Tribolium Castaneum Adults Research Articles

Insecticidal effect of two Turkish entomopathogenic nematode isolates against Tribolium castaneum (Herbst) larvae and adults at different conditions

Red flour beetle, Tribolium castaneum (Herbst.), is the most common pest of stored grains and products. Aerial and contact pesticides are used to control this pest. However, the red flour beetle has also developed significant resistance to phosphine, the main fumigant currently in use worldwide. The adverse effects of pesticides on non-target organisms, groundwater contamination, residues on food crops, and the emergence of insect resistance to chemicals have compelled the industry to prioritize the development of alternative control measures. Entomopathogenic nematodes find application in various agricultural systems. The insecticidal effect of two isolates of Steinernema feltiae Filipjev (Nematoda: Steinernematidae) and Heterorhabditis bacteriophora Poinar (Nematoda: Heterorhabditidae) against the different stages of T. castaneum. The entomopathogenic nematode isolates were examined at four concentrations (0, 250, 500, and 1000 IJs/ml) with a distilled water at 15 and 25 ± 1 °C temperatures. Results revealed that both S. feltiae (A-16) caused with 92.33% mortality rate while H. bacteriophora (O-7) caused with 76.77% mortality in the last instar larvae of the red flour beetle while these two species caused 75.38% and 66.85% mortality in adults, at 25 °C. The effect of nematodes decreased as the temperature decreased. According to results, the mortality rate of T. castaneum larvae treated with S. feltiae (A-16) with (54.62%) was significantly higher than that of H. bacteriophora (O-7) with (32.13%) 96 h after inoculation at 15 °C. The data indicated that 1000 IJs/ml was the most effective concentration of tested EPN isolates for all larval and adult stages.In this study, our findings indicate that S. feltiae (A-16) and H. bacteriophora (O-7) can be used as effective biological control agents against both the larval and adult stages of the red flour beetle. The results demonstrate that EPNs are promising candidates for biocontrol of T. castaneum. This information is useful in designing future biological control programs.

Effects of nutrition on recovery, mortality, and mobility of adult Tribolium castaneum after exposure to long-lasting insecticide-incorporated netting.

Long-lasting insecticide-incorporated netting (LLIN) has been used to deliver contact insecticides as an integrated pest management tool for stored product insect pests in food facilities. Although the presence of food is known to improve insect recovery after exposure, it is not clear whether food nutritional quality plays a role. Here, the red flour beetle Tribolium castaneum adults were exposed to two commercially available LLINs, Carifend (active ingredient α-cypermethrin) and D-Terrence (deltamethrin), then transferred to Petri dishes with foods with varying nutritional quality (e.g., 0-100% ratios of flour to non-nutritive cellulose). We investigated the effects of nutrition, LLIN type, and exposure time on post-exposure recovery, mortality, and mobility. After exposure for 2-168 h, the immediate mortality of T. castaneum adults ranged from 0.5% to 91.0% with Carifend and 0% to 75.3% with D-Terrence. Adult recovery and delayed mortality were significantly affected by nutritional quality, LLIN type, exposure time, and recovery time. For both LLINs, adult recovery increased over time, with a trend for higher recovery and lower mortality with increasing nutritional quality and decreasing exposure time. In addition, adult mobility decreased multiple-fold after Carifend or D-Terrence exposure for 30, 60 or 90 min compared to 10 min. This study shows nutrition significantly modulates the efficacy of LLIN against T. castaneum, and thus strengthens the rationale for implementing stringent sanitation protocols for food facility managers. © 2024 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Influence of molecular descriptors of plant volatilomics on fumigant action against the three major stored product beetle pests.

Plant volatilomics such as essential oils (EOs) and volatile phytochemicals (PCs) are known as potential natural sources for the development of biofumigants as an alternative to conventional fumigant pesticides. This present work was aimed to evaluate the fumigant toxic effect of five selected EOs (cinnamon, garlic, lemon, orange, andpeppermint) and PCs (citronellol, limonene, linalool, piperitone, andterpineol) against the Callosobruchus maculatus, Sitophilus oryzae, and Tribolium castaneum adults. Furthermore, for the estimation of the relationship between molecular descriptors and fumigant toxicity of plant volatiles, quantitative structural activity relationship (QSAR) models were developed using principal component analysis and multiple linear regression. Amongst the tested EOs, garlic EO was found to be the most toxic fumigant. The PCs toxicity analysis revealed that terpineol, limonene, linalool, and piperitone as potential fumigants to C. maculatus (< 20 µL/L air of LC50), limonene and piperitone as potential fumigants to T. castaneum (14.35 and 154.11 µL/L air of LC50, respectively), and linalool and piperitone as potential fumigants to S. oryzae (192.27 and 69.10 µL/L air of LC50, respectively). QSAR analysis demonstrated the role of various molecular descriptors of EOs and PCs on the fumigant toxicity in insect pest species. In specific, dipole and Randic index influence the toxicity in C. maculatus, molecular weight and maximal projection area influence the toxicity in S. oryzae, and boiling point and Dreiding energy influence the toxicity in T. castaneum. The present findings may provide insight of a new strategy to select effective EOs and/or PCs against stored product insect pests.

