Insecticidal potential and repellent and biochemical effects of phenylpropenes and monoterpenes on the red flour beetle, Tribolium castaneum Herbst

Mentha spp. essential oils: toxicity to Alphitobius diaperinus, activity against poultry pathogenic bacteria, and Beauveria bassiana compatibility

The botanical insecticide market is growing because of limitations placed on the use of certain synthetic chemical insecticides. In this sense, the lesser mealworm Alphitobius diaperius (Coleoptera: Tenebrionidae) is the main poultry pest. The insect causes weight loss and damage to the digestive system of poultry, and it is a vector and reservoir of pathogens. Consequently, this study explored the following hypotheses: (i) essential oils (EOs) derived from Mentha spp. are toxic to A. diaperius; (ii) these EOs are compatible with Beauveria bassiana, the natural enemy of the poultry pest, that parasite A. diaperinus; (iii) these EOs also exhibit activity against bacteria that are pathogenic to poultry. In topical applications and ingestion tests, EOs from Mentha arvensis, Mentha spicata, and Mentha piperita were toxic to A. diaperinus. Chromatographic analyses revealed that menthol is the predominant compound in M. arvensis and M. piperita, whereas carvone is the major compound in M. spicata. Both (-)- and (+)-menthol, along with (-)- and (+)-carvone, underwent testing with A. diaperinus. Nevertheless, their activity was not as potent as those of the EOs, suggesting a possible synergistic and/or additive effect. The EOs did not have any adverse effects on the conidial germination, vegetative growth, or conidia production per colony of the entomopathogenic fungus B. bassiana. Consequently, these EOs are compatible with this natural enemy. The EO extracted from M. spicata exhibited significant toxicity against Staphylococcus aureus (ATCC 25923), whereas the remaining EOs displayed moderate toxicity against this bacterium. The EOs derived from Mentha spp., as assessed in this study, hold promise for the development of botanical insecticides tailored for the control of A. diaperinus. These insecticides are selective in favor of the natural enemy B. bassiana and can also serve as effective sanitizers, thanks to their antibacterial properties.

Chemical Composition and Insecticidal Activities of Blumea balsamifera (Sambong) Essential Oil Against Three Stored Product Insects

Blumea balsamifera (L.) DC. (Asteraceae), also known as sambong, is a perennial herb used in China for medicinal purposes. The essential oil (EO) of B. balsamifera was extracted by hydrodistillation. Thirty chemical components of the EO were analyzed by gas chromatography-mass spectrometry (GC-MS) and GC, accounting for 88.0% (w/w) of the total oil. The EO of B. balsamifera was mainly composed of monoterpenes and sesquiterpenes, in which borneol (23.3%), β-caryophyllene (20.9%) and camphor (11.8%) were the major components. The insecticidal activities of the EO and its three main compounds against Tribolium castaneum, Lasioderma serricorne and Sitophilus oryzae were evaluated. The results of bioassays displayed that the EO of B. balsamifera did not have fumigant toxicity to the three target insects, but exhibited significant contact activity against L. serricorne (LD50 = 12.4 μg/adult) and S. oryzae (LD50 = 44.4 μg/adult). Meanwhile, the EO showed a notable repellent effect on T. castaneum at all testing concentrations and a general repellent effect on S. oryzae at high concentrations (78.63 nL/cm2). β-Caryophyllene showed the best performance in the contact toxicity bioassays against the three insects. The results indicated that B. balsamifera has the potential to be used as a source of botanical insecticides for the control of stored-product insects.

