Search Results (122)

Storage insects consist a continuous global threat to food safety. In this study, the efficacy of the entomopathogenic nematodes (EPNs) Steinernema khuongi and Heterorhabditis downesi was evaluated against larvae of Tribolium castaneum, Tribolium confusum, Tenebrio molitor, and Trogoderma granarium in wheat and maize at six concentrations and two exposure intervals. Both EPNs exhibited higher virulence when applied in wheat than in maize. Generally, larval mortalities were higher under H. downesi treatments vs. S. khuongi, both in commodities and exposures. Notably, the tested EPNs caused high mortalities to T. granarium larvae (range, 88.9–92.2%) and T. castaneum larvae (range, 81.1–94.4%), respectively, at 10,000 IJs/mL in wheat vs. mortality ranges 72.2–77.8% and 74.4–87.8% in maize, respectively. In contrast, T. confusum larvae were tolerant to both EPNs. Tenebrio molitor larvae were tolerant to S. khuongi (<34.0% mortality) whereas susceptible to H. downesi (>83.3% mortality) at 10,000 IJs/mL in wheat and maize. These findings highlight the potential of S. khuongi and H. downesi as beneficial organisms against several stored-product insect pests. Full article

Hypoxia-inducible factor (HIF) is recognized as a key transcription factor via regulating a variety of molecular responses to hypoxia, although the details are still unclear. In this study, based on bioinformatics analysis, the expression of the HIF-1α gene in T. castaneum (TcHIF-1α) under hypoxic treatments was determined. After TcHIF-1α knockdown by injecting dsRNA, larval mortality, the expression levels of oxidative stress-related genes, and enzymatic activities were measured; DNA damage was also evaluated through single cell gel electrophoresis. The result indicated that TcHIF-1α is highly conserved in structure. TcHIF-1α exhibited distinct temporal patterns, with a peak after 72 h of exposure to 2% O₂. Following TcHIF-1α knockdown, a significant increase in larval mortality (17.44 ± 5.91%) and moderate DNA damage level was found. This might be accompanied by ROS accumulation, lipid peroxidation (LPO), and suppression of antioxidant enzymatic activities. The expression of genes involved in ROS synthesis (e.g., NOX) was significantly upregulated, whereas genes responsible for mitigating oxidative stress (e.g., OGG1, XRCC1, PARP1, SOD1a) were markedly downregulated. These findings elucidate the critical role of HIF-1α in insect hypoxia adaptation by regulating the antioxidative stress, highlighting its potential as a promising target for developing novel pest control strategies. Full article

Microwave heating has been widely used for disinfestation in the food industry due to its selective heating. However, research on the effects of microwave heating on stored product insects is still relatively limited, which has restricted its broader application in grain pest control storage. Therefore, this study evaluated the lethal effects of different microwave powers and exposure times on three major pests in paddy and investigated the impact of microwave treatment on improving adult detection efficiency, intending to develop a rapid and efficient detection method for stored grain insects. The results showed that the mortality of Sitophilus oryzae, Tribolium castaneum, and Oryzaephilus surinamensis increased with the increase in microwave power and exposure time. Specifically, 100% mortality was achieved for both S. oryzae and T. castaneum at 700 W for 60 s exposure. However, higher power levels and longer exposure durations exacerbated the non-uniformity of grain temperature distribution and adversely affected the germination rate. In addition, microwave treatment at 350 W, 490 W, and 700 W significantly reduced fungal load in paddy. The moisture content and water activity of rice decreased with the increase in microwave power and exposure time, while the percentage of grain breakage remained largely unaffected. These findings indicated that microwave treatment can effectively control insects and fungi without significantly altering the main physical properties of paddy. Notably, microwave treatment with short exposure durations (20–30 s) at all three power levels is conducive to increasing the recovery percentage of S. oryzae adults, while microwave treatment at low power (350 W) with exposure durations of 25–40 s helps improve that of T. castaneum. Accordingly, microwave heating is not only a promising strategy for protecting stored grains but also has potential for development as a rapid detection method for specific insect pests. Full article

To address the issues of resistance and food safety stemming from the overuse of chemical fumigants in stored-grain pest control, this study aimed to systematically optimize the insecticidal process of pulsed electric field (PEF) treatment on Tribolium castaneum (T. castaneum) and to investigate its electro-neurotoxicity mechanism. Single-factor experiments were used to determine parameter ranges, and response surface methodology (RSM) was employed to analyze the effects of electric field strength, pulse frequency, and treatment time. The finite element method (FEM) was used to simulate the physical field distribution, and acetylcholinesterase (AChE) activity was measured to explore neurotoxicity. The results indicated that electric field strength, pulse frequency, and treatment time all had highly significant effects (p < 0.0001), with electric field strength being the primary factor. The optimal process parameters were determined to be: electric field strength of 26 kV/cm, pulse frequency of 20 kHz, and treatment time of 140 s. Under these conditions, the predicted and actual mortality rates were both 100%, and this efficacy was validated in rice samples. Simulation confirmed that PEF achieves physical targeting through a “tip effect” on the insect’s nerve endings; mechanism tests demonstrated that PEF treatment significantly inhibited AChE activity (p < 0.01). This study confirms the “electro-neurotoxicity” mechanism of PEF, providing theoretical support for this green physical control technology. Full article

