Search Results (52)

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

Stored grain pests cause significant economic losses during cereal grain storage. Insecticides have long been central to pest control; however, growing concerns over resistance, environmental harm, and human health demand alternative strategies. Diatomaceous earth (DE) treatments are a safe, eco-friendly alternative to insecticides, although their efficacy depends on the temperature, humidity, dose, and insect species. This study assessed the insecticidal effects of two natively-sourced raw (Ankara and Aydin) and one commercial (Silico-Sec) DE treatments against the key pest species Rhyzopertha dominica (F.) and Sitophilus granarius (L.) on stored wheat. Five doses (0, 250, 500, 750, and 1000 ppm) of each DE treatment were tested under two temperatures (25 °C and 30 °C) and two humidity levels (40% and 60%). Mortality was assessed at 7, 14, and 21 days after treatment (DAT). All DE treatments caused higher mortality in S. granarius than R. dominica. The highest mortality occurred in S. granarius at 30 °C and 40% RH with the highest dose. Aydin DE was most effective, but did not reach 100% mortality in S. granarius by 21 DAT. In contrast, it caused 100% mortality in R. dominica under the same conditions. There was no F₁ progeny produced by surviving individuals of both species. Given the similarity of the environmental conditions to the optimal conditions for DE efficacy present in Turkish storage facilities, natively sourced Aydin DE is a promising control option. 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

Rhyzopertha dominica and Tribolium castaneum are two significant insect pests that affect the quality, quantity, and commercial value of stored products. The aim of this study was to assess the chemical composition, repellency, and insecticidal activity of Pinus halepensis leaf EO on adults of Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). The EO of P. halepensis Mill. was extracted using hydrodistillation and analyzed for its chemical composition by GC-MS. The major components identified were 1-nonadecene (25.51%), 1-hexadecene (20.79%), pimaric acid (16.71%), and palmitic acid (12.47%). The repellency test was determined by the area-preference method. P. halepensis EO exhibited significant repellent activity against T. castaneum and R. dominica. It showed high class IV repulsion rates, reaching 63.60% against T. castaneum and 66.50% against R. dominica. The repellent effect was most potent at the highest concentration tested (16 µL/mL), achieving a 100% efficacy against T. castaneum after 4 h and after 3 h against R. dominica. The contact toxicity test was carried out by impregnating filter paper disks with increasing doses of the EO studied. P. halepensis EO was the most toxic against R. dominica (LC₅₀ = 17.11 µL/mL, LC₉₀ = 30.02 µL/mL) and T. castaneum (LC₅₀ = 20.92 µL/mL, LC₉₀ = 32.18 µL/mL) after 96 h of exposure. The ability of P. halepensis EO to repel and eliminate insects suggests that it could be used as a new treatment to prevent insect infestations of R. dominica and T. castaneum. Full article

Heat shock proteins (HSPs) are crucial molecular chaperones that help organisms maintain protein stability under stress conditions. As a major stored-product pest, Rhyzopertha dominica (Fabricius) faces distinct stresses compared to field insects, primarily due to the specific pest control methods applied during grain storage. In this study, a total of 53 HSP genes from five gene families (HSP90, HSP70, HSP60, sHSP, and DnaJ) were identified and characterized using bioinformatics methods. Among them, DnaJ was the largest and the most diverse HSP family in R. dominica. Transcriptome sequencing and RT-qPCR were then used to evaluate HSP gene expression patterns under four storage-related stresses, following a series of bioassays. Extreme high temperature was the strongest inducer of HSP expression, with 12 genes showing over a 10-fold increase. Controlled nitrogen atmosphere also led to considerable upregulation of HSP genes, especially in the HSP70 family. In contrast, phosphine fumigation and K-Obiol grain protectant caused very limited induction of HSP genes, which might have been due to the less severe protein damage caused by chemical stresses compared to physical stresses. Our study provides a theoretical basis for further research on HSP functions in R. dominica. Full article

The lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) and khapra beetle, Trogoderma granarium E. (Coleoptera: Dermestidae) are primary stored-grain insect pests. Differences in certain biological and physical parameters of both pest species and wheat genotypes were investigated under laboratory conditions. Zinc (Zn)-biofortified (Zincol-2016 and Akbar-2019) and conventional (Arooj-2022, Nawab-2021, Dilkash-2021, Bhakkar Star-2019) wheat genotypes were used in this study. Zn-biofortified genotypes outperformed the conventional ones, with significant differences observed in fecundity, percent adult emergence, total developmental duration, percent grain damage, and weight loss of both insect species. The results further revealed that the fecundity of R. dominica and T. granarium were lowest on Akbar-2019 in both the free-choice test (42.50 and 33.17) and no-choice test (35.50 and 32.50), respectively. Similarly, percent adult emergence of both insect species was also lowest on Akbar-2019 in both the free-choice test (69.78 and 70.28%) and no-choice test (67.38 and 70.71%). The total developmental period also showed significant variation among the tested genotypes. The longest developmental period was recorded in Akbar-2019, i.e., 44.33 and 58.83 days, for R. dominica and T. granarium, respectively. Similarly, percent grain damage (13.23 and 10.33%) and weight loss (3.62 and 2.12%) were found to be minimum in Akbar-2019 for both pest species, respectively. Additionally, a positive correlation was observed between grain moisture content and damage parameters, suggesting that the higher moisture content may aggravate the percent grain damage and weight loss. These findings indicate that the nutritional qualities of Zn-biofortified wheat genotypes negatively affected the development of both insect species; thus, it can be an efficacious approach not only for ensuring food security but also for protecting grains against storage pests. Full article

High-resolution water quality maps derived from imaging spectroscopy provide valuable insights for environmental monitoring and management, but the processing of all pixels of large datasets is extremely computationally intensive and limits the speed of map production. We demonstrate a superpixel approach to accelerating water quality parameter inversion on such data to considerably reduce time and resource needs. Neighboring pixels were clustered into spectrally similar superpixels, and bio-optical inversions were performed at the superpixel level before a nearest-neighbor interpolation of the results back to pixel resolution. We tested the approach on five example airborne imaging spectroscopy datasets from Hawaiian coastal waters, comparing outputs to pixel-by-pixel inversions for three water quality parameters: suspended particulate matter, chlorophyll-a, and colored dissolved organic matter. We found significant reduction in computational time, ranging from 38 to 2625 times faster processing for superpixel sizes of 50 to 5000 pixels (200 to 20,000 m²). Using 1000 paired output values from each example image, we found minimal reduction in accuracy (as decrease in R² or increase in RMSE) of the model results when the superpixel size was less than 750 2 m × 2 m resolution pixels. Such results mean that this methodology could reduce the time needed to produce regional- or global-scale maps and thereby allow environmental managers and other stakeholders to more rapidly understand and respond to changing water quality conditions. Full article

Post-harvest losses due to insect infestation and spoilage by bacteria and molds pose significant challenges to global cereal production. This study investigates the prevalence of resistance to phosphine, a commonly used grain protection agent, in stored-grain insects. The research, conducted in various storage facilities across Greece, examined 53 populations of key stored-product insect species. Two assessment protocols, namely, dose–response (at 50–1000 ppm for 3 days exposure) and CORESTA (at 300 ppm for 6 days), were used herein to estimate phosphine resistance. The results showed that 13.3% of field populations were resistant, and mortality rates increased with higher phosphine concentrations. Specifically, according to the dose–response protocol, among the 53 field populations, 37.7% were found to be resistant to phosphine, namely, two populations of O. surinamensis, one of S. oryzae, seven of T. confusum, one of C. ferrugineus, one of T. castaneum, and all populations of R. dominica, whereas, according to the CORESTA protocol, all populations were found to be susceptible to phosphine. The observed resistance patterns differ from those reported in other regions of the world. The study highlights the importance of tailored fumigation strategies, considering insect species varying susceptibility to phosphine. It recommends the use of best management practices and rotational strategies, such as combining phosphine with other methods, to develop effective resistance management plans. The results provide valuable insights into the dynamic landscape of phosphine resistance in stored-product insects and suggest potential avenues for further research and control measures. Full article

