Stored-product Pests Research Articles

Seed-Specific Dynamics: Unraveling Progeny Emergence Patterns in <em>Tribolium castaneum</em> (Herbst) (Coleoptera: Tenebrionidae) Infestations

Edible seeded crops are important nutrient source for both human and animals. Among the various causes of grain losses before consumption, stored-product pests claim an important place. Tribolium castaneum (Herbst) damages a wide array of food commodities including grains, during storage, but the information on progeny emergence on certain commodities still remains unexplored. A laboratory experiment was conducted to evaluate the progeny development of T. castaneum in commonly used edible seeds during storage. Twenty, one-month-old T. castaneum adults were introduced to 30 g samples of each seed type, with four replicates tested. Except for dhal and groundnut, all the other edible seed types were used only as whole seeds. Test samples of dhal and groundnut were used in their whole form as well as 50% broken seeds. Samples were maintained at 30±1°C and 65±1% relative humidity. After 7 days, adults were removed, and samples were kept for progeny development. Progeny adults and larvae were counted at 30 and 60 days. The adult progeny emergence was highest in oats, sesame and proso millet (Meneri). Larval emergence was higher in dhal (50% broken), groundnut (50% broken), barley and proso millet (Meneri). These findings provide important insights into the infestation of edible seeds by T. castaneum and opens-up avenues for adopting suitable methods to protect these during storage. As the presence of broken seed enhances the progeny development of T. castaneum, preventing such occurrences during grain processing and maintaining cleanliness are important practices during postharvest operations.

Bioassays of Fumigant Toxicity and Repulsiveness of Haplophyllum tuberculatum Extracts

Abstract Food grains were severely damaged by stored goods insects. The red flour beetle Tribolium castaneum, the cigarette beetle Lasioderma serricorne and the rice weevil Sitophilus orysae are some of the most destructive pests which attack raw cereals throughout the world. In stored grain mill, fumigation with synthetic fumigants was the most economical tool for managing stored pests. Nevertheless, the application of chemical pesticides caused adverse effects on humans and environment. Chloroform, acetone, methanol and water extracts and essential oil of Haplophyllum tuberculatum aerial parts were tested for their fumigant and repellent effect against adults of the three stored products pests (T. castaneum, L. serricorne and S. oryzae). GC/MS analysis of the essential oil resulted in determination of 19 compounds. The major constituents were β-phellandrene (16.17%), trans-p-menth-2-ene-1-ol, (13.22%) and cis-p-menth-2-ene-1-ol (8.29%). Thus, it seemed that the essential oil had the highest fumigant activity against L. serricorne after 12 h of exposure compared to the two other insects with a LC50 equal to 38.59 µ.l-1 air. The best repellency was observed for the chloroform and methanol extracts against T. castaneum. The respective repellent doses RD50 values were = 0.03 and 0.04 mg.ml-1 after 24 h of exposure. However, after 24 h of exposure acetone extract seems to be more repellent with respective repellent dose values of = 0.14 mg.ml-1 (RD50) against L. serricorne. H. tuberculatum essential oil and extract proved to be effective in control pest infestations in grains and dry food products.

Behavioral responses of Araecerus fasciculatus (Coleoptera: Anthribidae) to volatiles of selected stored Chinese medicinal plant products.

The olfactory responses of Araecerus fasciculatus Degeer to the volatiles of 5 traditional Chinese medicine plant products (CMPPs; i.e., Codonopsis pilosula Franch., Ophiopogon japonicus Linn. f., Astragalus membranaceus Fisch., Dendrobium nobile Lindl., and Angelica dahurica Fisch.) were studied using Y-tube, 4-arm, and 6-arm olfactometers. The volatile components of these CMPPs were analyzed using gas chromatography-mass spectrometry (GC-MS). A. fasciculatus significantly preferred the CMPPs volatiles in the order of O. japonicus > C. pilosula > A. membranaceus ≥ D. nobile = A. dahurica. In the volatile profiles of O. japonicus, C. pilosula, A. membranaceus, D. nobile, and A. dahurica, GC-MS identified 27, 61, 63, 52, and 71 components, respectively, and β-elemene (30.58%), hexanal (12.69%), selina-3,7(11)-diene (12.31%), d-limonene (18.59%), and α-curcumene (8.88%) were the most abundant volatile components. A. fasciculatus were attracted to β-elemene, α-selinene, and β-selinene (main components of the volatile profiles of the most preferred CMPPs of O. japonicus) at different concentrations, with 1, 50, and 25 µg/µl being the most attractive, respectively. The olfactory preferences of A. fasciculatus were β-elemene > α-selinene = β-selinene based on the 4-arm olfactometer bioassays for comparisons at their most attractive concentrations. Therefore, differences in the volatile profiles among CMPPs significantly influenced the olfactory responses of A. fasciculatus, offering insight into the mechanisms of host preferences in stored-product pests based on chemical ecology. β-elemene showed the greatest potential to be developed as an attractant for the monitoring and control of this pest.