Tribolium castaneum, the red flour beetle, is both a major pest of stored products and a valuable genetic model. Odorant Binding Proteins (OBPs), traditionally associated with olfaction, are now recognized as multifunctional, contributing to detoxification, immunity, and reproduction. This review synthesizes recent advances in the molecular structure, gene expression, and functional characterization of T. castaneum OBPs—particularly TcOBPC11, TcOBPC12, TcOBPC17, and TcOBP7G. Experimental evidence, including RNA interference, ligand-binding assays, and expression profiling, supports their role in defense against xenobiotics. Comparative genomic analyses reveal lineage-specific expansions and adaptive evolution, especially in Minus-C OBPs. Translational applications include RNA interference (RNAi)-based pest control, OBP-targeting repellents, and biosensors. Outstanding challenges remain, including structural resolution and functional redundancy. Future research integrating CRISPR, single-cell transcriptomics, and structural biology will be critical to decode OBP regulatory networks and leverage their potential in pest management and biotechnology. Full article

The present study aimed to document the diversity and seasonal dynamics of stored-product insects in an animal feed facility located in northern Greece. A total of 38 traps were installed across different operational areas of the facility and inspected over 51 consecutive sampling occasions. Captured insects were identified to the lowest possible taxonomic level, and their frequency and dominance were calculated. In total, 9047 insect species belonging to five orders, 14 families, and at least 18 insect species were recorded. The dominant species were Tribolium castaneum, T. confusum, Oryzaephilus surinamensis, Sitophilus granarius, Lasioderma serricorne, and Lepidoptera adults, which collectively accounted for more than 85% of all captures. The total number of insects exhibited marked seasonal fluctuations, with the highest captures during late summer and early autumn and minimal activity during winter. Positive and significant correlations were detected among several dominant species, notably between Lepidoptera and T. castaneum, suggesting overlapping environmental preferences within the facility. These findings provide a detailed overview of the insects associated with feed industries in Greece and underscore the importance of continuous monitoring for effective pest management. The results highlight the need for seasonally adjusted control measures and contribute to a better understanding of the dynamics of stored-product pests under industrial conditions. Full article

The relative efficacy of amorphous silica dusts, malathion, and pirimiphos methyl was assessed against S. oryzae and T. castaneum in stored wheat under laboratory conditions. Insecticidal performance was influenced by physical properties such as particle size, surface area, bulk density, and oil/water adsorption capacity. Fumed silicas showed the highest toxicity, particularly Wacker HDK H20 (LC₅₀ = 19.4 mg/100 g at 12% moisture). Precipitated silica, Sipernat 22, though less potent (LC₅₀ = 46.6 mg/100 g), displayed consistent efficacy across different moisture levels, making it a suitable inert carrier. Increasing grain moisture to 15% significantly reduced the effectiveness of all dusts. When insecticides were combined with silica, their toxicity increased markedly. Malathion on silica (0.2%) reduced LC₅₀ values to 21.5 and 23.3 µg a.i./100 g for T. castaneum and S. oryzae, respectively, compared to 52.3 and 84.7 µg a.i./100 g on talc. Pirimiphos methyl on silica (0.1%) was the most effective, achieving LC₅₀ values of 13.4 and 15.5 µg a.i./100 g. Long-term bioassays over 25 weeks showed declining mortality rates, particularly at 15% moisture. However, pirimiphos methyl on silica maintained over 90% mortality at 12% moisture throughout the period, indicating strong residual efficacy. The results highlight the synergistic potential of combining silica with chemical insecticides and the crucial role of environmental humidity in stored grain pest management. Full article

Sex-biased gene expression is a fundamental driver of sexual dimorphism and plays an important role in evolutionary divergence across species. Here, we conducted a comparative evolutionary analysis of sex-biased genes (SBGs) in 13 insect species spanning four major orders: Hemiptera, Diptera, Lepidoptera, and Coleoptera. In total, 42,488 SBGs were identified, with low interspecific conservation—86.5% of orthogroups were shared by six or fewer species. Phylogenetic analyses showed that SBGs generally follow evolutionary trajectories similar to other protein-coding genes but show branch length differences suggestive of accelerated evolution in Drosophila virilis and Tribolium castaneum. Male-biased genes were more conserved than female-biased genes, which often showed reversed expression patterns, particularly in T. castaneum. Functional annotation of three rapidly evolving orthogroups in T. castaneum indicates possible associations with sex-specific traits such as lifespan, muscle development, and immunity, which should be considered hypotheses for future functional validation. These findings highlight the complex evolutionary dynamics of sex-biased genes and their contributions to phenotypic diversity and adaptive evolution in insects, providing a basis for future studies on the molecular mechanisms of sexual dimorphism and lineage-specific adaptations. Full article