Rhyzopertha dominica causes significant economic losses in stored cereals. Insects’ digestive tract microbiome is crucial for their development, metabolism, resistance, and digestion. This work aimed to test whether the different chemical properties of different wheat and barley grain cultivars cause disturbances in insect foraging and rearrangements of the structure of the R. dominica microbiome. The results indicated that grain cultivars significantly influence the microbiome, metabolism, and insect foraging. Most observed traits and microbiome structures were not correlated at the species level, as confirmed by ANOSIM (p = 0.441). However, the PLS-PM analysis revealed significant patterns within barley cultivars. The study found associations between C18:2 fatty acids, entomopathogenic bacteria, an impaired nitrogen cycle, lysine production of bacterial origin, and insect feeding. The antioxidant effects also showed trends towards impacting the microbiome and insect development. The findings suggest that manipulating grain chemical properties (increasing C18:2 and antioxidant levels) can influence the R. dominica microbiome, disrupting their foraging behaviours and adaptation to storage environments. This research supports the potential for breeding resistant cereals, offering an effective pest control strategy and reducing pesticide use in food production. Full article

The increasing food crisis in times of ecological threats has challenged conventional agriculture to transform into a more efficient and sustainable agri-food system. The global priority of these activities has become, among others, the responsible and effective use of already produced food. This study aimed to assess the impact of the natural resistance of cereal grains to consumption by storage pests. The study presented here analyzed the impact of selected chemical factors from the grain of six species of cereals (wheat, triticale, rye, barley, oat, corn) on the development of one of the most dangerous storage pests—the lesser grain borer Rhyzopertha dominica F. The increased development of this beetle on the tested grain was determined based on the number of progeny, the mass of dust produced, and the loss of grain mass. Moreover, the correlations between the above-mentioned development parameters of the pest and the content in the grain of dry matter, crude ash, total protein, crude fat, starch, and water-soluble carbohydrates (WSCs) were examined. The results showed that the tested pest developed most intensively on barley and triticale grains and was least abundant on oat and corn grains. Chemical analysis of the selected grain showed that the low number of the R. dominica progeny population was correlated with a higher crude fat content and a lower total protein content in the cereal grain, and therefore, these chemical properties could affect the development of the pest. Knowledge of these relationships can be used in cereal breeding programs and when recommending cereals for more extended storage. This directly translates into improved local and global nutritional and food security. Moreover, it may also contribute to the reduction of pesticide use at the storage stage, which is one of the basic requirements for agricultural production in a sustainable agriculture system. Full article

Human monocytic ehrlichiosis, an emerging tick-borne disease, is caused by Ehrlichia chaffeensis. Infections with the pathogen are also common in the canine host. Our previous studies demonstrated that functional disruption within the E. chaffeensis phage head-to-tail connector protein gene results in bacterial attenuation, creating a modified live attenuated vaccine (MLAV). The MLAV confers protective immunity against intravenous and tick transmission challenges one month following vaccination. In this study, we evaluated the duration of MLAV protection. Dogs vaccinated with the MLAV were challenged with wild-type E. chaffeensis via intravenous infection at 4-, 8-, and 12-months post-vaccination. Immunized dogs rapidly cleared the wild-type pathogen infection and tested positive for bacteremia less frequently than unvaccinated controls. While immune responses varied among dogs, vaccinees consistently mounted IgG and CD4+ T-cell responses specific to E. chaffeensis throughout the assessment period. Our findings demonstrate that MLAV-mediated immune protection persists for at least one year against wild-type bacterial infection, marking a major advancement in combating this serious tick-borne disease. The data presented here serve as the foundation for further studies, elucidating the molecular mechanisms underlying virulence and vaccine development and aiding in preventing the diseases caused by E. chaffeensis and other tick-borne rickettsial pathogens. Full article

Phosphine (PH₃) has been widely used as a fumigant in food storage, but increasing PH₃ resistance in major pests makes finding alternative fumigants urgent. Methyl benzoate (MBe), a volatile organic compound regarded to be a food-safe natural product, has recently demonstrated significant toxicity against a variety of insect pests. This study is the first evaluation of the fumigation toxicity of three benzoate compounds, MBe, vinyl benzoate, and ethyl benzoate, against PH₃-susceptible and PH₃-resistant strains of Rhyzopertha dominica and Sitophilus oryzae. All strains were exposed to the compounds at concentrations up to 20 µL/1.5 L air for 24 h. Compared to vinyl benzoate and ethyl benzoate, MBe induced higher mortality rates in all strains at all concentrations. When food was made available, the lethal median concentration for MBe was 10–17-fold higher than when tested without food. Moreover, no significant differences were observed between the responses of the PH₃-susceptible and PH₃-resistant strains to the compounds. Notably, S. oryzae was more susceptible to MBe. In laboratory settings, MBe successfully controlled PH₃-resistant strains of R. dominica and S. oryzae, making it a viable option for PH₃-resistance management. Thus, MBe might be suitable for food security programs as an environmentally benign alternative fumigant. Full article

