Stored-product Pests Research Articles

Controversial impact of experimental soil inoculant containing Beauveria bassiana and Metarhizium anisopliae on Sitophilus granarius

AbstractThe insecticidal efficacy of the experimental bioinoculants (Natur Nova, Natur Agro Hungary Ltd., Hungary) containingBeauveria bassiana(Bals.-Criv). Vuill. andMetarhizium anisopliaeMetschnikoff against stored product pests modelled by granary weevil,Sitophilus granariusL. was evaluated on wheat in laboratory tests. In order to comparability, two applications were also set up: one purely ash-treated grain treatment against wireworms and a soil-injected one. Our results confirmed that some biopesticides can exert unexpected effect on non-target arthropods. However, the examined biopesticides were as empirically effected against the target arthropods regarding wireworms. Nevertheless, the application exempt from ash of the examined bioinoculants Natur Nova containingB. bassianaandM. anisopliaewere not suitable for the elimination of the stored product pests modelled byS. granarius. In contrast, the putative plant protection effect of these biopesticides was observed in the course of applying the agents in the recommended environment and pest species as well as when applying them with ash carrier.

Phytochemical Composition and Insecticidal Activities of Essential oil of Thymus munbyanus (Lamiales: Lamiaceae) Aerial Parts and Its Properties Against Biomarkers of Ephestia kuehniella zeller (Lepidoptera: Pyralidae)

This research aimed to assess the chemical composition of the essential oil (EO) of Thymus munbyanus subsp. coloratus cultivated in Annaba (Northeast Algeria) and to evaluate its potential insecticidal activity against newly molted pupae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). The yields of EO calculated from the dry matter of the aerial part of the plant were estimated at 2.56 % (w / w). Its chemical composition has been analyzed using gas chromatography/mass spectroscopy (GC / MS). 54 Compounds were identified and the main components were carvacrol (39.11 %), paracymene (15.47 %), and thymoquinone (10.59 %). In preliminary bioassays, various doses (5, 15, 25, 40, and 100 μl / mL) of the T. munbyanus EO were tested on newly molted pupae and the inhibition doses (ID) of adult emergence were determined. In a follow-up experiment, EO of T. munbyanus applied at its ID25(15.38 μl / mL) and ID50(25.22 μl / mL) was evaluated on acetylcholinesterase (AChE) and glutathion S-transferases (GSTs) activities. Biomarkers measurements in the treated pupae and adults (ID25 and ID50) revealed an inhibition in AChE activity and activation of the detoxification system as evidenced by induction in GSTs activities. Lastly, our results proved the potential use of this material as an alternative to synthetic insecticides for controlling stored product pests.

Synthetic and Natural Insecticides: Gas, Liquid, Gel and Solid Formulations for Stored-Product and Food-Industry Pest Control.