Bioactivities of thymol and p-cymene from the essential oil of Adenosma buchneroides against three stored-product insects

The adverse effects of relying solely on synthetic pesticides have become increasingly evident, leading many countries to explore alternatives sourced from plant-based green economies. Essential oil (EO) from stems and leaves of Adenosma buchneroides Bonati (A. buchneroides) was distilled by using hydrodistillation and subjected to gas chromatography-mass spectrometry (GC-MS) for component identification. Subsequently, EO as well as its main constituents (thymol and p-cymene) were tested for their insecticidal activity against the red flour beetle (Tribolium castaneum), the cigarette beetle (Lasioderma serricorne), and the booklouse (Liposcelis bostrychophila). The joint action of thymol and p-cymene produced an additive or synergistic effect. A. buchneroides essential oil (BHO) and the fixed ratio of the main compounds, thymol, and p-cymene both showed significant toxic activity against the target pests. This toxic effect is not simply the sum of individual effects, as it is influenced by various factors such as insect species and mode of action. These findings imply that the BHO and its phytoconstituents possess great potential to develop plant-derived biopesticides that will be safe for humans and the environment.

Plant Essential Oils as Biopesticides: Applications, Mechanisms, Innovations, and Constraints

The advent of the "Green Revolution" was a great success in significantly increasing crop productivity. However, it involved high ecological costs in terms of excessive use of synthetic agrochemicals, raising concerns about agricultural sustainability. Indiscriminate use of synthetic pesticides resulted in environmental degradation, the development of pest resistance, and possible dangers to a variety of nontarget species (including plants, animals, and humans). Thus, a sustainable approach necessitates the exploration of viable ecofriendly alternatives. Plant-based biopesticides are attracting considerable attention in this context due to their target specificity, ecofriendliness, biodegradability, and safety for humans and other life forms. Among all the relevant biopesticides, plant essential oils (PEOs) or their active components are being widely explored against weeds, pests, and microorganisms. This review aims to collate the information related to the expansion and advancement in research and technology on the applications of PEOs as biopesticides. An insight into the mechanism of action of PEO-based bioherbicides, bioinsecticides, and biofungicides is also provided. With the aid of bibliometric analysis, it was found that ~75% of the documents on PEOs having biopesticidal potential were published in the last five years, with an annual growth rate of 20.51% and a citation per document of 20.91. Research on the biopesticidal properties of PEOs is receiving adequate attention from European (Italy and Spain), Asian (China, India, Iran, and Saudi Arabia), and American (Argentina, Brazil, and the United States of America) nations. Despite the increasing biopesticidal applications of PEOs and their widespread acceptance by governments, they face many challenges due to their inherent nature (lipophilicity and high volatility), production costs, and manufacturing constraints. To overcome these limitations, the incorporation of emerging innovations like the nanoencapsulation of PEOs, bioinformatics, and RNA-Seq in biopesticide development has been proposed. With these novel technological interventions, PEO-based biopesticides have the potential to be used for sustainable pest management in the future.

The Potential of Magnolia spp. in the Production of Alternative Pest Control Substances

The irrational use of synthetic pesticides in agriculture has had negative impacts on ecosystems and contributed to environmental pollution. Botanical pesticides offer a clean biotechnological alternative to meet the agricultural challenges posed by pests and arthropods. This article proposes the use of fruit structures (fruit, peel, seed, and sarcotesta) of several Magnolia species as biopesticides. The potential of extracts, essential oils, and secondary metabolites of these structures for pest control is described. From 11 Magnolia species, 277 natural compounds were obtained, 68.7% of which were terpenoids, phenolic compounds, and alkaloids. Finally, the importance of a correct management of Magnolia species to ensure their sustainable use and conservation is stressed.

Cytochrome P450 gene CYP6BQ8 mediates terpinen-4-ol susceptibility in the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Cytochrome P450 proteins (CYPs) in insects can encode various detoxification enzymes and catabolize heterologous substances, conferring tolerance to insecticides. This study describes the identification of a P450 gene (CYP6BQ8) from Tribolium castaneum (Herbst) and investigation of its spatiotemporal expression profile and potential role in the detoxification of terpinen-4-ol, a component of plant essential oils. The developmental expression profile showed that TcCYP6BQ8 expression was relatively higher in early- and late-larval stages of T. castaneum compared with other developmental stages. Tissue expression profiles showed that TcCYP6BQ8 was mainly expressed in the head and integument of both larvae and adults. The expression profiling of TcCYP6BQ8 in developmental stages and tissues is closely related to the detoxification of heterologous substances. TcCYP6BQ8 expression was significantly induced after exposure to terpinen-4-ol, and RNA interference against TcCYP6BQ8 increased terpinen-4-ol-induced larval mortality from 47.78 to 66.67%. This indicates that TcCYP6BQ8 may be involved in T. castaneum's metabolism of terpinen-4-ol. Correlation investigation between the CYP6BQ8 gene and terpinen-4-ol resistance in T. castaneum revealed that the TcCYP6BQ8 gene was one of the factors behind T. castaneum's resistance to terpinen-4-ol. This discovery may provide a new theoretical foundation for future regulation of T. castaneum.

