The Innate Rates of Increase in Two Common Stored Grain Insects under Different Grain Storage Conditions and Times.

The determination of innate rate of increase (r) values under different grain storage conditions is critical for insect population predictions. The r values for Cryptolestes ferrugineus (Stephens) and Tribolium castaneum (Herbst) were calculated by using a new suggested method (continuous time analysis) and data from the literature, and these calculated r values were compared to identify the r values and carrying capacities under real grain storage conditions and times. The insects were reared in small glass vials (0.3 kg wheat), small PVC columns (2 kg wheat), large PVC columns (14 kg wheat), and shallow containers (14 kg wheat or wheat + cracked wheat). The wheat or cracked wheat had 13.8 to 14.5% moisture contents at different constant temperatures (17.5 to 42.5 °C) and fluctuating temperatures. The r values at the beginning of the population were the highest. Before r became negative, it gradually decreased with increasing time. After the r value became negative, it sometimes increased to positive; however, the rebounded r was much less than the initial r and gradually tended to stabilize within an up-and-down range. This up-and-down r was related to the carrying capacity. The larger the grain bulk, the higher the innate rate was for both species. The r values associated with 14 kg of wheat could be used to predict the insect population dynamics in stored grain bins.

Pathogenicity of Metarhizium rileyi (Hypocreales: Clavicipitaceae) against Tenebrio molitor (Coleoptera: Tenebrionidae).

Tenebrio molitor L., also known as the mealworm, is a polyphagous insect pest that infests various stored grains worldwide. Both the adult and larval stages can cause significant damage to stored grains. The present study focused on isolating entomopathogenic fungi from an infected larval cadaver under environmental conditions. Fungal pathogenicity was tested on T. molitor larvae and pupae for 12 days. Entomopathogenic fungi were identified using biotechnological methods based on their morphology and the sequence of their nuclear ribosomal internal transcribed spacer (ITS). The results of the insecticidal activity indicate that the virulence of fungi varies between the larval and pupal stages. In comparison to the larval stage, the pupal stage is highly susceptible to Metarhizium rileyi, exhibiting 100% mortality rates after 12 days (lethal concentration 50 [LC50] = 7.8 × 106 and lethal concentration 90 (LC90) = 2.1 × 1013 conidia/mL), whereas larvae showed 92% mortality rates at 12 days posttreatment (LC50 = 1.0 × 106 and LC90 = 3.0 × 109 conidia/mL). The enzymatic analyses revealed a significant increase in the levels of the insect enzymes superoxide dismutase (4.76-10.5 mg-1) and glutathione S-transferase (0.46-6.53 mg-1) 3 days after exposure to M. rileyi conidia (1.5 × 105 conidia/mL) compared to the control group. The findings clearly show that M. rileyi is an environmentally friendly and effective microbial agent for controlling the larvae and pupae of T. molitor.

A winning formula: sustainable control of three stored-product insects through paired combinations of entomopathogenic fungus, diatomaceous earth, and lambda-cyhalothrin.

This research aimed to assess the effectiveness of Metarhizium robertsii, diatomaceous earth (Protect-It), and lambda-cyhalothrin, for the long-term protection of stored wheat against three destructive grain insect pests, Rhyzopertha dominica, Tribolium castaneum, and Trogoderma granarium. Different treatments were applied, both alone and in paired combinations in laboratory and persistence trials. Single treatments exhibited significantly lower mortality rates in comparison to the paired treatments for all tested insect species. Among the single treatments, lambda-cyhalothrin (Lamb) resulted in significantly higher mortality rates in laboratory trials, followed by diatomaceous earth (DE) and M. robertsii (Mr), with insignificant differences between Mr and DE. Evidently, DE exhibited the highest persistence after 120 days of storage for all insect species and initial exposures, although variations in mortality rates among treatments were mostly insignificant. Overall, the most effective treatment in terms of mortality in laboratory, and persistence trials, and progeny production was DE + Lamb, followed by Mr + Lamb, and Mr + DE for all tested insect species. In general, the most susceptible insect species was R. dominica, followed by T. castaneum and T. granarium. This research highlights the effectiveness of M. robertsii, DE, and lambda-cyhalothrin in providing prolonged protection of stored wheat against all the examined grain insect species.

Insecticidal and Repellent Activities of Four Essential Oils Against Sitophilus zeamais (Coleoptera: Curculionidae).

