Challenge of Utilization Vegetal Extracts as Natural Plant Protection Products

Uptake and Biotransformation of Guvermectin in Three Crops after In Vivo and In Vitro Exposure

Guvermectin, as a novel nucleoside-like biopesticide, could increase the rice yield excellently, but the potential environmental behaviors remain unclear, which pose potential health risks. Therefore, the uptake and biotransformation of guvermectin in three types of crops (rice, lettuce, and carrot) were first evaluated with a hydroponic system. Guvermectin could be rapidly absorbed and reached equilibrium in roots (12-36 h) and shoots (24-60 h) in three plants, and guvermectin was also vulnerable to dissipation in roots (t1/2 1.02-3.65 h) and shoots (t1/2 9.30-17.91 h). In addition, 8 phase I and 2 phase II metabolites, transformed from guvermectin degradation in vivo and in vitro exposure, were identified, and one was confirmed as psicofuranine, which had antibacterial and antitumor properties; other metabolites were nucleoside-like chemicals. Molecular simulation and quantitative polymerase chain reaction further demonstrated that guvermectin was metabolized by the catabolism pathway of an endogenous nucleotide. Guvermectin had similar metabolites in three plants, but the biotransformation ability had a strong species dependence. In addition, all the metabolites exhibit neglectable toxicities (bioconcentration factor <2000 L/kg b.w., LC50,rat > 5000 mg/kg b.w.) by prediction. The study provided valuable evidence for the application of guvermectin and a better understanding of the biological behavior of nucleoside-like pesticides.

Chemical Composition, Repellent, and Phytotoxic Potentials of the Fractionated Resin Essential Oil from Araucaria heterophylla Growing in Tunisia

The resin essential oil (REO) of the Tunisian Araucaria heterophylla trunk bark was investigated for its chemical composition. Then, it was evaluated for its insecticidal and allelopathic activities. The REO was obtained by hydrodistillation for 9 h (yield of 4.2 % w/w). Moreover, fractional hydrodistillation was carried out at 3-hour intervals, resulting in 3 fractions (R1-R3), to facilitate chemical identification and localization of the aforementioned biological activities. GC/MS analysis of the obtained samples allowed the identification of 25 compounds, representing between 91.2 and 96.3 % of their total constituents, which consisted predominantly of sesquiterpene hydrocarbons, oxygenated sesquiterpenes and diterpene hydrocarbons. α-Copaene (10.8 %), γ-muurolene (5.8 %), α-copaen-11-ol (7.8 %), spathulenol (10.5 %), 15-copaenol (8.2 %), ylangenal (10.3 %), dehydrosaussurea lactone (7.7 %), and sandaracopimaradiene (11.4 %) were identified as major compounds. The second part aimed to assess the impact of the A. heterophylla EO and its three fractions for their insecticidal and repellent activity against Tribolium castaneum (Herbst), a stored grain pest, of which a strong repellent activity was noted. In addition, the studied samples showed high phytotoxic effects against Lactuca sativa. The third fraction (R3) performed a total inhibitory potential on seed germination and seedling growth of the target plant. Furthermore, alongside this discovery, an estimation was conducted through molecular docking analysis. Wherein the main compounds of the studied samples were docked into the active pocket of protoporphyrinogen IX oxidase (PDB: 1SEZ), a key enzyme in chlorophyll biosynthesis. Thus, it is recommended to use the REO of A. heterophylla as a natural herbicide.

The Repellent Capacity against Sitophilus zeamais (Coleoptera: Curculionidae) and In Vitro Inhibition of the Acetylcholinesterase Enzyme of 11 Essential Oils from Six Plants of the Caribbean Region of Colombia