Insect-resistant activities of Elsholtzia ciliata essential oil and its main components carvone against Tribolium castaneum in different development stages

The main objectives of the present study are to introduce a ecologically safe, and natural compound for controlling the red flour beetle, Tribolium castaneum. This study aims to thoroughly examine the effects of Elsholtzia ciliata essential oil (E. ciliata EO) and its primary components, carvone, on Tribolium castaneum eggs, larvae, pupae, and adults. The study also includes a simulated warehouse test to assess the efficacy of these substances as contact agents, fumigants, repellents, and antifeedants. All of these anti-insect activities were positively correlated with the concentrations of E. ciliata EO and carvone. Firstly, in the contact activity assay, E. ciliata EO and carvone completely inhibited the hatching of eggs and pupae of the T. castaneum at a concentration of 2.5 μL/cm2. The LC50 of E. ciliata EO and carvone were 7.62 and 4.33 μg/adult, respectively, against senior adults (5 weeks old). Secondly, in the fumigant activity assay, 60 mg/L of E. ciliata EO and carvone essentially completely inhibited pupae eclosion. On the other hand, the LD50 of E. ciliata EO and carvone against senior adults (5 weeks old) were 8.72 and 5.02 mg/L, respectively. Thirdly, for T. castaneum adults, at the highest test concentration, the repellent rate of the E. ciliata EO was above 90%. Fourthly, the larvae and adults of the T. castaneum could reach complete antifeedant activity by E. ciliata EO and carvone at the highest test concentrations. Finally, 3000 ppm of carvone was sufficient to kill all the pests in the warehouse in the simulated warehouse test. In conclusion, the results of this study will contribute to the better control of the storage pest, T. castaneum, and the development of environmentally friendly insecticides based on E. ciliata EO and carvone.

Physicochemical comparison of chitin characteristics in three major stored-product beetle pests: Implications for biofumigant toxicity

The present study investigates the chitin properties of stored-product insect pests and their association with the fumigant toxicity of garlic essential oil. Chitin isolates of Callosobruchus maculatus, Sitophilus oryzae, and Tribolium castaneum adults were characterized using FT-IR, XRD, EA, SEM-EDS, and NMR techniques. Fumigant toxicity assay was performed under airtight condition in glass vial. The S. oryzae contains highest chitin content (19 %), followed by T. castaneum (10 %) and C. maculatus (8 %). The degree of crystallinity was lower in C. maculatus (67.13 %) than in S. oryzae (77.05 %) and T. castaneum (76.56 %). Morphologically, C. maculatus chitin displayed a flat lamellar surface with pores, while S. oryzae and T. castaneum exhibited densely arranged microfibrils based surfaces. Fumigant toxicity assays revealed varied susceptibility levels, C. maculatus exhibited higher susceptibility (0.27 μL/L air of LC50) compared to S. oryzae and T. castaneum (14.35 and 3.74 μL/L air of LC50, respectively) to garlic essential oil. The higher chitin content, greater crystallinity, and densely arranged structures in S. oryzae might contribute to its tolerance towards fumigant. Additionally, physico-chemical properties and penetration potentiality of the bioactive constituents might be linked to the toxicity in insects. Understanding these relations can enrich knowledge of chitin's role in fumigant toxicity mechanism.