Simple SummaryCurrently, there is great global research interest in the use of novel methods of protection against agricultural, storage, and urban pests, particularly in the use of botanical substances and nontoxic materials. To ensure efficacy and safety, botanical and synthetic insecticides must be properly formulated and delivered in a species-specific way to their pest targets. The wide diversity of pests and environments—globally occurring at farms and food industry facilities—has inevitably resulted in a massive proliferation of application formulations and approaches. Although there are excellent summaries on particular aspects of the usage of synthetic and botanical pesticides, a general overview of application formulations on stored-product and food-associated pests is not currently available. This review provides an inventory of current and historical pesticide formulations. Its structure follows the traditional insecticide categorization based on four physical formulation types: gas, liquid, gel/foam, and solid. The review documents renewed research interest in optimizing traditional methods, such as insecticide baits, aerosols, sprays, fumigants, and inert gases, as well as the feasibility of integrating these methods with natural insecticides and physical measures (e.g., low temperatures) as combined application approaches. Several emerging technologies of pesticide formulations have been identified; they include electrostatic dusts or sprays, nanoparticles, hydrogels, inert baits with synthetic attractants, biodegradable cyanogenic protective coatings of grain, and RNA-based gene silencing compounds encapsulated in baits. Traditional and new formulations of natural compounds, including inert dust (diatomaceous earth) and botanicals (essential oils), have been considered as non-synthetic chemical control solutions for organic food production in developed countries and as affordable home-made insecticides in developing countries. The authors hope that the general coverage and extensive photographic documentation will make this review useful not only for scientists but also for students and practitioners.The selective application of insecticides is one of the cornerstones of integrated pest management (IPM) and management strategies for pest resistance to insecticides. The present work provides a comprehensive overview of the traditional and new methods for the application of gas, liquid, gel, and solid physical insecticide formulations to control stored-product and food industry urban pests from the taxa Acarina, Blattodea, Coleoptera, Diptera, Hymenoptera, Lepidoptera, Psocoptera, and Zygentoma. Various definitions and concepts historically and currently used for various pesticide application formulations and methods are also described. This review demonstrates that new technological advances have sparked renewed research interest in the optimization of conventional methods such as insecticide aerosols, sprays, fumigants, and inert gases. Insect growth regulators/disruptors (IGRs/IGDs) are increasingly employed in baits, aerosols, residual treatments, and as spray-residual protectants for long-term stored-grain protection. Insecticide-impregnated hypoxic multilayer bags have been proven to be one of the most promising low-cost and safe methods for hermetic grain storage in developing countries. Insecticide-impregnated netting and food baits were originally developed for the control of urban/medical pests and have been recognized as an innovative technology for the protection of stored commodities. New biodegradable acaricide gel coatings and nets have been suggested for the protection of ham meat. Tablets and satchels represent a new approach for the application of botanicals. Many emerging technologies can be found in the form of impregnated protective packaging (insect growth regulators/disruptors (IGRs/IGDs), natural repellents), pheromone-based attracticides, electrostatic dust or sprays, nanoparticles, edible artificial sweeteners, hydrogels, inert baits with synthetic attractants, biodegradable encapsulations of active ingredients, and cyanogenic protective grain coatings. Smart pest control technologies based on RNA-based gene silencing compounds incorporated into food baits stand at the forefront of current strategic research. Inert gases and dust (diatomaceous earth) are positive examples of alternatives to synthetic pesticide products, for which methods of application and their integration with other methods have been proposed and implemented in practice. Although many promising laboratory studies have been conducted on the biological activity of natural botanical insecticides, published studies demonstrating their effective industrial field usage in grain stores and food production facilities are scarce. This review shows that the current problems associated with the application of some natural botanical insecticides (e.g., sorption, stability, field efficacy, and smell) to some extent echo problems that were frequently encountered and addressed almost 100 years ago during the transition from ancient to modern classical chemical pest control methods.

A Combination Sulfuryl Fluoride and Propylene Oxide Treatment for Trogoderma granarium (Coleoptera: Dermestidae).

The khapra beetle, Trogoderma granarium, is an important quarantine pest of stored-products. While it is not established in the North America, frequent interceptions highlight the need for treatments to eradicate isolated populations if they occur. Methyl bromide has long been the standard fumigant used for this purpose; however, increasing restrictions on its use necessitate the development of new treatment options. Here we evaluate a treatment for khapra beetle using a combination of sulfuryl fluoride (SF) and propylene oxide (PPO). Experiments were conducted to determine the most tolerant stages and the effective rates for each compound. Combination treatments using both products were then evaluated at several temperatures to determine effective doses for quarantine level control. The egg stage was by far the most tolerant to SF, requiring concentration × time (CT) products roughly 10-fold greater than the next most tolerant stage, diapausing larvae. Diapausing larvae were significantly more tolerant to SF than non-diapausing larvae in a recently collected 'field' strain, but not in a more than 30-yr-old 'laboratory' culture. PPO treatments were shown to completely control the egg stage at CTs greater than 155 hr-mgL-1 at both 10 and 20°C. Resulting combination treatments with initial dose rates of 96 and 40 mgL-1 at 10°C and 80 and 40 mgL-1 at 20°C are proposed for SF and PPO, respectively. These combination treatments utilize SF's efficacy against the larval stage along with PPO's superior ovicidal properties to provide enhanced treatment efficacy over each product alone against all life stages of khapra beetle.

Effects of Essential Oils from 24 Plant Species on Sitophilus zeamais Motsch (Coleoptera, Curculionidae).