The repellent capacity against Sitophilus zeamais and the in vitro inhibition on AChE of 11 essential oils, isolated from six plants of the northern region of Colombia, were assessed using a modified tunnel-type device and the Ellman colorimetric method, respectively. The results were as follows: (i) the degree of repellency (DR) of the EOs against S. zeamais was 20-68% (2 h) and 28-74% (4 h); (ii) the IC50 values on AChE were 5-36 µg/mL; likewise, the %inh. on AChE (1 µg/cm3 per EO) did not show any effect in 91% of the EO tested; (iii) six EOs (Bursera graveolens-bark, B. graveolens-leaves, B. simaruba-bark, Peperomia pellucida-leaves, Piper holtonii (1b*)-leaves, and P. reticulatum-leaves) exhibited a DR (53-74%) ≥ C+ (chlorpyrifos-61%), while all EOs were less active (8-60-fold) on AChE compared to chlorpyrifos (IC50 of 0.59 µg/mL). Based on the ANOVA/linear regression and multivariate analysis of data, some differences/similarities could be established, as well as identifying the most active EOs (five: B. simaruba-bark, Pep. Pellucida-leaves, P. holtonii (1b*)-leaves, B. graveolens-bark, and B. graveolens-leaves). Finally, these EOs were constituted by spathulenol (24%)/β-selinene (18%)/caryophyllene oxide (10%)-B. simaruba; carotol (44%)/dillapiole (21%)-Pep. pellucida; dillapiole (81% confirmed by 1H-/13C-NMR)-P. holtonii; mint furanone derivative (14%)/mint furanone (14%)-B. graveolens-bark; limonene (17%)/carvone (10%)-B. graveolens-leaves.

Efficacy of Lamium album as a natural fungicide: impact on seed germination, ergosterol, and mycotoxins in Fusarium culmorum-infected wheat seedlings

Fusarium culmorum is a major wheat pathogen, and its secondary metabolites (mycotoxins) cause damage to plants, animals, and human health. In the era of sustainable agriculture, eco-friendly methods of prevention and control are constantly needed. The use of plant extracts as biocontrol agents has gained popularity as they are a source of active substances that play a crucial role in fighting against phytopathogens. This study evaluated the impact of Lamium album on wheat seed germination and seedling growth. In a pot experiment, the effect of L. album on wheat seedlings artificially inoculated with F. culmorum was evaluated by measuring seedling growth parameters, and by using chromatographic methods, ergosterol and mycotoxins levels were analyzed. The results showed that the phytotoxic effect of L. album flower extracts on wheat seed germination and seedling growth was concentration dependent. The radicle length was also reduced compared to the control; however, L. album did not significantly affect the dry weight of the radicle. A slight phytotoxic effect on seed germination was observed, but antifungal effects on artificially infected wheat seedlings were also confirmed with the reduction of ergosterol level and mycotoxins accumulation in the roots and leaves after 21 days of inoculation. F. culmorum DNA was identified in the control samples only. Overall, this study is a successful in planta study showing L. album flower extract protection of wheat against the pathogen responsible for Fusarium crown and root rot. Further research is essential to study the effects of L. album extracts on key regulatory genes for mycotoxin biosynthetic pathways.

Walnut By-Products and Elderberry Extracts-Sustainable Alternatives for Human and Plant Health

A current alternative for sustainable development through green chemistry is the replacement of synthetic compounds with natural ones through the superior capitalization of natural resources, with numerous applications in different fields. The benefits of walnuts (Juglans regia L.) and elderberries (Sambucus nigra L.) have been known since ancient times, due to the presence of phytochemicals such as flavonoids, polyphenols, carotenoids, alkaloids, nitrogen-containing compounds, tannins, steroids, anthocyanins, etc. These active compounds have multiple biological activities for human health, including benefits that are antibacterial, antioxidant, anti-inflammatory, antidiabetic, hepatoprotective, antihypertensive, neuroprotective, etc. Like other medicinal plants, the walnut and the elderberry possess important phytosanitary properties (antibacterial, antifungal, and insecticidal) and their extracts can also be used as environmentally safe biopesticides, with the result that they constitute a viable and cheap alternative to environmentally harmful synthetic products. During recent years, walnut by-products and elderberries have attracted the attention of researchers, and investigations have focused on the species' valuable constituents and active properties. Comparing the information from the literature regarding the phytochemical profile and biological activities, it is highlighted that, apart from the predominant specific compounds, the walnut and the elderberry have common bioactive compounds, which come from six classes (phenols and derivatives, flavonoids, hydroxycinnamic acids, tannins, triterpenoids, and phytosteroids), and act on the same microorganisms. From this perspective, the aim of this review is to provide an overview of the bioactive compounds present in the different constitutive parts of walnut by-products and elderberries, which present a specific or common activity related to human health and the protection of agricultural crops in the context of sustainable development.