Toxicity of Two Plant Essential Oils as Eco-friendly Fumigants against the Red Flour Beetle Tribolium castaneum

Background: This study aims to extract essential oils from Artemisia herba alba and Eucalyptus camaldolensis plants and evaluate their effectiveness as eco-friendly natural fumigants against larvae and adults of red flour beetle Tribolium castaneum. Methods: The current study was conducted under laboratory conditions for the period from 2023-4 to 2023-8 in the Plant Protection Laboratory in the Diyala Agriculture Directorate, Iraq. Different concentrations of 2, 4, 6, 8 and 10 µL-1 air for exposure period of 24, 48 and 72 hours. Result: Larval mortality rates reached 100% at concentrations of 8 and 10 µL L-1 air for Eucalyptus and Artemisia, respectively. The mortality rate increases with increasing concentration in adults, where the highest killing rate was recorded at 8.10 µL L-1 air, reaching 90% and 100% for Artemisia, while it reached 96.6% and 100% for Eucalyptus, respectively. Mortality rates were high throughout the duration of the first exposure and these rates increased as the exposure period increased to 48 hours and 72 hours, with the next highest killing rates for concentrations of 6, 8 and 10 µL L-1 air for Artemisia and Eucalyptus oils. There was no significant difference with pesticide treatment. This indicates the possibility of using essential oils in the applied field to manage pest populations in store products.

Efficacy of Four Insecticides Applied to Fortified Rice with Basil against Major Stored-Product Insect Species

Rice is one of the most important foods since it is grown in many countries and consumed by the majority of the population. Ensuring food security through the protection of stored-product commodities has become one of the most important priorities worldwide. In this study, the effects of three insecticidal formulations and an available diatomaceous earth formulation on basil-fortified rice against the major stored-product insects were evaluated. The label dose of each insecticidal formulation was used. Insect mortality was determined after 1, 3, 7, 14 and 21 days for each species. The entire experiment was repeated three times by preparing different lots of treated and untreated rice for each treatment. The results of the diatomaceous earth treatments showed that the most susceptible individuals were Sitophilus oryzae adults and Oryzaephilus surinamensis larvae, while the least susceptible individuals were Rhyzopertha dominica and Tribolium castaneum adults. The tested insecticides were effective against S. oryzae, as mortality was 100%. Between the two pyrethroids, deltamethrin was more effective than cypermethrin in the tested insecticides. Our findings indicate that there are available insecticides on the market which can be obtained successfully for the durable protection of agricultural commodities after the harvest stage.

Comparative Analysis of the Metabolic Profiles of Strains of Tribolium castaneum (Herbst) Adults with Different Levels of Phosphine Resistance Based on Direct Immersion Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry

The management of phosphine (PH3) resistance in stored grain pests is an essential component of implementing timely and effective pest control strategies. The prevailing standard method for PH3 resistance testing involves the exposure of adult insects to a specific concentration over a fixed period. Although it is widely adopted, this method necessitates an extensive period for assay preparation and diagnosis. To address this issue, this study employed Direct Immersion Solid-Phase Microextraction (DI-SPME) coupled with Gas Chromatography-Mass Spectrometry (GC-MS) to compare and analyze the metabolic profiles of PH3-sensitive (TC-S), PH3 weak-resistant (TC-W), and PH3 strong-resistant (TC-SR) Tribolium castaneum (Herbst) adults. A total of 36 metabolites were identified from 3 different PH3-resistant strains of T. castaneum; 29 metabolites were found to present significant differences (p &lt; 0.05) across these groups, with hydrocarbon and aromatic compounds being particularly prevalent. Seven metabolites showed no significant variations among the strains, consisting of four hydrocarbon compounds, two iodo-hydrocarbon compounds, and one alcohol compound. Further multivariate statistical analysis revealed a total of three, two, and nine differentially regulated metabolites between the TC-S versus TC-W, TC-S versus TC-SR, and TC-W versus TC-SR groups, respectively. Primarily, these metabolites comprised hydrocarbons and iodo-hydrocarbons, with the majority being associated with insect cuticle metabolism. This study demonstrates that DI-SPME technology is an effective method for studying differentially expressed metabolites in T. castaneum with different levels of PH3 resistance. This approach may help to provide a better understanding of the development of insect PH3 resistance and act as a valuable reference for the establishment of rapid diagnostic techniques for insect PH3 resistance.

Gut Bacteria Promote Phosphine Susceptibility of Tribolium castaneum by Aggravating Oxidative Stress and Fitness Costs.

