/L based on the mortality estimations. Pendimethalin-induced behavioral abnormalities in C. carpio were investigated using sublethal concentrations (i.e., 1/15th, 1/10th, and 1/5th of the 96-hour LC50 value) at intervals of 0, 7, 14, 21 and 28 days. Our research observed behavioral shifts such as reduced general activity, reduced foraging behavior, diminished schooling behavior, reduced reflex stimuli, increased opercula movements, irregular movements, mucus secretion, enhanced breathing rates and increased surface air gulping. Our studies showed that pendimethalin can produce both mortality and behavioral alterations in Cyprinus carpio, offering important insights into the pendimethalin fatal and sub-lethal effects. These results highlight how crucial it is to keep an eye on herbicide poisoning in aquatic habitats since even sub-lethal levels can have an effect on fish behavior and the general health of the ecosystem.

Immunomodulatory Effects of Nellikai Thenural Against Thiamethoxam-Induced Toxicity in Carassius auratus

The accumulation of pesticides in aquatic ecosystems poses significant risks to non-target organisms, particularly fish populations. The study evaluated the protective effects of Nellikai Thenural, a traditional Siddha formulation containing Emblica officinalis and honey, against thiamethoxam-induced toxicity in Carassius auratus (goldfish). The experimental design comprised four groups: control, Nellikai Thenural-treated (733 μg), thiamethoxam-exposed (114.84 mg/L), and co-administered (thiamethoxam + Nellikai Thenural) groups. The LC50 value of Nellikai Thenural was determined at 916 μg/ml/kg body weight through brine shrimp lethality assay. Hematological parameters revealed significant alterations in thiamethoxam-exposed fish, with decreased RBC count, hemoglobin levels, and WBC count. The administration of Nellikai Thenural effectively restored these parameters toward normal levels. Biochemical markers, including plasma proteins, immunoglobulins, and tissue-specific enzymes (ALP, ACP, AST), showed marked improvement in the co-administered group compared to thiamethoxam-exposed fish. Behavioral observations indicated reduced stress responses and improved swimming patterns in fish treated with Nellikai Thenural. The findings demonstrate the potential of Nellikai Thenural as a natural immunostimulant and protective agent against pesticide-induced toxicity in aquatic organisms.

Insecticidal Activity of Fatty Acids From the Fruit Extract of Momordica cymbalaria Fenzl Ex Naudin, Has Insecticidal Activities on Mosquito Larvae.

The fruit and other parts of Momordica cymbalaria are known to have medicinal properties. The study investigates the chemical composition and functional groups of M. cymbalaria fruits to assess the insecticidal potential of its bioactive metabolites. In silico approach was used to understand the mechanism behind the insecticidal nature of these metabolites. Ethyl acetate extract has 18 compounds, whereas 20 compounds were identified in methanol using gas chromatography-mass spectroscopy analysis. The extracts contain several functional groups, including alkanes, esters, carboxylic acids, amides and aromatic groups. The insecticidal bioassay using methanol and ethyl acetate extracts of M. cymbalaria on Aedes aegypti and Culex quinquefasciatus mosquito larvae shows that the LC50 value for A. aegypti was 65.7ppm, for C. quinquefasciatus was 96.9ppm and for ethyl acetate and methanol extract is 282.36 and 388.09ppm. Molecular docking of secondary metabolites was performed with five insect proteins, namely, odorant binding protein (OBP), cytochrome P450 (CYP450), prophenol oxidase (PPO), arylalkylamine n-acetyltransferease (aaNAT) and sterol carrier protein (SCP). Results show that methyl 6-cis, 9-cis, 11-trans-octadecatrienoate has high binding affinity with sterol carrier protein (SCP-2) besides showing binding with other insect proteins. The data suggest that methyl 6-cis, 9-cis, 11-trans-octadecatrienoate has multiple insecticidal actions and may serve as a green insecticide.