Simple SummaryThe maize weevil (Sitophilus zeamais Motsch) is a major pest in stored grain, responsible for significant economic losses and having a negative impact on food security. Due to the harmful effects of traditional chemical controls, it has become necessary to find new insecticides that are both effective and safe. In this sense, plant-derived products such as essential oils (EOs) appear to be appropriate alternatives. Therefore, laboratory assays were carried out to determine the chemical compositions, as well as the bioactivities, of various EOs extracted from aromatic plants on the maize weevil. The results showed that the tested EOs were toxic by contact and/or fumigance, and many of them had a strong repellent effect. Samples of 14 EOs and 17 of their main constituents (monoterpenes) had high fumigant toxicity against S. zeamais adults and might constitute a viable control method of this pest.Chemical control of the maize weevil (Sitophilus zeamais) has been ineffective and presents serious collateral damage. Among plant-derived insecticides, essential oils (EOs) are suitable candidates to control this stored products pest. In this work, the insecticidal activities of 45 natural EOs against S. zeamais adults were screened, and the most promising ones (24 EOs) were characterized by GC–MS. The repellent and toxic effects (contact and fumigant) of these 24 EOs were determined, and by a cluster analysis they were classified into two groups considering its fumigant activity and contact toxicity. For the EOs with the highest fumigant potential (14 oils) and their main active constituents (17 compounds), lethal concentrations were determined. The most active EOs were those obtained from L. stoechas and L. alba, with LC50 values of 303.4 and 254.1 µL/L air and characterized by a high content of monoterpenes. Regarding the major compounds, the oxygenated monoterpenes R-(+)-pulegone (LC50 = 0.580 mg/L air), S-(-)-pulegone (LC50 = 0.971 mg/L air) and R-(-)-carvone (LC50 = 1.423 mg/L air) were the most active, as few variations in their concentrations significantly increased insect mortality.

Combined and individual effects of diatomaceous earth and methyl eugenol against stored products insect pests

The insecticidal activity of a proprietary diatomaceous earth, Detech, and methyl eugenol was tested with Sitophilus granarius (L., 1758), Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae), Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrychidae), Tribolium confusum Jaquelin Du Val, 1868 (Coleoptera: Tenebrionidae) adults at Stored Products Pest Laboratory of Plant Protection Central Research Institute (Ankara, Turkey) in 2020. A range of doses of Detech (100, 250 and 500 mg kg-1) and methyl eugenol (5, 10 and 15 mg kg-1) were used. To determine insect mortality, at a range of times after treatment, and half-doses of both products were also studied in order to examine simultaneous use for synergistic effect. The greatest effect of Detech on R. dominica , S. zeamais , S. granarius and T. confusum was observed with 500 mg kg-1 giving 81, 29, 26 and 18% mortality 28 d after treatment (DAT), respectively. Methyl eugenol at 15 mg kg-1 gave complete mortality with R. dominica adults 3 DAT. Simultaneous application of both products did not give complete mortality in test insects. The data show that Detech and methyl eugenol are promising treatments for the control of insect pests of stored products.

Symbiont Genomic Features and Localization in the Bean Beetle Callosobruchus maculatus.

A pervasive pest of stored leguminous products, the bean beetle Callosobruchus maculatus (Coleoptera: Chrysomelidae) associates with a simple bacterial community during adulthood. Despite its economic importance, little is known about the compositional stability, heritability, localization, and metabolic potential of the bacterial symbionts of C. maculatus. In this study, we applied community profiling using 16S rRNA gene sequencing to reveal a highly conserved bacterial assembly shared between larvae and adults. Dominated by Firmicutes and Proteobacteria, this community is localized extracellularly along the epithelial lining of the bean beetle's digestive tract. Our analysis revealed that only one species, Staphylococcus gallinarum (phylum Firmicutes), is shared across all developmental stages. Isolation and whole-genome sequencing of S. gallinarum from the beetle gut yielded a circular chromosome (2.8 Mb) and one plasmid (45 kb). The strain encodes complete biosynthetic pathways for the production of B vitamins and amino acids, including tyrosine, which is increasingly recognized as an important symbiont-supplemented precursor for cuticle biosynthesis in beetles. A carbohydrate-active enzyme search revealed that the genome codes for a number of digestive enzymes, reflecting the nutritional ecology of C. maculatus. The ontogenic conservation of the gut microbiota in the bean beetle, featuring a "core" community composed of S. gallinarum, may be indicative of an adaptive role for the host. In clarifying symbiont localization and metabolic potential, we further our understanding and study of a costly pest of stored products. IMPORTANCE From supplementing essential nutrients to detoxifying plant secondary metabolites and insecticides, bacterial symbionts are a key source of adaptations for herbivorous insect pests. Despite the pervasiveness and geographical range of the bean beetle Callosobruchus maculatus, the role of microbial symbioses in its natural history remains understudied. Here, we demonstrate that the bean beetle harbors a simple gut bacterial community that is stable throughout development. This community localizes along the insect's digestive tract and is largely dominated by Staphylococcus gallinarum. In elucidating symbiont metabolic potential, we highlight its possible adaptive significance for a widespread agricultural pest.