Knowledge about resistance mechanisms can provide ideas for pesticide resistance management. Although several studies have unveiled the positive or negative impacts of gut microbes on host pesticide resistance, minimal research is available regarding the association between gut microbes and host phosphine resistance. To explore the influence of gut bacteria on host phosphine susceptibility and its molecular basis, mortality, fitness, redox responses, and immune responses of adult Tribolium castaneum were determined when it was challenged by phosphine exposure and/or gut bacteria inoculation. Five cultivable gut bacteria were excised from a population of phosphine-resistant T. castaneum. Among them, only Enterococcus sp. inoculation significantly promoted host susceptibility to phosphine, while inoculation of any other gut bacteria had no significant effect on host phosphine susceptibility. Furthermore, when T. castaneum was exposed to phosphine, Enterococcus sp. inoculation decreased the female fecundity, promoted host oxidative stress, and suppressed the expression and activity of host superoxide dismutase, catalase, and peroxidase. In the absence of phosphine, Enterococcus sp. inoculation also elicited overactive immune responses in T. castaneum, including the immune deficiency and Toll signaling pathways and the dual oxidase-reactive oxygen species system. These results indicate that Enterococcus sp. likely promotes host phosphine susceptibility by aggravating oxidative stress and fitness costs.

Preference of Major Stored Product Insects in Fortified Rice with Basil

As the world’s population grows, the needs for feeding it follow the same path. Considering these conditions, ensuring the quantity and quality of raw materials, such as cereals, seems imperative. Stored product insects are responsible for significant losses in the post-harvest stages of agricultural products and the available chemical methods for their control are decreasing, due to their negative impact on the environment and humans. To this end, the evaluation of the efficacy of non-chemical methods for the management of storage insects is crucial. In the present study, we conducted two trials of choice tests based on rice fortified with basil to determine its potential as a non-chemical repellent of stored product insects. In the first trial, we evaluated the repellent activity of rice enriched with basil on adults of Sitophilus oryzae, Rhyzopertha dominica, Tribolium castaneum and Oryzaephilus surinamensis, as well as on T. castaneum larvae. In the second trial, the same procedure was followed with deltamethrin-treated rice fortified with basil. The results of the first trial showed that for most of the insect species tested, the rice fortified with basil was moderately repellent, while for O. surinamensis, it was attractive. Surprisingly, in the second trial, the deltamethrin-treated rice fortified with basil showed a repellent effect on O. surinamensis adults and T. castaneum larvae, while no repellency was observed for the rest of insect species examined. Observation time was not significant for any of the insect species, combinations and trials, with the exception of the rice fortified with basil vs. Blanc combination in O. surinamensis. Our findings suggest that the use of deltamethrin-treated rice fortified with basil was effective as a repellent for O. surinamensis adults and T. castaneum larvae.

Treatment of Four Stored-Grain Pests with Thiamethoxam plus Chlorantraniliprole: Enhanced Impact on Different Types of Grain Commodities and Surfaces.

An insecticide containing the neonicotinoid thiamethoxam + the diamide chlorantraniliprole was evaluated against adults of Rhyzopertha dominica, Tribolium castaneum, Trogoderma granarium, and Sitophilus oryzae under laboratory bioassays both on freshly treated grain as well as on treated grain stored over 90 days for its persistence in efficacy. In laboratory bioassays, the insecticide was applied on wheat, maize, or rice at four doses, while in persistence bioassays on wheat at the same doses. Mortality and progeny were assessed in both laboratory and persistence bioassays. After 14 days of exposure, S. oryzae exhibited 100% mortality on all three commodities at the highest dose, while R. dominica showed complete mortality on wheat or rice and T. castaneum on wheat. For a period of 90 days, S. oryzae exhibited 42.69% mortality, followed by R. dominica (35.26%), T. castaneum (27.08%), and T. granarium (18.63%) at the highest dose. Progeny was successfully suppressed in all cases of complete mortality in laboratory bioassays and for S. oryzae for 90 days in persistence bioassays. Laboratory trials were also performed on plywood, concrete, ceramic tile, and steel at one dose. The highest mortality was observed on steel, followed by concrete, ceramic tile, and plywood for all insect species tested. This study demonstrates that thiamethoxam + chlorantraniliprole is effective against the tested species depending on exposure, storage period, surface, commodity, and dose.

Chemical Composition, Toxicity and Repellency of Inula graveolens Essential Oils from Roots and Aerial Parts against Stored-Product Beetle Tribolium castaneum (Herbst).