This study investigated the physiological regulatory mechanisms by which exogenous trehalose intake enhances the adaptation of the global stored-grain pest T. castaneum to high-concentration carbon dioxide (CO₂) stress. By supplementing exogenous trehalose under high-CO₂ controlled atmosphere stress, we measured the activities of key detoxification enzymes (e.g., carboxylesterase and cytochrome P450) and the levels of carbohydrate substances (e.g., glycogen, glucose, and trehalose). The results demonstrated that trehalose feeding significantly alleviated CO₂ induced mortality in T. castaneum and prolonged their survival time. In terms of detoxification metabolism, a trehalose-rich diet significantly reduced the activities of cytochrome P450 and carboxylesterase, while the glucose content in the beetles decreased markedly. These findings indicate that trehalose accumulation mitigates physiological damage caused by high-CO₂ stress in T. castaneum. Furthermore, exogenous trehalose intake did not disrupt carbohydrate metabolic homeostasis in the beetles, as trehalase activity and the levels of various carbohydrates remained relatively stable. This study elucidates the role of trehalose metabolism in T. castaneum’s adaptation to high-CO₂ environments, providing a theoretical foundation for optimizing controlled atmosphere grain storage technology and developing novel pest control strategies. Full article

Resistance to the fumigant phosphine (PH₃) was studied for 28 populations of Rhyzopertha dominica from eight states of the USA and four provinces of Canada, as well as for 34 populations of Tribolium castaneum from twelve states of the USA and four provinces of Canada, using both a discriminating dose bioassay and molecular marker analysis. We used a molecular marker analysis for a point mutation in the gene that encodes dihydrolipoamide dehydrogenase and facilitates the “strong resistance” phenotype in both species. Our results showed that PH₃ resistance was correlated with higher frequencies of the strong resistance R allele in both species (R² = 0.59 in R. dominica and R² = 0.79 in T. castaneum). We also found that recessive R allele frequency did not correlate well with the geographic distribution of the resistant populations of these two species (R² = 0.21 in R. dominica and R² = 0.15 in T. castaneum). Therefore, populations of both species with higher R allele frequencies had higher resistance levels to PH₃. Our results showed that the geographic distribution of PH₃ resistance in both species varied and was not related geographically, but this supports the idea that the adaptive evolution of PH₃ resistance in these species is caused by selection pressure for their resistance genes. Full article

Contact insecticides are classified into two categories: as grain protectants, which are applied directly on grains, and as surface treatments, which are applied on cracks and crevices. The aim of this study was to evaluate the long-term residual efficacy of these insecticides across different surfaces and target species. Thus, we investigated the efficacy of three insecticidal formulations, spinosad, alpha-cypermethrin, and pirimiphos-methyl against stored product beetles on different surfaces (concrete, metallic, plastic, and ceramic). Adults of Tribolium castaneum, Sitophilus granarius, and Lasioderma serricorne were used in the experiments. Bioassays were carried out during a six-month period, with mortality measured after 3, 7, 14, and 21 days after exposure. Among the different insecticides tested, spinosad was the least effective against T. castaneum, especially on concrete, where mortality had decreased to zero by Month 2, whereas in most of the cases, close to 100% was recorded. Regarding S. granarius, pirimiphos-methyl and spinosad remained effective on ceramic and metallic surfaces for a six-month period, whereas alpha-cypermethrin had the lowest mortality rate. For L. serricorne, spinosad caused high mortality levels, whereas pirimiphos-methyl was the least effective after Month 4. Based on our finding, among the tested insecticides, spinosad had the long-term residual effect on stored product protection. Full article

The regulation of locomotor behavior is essential for insects to perform their life activities. The central nervous system plays a pivotal role in modulating physiological behaviors, particularly movement, with neuropeptides serving as key modulators of these processes. Among these, adipokinetic hormone (AKH) was originally identified in insects as a neurohormone involved in lipid mobilization. This study investigates the functional role of AKHs (AKH1 and AKH2) and their receptor (AKHR) in regulating locomotion in the red flour beetle, Tribolium castaneum. Using functional calcium reporter assays, we demonstrated that AKHR is activated by two mature AKH peptides from T. castaneum, with half-maximal effective concentrations (EC₅₀) falling within the nanomolar range. Gene expression analysis confirmed the presence of AKH1 and AKH2 transcripts in the brain, while AKHR expression was localized to the fat body and carcass. The silencing of AKHs or AKHR through RNA interference resulted in a significant reduction in both movement distance and duration. Collectively, these findings highlight the regulatory influence of AKH/AKHR signaling in locomotor activity in T. castaneum, thereby advancing our understanding of the molecular mechanisms underlying locomotor control in this economically important insect species. Full article