Extraction and evaluation of chitosan as an insecticide against saw-toothed grain beetle, <i>Oryzaephilus surinamensis</i> L. (Coleoptera: Silvanidae)

Rice samples infested with saw-toothed grain beetles have been collected from a local market in the city of Kirkuk/Iraq. The study was conducted in Kirkuk during the period 15 December 2023 to 25 April 2024, at College of Pure Sciences at the University of Kirkuk, Iraq. Chitosan was utilised in the study to examine its toxic effects at three different concentrations (0.5, 1.0, 1.5 ppm) on the life cycle of the saw-toothed grain beetle, focusing on oviposition rate, duration of larval and pupal stages, and mortality rate of its adults. The chemical demonstrated a substantial effect in lowering the number of eggs laid as the concentration increased, with the control treatment registering the highest oviposition rate of 314.14 eggs compared to 209.31, 117.03, and 61.12 eggs for chitosan concentrations of 0.5, 1.0, and 1.5 ppm, respectively. The shortest egg incubation period recorded was 8.17 days, Incubation times for chitosan treatments increased significantly to 9.66, 11.69, and 14.00 days for concentrations of 0.5, 1.0, and 1.5 ppm, respectively, demonstrating an inverse association with concentration levels. Furthermore, the emergence rate of beetles decreased as concentration increased. The emergence counts for the chitosan treatments at concentrations of 0.5, 1.0, and 1.5 ppm dropped to 133.11, 55.69, and 30.12 beetles, respectively, with the control treatment having the highest average emergence of 289.43 beetles. The larval stage duration showed a direct proportionality with chitosan concentrations, with the 1.5 ppm concentration marking the longest larval duration at 22.00 days, significantly surpassing all other concentrations. The control treatment recorded the shortest duration at 13.56 days, whereas 0.5 and 1.0 ppm concentrations resulted in duration of 17.19 and 19.66 days, respectively. For the pupal stage, significant differences were observed with increasing chitosan concentration; the control treatment displayed the shortest pupal duration at 4.33 days. A direct relationship was found between the concentrations and pupal stage duration, reducing the period to 6.00, 7.59, and 9.07 days for concentrations of 0.5, 1.0, and 1.5 ppm, respectively. Chitosan exhibited significant differences from the second day of the experiment, as the mortality rate increased with concentration and over time. The concentration of 1.5 ppm showed the highest mortality rate at 98.62% after 16 days, whereas the control treatment recorded the lowest rate at 33.17%. Based on the results of the current study, chitosan can be utilized as an effective pesticide for controlling stored-product pests, particularly the saw-toothed grain beetle.

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.

Behavioural responses of Sitophilus granarius (L.) and Rhyzoperta dominica (F.) to odours of old and modern wheat genotypes

Sitophilus granarius (L.) and Rhyzopertha dominica (F.) are among the major stored-product pests worldwide. The identification of low or un-attractive wheat genotypes toward storage pests and their Volatile Organic Compounds (VOCs) profile is useful in breeding programs and in characterization of behaviourally active compounds suitable in developing semiochemical-based control means. Old wheat cultivars are genetic resources useful for breeding purposes. In this study, the VOC profiles of old genotypes, Senatore Cappelli, old Saragolla, Dauno III, and modern wheat varieties, Mec, Ofanto, Svevo, and Faridur, were characterized by headspace - solid phase microextraction (HD-SPME) and gaschromatography coupled with mass spectrometry (GC-MS) and their attractiveness towards S. granarius and R. dominica adults was evaluated in two-choice pitfall bioassays and Y-tube olfactometer, respectively. Sitophilus granarius adults were significantly attracted to odours of all varieties, with females being significantly more attracted by Faridur, Ofanto, Mec, and old Saragolla compared to Svevo. Rhyzopertha dominica males and females exhibited a significant olfactory preference for the odours of Faridur, Mec, and old Saragolla. The olfactory preferences of both species could be related to differences emerged in varietal VOC profiles. The most attractive variety for both species, Faridur, was rich in alcohols, alkanes, and terpenes. Old Saragolla, Ofanto, and Mec were rich in alcohols and organic acids. Dauno III was the richest variety in alcohols and lactones, and the poorest in aldehydes and terpenes compared to other varieties. Svevo showed the lowest amounts of alcohols and the highest value of aldehydes; Senatore Cappelli was rich in aldehydes, organic acids, and alkanes. The possible effects of the differences in VOC profiles on the olfactory preferences of insects are discussed. The study offers new knowledge for further investigation testing VOCs of the most and the lowest attractive varieties to identify effective attractants or strong repellents towards S. granarius and R. dominica.