Insecticidal Activity of a Component, (-)-4-Terpineol, Isolated from the Essential Oil of Artemisia lavandulaefolia DC. against Plutella xylostella (L.)

Plutella xylostella (L.) is one of the most serious pests of cruciferous vegetables. Our previous work demonstrated that the essential oil of Artemisia lavandulaefolia DC. exhibits promising insecticidal activities against P. xylostella. This study further characterizes the key components that are responsible for the insecticidal effect. In total, 47 compounds (96.52% of the total compounds) were identified from the total oil using GC-MS, and the major compounds were eucalyptol (21.57%), D(+)-camphor (17.33%), (-)-4-terpineol (9.96%) and caryophyllene oxide (10.96%). Among them, (-)-4-terpineol showed significantly larvicidal and fumigant activities against P. xylostella. The LD₅₀ of (-)-4-terpineol was 43.15 mg/mL at 12 h and 31.22 mg/mL at 24 h for 3rd instar larvae, and the LC₅₀ for adults was 8.34 mg/mL at 12 h and 7.35 mg/mL at 24 h. In addition, the adults treated with (-)-4-terpineol showed varying degrees of inhibitory activity toward glutathione S-transferase, catalase, acetylcholinesterase and Na⁺/K⁺-ATPase at different post-treatment intervals and concentrations. The results indicate that (-)-4-terpineol has promising insecticidal activities against P. xylostella, and it has good inhibitory effects on the four enzymes of P. xylostella adults.

Chemical Composition of Essential Oils from Three Rhododendron Species and Their Repellent, Insecticidal and Fumigant Activities

In order to assess the repellent, contact, and fumigant properties of three essential oils (EOs) from Rhododendron species in China against adults of Tribolium castaneum, Lasioderma serricorne, Sitophilus oryzae, this study analyzed their chemical components. The three EOs were extracted by hydrodistillation from leaves of Rhododendron species, including R. davidsonianum, R. heliolepis and R. strigillosum. Sesquiterpenoids and monoterpenes were the main components of the three EOs that were detected by GC/MS and GC-FID. α-Pinene, β-Caryophyllene, α-Humulene, Kaura-16-ene and Sandaracopimaradiene was among the comparatively high components. In this study, the EOs of three Rhododendron species demonstrated repellent activities against T. castaneum and L. serricorne in 2 h and 4 h exposure, but the repellent activity to S. oryzae was not obvious. The three EOs from R. davidsonianum, R. heliolepis and R. strigillosum also had contact activities and fumigant activities against the Tribolium castaneum (LC50 =13.453 mg/L air, 4.728 mg/L air, 4.529 mg/L air and LD50 =15.027 μg/adult, 15.017 μg/adult, 10.994 μg/adult, respectively), Lasioderma serricorne (LC50 =8.584 mg/L air, 6.044 mg/L air, 6.355 mg/L air and LD50 =4.566 μg/adult, 7.067 μg/adult, 3.652 μg/adult, respectively) and Sitophilus oryzae (LC50 =3.304 mg/L air, 6.795 mg/L air, 7.130 mg/L air and LD50 =10.200 μg/adult, 15.021 μg/adult, 9.178 μg/adult, respectively) adults. The above results not only opened a potential prospect for applications of Rhododendrons in the prevention and control of insects in stored products, but also provide a basis for the comprehensive utilization of the rich natural Rhododendron plant resources.