To contribute to the search for effective substances in pest control, this study describes the fumigant and contact toxicity against Tribolium castaneum and Sitophilus zeamais of four essential oils (EOs) and some of their major chemical constituents. The EOs from Tagetes zypaquirensis, Anethum graveolens, Satureja viminea and Minthostachys mollis were obtained by steam distillation and chemically characterized using GC–MS. In the development of research, some monoterpenoids were isolated from the EOs, others were purchased commercially, and some were synthesized from the most active monoterpenoids present in EOs. The main components in the EOs were dill ether (28.56%), α-phellandrene (25.78%) and carvone (23.67%) for A. graveolens, piperitone oxide (30.40%) and pulegone (25.91%) in M. mollis, pulegone (37.40%) and p-menth-3-en-8-ol (11.83%) for S. viminea, and dihydrotagetone (32.13%), myrcene epoxide (19.64%) and β-myrcene (5.30%) for T. zypaquirensis. The results highlight the fumigant action (LC₅₀) and contact toxicity (LD₅₀) of EO from M. mollis against T. castaneum (LC₅₀ of 4.8 µL/L air and LD₅₀ of 6.5 µg/insect) and S. zeamais (LC₅₀ of 7.0 µL/L air and LD₅₀ of 5.81 µg/insect). Among the chemical constituents evaluated, R-carvone 2, piperitone oxide 5 and R-pulegone 6 stand out for their insecticidal potential against S. zeamais (LC₅₀ between 3.0 and 42.4 µL/L, while LD₅₀ between 14.9 and 24.6 µg/insect) and T. castaneum (LC₅₀ between 2.2 and 4.8 µL/L, while LD₅₀ between 4.8 and 13.1 µg/insect). Preliminary structure–activity analysis suggests that the presence of the carbonyl group with conjugated double bonds in cyclic monoterpenes is important for the insecticidal potential exhibited. Full article

With over 1000 species of pests causing losses in both the quantity and quality of stored food, insect contamination poses significant challenges. The present study assesses the efficacy of the combination of λ-cyhalothrin and chlorantraniliprole against four key storage pests—Trogoderma granarium, Sitophilus oryzae, Rhyzopertha dominica, and Tribolium castaneum. Laboratory bioassays demonstrated species-dependent mortality, with S. oryzae and R. dominica suffering 100% mortality in several tested scenarios. A 90-day persistence trial revealed decreased efficacy over time, especially for T. granarium (32.0–71.4% at 0 days and 0.0–7.5% at 90 days) and T. castaneum (38.8–82.7% at 0 days and 0.0–12.7% at 90 days) vs. S. oryzae and R. dominica. Progeny production of S. oryzae and R. dominica was almost suppressed in persistence trials (0.4 individuals per vial and 1 individual per vial, respectively) after 30 days of storage at the dose of 5 mg/kg wheat. The results highlight the variability in insecticidal performance based on species, dose, exposure, and commodity type, emphasizing the need for tailored pest management strategies in the storage environment. Full article

As a tropomyosin-binding component, troponin T (TnT) is essential for the Ca²⁺ regulation of striated muscles’ contraction and locomotion activity, but its impacts on the growth and development of insects have rarely been reported. In this study, TnT was identified and functionally characterized in Tribolium castaneum by RNA interference (RNAi) and transcriptome analysis. The TnT of T. castaneum contained a 1152 bp open reading frame encoding 383 amino acids. It displayed the highest expression in late pupae and was highly expressed in the integument and CNS. Both the larval and early pupal injection of dsTnT led to 100% cumulative mortality before the pupal–adult transition. Late pupal RNAi caused 26.01 ± 4.29% pupal mortality; the survivors successfully became adults, but 49.71 ± 6.51% died in 10 days with a dried and shriveled abdomen, poorly developed reproductive system and no offspring. Additionally, RNA sequencing results indicated that key ecdysteroid and juvenile hormone biosynthesis genes (CYP314A1, aldehyde dehydrogenase family 3 member B1 and farnesol dehydrogenase) were affected, as well as several cuticle protein, nutrition metabolism and immune-related genes, suggesting that TnT may play prominent roles in development, metabolism and reproduction by affecting these pathways. This study could provide a brand-new target gene in the RNAi strategy for pest control. Full article