Studies on the Response of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) to Multicolour Light System

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) commonly known as rust red flour beetle was a universal pest of stored produce with an extensive feeding diversity. The management of T. castaneum in field conditions was through fumigation and spraying of suitable insecticides. Even though many plant products were found effective against pests in invitro conditions, they could not be mixed with the stored produce for fear of losing the table quality. Physical forces seemed to be good alternatives to chemical treatment as far as stored grain pests were concerned. The use of gamma and UV radiations, microwaves and ultrasonic sound waves against T. castaneum and other stored grain pests had been tried by many authors. The objectives of this study were to check the adult beetles and final instar grubs of T. castaneum to different colours of light and it showedpreference for clear tungsten (white) light, while they were averse to red coloured light. This trend was explicit even after the entrainment of beetles to red colour light for further generations. Based on these results it could be presumed that T. castaneum adults preferred to move away from red coloured light. By changing the colour of bright light to dark lighting in warehouses, it could be possible to manage T. castaneum in small measure. Total eradication of stored product pests like T. castaneum was at least possibility and the selection of a proper management system could help to solve the stored produce pest problem to a greater magnitude.

Challenges in Assessing Repellency via the Behavioral Response by the Global Pest Tribolium castaneum to Protect Stored Grains.

Food security is an increasingly pressing global issue, and by 2050, food production will not be sufficient to feed the growing population. Part of global food insecurity can be attributed to post-harvest losses, including quantity and quality losses caused by stored-product pests like insects. It is thus timely to find management strategies to mitigate these losses and counteract food insecurity. The red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), a global stored-product pest with a wide range of food sources, was used in this study to assess repellency to a selection of essential oils. Multiple behaviorally relevant methods were used to determine the efficacy of the essential oils in assays to pinpoint the most promising repellents. Experiments were used to assess individual and group behaviors with or without airflow and examined the behavioral variation in distance moved and the time spent away from the oil. It was found that exposure to essential oils and conditions of experimentation considerably influenced T. castaneum's behavioral response, but a clear candidate for repellency could not be chosen based on the collected data. Follow-up research is needed to pinpoint repellents for integrated pest management practices to protect grains from stored-product pests and to justify their use in and around commodities.

Survival and development of Cadra cautella (Walker) (Lepidoptera: Pyralidae) on cocoa bean and cocoa powder

The almond moth Cadra cautella (Walker) is a notable stored product pest which can cause detrimental loss on stored cocoa. Cocoa can be stored in bean and powder forms. The information about survival and development of C. cautella on stored cocoa is limited. This research aimed to determine the effect of cocoa powder and cocoa bean in the storage against the survival and development of C. cautella. This research was conducted in Plant Pests Laboratory, Department of Plant Pests and Diseases, Faculty of Agriculture, Universitas Brawijaya. This research consisted of two treatments namely cocoa bean and cocoa powder with no choice method and repeated six times. The observed variables were number of larvae, pupae, male and female almond moth of F1 progeny, and developmental time of this insect. The t-test analysis was applied to determine the treatment effect. Results showed that the number of larvae, pupae, adult males and females of F1 progeny cultured on cocoa powder were significantly higher than on cocoa bean. The total developmental time and life cycle of almond moth were shorter on cocoa powder than on cocoa bean. Therefore, to store cocoa in powder form is riskier to the almond moth infestation rather than in bean form. Hence, it is suggested to take more concern on the cocoa powder storage better in order to minimize the almond moth infestation.