Characterization of the complete mitochondrial genome of a barklouse, Lepinotus sp. (Psocodea: Trogiomorpha: Trogiidae)

Barklice in the genus Lepinotus (Psocoptera: Trogiidae) are small, soft-bodied stored-product pests that are difficult to control. We sequenced and annotated the mitochondrial (mt) genome of Lepinotus sp. The mt genome of Lepinotus sp. is 16,299 bp in size with 74.4% A + T content. The gene order was highly conserved in some of the Trogimorpha barklice. Two types of tandem repeat units were identified in CR of Lepinotus sp. The phylogenetic analysis showed that Trogiidae species was the sister group to Lepidopsocidae barklice, and the suborder Troctomorpha was polyphyletic.

Evaluation of Insecticidal Effects of Plants Essential Oils Extracted from Basil, Black Seeds and Lavender against Sitophilus oryzae.

The risk of using synthetic insecticides to the environment, human health, and the emergence of new genera of pests resistant to that kind of drugs, have led to attention in natural compounds. The present study aimed at evaluating the insecticidal activity of 0.25–6 mg/cm2 of basil (Ocimum basilicum), black seeds (Nigella sativa), and lavender (Lavandula angustifolia) essential oils (EOs) against one of the major stored product pests, Sitophilus oryzae (L.). This was done by assessing mortality and repellent percentage assay in the adult stage, as well as analysing up and down-regulated genes associated with toxicity effect of selected EOs. The three studied EOs showed a toxic effect on S. oryzae; where O. basilicum and L. angustifolia EOs explicated 100% mortality at 6 mg/cm2 after 48 and 24 h, respectively. The highest repellence activity was recorded for O. basilicum EO at 0.75 mg/cm2 with value 82.3% after exposure time 5 h. In the highest dose (6 mg/cm2), the maximum up-regulated expression level of detoxification DEGs genes (CL1294 and CL 8) and cytochrome p45o gene (CYP4Q4) in Lavandula angustifolia EOs exhibited 8.32, 6.08, and 3.75 fold changes, respectively, as compared with 4.76 fold at 10 ppm malathion and 1.02 fold change in acetone control.

Effects of Dehumidification on the Survivorship of Four Psocid Species.

Psocids are damaging stored-product pests. In this study, eggs and early-instar nymphs, adults, and all life stages of Liposcelis entomophila, L. decolor, L. bostrychophila, and L. paeta were subjected to 43, 50, or 75% (Control) relative humidity (RH) for 2, 4, 6, 8, 10, 12, 14, or 16 d at 30.0°C. All adults of these species died within 8 d at both 43 and 50% RH, except for L. bostrychophila, which required 12 d at 50% RH for 100% mortality to occur. For all life stages and eggs and early-instar nymphs, maximum survival times (times to 100% mortality) at 43 or 50% RH for L. entomophila, L. decolor, L. bostrychophila, and L. paeta, were 8 and 10 d, 8 and 12 d, 12 and 14 d, and 12 and 16 d, respectively. During this study, numbers of nymphs and adults of all species 14 d after the RH treatments increased within the 75% RH Control arenas. Different species and life stages responded differently to 43 and 50% RH, as time to kill all stages of the four psocid species was 8-12 and 10-16 d, respectively. Results indicate that using a specific RH environment may be effective in psocid management.