In this work, essential oils extracted from roots and aerial parts of Inula graveolens by hydrodistillation and their fractions obtained by chromatographic simplification were first investigated for their chemical composition by GC/MS and then evaluated for the first time for their repellency and contact toxicity properties against Tribolium castaneumadults. Twenty-eight compounds were identified in roots essential oil (REO), which accounted for 97.9 % of the total oil composition, with modhephen-8-β-ol (24.7 %), cis-arteannuic alcohol (14.8 %), neryl isovalerate (10.6 %) and thymol isobutyrate (8.5 %) as major constituents. Twenty-two compounds were found in the essential oil from aerial parts (APEO), which accounted for 93.9 % of the total oil, with borneol (28.8 %), caryophylla-4(14),8(15)-dien-6-ol (11.5 %), caryophyllene oxide (10.9 %), τ-cadinol (10.5 %) and bornyl acetate (9.4 %) as main compounds.REO and APEO displayed stronger repellency after 2 h of exposure (80.0 and 90.0 %, respectively) against T. castaneum at the concentration of 0.12 μL/cm2 . After fractionation, fractions R4 and R5 exhibited greater effects (83.3 % and 93.3 %, respectively) than the roots essential oil. Furthermore, the fractions AP2 and AP3 showed higher repellency (93.3 and 96.6 %, respectively) than the aerial parts oil. The LD50 values of oils from roots and aerial parts topically applied were 7.44 % and 4.88 %, respectively. Results from contact toxicity assay showed that fraction R4 was more effective than the roots oil with LD50 value of 6.65 %. These results suggests that essential oils of roots and aerial parts from I. graveolens may be explored as potential natural repellent and contact insecticides against T. castaneum in stored products.

Chemical Composition and Insecticidal Activity against Tribolium Castaneum of Thapsia garganica L. Seed Essential Oil.

Due to the several side effects of synthetic pesticides, including environmental pollution, threats to human health, and the development of pest resistance to insecticides, the use of alternative healthy, available and efficient agents in pest management strategies is necessary. Recently, the use of essential oil obtained from aromatic plants has shown significant potential for insect pest management. For this reason, the essential oil isolated from seeds of Thapsia garganica L. was investigated for the first time for its chemical profile, and its toxicity and repellency effects against Tribolium castaneum adults. Qualitative and quantitative analyses of the chemical composition by gas chromatography coupled to mass spectrometry (GC/MS) revealed the presence of 18 organic volatiles representing 96.8 % of the total constituents. The main compounds were 1,4-dimethylazulene (51.3 %) followed by methyl palmitate (8.2 %), methyl linoleate (6.2 %) and costol (5.1 %). Concerning the repellent effect, results revealed that SEO (Seed Essential Oil) was very repellent towards T. castaneum adults, with 100 % repellency after 2 h of exposure. Furthermore, the essential oil exhibited remarkable contact toxicity against T. castaneum (93.3 % of mortality) at the concentration of 10 % (v/v). The median lethal dose (LD50 ) of the topical application of the seed essential oil was 4.4 %. These encouraging outcomes suggested that the essential oil from T. garganica seeds could be considered a potent natural alternative to residual persistent and toxic insecticides.

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.

The Effect of Some Quercus spp. (Oak) Extracts on Adult Tribolium castaneum Mortality

The Effect of Some Quercus spp. (Oak) Extracts on Adult Tribolium castaneum Mortality

Carlina acaulis essential oil: a candidate product for agrochemical industry due to its pesticidal capacity