Evaluation of the crude chitinases toxicity on the reproductive system of Callosobruchus maculatus (Coleoptera: Bruchidae)

Insecticides represent the most used control method against the insect pests of stored food products. But there are strains of insects which are resistant to these insecticides: it is the case of the beetle of the chickpea Callosobruchus maculatus. The present study has for objective the evaluation of the biological activity of chitinolytic enzymes extracted from the fish offals Scorpaena scrofa (scorpion fish) on this beetle at different doses (3%, 6%, 9%, 12%, 15% and 21%) prepared with the buffer solution. The results obtained from three treatments (T1, T2 and T3) realized according to the dose of the crude enzyme and the time of exposure were compared with those of the controls and have showed a very significant efficiency of our crude enzyme on the reduction of the fertility rate of 100% by treating the couple (T1) at the same time as to treat the male (T3) and the female (T2) separately with the strongest dose (21%) for 48 h of exposure. It would be thus desirable to demonstrate the activity of these enzymes in the real conditions of storage.

Effects of Some Plant Powders on Immatures of Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) on Stored Cocoa Beans

Rice moth, Corcyra cephalonica, an important insect pest of many stored food products has been reported as one of the most important pest of cocoa bean, which causes significant reduction in weight and quality of beans. High pesticides level in cocoa beans pose danger to human health and may hinder its acceptance in the global market due to regulations on Maximum Residue Limit (MRL). This study therefore, evaluated the insecticidal effects of the powders of Piper guineense, Aframomum melegueta, Eugenia aromatica and Rice husk on egg hatchability and larva mortality of C. cephalonica. Powder efficacies as insecticides were tested by applying varying rates (0.0, 0.1, 0.2, 0.3 and 0.4g) on petri dish lined with filter paper and the developmental stages (20 eggs and 10 larvae) of the insect were introduced in a Completely Randomized Design experiment. Egg hatchability was recorded at 24 h interval for 96 h. Larvae mortality was recorded at every 24 and 48 h of introduction. All powders completely inhibited egg hatchability at 0.3 and 0.4g rates. P. guineense and A. melegueta recorded 60% and 50% larva mortality at 48hour post treatment. Mean adult emergence was zero at higher rates in all treatments. Powders of P. guineense and A. melegueta were effective as contact bio-insecticide against C. cephalonica immature stages

Determination of Biology and Prey Preference of the Predator Insect, Xylocoris flavipes (Reuter) (Heteroptera: Anthocoridae) Against Storage Pests

This study was carried out to determine the biology of Xylocoris flavipes Reuter (Heteroptera: Anthocoridae), an important predator of stored product pests, and its prey preference on some warehouse pests. The study was conducted under laboratory conditions at 25±2ºC temperature and 55±10% humidity. Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs were used to determine the biology of X. flavipes. E. kuehniella, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae), and Trogoderma granarium Everts (Coleoptera: Dermestidae) larvae were utilized to detect the prey preferences of X. flavipes. The mean development time (days) of five nymphs, female and male adults of Xylocoris flavipes on E. kuehniella eggs were as follows: 4.2±0.63; 3.1±0.57; 2.9±0.57; 3.0±0.00; 4.5±0.53; 104.2±17.01; 114.6±12.34, respectively. The average egg consumption for the aforementioned stages was: 5.0±1.76; 9.9±3.07; 9.1±6.01; 13.3±4.14; 22.5±4.79; 515.6±75.46; 286.2±24.39, respectively. Although mature male X. flavipes survived longer than females, females consumed more E. kuehniella eggs than males. The mean oviposition period of the females was 36.7±12.39 days, and the average laid egg number was 117.3±29.86. The consumed E. kuehniella eggs and larvae, T. confusum, and T. granarium larvae during the predator nymph period were on average 63.1±6.01; 49.6±2.76; 26.8±3,52; 12.8±4.29, respectively. The average development time (days) of the nymphs for the aforementioned consumption stages were 16.4±1.96; 15.4±0.52; 16.2±1.14; 21.6±4.62, respectively. The consumed E. kuehniella eggs and larvae, T. confusum, and T. granarium larvae during the predator adult period were on average 570±231.32; 249.5±142.10; 218.1±110.57; 22.2±6.23, respectively. The average development time (days) of the adults for the aforementioned consumption stages were 87.5±30.92; 75.9±41.18; 89.3±43.55; 24.5±7.18 days, respectively. X. flavipes preferred mostly E. kuehniella eggs among the preys during the nymph and adult stages, and least T. granarium larvae.