Botanical Pesticides: Role of Ricinus communis in Managing Bactrocera zonata (Tephritidae: Diptera)

The melon fruit fly, Bactrocera zonata (Coquillett) (Diptera: Tephritidae), is a notorious pest, posing a significant threat to a wide range of fruits and vegetables, leading to substantial agricultural losses worldwide. With growing concerns over chemical pesticide resistance and environmental safety, plant-based insecticides have emerged as eco-friendly and economically sustainable alternatives. In this context, the present study delves into the insecticidal potential of Ricinus communis extracts against B. zonata. The crude extract of R. communis was systematically fractionated using a series of organic solvents with increasing polarities. The fraction demonstrating the highest insecticidal activity was further purified for the isolation of bioactive compounds, employing advanced chromatographic techniques such as Column Chromatography, coupled with state-of-the-art analytical methods including Gas Chromatography-Mass Spectrometry (GC-MS) and Fourier Transform Infrared Spectroscopy (FTIR). Bioassays were conducted on B. zonata using the crude extract and its fractions in n-hexane, methanol, and ethyl acetate. Among the isolated compounds, 11,14,17-Eicosatrienoic acid was identified in both the methanol and ethyl acetate fractions. This compound exhibited remarkable insecticidal efficacy, with an LC50 value of 1.36%, a linearity of R2 = 0.64, and a statistically significant probability (p &lt; 0.01). Particularly, 11,14,17-Eicosatrienoic acid emerged as the most potent bioactive agent against B. zonata highlighting its potential as a natural insecticide. These findings underscore the potential of R. communis as a valuable source of bioactive compounds for the sustainable management of B. cucurbitae. This study not only broadens the scope of plant-based pest control strategies but also opens avenues for further exploration of natural compounds in integrated pest management.

Silver-Doped Zinc Ferrite Nanoparticles: Trigger ROS-Dependent Apoptosis and Inhibit Migration in MCF-7 Breast Cancer Cells

This study describes the fabrication of nanostructured silver-doped zinc ferrite nanoparticles (AgxZn1-xFe2O4, where x = 0.0 and 0.05) using a chemical co-precipitation method. Field-emission scanning electron microscopy (FE-SEM) analysis was performed to investigate the surface characteristics and particle size of the pure and Ag-doped nanoparticles. X-ray diffraction (XRD) patterns confirmed the formation of a single-phase cubic structure for the zinc ferrite nanoparticles. The anti-cancer potential of the nanoparticles was evaluated using the MTT assay (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) against human breast cancer cells (MCF-7). The results showed that (AgxZn1-xFe2O4, where x = 0.05) nanoparticles with x = 0.05 exhibited significant cytotoxicity. At a concentration of 100 µg/mL, these nanoparticles reduced cell viability to 26.27%, with a calculated LC50 value (concentration lethal to 50% of cells) of 41.30 µg/mL after 24 hours of treatment. Notably, the LC50 value for (AgxZn1-xFe2O4, where x = 0.05) nanoparticles in normal L929 fibroblast cells was over four times higher compared to MCF-7 cancer cells, indicating a degree of selectivity for cancer cells. Further investigation revealed that (AgxZn1-xFe2O4, where x = 0.05) treatment significantly increased the generation of reactive oxygen species (ROS) within the cancer cells. This was confirmed by fluorescence intensity measurements, which showed a substantial increase from 1260.61 (control) to 15600 for cells treated with (AgxZn1-xFe2O4, where x = 0.05) nanoparticles. This included flow cytometry analysis of apoptosis (programmed cell death), migration assays to evaluate metastasis potential, measurement of antioxidant enzyme activity (SOD and catalase) to understand the impact on the cellular antioxidant system, indirect ELISA to detect caspase activity (a marker of apoptosis), cell cycle analysis, and finally, real-time PCR analysis to determine the mRNA expression of p53, a tumor suppressor gene. The apoptosis assay confirmed a significant increase in apoptotic cells upon treatment with (AgxZn1-xFe2O4, where x = 0.05) nanoparticles. This activity is likely mediated by the generation of ROS and subsequent oxidative stress within the cancer cells. These findings highlight the potential of these nanoparticles as a promising therapeutic strategy for cancer treatment.

Nano-chitosan as a bio-enhancer for improving insecticide formulations: A study on indoxacarb and methomyl against cotton leafworm

This study was designed to improve the effectiveness and safety of two commercial insecticides, Camvaal EC 15 % (indoxacarb) and Nudrin SP 90 % (methomyl), against Spodoptera littoralis (Boisd.) through nanotechnology. Insecticide nanoemulsions were enhanced using nano-chitosan as a natural biopolymer. Nanoformulations of Camvaal and Nudrin were synthesized and characterized by Transmission Electron Microscopy (TEM) and Zetasizer Nano instruments. The insecticidal efficacy against the 4th instar of S. littoralis larvae revealed that the nano-formulations were more effective than the commercial formulations. LC50 values decreased from 0.049 to 0.009 mg/L for Camvaal and from 20.82 to 4.97 mg/L for Nudrin, indicating 81.63 and 76.09 % increased efficiency, respectively. Semi-field persistence studies established higher residual activity of the nano-formulations with LT50 values extending from 16.75 days (commercial) to 40.66 days (nano-formulation with chitosan). Cytotoxicity tests on human skin cells showed that nano-chitosan effectively lowered the toxicity of the insecticides with mortality percentages of 10 % for Camvaal and 12.30 % for Nudrin nano-formulations at 1000 μg/mL, compared to 100 and 73.20 % for the commercial products, respectively. These results reveal that nano-chitosan can be used as a bio-enhancer for the formulation of safer and more effective insecticides for sustainable pest control in agriculture.