Carlina acaulis L. is a herb mainly used in central Europe as traditional medicine or food. Recently, C. acaulis essential oil (EO) and its nanoemulsion showed elevated efficacy against several insects of medical and agricultural importance. In the current study, efficacy of C. acaulis EO was estimated against several stored product pests. The EO was sprayed on wheat to control Acarus siro L. (adults, nymphs), Alphitobius diaperinus (Panzer) (adults, larvae), Oryzaephilus surinamensis (L.) (adults, larvae), Rhyzopertha dominica (F.) (adults), Sitophilus oryzae (L.) (adults), Tenebrio molitor L. (adults, larvae), Tribolium castaneum (Herbst) (adults, larvae), and Tribolium confusum Jacquelin du Val (adults, larvae). Carlina acaulis EO was mainly composed by carlina oxide (98.8%), with benzaldehyde (1.2%) and ar-curcumene (traces) as minor components. Both adults and nymphs of A. siro showed high mortality, i.e., 91.1 and 95.6%, after 7 days of initial exposure to 1000 ppm (1000 μL C. acaulis EO/kg wheat), respectively. This concentration provided the death of 25.6% of the exposed A. diaperinus adults at the termination of trials. Total mortality (100.0%) of A. diaperinus larvae was reached 2 and 4 days after initial exposure on wheat sprayed with 1000 and 500 ppm of C. acaulis EO, respectively. One thousand (1000) ppm of EO killed 96.7% of O. surinamensis adults and all larvae 7 and 2 days after initial exposure, respectively. Concerning adults of R. dominica and S. oryzae, 1000 ppm achieved complete mortality after 4 and 6 days of initial exposure, respectively. Tenebrio molitor adults reached 81.1% mortality after their 7-days exposure to 1000 ppm C. acaulis EO. All T. molitor larvae were dead after 7 or 4 days of initial exposure to 500 and 1000 ppm, respectively. Carlina acaulis EO caused 97.8 and 100.0% mortality to adults of T. castaneum after 7 and 5 days of initial exposure to 1000 and 500 ppm, respectively. Complete mortality was observed after 16 h (1000 ppm) and 2 days (500 ppm) of initial exposure for T. castaneum larvae. Similarly, both examined stages of T. confusum achieved 100.0% mortality at the concentrations of 500 and 1000 ppm, after 7 and 4 days (adults), and 1 day and 16 h (larvae) of exposure, respectively. Overall, C. acaulis EO demonstrated pesticidal efficacy higher to pirimiphos-methyl, a conventional organophosphate insecticide, against a wide range of stored-product pests. Therefore this EO represents a reliable option for further developing eco-friendly and non-hazardous pest management strategies.

Antagonistic storage potential of Tagetes minuta, Eupatorium fortunei and Ocimum basilicum oils with volatile secondary metabolites against Tribolium castaneum and Lasioderma serricorne

Antagonistic storage potential of Tagetes minuta Linnaeus, Eupatorium fortunei Turcz. and Ocimum basilicum L. volatile oils hydrodistillated with main secondary metabolites against two storage pests, Tribolium castaneum and Lasioderma serricorne adults were evaluated. More than 95% volatile secondary metabolites obtained at different hydrodistillation time were identified by gas chromatography-mass spectrometry (GC-MS), and analyzed with principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). Further insecticidal assay exhibited interesting results that T. minuta oil showed the strongest fumigant toxicity against both T. castaneum (LC50 = 6.68 mg/L air) and L. serricorne (LC50 = 3.13 mg/L air) among the three essential oils. As one of the main volatile secondary metabolites, methylthymol was found to possess more powerful fumigant (LC50 = 2.42 mg/L air) and contact toxicity (LD50 = 5.43 µg/adult) against T. castaneum. While, precocene I exhibited the strongest insecticidal toxicity on L. serricorne with the LC50 value of 0.88 mg/L air and LD50 of 3.46 µg/adult, respectively. During the repellent assay, T. minuta oil showed the same repellent rate against both T. castaneum and L. serricorne at the highest concentration of 78.63 nL/cm2. The results proved that the essential oils as well as the main volatile secondary metabolites have potential to be developed into novel natural botanical resources on antagonistic storage with traditional Chinese medicine (TCM).

Antifungal Activity of Benzoquinones Produced by Tribolium castaneum in Maize-Associated Fungi.

Simple SummaryThe environmental conditions selected to store food products can be favorable to the development of different biotic degradation agents, such as insects and fungi. The interactions between these two groups of organisms may be multiple, and not restricted to antagonistic relationships. Competition may arise between stored products associated fungi, and insects, as they often thrive for the same food sources. Adults of Tribolium castaneum insects, a major stored food-product pest worldwide, produce benzoquinones, which are released as chemical defenses against other organisms. This study evaluated the effect of these substances on the development of six maize-associated fungal species: Aspergillus flavus, A. fumigatus, A. niger, Fusarium sp., Penicillium sp., and Trichoderma sp. The results obtained showed that all the fungi tested are susceptible to the benzoquinones produced by T. castaneum, but the level of sensivity is species specific, with most of the fungi showing a delayed growth. The contact of Penicillium sp. with a mixture of two benzoquinones, produced by T. castaneum, was deadly. Revealing the nature of the relationship between some fungal species and adults of T. castaneum can be a step forward for a better management in the preservation of stored food products.Tribolium castaneum (Herbst) adults produce 1,4-benzoquinone (BQ), methyl-1,4-benzoquinone (MBQ), and ethyl-1,4-benzoquinone (EBQ). These components are chemical defenses used as repellents and irritants, and BQ has a negative impact on the growth of some fungal species. In this work, the inhibitory and/or lethal effects of these benzoquinones on the development of six fungi identified in maize, namely Aspergillus flavus, A. fumigatus, A. niger, Fusarium sp., Penicillium sp., and Trichoderma sp., were evaluated. Ten-day-long disk diffusion trials were performed using benzoquinones. The experiments simulated the activity of BQ (B1) or “EBQ + MBQ” (B2) released by 40-day-old insect adults (n = 200), considering a total average release of 45 µg per adult. Inhibition halos imposed by benzoquinones on fungal growth showed a significant effect when compared with the controls (water and solvent). Mycelial growth was decreased for all fungi, with the level of response depending on the fungal species. B1 and B2 displayed an inhibitory effect against all fungi, but Trichoderma sp. and A. niger showed rapid recoveries. B2 showed a lethal effect on Penicillium sp. The inhibitory and lethal activities of benzoquinones released by T. castaneum adults may contribute to regulate fungal growth, and understanding their interaction is important to develop innovative control strategies.