Pesticides vs. Biopesticides: From Pest Management to Toxicity and Impacts on the Environment and Human Health

The environmental pollution that occurs in direct response to the widespread use of man-made/conventional pesticides results from many chemicals that require a long period of time, often decades, to degrade. The synthetic nature of pesticides also harms animals, beneficial insects, microorganisms, and plants, as well as humans. Fortunately, however, there are many natural pesticides, the so-called biopesticides, that are also effective against pests and more importantly, do not interfere with the well-being of ecosystems. Consequently, most biopesticides are safer for use around people and pets than man-made pesticides because, for example, they can be easily washed away from fruits and vegetables. The natural habitat is a rich resource with a wide selection of plants, many of which are also used to treat diseases in humans, animals, and plants. Out of concern for public health, environmental safety, and the stringent regulation of pesticide residues in agricultural commodities, the use of biopesticides is becoming increasingly important, but questions regarding potential pest resistance to these products may arise, just as is the case with conventional pesticides. Therefore, the performance and potential role of biopesticides in the management of plant pests should be prioritized due to their sustainability and importance to human and environmental welfare. In this review, we propose to highlight a scenario in which we discuss in detail the main constraints posed by the use of pesticides compared to biopesticides, starting with issues regarding their definition and continuing on to issues related to their toxicity and their impact on the environment and human health.

Growth and metabolism of pea (Pisum sativum) via biostimulants based on greener ZnO nanoparticles

The purpose of this study was to identify the most important physiological and biological effects of green synthesis ZnO nanoparticles at a size of 65 nm, biostimulant (Folcare) and interaction biostimulant ZnO NPs on plant growth and metabolism. As our understanding of biostimulants' preventive and restorative modes of action has increased, it is critical to maintain the best crop output and quality possible. The reduction of fertilizers must be substituted by strategies that improve the nutrients uptake or their utilization by the plants. New processing methods are required as an efficient green process or an integrated (hybrid) process for different new technologies of interest. The effects of NPs, biostimulant, and combination ZnO NPs biostimulant on plant cell metabolism were examined in cytosol, chloroplast, and mitochondria of cells from the stems, roots, and leaves. The interaction NPs/biostimulant had a beneficial effect on the morphological and physiological indicators of plant health than when nanoparticles and biostimulant are applied separately. Folcare biostimulant coupled with zinc oxide nanoparticles improved pea crops growth. The improved of the quality of pea plants can be explained at least, in part, by increase in antioxidant activities during plant growth phenophase.

Effects of Flavonoids and Phenols from Moringa oleifera Leaf Extracts on Biofilm Processes in Xanthomonas campestris pv. campestris

Xanthomonas campestris pv. campestris is the causal agent of black rot in crucifers, a plant disease with significant economic impact. Xanthomonadaceae is a large family of Gram-negative bacteria that cause symptoms by blocking water flow in plants by invading the xylem. To accomplish this, the main mechanism the bacteria use to adapt to environmental changes and colonize tissues is biofilm formation. In recent years, growing interest in natural antimicrobial compounds has led to the study of different phytocomplexes derived from plants. In this work, Moringa oleifera was selected, as its leaves are rich in phenols, essential oils, and vitamins that exert antibacterial activity. X. campestris pv. campestris biofilm, one of its major virulence factors, was studied. Biofilm formation and removal were analyzed on abiotic and biotic surfaces with and without M. oleifera leaf extracts. The data from the analysis show that Moringa oleifera leaf extracts and single phenols were able to inhibit biofilm growth on abiotic surfaces, but the activity of the whole phytocomplex was significantly higher compared to that of individual phenols. The effect of Moringa oleifera extracts on cabbage leaves in vivo was also found to be very important, as scanning electron microscopy showed that treatment with the extracts led to clear unblocking of the xylem, implying many advantages for use in black rot control.

Phytochemicals as alternative fungicides for controlling plant diseases: A comprehensive review of their efficacy, commercial representatives, advantages, challenges for adoption, and possible solutions