Origanum majorana Essential Oil-A Review of Its Chemical Profile and Pesticide Activity

Origanum majorana is a medicinal and aromatic plant that belongs to the Lamiaceae family. It is cultivated in several parts of the world and, due to its splendid aroma and taste, is widely used for culinary purposes and in perfumes. The essential oil of the plant, to which is attributed its aroma, contains many secondary metabolites with valuable biological activity. One of them is the pesticide activity, which has attracted much interest. Given the necessity of replacing synthetic pesticides, essential oils are studied in an attempt to find naturally derived products. Thus, the aim of this review paper is to discuss the chemical profile of O. majorana essential oil and to present data regarding its insecticidal, repellent and fumigant activity. Data were collected from 1992 to 2022. Databases, including PubMed, Google Scholar, ScienceDirect and Scopus, were used for the research, and keywords, including O. majorana, sweet marjoram, essential oil, volatiles, pesticide, insecticide and repellent activity, were used. The results of this review paper indicate that O. majorana essential oil can be an alternative agent to manage pests. However, still, much research should be conducted to evaluate its toxicity against beneficial insects and to ensure its safety for human health.

TRPA1-mediated repellency behavior in the red flour beetle Tribolium castaneum

The sensory perception of irritant chemicals results in escape and repellency behavioral patterns in insects. Transient receptor potential channels are cation channels that function as sensor proteins for several types of signals, such as light, sound, temperature, taste, as well as chemical and physical stimuli; among these, the TRPA channel is widely conserved and activated by irritant chemicals. Certain plant-derived essential oils (EOs), produced by secondary metabolism, are mixtures of volatile compounds, which are used as repellents because they contain environmentally sustainable ingredients. Citronellal, which is present in citronella EO from Cymbopogon species, is a potentially viable insect repellent; however, the repellency capability against coleopteran beetles remains limited. We investigated the citronellal-derived repellency behavior for the red flour beetle Tribolium castaneum, in which TcTRPA1 and odorant receptor co-receptor (Orco) expressions were mediated by RNA interference. Area-preference tests showed dose-dependent repellency behavior for citronellal; additionally, both TcTRPA1 and TcOrco double-strand RNA (dsRNA) micro-injection showed clear TcTRPA1 and TcOrco transcript reductions, and only TcTRPA1 dsRNA treatment significantly impaired repellency behavior. The relative expression level of the TcTRPA1 transcripts, evaluated by quantitative reverse-transcription PCR (qRT-PCR), revealed dominant expression in the antennae, indicating the antennae-expressed TcTRPA1-mediated repellency behavior.

Effectiveness of Herbal Essential Oils as Single and Combined Repellents against Aedes aegypti, Anopheles dirus and Culex quinquefasciatus (Diptera: Culicidae)

Mosquito repellents reduce human-vector contact of vector-borne diseases. We compared the repellent activity of 10 undiluted essential oils (anise, basil, bergamot, coriander, patchouli, peppermint, petitgrain, rosemary, sage and vetiver) against A. aegypti, A. dirus and C. quinquefasciatus using the arm-in-cage method. Petitgrain oil was the most effective against A. aegypti (270 min). Peppermint oil was the most effective against A. dirus (180 min). Interestingly, all single oils had attributes of repellency against C. quinquefasciatus (ranged, 120−360 min). Moreover, we integrated their binary combinations of highly effective essential oils against A. aegypti and A. dirus to potentially increase the protection time. A 1:1 combination of petitgrain/basil, petitgrain/coriander, basil/coriander and basil/sage reduced the median complete-protection time of 150 min for A. aegypti; a combination of sage and patchouli oils prolonged the median complete-protection time of 270 min for A. dirus. Combining essential oils effect protection time from these two mosquito species.