Effects of modified atmospheres, temperature and humidity on the growth and development of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in feihe infant milk powder

Tribolium castaneum (Herbst) is a common stored product pest that damages various stored goods across the global. To identify the effects of modified atmospheres (MA), humidity and temperature on the growth and development of T. castaneum in Feihe infant milk powder, the modified atmospheres were set at 75% nitrogen (N2) and 25% carbon dioxide (CO2), with air as the control. Two different temperatures and humidities were set at 30 °C, RH 80% and 25 °C, RH 40%. The results revealed that T. castaneum larvae exposed to the warm and moist southern conditions (30 °C, RH 80%) feeding on flour and yeast diet had a significantly shorter developmental duration. The larval weights were significantly increased in T. castaneum feeding flour and yeast diet compared with those of T. castaneum feeding milk powder under high temperature. The elevated temperature significantly increased the mortality of larvae. However, 4.4% of the survival larvae successfully grow into adults at the cool and dry northern conditions (25 °C, RH 40%). The mortality rate of eggs was 100% when eggs were sealed and treated by MA under warm and moist temperature and humidity for 96 h, and the mortality rate of 5th instar larvae increased to 100% on 7th day. Moreover, the activities of CAT and GST were decreased in all stages of T. castaneum feeding on infant milk under temperature and humidity stress. Additionally, 5th instar larvae fed with infant milk powder showed significantly fluctuated activity of POD, SOD and P450 in all stages of T. castaneum. However, T. castaneum is more susceptible to milk powder sealing with air under warm and moist temperature and humidity. The present investigation demonstrated that temperature treatment and modified atmospheres effectively prevented growth and development of T. castaneum in milk powder. These results also contribute to suitable strategies for storage of milk power.

Odourless vegetable oils as insect pest repellents for short-term protection of various food packaging materials

The repellent activity of two odourless vegetable oils (sweet almond—SAO and soybean—SO) applied on filter paper and four types of food packaging materials (polyethylene film, plastic gunnysacks, cardboard, and wood) was tested against three species of stored product pests (Sitophilus granarius, Tribolium castaneum, and Oryzaephilus surinamensis). The repellence of three doses was evaluated after 24 h, and after 7, 14, 21, and 28 days. Both oils exhibited a repellent effect when applied to filter paper, but this effect decreased with time and concentration. The most susceptible species was T. castaneum. The maximum repellence was 84% and 76% for SO and SAO, respectively. On packaging materials, the repellent effect diminished after a certain period of time, ranging from 7 to 28 days. Subsequently, the oils even became attractive. Generally, the repellent effects of both SO and SAO were higher on cardboard and wood slab than on polyethylene film and plastic gunnysacks. As such, in the case of SO, the repellence against T. castaneum was 88% 24 h after application on cardboard, whilst 68% on plastic bag. This work demonstrated the repellent potential of vegetable oils in the short term for the protection of packaged food against stored product pests.

Insecticidal, physiological, and biochemical effects of Schinus molle essential oil on the adults of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

Rhyzopertha dominica (F.) is considered as a major stored product pest. Conventional insecticides induce adverse effects on the environment. Plant derivative products constitute a promising alternative for pest control. The purpose of our research was to identify the chemical profile of essential oil (EO) extracted from Schinus molle L. (Anacardiaceae) and to evaluate the fumigant and the contact toxicity, and the repellent activity of this oil on adults of Rhyzopertha dominica F. (Coleoptera), a major pest in products that are stored around the world. The effects of this oil were examined on biochemical profile (energy reserves and Proteins), selective biomarkers like acetylcholinesterase (AChE), glutathione S-transferases (GST) and glutathione (GSH), and nucleic acids (DNA and RNA). Digestive enzymes were also investigated. The major chemical compounds identified by the GC-MS were α-phellandrene (16.613%), ß-phellandrene (12.104%), elemol (9.028%) and β-eudesmol (5.872%). Then, we evaluated the repellent activity, and also the effects in nutritional reserves and some biomarkers. This EO exhibited an insecticidal and repellent activity as a function of the exposure time and concentrations. Contact (LC50 at 24 h: 19.99 μL/mL) is the most effective mode of application compared to fumigation (LC50 at 24h: 174.30 μL/L air). S. molle EO was also investigated in digestive enzymes’ activities (α-amylase, lipase, chitinase and protease). Our results revealed a decrease in both α-amylase, lipase, protease and chitinase activities in treated adults compared to controls. In addition, we noticed a neurotoxic activity of S. molle EO traduced by a decrease of AChE. An induction of the detoxification system was observed via a decrease in GSH rate and an increase in GST activity. Moreover, the treatment induces an alteration of biochemical profile of R. dominica adults. Lastly, essential oil was examined on nucleic acids. Results showed an increase in DNA and RNA amount in treated adults when compared with control. Due to their effective source of bioactive compounds, the EO from the studied plant could be used as an alternative strategy for the management of stored product pests.