Fungal infections are responsible for about 70-80% of the losses in agricultural production brought on by microbial diseases. Synthetic fungicides have been employed to manage plant diseases caused by phytopathogenic fungi but their use has been criticized due to unfavorable side effects. As alternative strategies, botanical fungicides have caught the interest of many researchers in recent years. There are numerous experimental studies on the fungicidal activities of phytochemicals against phytopathogenic fungi, but there is not a thorough review article that summarizes these experimental studies. The purpose of this review is therefore to consolidate data from in vitro and in vivo studies on the antifungal activity of phytochemicals reported by various researchers. This paper describes antifungal activities of plant extracts and compounds against phytopathogenic fungi, approved botanical fungicides, their benefits, obstacles and mitigation strategies. Relevant sources were collected using online data bases such as Google Scholar, PubMed and Science Direct, and comprehensively reviewed for preparation of this manuscript. This review revealed that phytochemicals are effective to manage plant diseases caused by phytopathogenic fungi. Botanical fungicides are endowed with benefits such as resistance inhibition, being ecofriendly, effective, selective, and more affordable compared to synthetic fungicides. However, there are only small number of approved botanical fungicides due to the many challenges that hinder their adoption and utilization for a wider scale production. Farmers' reluctance, lack of standardized formulation techniques, strict legislation, rapid degradation, and other factors hinder their adoption and utilization. The ways to address these challenges include increasing awareness among farmers, conducting more research to identify potential plants with fungicidal properties, standardizing extraction and formulation techniques, implementing the idea of plant breeding to increase bioactive agents, identifying favorable environments for site-specific plant species production, discovering synthetic analogues of the active ingredient to maintain quality standards, establishing reasonable regulation procedures and price points for a quicker market introduction. To put all these into practice, we recommend collaboration of regulatory agencies and researchers from a variety of fields.

Aqueous Extracts of Organic Mulch Materials Have Nematicide and Repellent Effect on Meloidogyne incognita Infective Juveniles: A Laboratory Study

While the nematicidal effectiveness of mulching against root-knot nematodes (Meloidogyne spp.) is calculated within organic crop protection, underlying mechanisms are not yet fully explored. Laboratory experiments were set up to determine whether mulch-derived substances cause mortality directly, or repel Meloidogyne juveniles from crop rhizosphere. Mortality and area choice tests were conducted with mulch-derived extracts, supported by the measurements on tannic acid content and the pH values of extracts as supplementary examinations. In our study, leaf litter and straw extracts were generally found lethal to the juveniles, which is in line with the results from area preference tests. However, compost extract had no effect on Meloidogyne incognita juveniles. Tannic acid content showed positive correlation with mortality only in the case of straw and sycamore leaf litter extracts. Tannic acid and pH weakly correlated with repellent effect of the applied extracts generally. Our results have inspired further experiments to explore nematicidal components of leaf litters, contributing to the development of a new approach in crop protection based on the repellent effect of these materials.

Hydrolysis, Photolysis, and Biotoxicity Assessment of a Novel Biopesticide, Guvermectin

Guvermectin is a biopesticide isolated from the secondary metabolites of Streptomyces sp. NEAU6, an endogenous actinomyces of a Chinese medicine named Paris polyphylla. However, the environmental degradation behavior and biotoxicity of guvermectin are still unclear, which may affect its rational application. Therefore, the degradation of guvermectin in water at different pH values (pH 4, pH 6, pH 7, and pH 9) and with or without light was investigated in the laboratory. The results showed that guvermectin could be degraded in pH 4 solution, and the presence of light irradiation enhanced the degradation process with a DT₅₀ of 2.95 and 12 days for photolysis and hydrolysis, respectively. However, guvermectin was fairly stable in other conditions. Three products transformed from guvermectin degradation were identified by UPLC-QTOF/MS. Biotoxicity assessment was performed on Danio rerio and Daphnia magna Straus by ECOSAR prediction and in vivo biological tests. The test data showed that guvermectin and its transformation products exhibited low toxicities to D. rerio and D. magna Straus (LC₅₀/EC₅₀ > 100 mg a.i./L), and the transformation products had lower toxicity than their parent substance. The results provided a reference for elucidating the potential risk of guvermectin to nontarget organisms and promoting its rational use.

Phytotoxic, insecticidal, and antimicrobial activities of Ajania tibetica essential oil

The chemical profile of Ajania tibetica essential oil (EO) and its phytotoxic, insecticidal, and antimicrobial activities were assessed. Monoterpenes (79.05%) and sesquiterpenes (10.33%) were dominant in the EO, with camphor, (+/-)-lavandulol and eucalyptol being the major constituents, representing 55.06% of the total EO. The EO possessed potent phytotoxicity against Poa annua and Medicago sativa starting from 0.5 mg/mL, and when the concentration rose to 5 mg/mL, seed germination of both tested species was 100% suppressed. Ajania tibetica EO displayed significant pesticidal activity against Aphis gossypii with an LC50 value of 17.41 μg/mL; meanwhile, the EO also showed antimicrobial activity against Escherichia coli, Bacillus subtilis, Verticillium dahlia and Aspergillus niger using broth microdilution and disc diffusion methods. For the tested bacterial and fungal strains, the EO exhibited a repressing effect, with minimum inhibitory concentrations (MICs) ranging from 0.3125 to 1.25 mg/mL for bacteria and from 1.25 to 2.5 mg/mL for fungi, whereas the minimum microbicidal concentrations (MMCs) were 5 mg/mL for bacteria and 2.5 mg/mL for fungi. Our study is the first report on the chemical profile as well as the phytotoxicity, insecticidal and antimicrobic activity of A. tibetica EO, indicating its potential value as an alternative synthetic pesticide.