Encapsulation of Eucalyptus largiflorens Essential Oil by Mesoporous Silicates for Effective Control of the Cowpea Weevil, Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae)

Although the use of synthetic chemicals is the principal method for insect pest management, their widespread application has led to numerous side effects, including environmental pollution and threats to human and animal health. Plant essential oils have been introduced as promising natural substitutes for synthetic insecticides. However, high volatility and/or low durability are the main limiting factors for essential oil application for control of insect pests. Accordingly, along with an evaluation of the fumigant toxicity of Eucalyptus largiflorens essential oil against the cowpea weevil, Callosobruchus maculatus, essential oil was nanoencapsulated by two mesoporous silicates, MCM-41 and zeolite 3A, to enhance fumigant persistence and toxicity. The chemical profile of essential oil was also analyzed through gas chromatographic-mass spectrometry. E. largiflorens essential oil showed significant concentration-dependent toxicity against insect pests; a concentration of 5.16 μL/L resulted in 100% mortality after 48 h. The toxicity of essential oil could be attributed to the presence of various insecticidal terpenes, such as spathulenol (15.6%), cryptone (7.0%), and 1,8-cineole (5.8%). Fumigant persistence was increased from 6 days to 19 and 17 days for pure and capsulated essential oil with MCM-41 and Zeolite 3A, respectively. The insect mortality also increased from 99 insects in pure essential oil to 178 and 180 insects in MCM-41 and Zeolite 3A encapsulated formulations, respectively. Therefore, the encapsulation of E. largiflorens essential oil by MCM- 41 and Zeolite 3A is a beneficial method for enhancing its persistence and toxicity against C. maculatus.

Functional analysis of a cytochrome P450 gene CYP9Z6 responding to terpinen-4-ol in the red flour beetle, Tribolium castaneum

Tribolium castaneum is an agricultural and stored pest found throughout the world. The cytochrome P450 genes of T. castaneum can encode various detoxification enzymes and catabolize heterologous substances, conferring tolerance to insecticides. Herein, we describe the identification of a P450 gene (CYP9Z6) from T. castaneum and investigated its expression profile and potential role in the detoxification of terpinen-4-ol. TcCYP9Z6 expression was significantly induced after exposure to terpinen-4-ol, and RNA-mediated silencing of TcCYP9Z6 increased terpinen-4-ol-induced larval mortality from 47.75% to 63.92%, showing that TcCYP9Z6 is closely related to the detoxification of terpinen-4-ol. The developmental expression profile revealed that TcCYP9Z6 was mainly expressed in late adults and late larvae. Tissue expression profiling revealed that the highest TcCYP9Z6 expression occurred in the head, in both the adult and the larval tissues, followed by the gut in larvae and the antennae in adults. These developmental stages and tissues with high TcCYP9Z6 expression are closely related to the detoxification of heterologous substances. These results indicated that TcCYP9Z6 may play a pivotal role in the detoxification of terpinen-4-ol, which provides support for using TcCYP9Z6 a potential gene for the RNAi-mediated prevention and control of T. castaneum.

Screening organic repellent compounds against Lutzomyia longipalpis (Diptera: Psychodidae) present in plant essential oils: Bioassay plus an in silico approach

In the Americas, Lutzomyia longipalpis is the most relevant sand fly species for the transmission of visceral leishmaniasis. For its vector control in Brazil, insecticide spraying has not shown persistent reduction in disease prevalence while some sand fly populations are reported resistant to the insecticides used in spraying. The usage of repellents and personal protection behavior can reduce vector borne diseases prevalence. Therefore, the search for new repellent compounds is needed to use together with insecticide spraying, especially from natural sources to overcome the resistance developed by some sand fly populations to the compounds commercially used. In silico strategies have been applied together with repellency bioassays successfully identifying new bioactive compounds from natural sources. Thus, the present study aimed to screen repellent potential of neem (Azadirachta indica), citronella (Cymbopogon winterianus), bushy matgrass (Lippia alba) and 'alecrim do mato' (Lippia thymoides) essential oils against L. longipalpis and to identify potential repellent compounds by chemical analysis and in silico approach. Plant essential oils were extracted from leaves and repellency bioassays were performed on volunteers using colony reared L. longipalpis. Aside from neem oil, all other tested essential oil has shown a reduced number of sand fly bites using higher concentrations. Chemical composition from oils was assessed and its compounds were screened on a pharmacophore model using odorant binding protein 1 (OBP1). All essential oils were majorly composed of either oxygenated monoterpenes, except for the oil extracted from neem which was composed of sesquiterpene hydrocarbons. Molecular docking was performed with the compounds that best superimposed in the OBP1 pharmacophore model, identifying those binding to OBP4, which is associated with insect repellency behavior. Citronellol, Citronellol acetate, Citronellal and Geranyl acetate showed similar interactions with OBP4 binding site as DEET. Thus, it is suggested that these compounds are able to bind to L. longipalpis OBP4 generating repellent behavior in sand flies.