Sublethal Effects of Chlorantraniliprole on the Mobility Patterns of Sitophilus spp.: Implications for Pest Management.

Chlorantraniliprole, an anthranilic diamide insecticide, has emerged as a promising solution for controlling agricultural pests because of its low mammalian toxicity and selectivity towards non-target organisms. This study investigated the sublethal effects of chlorantraniliprole on the mobility behavior of two significant stored-product pests, Sitophilus oryzae (L.) and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Contact toxicity assays revealed varying susceptibility levels between the two species, with S. zeamais showing higher sensitivity. Subsequent analysis of mobility behavior, both in the presence and absence of food, indicated significant differences between chlorantraniliprole-exposed and control groups. While S. oryzae exhibited altered locomotion patterns and a decreased number of food approaches at sublethal concentrations, S. zeamais displayed increased walking time and reduced immobility periods. These findings highlight the importance of considering sublethal effects in understanding the overall impact of chlorantraniliprole on stored-product pests. Further research into the long-term consequences of sublethal exposure is warranted to inform more effective pest management strategies in storage.

Toxicity of Essential Oil from Plectranthus amboinicus (Lamiales: Lamiaceae) against Sitophilus zeamais (Coleoptera: Curculionidae)

Abstract Maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), is a major insect pest of stored grain products, causing extensive damage to both grain quantity and quality. The application of synthetic insecticides to control this insect has a negative impact on human health and the environment. Essential oils derived from natural plants are recognized as user- and environmentally friendly alternatives. The use of essential oils from Lamiaceae, which exhibit toxic properties through contact, fumigation, and repellency, provides another option for protecting stored products from various insect pests. The aim of this research was to study the chemical constituents and insecticidal activity of essential oil extracted from the leaves of Indian borage, Plectranthus amboinicus (Lour.) (Lamiales: Lamiaceae), against S. zeamais adults.The chemical composition of the essential oil was analyzed using gas chromatography–mass spectrometry, and the insecticidal activity against adult maize weevils was investigated in the laboratory. The experimental plan followed a completely randomized design with five replications of seven treatments or concentrations of the essential oil: 0, 0.5, 1, 1.5, 2, 2.5, and 3 µl/ml air. The results revealed that the essential oil from the leaves of P. amboinicus contained 23 chemical constituents (97.51%). Thymol (49.96%) was identified as the main compound followed by caryophyllene, trans-α-bergamotene, 3-methyl-4-isopropylphenol, γ-terpinene, p-cymene, caryophyllene oxide, humulene, 4-hydroxy-2-methylacetophenone, 2-hydroxy-2-phenylbutyramide, (2-oxazolidinylidene)malononitrile, hexestrol, terpinen-4-ol, 1-octen-3-ol, (1R,7S,E)-7-isopropyl-4,10-dimethylenecyclodec-5-enol, α-bisabolene, isoaromadendrene epoxide, α-farnesene, 4-carene, α-muurolene, 3-hexen-1-ol, ledene oxide-(II), and α-myrcene, respectively. The fumigation toxicity (median lethal concentration) to maize weevil adults at 48 h was 292.53 µl/ml air. The essential oil from the leaves of P. amboinicus, when applied at a concentration of 2 µl/ml air for 144 and 168 h, resulted in adult maize weevil mortality exceeding 90%. The highest concentration tested (3 µl/ml air) led to exceptionally high mortality rates, with 99–100% of the maize weevils succumbing to the treatment. These findings demonstrate that essential oil from P. amboinicus leaves holds promise as a fumigation insecticide for reducing the population of maize weevils, a significant pest in stored products.