Detection of Phosphine Resistance in Field Populations of Four Key Stored-Grain Insect Pests in Pakistan.

Simple SummaryThe resistance of coleopteran stored-product pests to phosphine fumigation is becoming a global phenomenon. However, there is limited literature available and a lack of knowledge on this issue in Pakistan. Thus, in the current study, we estimated the status of phosphine resistance among ten populations of Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), Sitophilus granarius (L.) (Coleoptera: Curculionidae), Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Trogoderma granarium Everts (Coleoptera: Dermestidae), originated from different regions of Pakistan. Laboratory-susceptible populations of all insect species were also considered in the tests. Concentration–response bioassays were conducted for each insect species. All of the tested populations of each species were found to be resistant to phosphine. However, they varied with regard to their levels of resistance. Overall, R. dominica exhibited the highest resistance level, followed by T. castaneum, T. granarium and S. granarius. Although phosphine is effective against several stored-product pests, the development of resistance may lead to failures in its application in Pakistan.In Pakistan, the control of stored-product insect pests mainly relies on the use of phosphine gas along with other control tactics. The aim of this study was to determine the level of phosphine resistance among ten differently located populations of the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), the granary weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae), the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae). Laboratory-susceptible populations of all insect species were also considered in the experiments. Concentration–response bioassays were conducted for each species. All of the tested populations (10 out of 10) of each species were found to be resistant to phosphine, but varied in their level of resistance. Probit analysis estimated LC50 at 2.85, 1.90, 2.54 and 2.01 ppm for laboratory-susceptible populations of R. dominica, S. granarius, T. castaneum and T. granarium, respectively. Against R. dominica, the highest and lowest resistance levels were observed in the Rahim Yar Khan (LC50 at 360.90 ppm) and Rawalpindi (LC50 at 210.98 ppm) populations, respectively. These resistant populations were 126.67- and 74.02-fold more resistant than the laboratory population. The Multan and Lahore populations of S. granarius exhibited the maximum (LC50 at 122.81 ppm) and minimum (LC50 at 45.96 ppm) resistance levels, respectively, i.e., they were 64.63- and 24.18-fold more resistant than the laboratory population. The Layyah population of T. castaneum showed the maximum resistance level (LC50 at 305.89 ppm) while the lowest was observed in the Lahore population (LC50 at 186.52 ppm), corresponding to 120.42- and 73.43-fold more resistant than the laboratory population, respectively. Regarding T. granarium, the Layyah population showed the maximum resistance level (LC50 at 169.99 ppm) while the Lahore population showed the minimum resistance (LC50 at 74.50 ppm), i.e., they were 84.57- and 37.06-fold more resistant than the laboratory population, respectively. Overall, R. dominica presented the highest resistance level, followed by T. castaneum, T. granarium and S. granarius. The current study suggests that the application of phosphine may not be an adequate control strategy for the management of the above tested insect pests in Pakistan.

Bioactivity of Some Botanical Powders Against Wheat Weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae), and Confused Flour Beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae)

Stored-product pests attack cereal grains and legume seeds post-harvest. They not only damage the grain but also decrease its weight and quality. Therefore, the aim of the present study was to investigate the bioactivity of resin powders extracted from Pistacia lentiscus L. bark, Boswellia carterii birdwood bark, and Elettaria cardamomum seeds against two of the most important stored-product pests, Sitophilus granarius (L.) and Tribolium confusum Jacquelin du Val. We used three bioassay methods, repellent effect, reduction of progeny, and grain weight loss and investigated the effects of the powders on the life cycles of the insects. Wheat grains were mixed with the three botanical powders separately, at different concentrations (3, 5, 7, and 10 % w/w). Sitophilus granarius and T. confusum were fed these mixtures. Repellent activity was examined after 2, 4, 8, 12, and 24 h. The E. cardamomum powder displayed the maximum repellent activity (100 %) against both S. granarius and T. confusum after 24 h at 3 % concentration. The P. lentiscus powder reached maximum repellent activity (80 %) against S. granarius and T. confusum at 7 % concentration after 12 h and 24 h, respectively. The B. carterii powder achieved maximum repellent activity against S. granarius and T. confusum (73.3 % and 86.7 %) at 10 % concentration after 24 h and 12 h, respectively. No progeny was produced in grains treated with 3 % P. lentiscus powder, 7 % E. cardamomum powder, or 7 % B. carterii powder. Thus, protection against both beetles started from 3 % concentration when P. lentiscus powder was used and from 7 % and 10 % (against S. granarius and T. confusum, respectively) when E. cardamomum powder was used. A 7 % B. carterii concentration completely saved the grains from S. granarius damage, and a 10 % concentration offered 99.5 % protection against T. confusum. However, all tested powders significantly affected all the studied parameters (life cycle and grain weight loss). The results show that the three botanical powders provide high repellent activity against S. granarius and T. confusum, which might be useful in protecting stored grains from these insects.