Biocontrol Potential of Essential Oils in Organic Horticulture Systems: From Farm to Fork

In recent decades, increasing attention has been paid to food safety and organic horticulture. Thus, people are looking for natural products to manage plant diseases, pests, and weeds. Essential oils (EOs) or EO-based products are potentially promising candidates for biocontrol agents due to their safe, bioactive, biodegradable, ecologically, and economically viable properties. Born of necessity or commercial interest to satisfy market demand for natural products, this emerging technology is highly anticipated, but its application has been limited without the benefit of a thorough analysis of the scientific evidence on efficacy, scope, and mechanism of action. This review covers the uses of EOs as broad-spectrum biocontrol agents in both preharvest and postharvest systems. The known functions of EOs in suppressing fungi, bacteria, viruses, pests, and weeds are briefly summarized. Related results and possible modes of action from recent research are listed. The weaknesses of applying EOs are also discussed, such as high volatility and low stability, low water solubility, strong influence on organoleptic properties, and phytotoxic effects. Therefore, EO formulations and methods of incorporation to enhance the strengths and compensate for the shortages are outlined. This review also concludes with research directions needed to better understand and fully evaluate EOs and provides an outlook on the prospects for future applications of EOs in organic horticulture production.

Study on Gas Chromatographic Fingerprint of Essential Oil from Stellera chamaejasme Flowers and Its Repellent Activities against Three Stored Product Insects

The objective of this study was to establish the chromatographic fingerprints of the essential oil (EO) from Stellera chamaejasme flowers collected from various natural sites by gas chromatography (GC) combined with chemometric methods. The EO was obtained by hydrodistillation, and its chemical composition was analyzed by gas chromatography-mass spectrometry (GC-MS). Most components were identified as ketones and the relatively high-content components were fitone (38.973%), n-hentriacontane (5.807%), myristic acid (4.944%) and phytol (3.988%). In addition, the repellent activities of the EO from S. chamaejasme flowers and its four main chemical compounds were evaluated against three stored product pests (Tribolium castaneum, Lasioderma serricorne, Liposcelis bostrychophila) for the first time. In this work, the EO and the four chemical compounds showed a repellent effect against three storage pests after 2 and 4 h exposure. The experimental method and repellent activity of S. chamaejasme flower EO could provide a basis for the development of botanical pesticide and the utilization of the rich plant resources of S. chamaejasme in the future.

Insecticidal and Repellent Activity of Thymus quinquecostatus Celak. Essential Oil and Major Compositions against Three Stored-Product Insects

Thymus quinquecostatus Celak. of the Lamiaceae family has a long history of dual use of medicine and food with high economic value, and has been proved to have good antioxidative, antimicrobial, and antidiabetic activities. Essential oil (EO) extracted from the aerial part of T. quinquecostatus was obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry (GC/MS) and GC. Totally 45 compounds were identified accounting for 98.5 % of the EO. The major constituents of the EO were linalool (52.003 %), borneol (10.911 %) and anethole (5.325 %). Fumigant, contact and repellent activity of T. quinquecostatus essential oil (EO) against Tribolium castaneum (Coleoptera: Tenebrionidae), Lasioderma Serricorne (Coleoptera: Anobiidae), Liposcelis bostrychophila (Psocoptera: Liposcelididae) were evaluated in this work. T. quinquecostatus EO and three major constituents showed varying degrees of insecticidal and repellent activities to three stored-product insects. Anethole stated the best fumigant and contact activity than others did to all three insect species. EO and compounds showed general repellent activity against three target insects. This work suggests that the EO of T. quinquecostatus has promising potential to be developed into botanical pesticides and repellents controlling pest damage in warehouses and grain stores.