Toxicity and Repellent Activity of Hedychium flavum Rhizome Essential Oil and Major Constituents Against Stored Product Insects1

Abstract An essential oil extracted from the rhizome of wild ginger, Hedychium flavum Roxburgh (Zingiberaceae), was evaluated for its toxic and repellent activity against adults of the stored product pests Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), Lasioderma serricorne (F.) (Coleoptera: Anobiidae), and Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae). Gas chromatography–flame ionization detection and gas chromatography–mass spectrometry revealed 24 compounds that composed 90.52% of the constituents of the extracted oil. The main compounds identified were β-pinene (33.52%), linalool (15.56%), and 1,8-cineole (11.20%). These three compounds and the rhizome essential oil were further assayed for their contact toxicity, fumigant, and repellent properties against the three stored product pests. Contact toxicity bioassays determined median lethal dosages (LD50 values) of the essential oil as 22.3 µg/adult for T. castaneum, 11.3 µg/adult for L. serricorne, and 109.9 μg/cm2 for L. bostrychophila. Analysis of the fumigant toxicity bioassay established LC50 values of 15.6 mg/L air for T. castaneum and 7.6 mg/L air for L. serricorne. The rhizome essential oil had higher repellent activity against the three stored product pests. Our results indicate the potential of the essential oil from rhizomes of H. flavum and its three main components as potential botanical insecticides for management of stored product pests.

Surface application of diatomaceous earth, SilicoSec® are effective on Sitophilus granarius and Rhyzopertha dominica, but less against Tribolium confusum

Diatomaceous earth (DE) has a promising potential in the control of stored-product pests. Most of the studies on the insecticidal potential of DE products are based on their persistent effects or the mortality they lead to via mixing with the grain. However, the knowledge on the performance of DEs on a particular surface is limited. In the current study, the insecticidal efficacy of a DE product, SilicoSec® was investigated against adults of Sitophilus granarius, Rhyzopertha dominica, and Tribolium confusum by surface application at 2.5, 5.0, 10.0, and 20.0 g/m2 on a concrete surface that is commonly used in storage structures. In S. granarius experiment, the highest immediate mortalities (89.2-99.2%) were obtained by the 5-day exposure even at the lowest rate (2.5 g/m2), while the highest delayed mortalities were 92.5% and 85% at rates of 2.5 and 20 g/m2, respectively by the 3-day exposure. In R. dominica experiment, the highest immediate mortalities (92.5-98.3%) were obtained by the 3-day exposure even at the lowest rate, while the highest delayed mortalities were 90.1 and 98.3% at rates of 10 and 20 g/m2, respectively, by the 1-day exposure. In T. confusum experiment, the highest immediate mortalities (83.3-91.0%) were obtained by the 7-day exposure at 10 or 20 g/m2, while the highest delayed mortalities were obtained by the 7-day exposure, and were 90.0 and 95.9% at rates of 10 and 20 g/m2, respectively. In conclusion, the insecticidal effect of surface application of SilicoSec® was high, moderate, and low against S. granarius, R. dominica, and T. confusum, respectively at concrete surfaces. A rate of 2.5 g/m2 of SilicoSec® provided an efficient control for S. granarius and R. dominica by 3- and 5-day exposures, respectively, while comparable mortality was obtained at a higher rate (10 or 20 g/m2) and exposure time (7-day) for T. confusum.

Development of the edible Tenebrio molitor at different temperatures: a Poisson log-linear regression modeling approach

Tenebrio molitor gained recognition for its nutritional value for human and/or animal consumption, its utilization as a model species in research studies, and its ability to degrade many types of plastics. However, it is a stored-product pest infesting a wide range of commodities in storages. The impact of temperature on the development of T. molitor was evaluated, taking into account confounding effects of other covariates such as developmental stage and larval instar. The time for larval development was longer at 22.5 °C than at 25 °C, 27.5 °C, and 30 °C. Tenebrio molitor spent most of its lifetime as larva > egg, pupa, since the outcome of our model inference resulted that the estimated probability of longer duration in larvae is approximately 25.5 times higher compared to eggs and pupae, and passed through 26 instars before it became pupa. Duration of larval instars increased significantly up to L22 and then decreased until L26. Among larval instars, L22 exhibited the highest developmental duration while the lowest was recorded for L1. These findings enhance the knowledge about the biology of T. molitor, leading to precise decisions for its successful culture.