Insecticidal activities of the essential oil of Rhynchanthus beesianus rhizomes and its constituents against two species of grain storage insects.

The aim of this research was to evaluate insecticidal activities of the essential oil of Rhynchanthus beesianus rhizomes against adults of Liposcelis entomophila and Tribolium castaneum. Gas chromatography-mass spectrometry analyses revealed the presence of 44 compounds with β-eudesmol (19.1%), elemol (8.1%), α-terpineol (8.0%), methyl eugenol (6.5%), and caryophyllene (4.8%) being the major constituents. Bioactivity-directed chromatographic separation of the oil led to the isolation of four constituents, elemol, β-eudesmol, methyl eugenol, and α-terpineol. The essential oil exhibited fumigant toxicity against the adults of L.entomophila and T.castaneum with LC50 values of 0.57 and 4.96mg/L air while the two isolates, methyl eugenol and α-terpineol possessed fumigant toxicity against the booklice (LC50=0.15 and 0.48mg/L air, respectively) and the beetles (LC50=1.81 and 4.96mg/L air, respectively). The oil also possessed contact toxicity against the booklice and the beetles with LD50 values of 121.56μg/cm2 and 54.93μg/adult, respectively, while the two isolates β-eudesmol and elemol showed contact toxicity against L.entomophila (LD50=99.21 and 35.19μg/cm2, respectively) and T.castaneum (LD50=35.26 and 8.89μg/adult, respectively). The results indicate that the oil of R.beesianus rhizomes and its isolates have potential as a source for natural insecticides.

Variability of insecticidal activity of Cupressus sempervirens L., Juniperus phoenicea L., Mentha rotundifolia (L.) Huds, and Asphodelus microcarpus Salzm. & Viv. extracts according to solvents and extraction systems

Medicinal plants represent an enormous potential source of chemical derivatives with many therapeutic properties whose variability is modified by exogenous factors. The present research focused on the evaluation of the effects of solvents with different polarities (hydro-methanolic, hydro-ethanolic, hydro-acetonic, and aqueous) and the extraction methods: maceration extraction (ME), and ultrasound-assisted extraction (UAE) on the total phenolic content (TPC), total flavonoid content (TFC), and total condensed tannins (TCT) in Cupressus sempervirens L., Juniperus phoenicea L., Mentha rotundifolia (L.) Huds, and Asphodelus microcarpus Salzm. & Viv. extracts. The toxicity by contact of the plant extracts obtained against Tribolium castaneum (Herbst) adults was studied. The quantitative characterization revealed significant differences (p ˂0.05) in the secondary metabolites of the different extracts analyzed depending on the method and solvent used. The result of the contact test indicated that the hydro-acetonic extracts obtained by ultrasound-assisted extraction exhibited the strongest insecticidal power with a corrected mortality of 59.25 ± 6.41% and 51.72 ± 11.54% for C. sempervirens L. and J. phoenicea L., respectively, and a mortality rate of 66.66 ± 5.77% was recorded for the hydro-methanolic extract of M. rotundifolia (L.) Huds. While in A. microcarpus Salzm. & Viv., the highest mortality rate (33.33 ± 7.07%) was registered in the hydro-acetonic extract obtained by maceration. The results show that there is a strong relationship between the efficacy of extracts as biopesticides and their abundance in biomolecules.