Exploring the Antioxidant and Bioinsecticidal Activity of Spontaneous Flora Vegetal Extracts for Plant Protection and Prevention of Soil Contamination

The purpose of this article was to evaluate the application of different plant extracts with bioinsecticidal action and antioxidant activity for plants and soil protection, by substitution of the application of synthetically formulated pesticides with eco-friendly compounds. In this framework, this research focused on the utilization of plant extracts from the spontaneous flora of Moldova (Romania) as bioinsecticides for the control of field pests of the species Leptinotarsa decemlineata and their antioxidant activity. Plant extracts of oregano (Origanum vulgare), yarrow (Achillea millefolium), wormwood (Artemisia absinthium), and cowslip (Primula veris) were assessed for their antioxidant activity by the microplate spectrophotometric-based method (for polyphenols and flavonoids content and for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenger activity) and were characterized by FTIR spectroscopy spectra. To evaluate the bioinsecticidal properties of the plant extracts, the mortality (%) and neuroleptic manifestations appearing in the middle of the monitoring period for larvae and adults of the Leptinotarsa decemlineata species were identified. Mortality (%) was statistically analyzed using a one-way analysis of variance (ANOVA) and the resulting experimental results were compared with the LSD-Fisher’s test (p < 0.05). The highest mortality (%) was observed after 24 h of treatment with extracts of Origanum vulgare at 100% concentration, while the maximum effect was recorded after 48 h for Origanum vulgare at 60% and 100% concentrations.

Medicinal Plant Growth in Heavy Metals Contaminated Soils: Responses to Metal Stress and Induced Risks to Human Health

Accelerating heavy metal pollution is a hot issue due to a continuous growth in consumerism and increased activities in various global industries. Soil contamination with heavy metals has resulted in their incorporation into the human food web via plant components. Accumulation and amplification of heavy metals in human tissues through the consumption of medicinal plants can have hazardous health outcomes. Therefore, in this critical review we aim to bring together published information on this subject, with a special highlight on the knowledge gaps related to heavy metal stress in medicinal plants, their responses, and human health related risks. In this respect, this review outlines the key contamination sources of heavy metals in plants, as well as the absorption, mobilization and translocation of metal ions in plant compartments, while considering their respective mechanisms of detoxification. In addition, this literature review attempts to highlight how stress and defensive strategies operate in plants, pointing out the main stressors, either biotic or abiotic (e.g., heavy metals), and the role of reactive oxygen species (ROS) in stress answers. Finally, in our research, we further aim to capture the risks caused by heavy metals in medicinal plants to human health through the assessment of both a hazard quotient (HQ) and hazard index (HI).

Cyclodepsipeptides: Isolation from Endophytic Fungi of Sarcophyton ehrenbergi and Verification of Their Larvicidal Activity via In-Vitro and In-Silico Studies

Culex pipiens mosquitoes are vectors to many viruses and can transmit diseases such as filariasis and avian malaria. The present study evaluated the larvicidal activity of marine-derived endophytic fungi Aspergillus nomius and Aspergillus flavus from the soft coral Sarcophyton ehrenbergi along with two known cyclodepsipeptide compounds, scopularide A (1) and B (2), isolated from A. flavus extract, against third-instar larvae of C. pipiens, using distilled water as a negative control and toosenedanin as a positive control. The structures of the isolated compounds were confirmed by various spectroscopic analyses. The lethal concentrations (LC₅₀ and LC₉₀) were calculated by probit analysis. Scopularide A was the most potent after 96 h treatment, with LC₅₀ and LC₉₀ values of 58.96 and 994.31 ppm, respectively, and with 82.66% mortality at a concentration of 300 ppm. To unravel the biochemical mechanism of the tested extracts and compounds, their effects against protease, chitinase, phenoloxidases and lipase enzymes from the whole-body tissue of C. pipiens were evaluated after 72 h treatment at LC₅₀ dose. Superior activity was observed for A. flavus extract against all tested enzymes. A molecular docking study was conducted for scopularide A and B on the four tested enzymes, to further verify the observed activity. Results revealed good binding affinities for both compounds as compared to the docked ligands, mainly via a number of hydrogen bonds. This was the first study to report the isolation of endophytic fungi A. flavus and A. nomius from the marine soft coral S. ehrenbergi. The endophytic fungal extract of A. flavus was found to be a promising source for a natural larvicidal agent against C. pipiens populations.