Application of bio-based nanopesticides for pine surface retention and penetration, enabling effective control of pine wood nematodes

The Pine wood nematode disease is a significant biological threat to forestry management and ecological restoration worldwide, with chemical control remaining the primary approach. However, the cryptic nature of pine wood nematodes (PWN) limits the effectiveness of conventional pesticides. This study explores the development of a cellulose network carrier-based nanopesticide (Se@CSM/PDA@AZO-CNF) loaded with selenium nanoparticles, offering dual responsiveness to light and temperature. This innovative design enables the precise release of pesticides under natural conditions, supporting a controlled response. Incorporating selenium nanoparticles into the cellulose-based nanopesticide improved pesticide permeability and deposition in pine trees. The contact angle of pesticides on pine needles decreased by 23°, their resistance to washing increased by 39 %, and cumulative release was significantly enhanced under UV light and low temperatures. Fluorescence tracer experiments demonstrated efficient uptake of Se@CSM/PDA@AZO-CNF nanopesticide by PWN. The hydrogel displayed an LC50 value of 29.1 mg/L against PWN. These findings highlight the potential of this nanopesticide to improve pesticide delivery and efficacy in controlling pine wood nematode disease.

Dose-specific Toxicity of Naphthalene (Polycyclic Aromatic Hydrocarbon) and Subsequent Recovery by Humic Feed-O-Fert on Anabas testudineus (Bloch): Blood Biochemical and Morphological Introspections

Polycyclic aromatic hydrocarbons (PAHs) are pervasive contaminants in aquatic ecosystems, yet their specific effects on blood pathophysiology, including alterations in blood biochemical and morphological introspections, remain largely unexplored. As consequence, the present study is aimed to record the toxicity of naphthalene exposure for 21-d under two selected doses 0.7075mg/L (T1) and 1.415mg/L (T2), i.e., 25 and 50% of LC50 value [2.83mg/L] respectively and subsequent recovery with one improved organic solid waste, feed-promoter Humic feed-o-fert (HF) of 0.5g/L for the same duration of 21-d. The results showed significant increment in values in blood biochemical parameters, viz., cholesterol (CHOLES), glucose (GLU), glutamine pyruvic transmission (GPT), calcium (Ca), alkaline phosphatase (ALP), high density lipoprotein (HDL) and low density lipoprotein (LDL), and some displayed decreasing trend like protein (PRO), albumin (ALB) and triglyceride (Trig) under this exposure. During recovery phase with HF, the nature of biochemical changes became reversed showing significant restoration and repairment in comparison to naphthalene treatment. Morphological alterations of blood cells revealed maximum changes and appearance, such as tear drop-like cells (Tr), sickle cells (Sk), swelled cells (Sc) and vacuolated cells (Va) under two doses of exposure in 21-d, but under recovery with HF the cells approached towards regaining the normal contour of leucocytes (L), erythrocytes (Er) and tear drop like cells (Tr). So, it can be inferred that Humic feed-o-fert (HF) here played an important role to resist the haematological impairments in fish against the naphthalene (PAH) exposure. Further, Humic feed-o-fert (HF) may contribute in aquatic ecosystem restoration against the environmental contaminants, especially PAHs in aquaculture.