Impact of plasma irradiation on Tribolium castaneum

Radio frequency plasma (RFP) could provide reliable, compact, cost-effective irradiation applications against insect pests of stored food and feed products. Sensitivity of red flour beetle Tribolium castaneum to RFP has been investigated using an irradiation applicator system with the two types of inert gases, argon (Ar) and helium (He), at 100 W for five exposure time levels of 0, 20, 40, 60 and 90 s, respectively. We demonstrated that He RFP was more efficient against T. castaneum than Ar RFP. In addition, a positive correlation was observed between mortality percentages of treated insect stages and exposure times for both He and Ar RFP. The adult stage showed the highest tolerance to RFP irradiation followed by larvae and pupae; however, it was more susceptible than larvae within 24 h after He RFP treatments. The optimum exposure time was 90 s with He RFP, where a full mortality at all tested stages was accomplished, while mortalities of 71.4, 65.3 and 36.7% were recorded for pupae, larvae and adult stage, respectively, after an Ar RFP treatment of 90 s. In case of treated adults, the reproduction rate was higher than treated larvae and pupae. Our findings indicated that He RFP was an effective method for inhibiting T. castaneum development and impacting the insect life cycle and could be considered a promising tool for pest control of stored food.

Nanoencaspsulation of cysteine protease for the management of stored grain pest, Sitotroga cerealella (Olivier)

Attaining food security is crucial to feed increasing population. Minimizing post harvest losses is a good solution to food scarcity. Hence, cereals are staple food for most of the developing countries, there is a need to develope a biopesticide against stored product pests to avoid post-harvest losses. Current study involves the development of an eco-friendly tool to manage stored product insect pests by nanoencapsulation of 25 kDa cysteine protease isolated from Albizia procera (ApCP). The nanoencapsulation was tested on Sitotroga cerealella. The ApCP was tested as an insecticide (with and without GQDs encapsulation) at three different concentrations (7.0, 3.5 and 1.7 mg of ApCP/g of wheat flour pellets). Sitotroga cerealella was fed to treated diet and tested for life cycle stages. ApCP was 100% more efficient against the test insect after encapsulation with GQDs, at 7.0 and 3.5 mg/g concentrations, resulting in no population build-up, while 1.7 mg/g concentration exhibited fewer population numbers. ApCP exhibited increased insectidial efficacy due to encapsulation with GQDs. The results suggested that ApCP encapsulation with GQDs has the potential to control the insect pest and could be commercially developed as a biopesticide.

Developing a Hazomalania voyronii Essential Oil Nanoemulsion for the Eco-Friendly Management of Tribolium confusum, Tribolium castaneum and Tenebrio molitor Larvae and Adults on Stored Wheat.