Toxicity and repellent activity of monoterpene enantiomers to rice weevils (Sitophilus oryzae)

BACKGROUND

The rice weevil, Sitophilus oryzae (L., 1763) (Coleoptera: Curculionidae), is a stored grain/seed pest of several crops. Botanicals represent an option to manage this pest, especially those with high toxicity determined by its structure and physicochemical properties and low residue left behind on treated grains/seeds. Enantiomers are bioactive molecules in organic processes. The aim of this study was to evaluate the insecticidal activity of two enantiomeric forms of the monoterpenes citronellal, limonene, linalool, menthone and α-pinene against S. oryzae adults through contact, fumigant and repellent assays.

RESULTS

All results were compared with absolute acetone as the negative control and those from contact assays also with malathion as the positive control. (S)-(-)-linalool was the most toxic by contact to S. oryzae and (S)-(-)-menthone through fumigation, while the two enantiomeric forms of menthone and α-pinene were the best repellents.

CONCLUSIONS

The high toxicity of only one of the two monoterpene enantiomers showed the importance of form and percentage of enantiomer in the commercial product, which affect the success of the product to controlling S. oryzae. © 2021 Society of Chemical Industry.

Control of red flour beetle (Tribolium castaneum) in feeds and commercial poultry diets via using a blend of clove and lemongrass extracts

The insects' infestation decreases the nutritive value of the stored grains and causes losses in its weight, quality, or economic values. The aim of the present study was to investigate the efficiency of a natural product of clove and lemongrass extracts in controlling of red flour beetle (Tribolium castaneum) in different feedstuffs and commercial poultry diets. Different concentrations of the tested product (5, 10, 20, 50, 100 mg) were mixed with 10 g of different feedstuffs and poultry diets, and incubated at different time points. The percent repellency (PR), toxicity effect, and antifeedant activity of the plant extracts compound were assessed. The PR was detected depending on the choice method. It was found that the PR was dose and time dependent. The highest doses (50 or 100 mg/10 g feed) achieved the highest repellency effect reaching 70% at 24 h post-application (PA). The minimal PR was reported by the lowest dose of 5 mg/10 g feed reaching 50% at 24 h PA. Moreover, the PR was found to decrease by time. The toxicity effect of this natural product on T. castaneum was cumulative, not acute, in which it was recorded after 1 month of application. Besides, this effect needs high doses of the product (at dose 500 or 1000 mg/50 g feed). The used product achieved a clear antifeedant activity against T. castaneum, as the feeding deterrent index (FDI %) for corn grains was 98.5% at 1.0 and 2.0% concentration, whereas for wheat grains there was a significant difference between both concentration (96.0 vs. 74.4%). In addition, the weight loss of control corn and wheat grains was higher than the treated ones, and it was about 3.15% and 2.0% per month for corn and wheat, respectively. In conclusion, the clove and lemongrass extracts had a repellency effect reaching to 70%. Moreover, it had a lethal effect on T. castaneum. In addition, it can reduce the weight loss of the infested feeds and consequently increasing its FDI %. Therefore, the clove and lemongrass extract blend can be used to protect the feedstuffs from the damage by this insect.

Analysis of the Essential Oils of Eucalyptus camaldulensis Dehnh. and E. viminalis Labill. as a Contribution to Fortify Their Insecticidal Application