A novel encapsulation method for lemongrass essential oil in nanoemulsion and SiO2 nanoparticles against the storage mite Aleuroglyphus ovatus (Acari: Acaridae)

Lemongrass essential oil (LEO), which is extracted from Cymbopogon citratus, has emerged as a promising alternative to traditional synthetic pesticides. In the present study, we fabricated pure LEO and its nanomaterials (nanoemulsion [NE] and SiO2 nanoparticles [NPs]) and investigated their acaricidal effects on Aleuroglyphus ovatus (Acari: Acaridae), a common storage pest mite. A loading capacity (LC) of 57.45% was obtained, showing successful encapsulation of LEO in SiNPs. The contact mortality, fumigant mortality, ovicidal activity, repellent activity, and toxic effects of LEO on A. ovatus were investigated. The median lethal concentration (LC50) values of contact mortality of LEO, LEO-NE, and LEO-SiNPs against adult mites were 0.067, 0.053, and 0.019 mg/cm2, respectively, after 24 h of exposure. Similarly, the corresponding LC50 values of fumigant activity were 0.044, 0.096, and 0.067 mg/cm3, respectively. All products had greater contact and fumigant effects on nymphs and larvae than they did on adults. After 5 days of exposure to the products, LEO-NE and LEO-SiNPs had greater inhibitory effects on hatching than did pure LEO. LEO-SiNPs exhibited a rapid and significant repellent effect at 3 h (82.22%) and were effective even after 24 h (35.56%), indicating their persistent and long-term acaricide activity. A study of toxicity symptom revealed two different manifestations of toxicity in mites after exposure to these products (knock-down type and immobilized type). Taken together, these findings suggest that LEO and its nanomaterials exhibit significant acaricidal activity against A. ovatus.

Sensitivity of the pathogen of barley brown rust (&lt;i&gt;Puccinia hordei&lt;/i&gt; G.H. Otth.) to fungicides – derivatives of triazoles and strobilurins

The sensitivity of the North Caucasian population of the pathogen of barley brown rust (Puccinia hordei G.H. Otth.) to fungicides derived from triazoles and strobilurines (preparations Amistar Gold, SK; Amistar Extra, SK; Baliy, KME; Delaro, KS) was determined. The work was carried out under controlled conditions of the greenhouse complex of the Federal National Research and Development Fund on winter barley of the susceptible Vivat variety of the Agricultural Scientific Center “Donskoy”. Winter barley plants in the germination phase were infected with the North Caucasian population of the barley brown rust pathogen. Fungicide treatment was carried out at the first signs of the disease with application rates of 0 (control, without treatment), 50, 100, 150 and 200% (the recommended application rate is assumed to be 100%). It was found that when treating infected barley plants with the fungicide Baliy, KME with different application standards, the biological effectiveness varied from 87.3 to 100%, Delaro, KS – from 78.1 to 100%, Amistar Extra, SK – from 79.2 to 100%, Amistar Gold, SK – from 85.3 to 100%. The use of the recommended dose of treatment(100%) contributed to a decrease in the development of brown rust in all variants by more than 96.9%. When using increased rates of fungicides (150, 200%), the biological efficiency was 100%. The high sensitivity of the North Caucasian population of the pathogen P. hordei to the active substances of the studied fungicides has been proven. For all the studied drugs, the values of LC50 and LC95 were significantly lower in comparison with the recommended concentration in the working solution. The result obtained was due to the content of active substances in fungicides from different chemical classes with different mechanisms of action, which provided high efficiency in suppressing the development of barley brown rust and reduced the risk of resistance.

Effects of atrazine, diuron and glyphosate mixtures on zebrafish embryos: acute toxicity and oxidative stress responses.

Synthetic pesticides are known for their toxic effects on non-target aquatic organisms. However, little is known about their effects when present in mixtures, which are closer to realistic exposure scenarios. Therefore, this study evaluates the toxicity of pesticides such as diuron, atrazine and glyphosate, individually and in combination, in zebrafish embryos, investigating their mechanisms of oxidative stress. The results revealed acute toxicity for diuron and atrazine, with LC50 values of 9.6 mg/L and 53.57 mg/L for 96-h-old zebrafish, respectively. On the other hand, no effect was observed for glyphosate alone at the maximum concentration tested (100 mg/L). The mixture of diuron and atrazine showed a synergistic effect, resulting in a decrease in the LC50 of each pesticide. Mixtures of diuron + glyphosate and atrazine + glyphosate were considered additive and antagonistic, respectively. All biomarkers analyzed (AChE, LDH, GST, CAT and GPx) showed significant changes. Furthermore, an increase in ROS production was observed in larvae exposed to individual and in the mixture composed of atrazine and diuron. These findings indicate that atrazine and diuron exhibit increased toxicity when combined, with their mechanisms of action-both in isolation and in mixtures-being at least partially linked to oxidative stress.