Most insecticides commonly used in storage facilities are synthetic, an issue that generates concerns about food safety and public health. Therefore, the development of eco-friendly pest management tools is urgently needed. In the present study, a 6% (w/w) Hazomalania voyronii essential oil-based nanoemulsion (HvNE) was developed and evaluated for managing Tribolium confusum, T. castaneum, and Tenebrio molitor, as an eco-friendly wheat protectant. Larval and adult mortality was evaluated after 4, 8, and 16 h, and 1, 2, 3, 4, 5, 6, and 7 days, testing two HvNE concentrations (500 ppm and 1000 ppm). T. confusum and T. castaneum adults and T. molitor larvae were tolerant to both concentrations of the HvNE, reaching 13.0%, 18.7%, and 10.3% mortality, respectively, at 1000 ppm after 7 days of exposure. However, testing HvNE at 1000 ppm, the mortality of T. confusum and T. castaneum larvae and T. molitor adults 7 days post-exposure reached 92.1%, 97.4%, and 100.0%, respectively. Overall, the HvNE can be considered as an effective adulticide or larvicide, depending on the target species. Our results highlight the potential of H. voyronii essential oil for developing green nanoinsecticides to be used in real-world conditions against key stored-product pests.

Statistical approach to synthesise biogenic silica nanoparticles from rice husk and conjugated with Justicia adhatoda extract as green, slow-release biocide.

Biogenic silica synthesised from rice husk was used as a controlled release system of an eco‐friendly biocide consisting of a Justicia adhatoda extract. Fourier‐transform infrared spectroscopy (FTIR) indicated the presence of ester bonds between the silica support and the conjugated Justicia adhatoda extract. Surface area analysis and microscopy confirmed a high level of Justicia adhatoda extract loading in the silica support. The phytochemical investigation of Justicia adhatoda was done by Gas chromatography–mass spectrometry (GC‐MS) spectroscopy. Moreover, compared with the naked biogenic silica nanoparticles, a better thermal stability was determined for the conjugated system of the extracted compounds. Trial of kinetic release of silica: Justicia adhatoda ∼29% of loaded Justicia adhatoda was released within 1 h and then the rate of release became slow. Net release of Justicia adhatoda was observed up to 50% within 7 h. The Justicia adhatoda compounds released from silica also showed the improved mortality rate against stored product pest rice weevil (Sitophilus oryzae).

The first record of Omosita nearctica Kirejtshuk (Coleoptera, Nitidulidae) in South Africa, with the first description of its mature larva

Sap beetles of the genus Omosita Erichson are stored-product pests that are also associated with carrion, potentially making them biosecurity risks and forensic tools. The discovery of a specimen of the Nearctic species Omosita nearctica Kirejtshuk in South Africa prompted an investigation a decade later to determine if this species had established itself in the country, which was confirmed by the collection of further breeding specimens that also facilitated the first description of mature larvae of O. nearctica. A new key to adults of all Omosita species is presented.

(Quasi)-Binomial vs. Gaussian Models to Evaluate Thiamethoxam, Pirimiphos-Methyl, Alpha-Cypermethrin and Deltamethrin on Different Types of Storage Bag Materials Against Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae).

Simple SummaryEphestia kuehniella Zeller (Lepidoptera: Pyralidae) and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) are major stored-product pests globally. The use of contact insecticides constitutes an option of effective management of these species. Therefore, we evaluated the activity of thiamethoxam, pirimiphos-methyl, alpha-cypermethrin, and deltamethrin for the management of E. kuehniella and T. confusum larvae on three types (plastic and paper) of storage bag materials under three exposure scenarios. In addition to typical linear regression, we introduced a binomial and quasi-binomial modeling approach to analyze our data. Thiamethoxam and pirimiphos-methyl exhibited significantly higher mortality rates on E. kuehniella and T. confusum than alpha-cypermethrin and deltamethrin. Mortality rate of T. confusum larvae was significantly higher than E. kuehniella larvae. Treatments revealed significant differences in the mortalities of both species. Our results indicate that the application of contact insecticides to storage bag materials is an efficient management tool against larvae of E. kuehniella and T. confusum.The Mediterranean flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) and the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) are worldwide spread and notorious organisms of numerous stored-products. Both species are dangerous for bagged commodities as penetrators and invaders. The aim of the current study was to examine the efficacy of thiamethoxam, pirimiphos-methyl, alpha-cypermethrin, and deltamethrin, against E. kuehniella and T. confusum larvae, on different types of storage bag materials, i.e., woven propylene, biaxially oriented polypropylene and kraft paper through a (quasi)-binomial modeling approach. The type of the tested storage bag material did not affect the mortality rates of both species when treated with the tested insecticides. Thiamethoxam and pirimiphos-methyl showed statistically significant higher mortality rates on E. kuehniella and T. confusum (beta coefficient = 0.141; p-value < 0.05) compared to alpha-cypermethrin and deltamethrin. In addition, T. confusum exhibited significantly higher mortality rate in comparison to E. kuehniella. Our results also showed that the tested doses and surface treatments had a significant effect on the mortality E. kuehniella and T. confusum larvae. Significantly higher mortality rates were recorded when larvae were exposed on bag materials having both surfaces treated or on the single treated surface than when they were exposed on the untreated surface. Our findings can be useful towards an effective management strategy against stored-product insect pests.