The use of synthetic chemicals, with harmful effects on the environment and human health, is the principal strategy in the management of stored-product insect pests such as Oryzaephilus surinamensis and Sitophilus oryzae. Various studies in recent years have highlighted the possibility of using plant essential oils as available and low-risk factors in insect pest management. Therefore, in the present study, the possibility of controlling O. surinamensis and S. oryzae was investigated using Eucalyptus camaldulensis and Eucalyptus viminalis leaf essential oils. The essential oils were obtained by hydrodistillation of the leaves of the 2 Eucalyptus species, and the chemical compositions were determined by gas chromatographic-mass spectral analysis. The essential oil of E. camaldulensis was dominated by p-cymene (24.8%), cryptone (18.9%), and spathulenol (12.4%), while the major components in E. viminalis essential oil were 1,8-cineole (51.6%) and α-pinene (15.8%). The essential oils displayed promising fumigant toxicity against insect pests, which was positively dependent on utilized concentrations and exposure times. Oryzaephilus surinamensis, with low median lethal concentrations, was more susceptible than S. oryzae to the essential oils after 24, 48, and 72 hours. Also, E. viminalis essential oil, with a high level of insecticidal monoterpenes such as 1,8-cineole and α-pinene, was more toxic to insect pests than E. camaldulensis oil. According to the results of the current study, E. camaldulensis and E. viminalis essential oils, rich in insecticidal terpenes, can be alternative candidates to synthetic chemicals in the management of O. surinamensis and S. oryzae.

Essential Oils Extracted from Different Species of the Lamiaceae Plant Family as Prospective Bioagents against Several Detrimental Pests

On the basis of the side effects of detrimental synthetic chemicals, introducing healthy, available, and effective bioagents for pest management is critical. Due to this circumstance, several studies have been conducted that evaluate the pesticidal potency of plant-derived essential oils. This review presents the pesticidal efficiency of essential oils isolated from different genera of the Lamiaceae family including Agastache Gronovius, Hyptis Jacquin, Lavandula L., Lepechinia Willdenow, Mentha L., Melissa L., Ocimum L., Origanum L., Perilla L., Perovskia Kar., Phlomis L., Rosmarinus L., Salvia L., Satureja L., Teucrium L., Thymus L., Zataria Boissier, and Zhumeria Rech. Along with acute toxicity, the sublethal effects were illustrated such as repellency, antifeedant activity, and adverse effects on the protein, lipid, and carbohydrate contents, and on the esterase and glutathione S-transferase enzymes. Chemical profiles of the introduced essential oils and the pesticidal effects of their main components have also been documented including terpenes (hydrocarbon monoterpene, monoterpenoid, hydrocarbon sesquiterpene, and sesquiterpenoid) and aliphatic phenylpropanoid. Consequently, the essential oils of the Lamiaceae plant family and their main components, especially monoterpenoid ones with several bioeffects and multiple modes of action against different groups of damaging insects and mites, are considered to be safe, available, and efficient alternatives to the harmful synthetic pesticides.

Bioherbicidal activity of terpenes and phenylpropenes against Echinochloa crus-galli

This study was undertaken to evaluate the herbicidal activity of twelve natural compounds belonging to monoterpenes, phenylpropenes, and sesquiterpenes against Echinochloa crus-galli under laboratory and glasshouse conditions. Experiments were conducted to determine the impact of different concentrations (0.5, 1, 2, 4 and 8 mM) of these compounds on the seed germination and root and shoot growth of barnyard grass. trans-Cinnamaldehyde, eugenol, and thymol caused the highest impact on barnyard grass reducing its seed germination and shoot growth. p-Cymene (EC₅₀ = 0.22 mM) and trans-cinnamaldehyde (EC₅₀ = 0.34 mM) were the most potent compounds in limiting the root growth of the E. crus-galli. In a post-emergent experiment, thymol, trans-cinnamaldehyde, eugenol, farnesol, and nerolidol significantly reduced the shoot growth, fresh and dry weight of two-leaf stage barnyard grass after 2 days of the foliar treatment with the concentrations of 0.5, 1.0 and 2.0%. These compounds induced severe visible injury symptoms where trans-cinnamaldehyde, eugenol, farnesol and nerolidol showed a complete weed control at 1.0 and 2.0%. These compounds were successfully formulated as emulsifiable concentrates and showed higher herbicidal activities against barnyard grass. Altogether, our data showed that trans-cinnamaldehyde, eugenol, thymol, farnesol, and nerolidol can be developed as novel bioherbicides for managing E. crus-galli.