Monitoring the insecticide susceptibility of a newly introduced invasive species, Tuta absoluta (Meyrick), in China

The South American tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a newly introduced invasive destructive pest that poses a major threat to tomato production in China. Chemical control is a predominantly measure for controlling this pest. Monitoring of insecticide efficacy is the basic tool for proactive evidence-based resistance management. As a new invasive species, the insecticide susceptibility of T. absoluta to main insecticides has been uncertainty so far in China. Here, we investigated the insecticide susceptibilities of seven populations (Yunnan, Guizhou, Sichuan, Gansu, Inner Mongolia, Shanxi and Xinjiang) of T. absoluta across China. The response of these populations was evaluated through laboratory bioassays with the main insecticides used for T. absoluta control: chlorantraniliprole, chlorpyrifos, indoxacarb, emamectin benzoate, spinosad and Bacillus thuringiensis. Analysis of the results showed the largest LC50 values for chlorpyriphos were generated in populations from Shanxi and Yunnan, resulting in 22.59-fold and 11-fold differences, respectively, compared with the values generated in the most susceptible population (Inner Mongolia). The LC50 values observed for chlorantraniliprole in Shanxi and Gansu were 24.66-fold and 20.83-fold greater, respectively, than the LC50 value observed in the most susceptible population (Guizhou). However, almost all populations of T. absoluta presented low resistance levels to indoxacarb, emamectin benzoate, spinosad and B. thuringiensis. Our study sheds light on most insecticides can provide sufficient control of T. absoluta in China, however, scientific selection and use of insecticides, such as rotational use of insecticides of different modes of action classes, also need to adopt as soon as possible, because a moderate level of resistance has already been observed somewhere on chlorantraniliprole and chlorpyrifos.

Effects of copper nanoparticles synthesized from the entomopathogen Metarhizium robertsii against the dengue vector Aedes albopictus (Skuse, 1894).

Aedes albopictus, known as the Asian tiger mosquito, is a significant vector for dengue fever, chikungunya, zika virus, yellow fever. Current control methods rely on chemical insecticides, which face challenges such as resistance, environmental harm, and impact on non-target species Eudrilus eugeniae and Artemia salina. This study evaluates the toxic effects of biogenic copper nanoparticles (CuNPs) synthesized using Metarhizium robertsii intracellular extract obtained from our previous research. The CuNPs were tested against A. albopictus and non-target species at 24 and 48 hours post-treatment. Results demonstrated that entomopathogenic fungi-derived CuNPs exhibited potent mosquitocidal activity, resulting in 97.33% mortality in larvae, 93.33% in pupae, and 74.66% in adults at 48 hours post-treatment. The CuNPs derived from M. robertsii showed lower LC50 values of 74.873 mg/L in larvae, 76.101 mg/L in pupae, and 136.645 mg/L in adults at 48 hours post-treatment. Additionally, 12 hours post-treatment, catalase (an antioxidant enzyme) activity decreased 1.5-fold in a dose-dependent manner, while glutathione S-transferase (a detoxification enzyme) activity increased 7.8-fold. CuNPs demonstrated lower toxicity to non-target species, with 24% mortality in A. salina and 24.44% mortality in E. eugeniae at 24 hours post-treatment. The LC50 values were 634.747 mg/L for A. salina and 602.494 mg/L for E. eugeniae at 24 hours post-treatment. These findings indicate that entomopathogenic fungi-derived CuNPs are a promising, target-specific candidate for controlling A. albopictus at various life stages (larvae, pupae, and adults).

Discovery of new insecticidal cyclic hexapeptides from Fusarium tricinctum HM76 and their biosynthesis

Fungi often produce a variety of natural products that are toxic to insects, making them an important resource for the discovery of new insecticides. In previous screenings, the crude extract from the wheat pathogen Fusarium tricinctum HM76 exhibited notable insecticidal activity. A chemical investigation of the extract led to the isolation of six undescribed cyclic hexapeptides Futrines (1–6). Their structures were determined through elucidation of NMR and HRESIMS data, as well as chiral HPLC analysis. All the isolated compounds were tested for insecticidal activities against Aphis citricola Van der Goo and Tetranychus cinnabarinus Boisduval. Notably, compounds 2 and 6 demonstrated significant insecticidal activities against T. cinnabarinus and A. citricola, with LC50 and LD50 values of 0.212 mg/mL and 2.230 ng/nymph, respectively. Additionally, the biosynthetic gene cluster responsible for the production of futrines was identified through gene knockout, offering insight into their biosynthetic mechanism. These findings highlight the potential of these cyclic hexapeptides as promising candidates for new insecticide development.