We evaluated the persistence and efficacy of two different, in granulometry and content of diatoms, diatomaceous earth (DE) formulations (i.e., DE5 and DE6), against two major beetle species of stored products, i.e., Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). The formulations were applied as powders in soft wheat and maize in two doses of 500 and 1000 mg kg⁻¹ (ppm). Samples of the treated grains were taken on the day of application and every 30 days until completion of the six-month period of storage. Adults of S. oryzae and R. dominica were exposed to the treated grains at 25 °C and 55% relative humidity, and the mortality was measured after 7, 14, and 21 days of exposure. Rhyzopertha dominica survival was not affected by any combination of DE formulation, dose, and commodity. Contrariwise, the DEs caused significant adult mortality of S. oryzae, in most of the cases tested. We observed that DE6 was equally effective in both wheat and maize, and no considerable variations were observed in S. oryzae mortality during the 6-month experimental period. Furthermore, DE6 was more effective against S. oryzae than DE5, a difference that could have potentially contributed to the variations in the diatom granulometry between these two DEs. Thus, a DE treatment of 1000 ppm was shown to provide long-term protection of wheat and maize against S. oryzae, but this is strongly dependent on the DE formulation, commodity, and insect species. Overall, such natural resource-based inert silicaceous deposits could be used with success in stored-product protection with only some minor modifications, such as sieving and drying of the raw deposit. Full article

Tribolium castaneum, Trogoderma granarium, Oryzaephilus surinamensis, Sitophilus oryzae, Rhyzopertha dominica, and Cryptolestes ferrugineus are all major pests of stored grains. In this study, the efficiency of single and joint applications of the entomopathogenic nematode (EPN) Steinernema carpocapsae at two different doses (50 and 100 IJs cm⁻²) and the entomopathogenic fungus (EPF) Beauveria bassiana for the management of the aforementioned pests was estimated. At single treatments, both doses of S. carpocapsae caused higher mortality rates to all six pest species compared to B. bassiana. The combined treatment of EPF and EPN resulted in higher mortality compared to single treatments. Mortality was strongly influenced by the exposure interval and the application dose of the EPN at both single and combined treatments. Maximum mortality was observed for the application of the combined treatment at the high dose of S. carpocapsae and B. bassiana. Among the different insect species tested, the maximum mortality rate was observed for R. dominica (96.62%), followed by S. oryzae (90.48%), T. castaneum (87.23%), C. ferrugineus (76.05%), O. surinamensis (70.74%), and T. granarium (57.71%). The outcomes of this study demonstrate the potential of utilizing specific combinations of EPF and EPN as effective natural enemies against stored-grain pests. Full article

Diatomaceous earth (DE) formulations are promising alternatives over the use of traditional insecticides. In the present study, a series of laboratory bioassays was carried out to assess the efficacy of three diatomaceous earth formulations, i.e., Silicid, Celatom^® MN-23, and SilicoSec^®, for the control of a wide range of stored-product insect species in soft wheat. The species tested were Tribolium confusum, Tribolium castaneum, Sitophilus oryzae, Sitophilus granarius, Rhyzopertha dominica, Oryzaephilus surinamensis, and Alphitobious diaperinus. Different dose rates, i.e., 0 (control), 100, 300, 500, and 1000 ppm, were used for each of the aforementioned dust formulations. Mortality levels of the exposed individuals were assessed after 3, 7, 14, and 21 days of exposure. Moreover, progeny were counted 65 days later. Based on our results, dust formulations were effective for the control of most of the stored-product beetle species tested. Among the DE formulations tested, Silicid could adequately control the stored-product insect species. Complete suppression of offspring was observed only for secondary species (T. confusum, T. castaneum, O. surinamensis, and A. diaperinus). For primary species (S. oryzae, S. granarius, and R. dominica), the lowest number of progeny was observed in wheat treated with Silicid. For instance, in the case of R. dominica, significantly fewer individuals were produced in Silicid-treated wheat at the highest dose rate. The results of the present study aim to encourage the utilization of DE in stored-product protection as an integrated pest management tool. Additional experimentation is required to apply the tested DE formulations in the field and on different surfaces. Full article