Volatile Infochemicals from Rhyzopertha dominica Larvae and Larval Feces Involved in Theocolax elegans Host Habitat Location.

Simple SummaryFood protection is a key issue to guarantee food security. One of the major criticisms is related to insect pests, which can severely damage stored products. Control of stored product pests widely relies on synthetic pesticides, which are potentially harmful to human health and the environment. In this context, the application of chemicals during post-harvest should be limited, and natural enemies, like parasitoid wasps, might be useful for biologically based pest management programs. The effectiveness of this approach under field conditions is still uncertain, and more information about parasitoid biology and behavior can be valuable to improve mass rearing and control strategies. This study investigates the host habitat location behavior of Theocolax elegans, a generalist parasitoid attacking several stored product pests, including Rhyzopertha dominica, a key pest species of stored grains. Bioassays demonstrated that the parasitoid females were not attracted by intact kernels; indeed, the parasitoid females were strongly attracted by infested wheat and by the host feces, locating the suitable hosts through the characteristic volatile infochemicals emitted by these substrates. Results from the present research are encouraging and suggest that biological control agents might be used to reduce the amount of synthetic insecticides.The development of biologically based approaches for stored product pest control is needed to reduce chemical inputs. Bioassays were performed to investigate host habitat location in the trophic interaction durum wheat/Rhyzopertha dominica/Theocolax elegans. GC-MS analyses were carried out to identify some chemical compounds produced by the host-related substrates. Choice and no-choice experiments demonstrated that female parasitoids were poorly attracted to intact kernels with respect to the infested substrates. Furthermore, T. elegans females performed longer residence time on infested wheat, and they generally displayed a short-term like fidelity for this cue, remaining on it during the whole observation. Infested wheat emitted one chemical (fenchone), which is possibly linked to host larvae presence, while the feces produced by host larvae emitted some other characteristic compounds. Results demonstrated that the presence of host larvae is a key factor for T. elegans host habitat location, considering that the attractiveness of the undamaged wheat is irrelevant. Furthermore, parasitoid females tended to stay on attractive cues, limiting the risk of contamination of other commodities. Biological control tools may be useful to improve the efficiency of pest management programs, but their application should be carefully evaluated.

Insecticide activity and toxicity of essential oils against two stored-product insects

The weevils Sitophilus oryzae L. and Sitophilus zeamais Motsch. are stored-product pests that are mainly controlled with synthetic insecticides. Insecticides made from essential oils (EOs) from bioactive plants can provide alternative control options that are safer and less environmentally damaging. This study investigated the chemical composition and insecticide activity of the EOs of Tagetes minuta L., Baccharis uncinella DC, Baccharis dracunculifolia DC, Salvia officinalis L., Mentha arvensis L., and Melaleuca alternifolia C. against S. oryzae and S. zeamais. The number of compounds we identified in the EOs studied ranged between 10 for T. minuta and 21 for B. uncinella. Only the EOs of T. minuta and M. arvensis showed insecticidal activity. Fumigation was more effective than the contact method for both EOs. The EO of M. arvensis had the highest level of toxicity in the contact method, with an LC50 of 71.58 μL/L for S. oryzae and 67.31 μL/L for S. zeamais. It also had the highest toxicity in the fumigation method (LC50 of 56.41 μL/L for S. oryzae and 47.03 μL/L for S. zeamais) with the lowest lethal time (LT50 of 8.9 h for S. oryzae and 8.1 h for S. zeamais). The EO of M. arvensis, therefore, has the greatest potential for development as a new botanical insecticide for the control of stored-product adult weevils.