Novel Chitosan-Based Schiff Base Compounds: Chemical Characterization and Antimicrobial Activity

Chitosan (CS) and its derivatives are receiving considerable attention for their great biocompatibility and broad-spectrum activities in many fields. In this work, we aimed to characterize the antimicrobial activity of novel chitosan Schiff bases (CSSB). CS was synthesized by double deacetylation of chitin (Cn) after its extraction from the armors of crustaceans Astacus leptodactylus, and CSSB-1 and CSSB-2 were synthesized by interaction of CS with 4-(2-chloroethyl) benzaldehyde (aldehyde-1) and 4-(bromoethyl) benzaldehyde (aldehyde-2), respectively, at room temperature. The synthesized compounds were characterized by elemental analysis, gel permeation chromatography (GPC), infrared spectroscopy (FTIR), thermogravimetry (TG), and differential scanning calorimetry (DSC). The antimicrobial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria and against yeasts (Candida albicans) was significantly increased due to their higher solubility as compared to unmodified CS opening perspectives for the use of these compounds for antimicrobial prevention in different fields as, for example, food industry, cosmetics, or restoration.

Proteus, Matrine, and Pyridalyl Toxicity and Their Sublethal Effects on Orius laevigatus (Hemiptera: Anthocoridae)

Proteus, matrine, and pyridalyl were tested in the laboratory for their effects upon Orius laevigatus (Fieber), which is a polyphagous predator used for IPM programs of Frankliniella occidentalis (Pergande). Against female adults, the most toxic insecticide was Proteus (LC50 = 44.3 µl L-1), followed by pyridalyl (LC50 = 83.8 µl L-1) and matrine (LC50 = 102.7 µl L-1). The mortality of female adults was checked 24, 48, 72, and 96 h after exposure to 14-d residues of the treatments on strawberry leaves. The residual of Proteus was less toxic; the remaining products caused the lowest mortality at different times after exposure. Sublethal treatments (LC25) significantly prolonged the developmental duration of total immature stages from 17.6 d in control to 21.6 and 20.0 d in Proteus and pyridalyl treatments, respectively. Also, the fecundity of O. laevigatus treated with Proteus, pyridalyl, and matrine decreased to 58.8%, 75.6%, and 96.7%, respectively, in comparison to the control. Compared with the control population (0.118 d-1), the intrinsic rate of increase (r) of F1 generation decreased by 0.053, 0.095, and 0.110 d-1 in Proteus, pyridalyl, and matrine treatments, respectively. The consumption rate of control bugs reached 14.0 thrips during 24 h. The adults fed on Proteus treatment had the lowest consumption rate in this period (9.4 preys). Overall, matrine proved to be harmless with reproductive capacity and r similar to what was recorded in control bugs. We concluded that matrine can be used as an alternative for the synthetic insecticide to integrate with O. laevigatus.

Allelopathic, Phytotoxic, and Insecticidal Effects of Thymus proximus Serg. Essential Oil and Its Major Constituents

The chemical profile of Thymus proximus essential oil (EO) and its allelopathic, phytotoxic, and insecticidal activity was evaluated. Carvacrol, p-cymene, and γ-terpinene were detected as the major components of the EO, representing 85.9% of the total oil. About 50 g fresh plant material of T. proximus in a 1.5-L air tight container completely inhibited the seed germination of Amaranthus retroflexus and Poa anuua. Meanwhile, the EO exhibited potent phytotoxic activity, which resulted in 100% germination failure of both the test species when 2 mg/ml (for A. retroflexus) and 5 mg/ml (for Poa annua) oil was applied. The EO also triggered a significant insecticidal activity on Aphis gossypii with a LC₅₀ value of 6.34 ppm. Carvacrol was identified as the main active compound responsible for both the plant suppressing effect and the insecticidal activity of the EO. Our study is the first on the allelopathic, phytotoxic, and insecticidal activity of T. proximus EO, and the determination of the responsible compound, which indicated their potential of being further explored as environment friendly biopesticides.