Objective: This study aimed to evaluate the efficacy of Corymbia citriodora, Melaleuca alternifolia (Myrtaceae), Mentha × piperita (Lamiaceae), and Schinus terebinthifolius (Anacardiaceae) essential oils as an alternative to manage Sitophilus zeamais (Coleoptera: Curculionidae) adults. Methods: Acute contact toxicity, acute toxicity on treated maize grain, fumigation toxicity, repellency bioassays, and GC-MS analysis of the essential oils were carried out. Results: Corymbia citriodora, M. alternifolia, M. × piperita, and S. terebinthifolius oils were toxic at different levels to S. zeamais through residual contact, ingestion and via fumigation, and were also repellent to adults of this pest. Melaleuca alternifolia oil was the most active in contact (LC50 = 18.98 µL.mL-1), ingestion (LC50 = 1.03 µL.g-1), and fumigant (LC50 = 20.05 µL.L-1 air) bioassays. Citronelal (53.6% in C. citriodora), terpinen-4-ol (46.9% in M. alternifolia), menthol (44.8% in M. × piperita), and ß-caryophyllene (16.2% in S terebinthifolius) are the major constituents of these oils. Conclusions: Melaleuca alternifolia and M. × piperita essential oils can be used by residual contact, while those of C. citriodora, M. alternifolia, and M. × piperita by mixing with maize grains. Melaleuca alternifolia essential oil can be used as a fumigant, while those of C. citriodora and S. terebinthifolius as repellents for S. zeamais adults.

Biology, Ecology, and Behavior of Rusty Grain Beetle (Cryptolestes ferrugineus (Stephens)).

Cryptolestes ferrugineus, the rusty grain beetle, is a cosmopolitan pest that has adapted to cool and warm climates due to its unique biology, ecology, and behavior. The rusty grain beetle is a pest of high economic importance; hence, understanding their biology, ecology, and behavior could be useful in designing effective management strategies. An extensive literature survey was conducted using the databases Web of Science and Scopus. Information on country-wise publications from 1949 to 2023 on C. ferrugineus was provided, and a table illustrating the distribution of C. ferrugineus was also presented to demonstrate the global significance of C. ferrugineus. We overviewed their life stages, morphology, and factors influencing their biology, ecology, and behavior, such as refuge-seeking behavior, flight activity, mating behavior, interspecific interaction with other species, movement, and distribution. Mathematical models focusing on C. ferrugineus population dynamics and movement were also presented. In order to advance our knowledge on C. ferrugineus, the following possible avenues for future research were outlined: application of molecular markers and population genetic approaches to understand their evolutionary history; mechanisms responsible for adaptation and resistance to insecticide; interspecific interaction in storage facilities and wider landscapes; and identification of microbial roles in the ecology, behavior, and control of C. ferrugineus.

Insecticidal and biochemical effects of Dillenia indica L. leaves against three major stored grain insect pests.

The Last four decades have witnessed the banning of several synthetic insecticides mainly due to the development of resistance to the target pests and due to hazardous effects on humans and the environment. Hence, the development of a potent insecticide with biodegradable and eco-friendly nature is the need of the hour. In the present study, the fumigant property, and biochemical effects of Dillenia indica L. (Dilleniaceae) were studied against three coleopterans stored-products insects. The bioactive enriched fraction (sub-fraction-III) was isolated from ethyl acetate extracts of D. indica leaves and found toxic to rice weevil, Sitophilus oryzae (L.) (Coleoptera); lesser grain borer Rhyzopertha dominica (L.) (Coleoptera) and red flour beetle, Tribolium castaneum (Herbst.) (Coleoptera) with the LC50 values of 101.887, 189.908 and 115.1 µg/L respectively after 24 h exposure. The enriched fraction was found to inhibit the function of acetylcholinesterase (AChE) enzyme when tested against S. oryzae, T. castaneum, and R. dominica with LC50 value of 88.57 µg/ml, 97.07 µg/ml, and 66.31 µg/ml respectively, in in-vitro condition. It was also found that the enriched fraction caused a significant oxidative imbalance in the antioxidative enzyme system such as superoxide dismutase, catalase, DPPH (2,2-diphenyl-1-picrylhydrazyl), and glutathione-S-transferase (GST). GCMS analysis of the enriched fraction indicates three major compounds namely, 6-Hydroxy-4,4,7a-trimethyl-5,6,7,7a-tetrahydrobenzofuran-2(4H)-one, 1,2-Benzisothiazol-3(2H)-one, and Benzothiazole, 2-(2-hydroxyethylthio)-. Finally, we concluded that the enriched fraction of D. indica has insecticidal properties and the toxicity may be due to the inhibition of the AChE enzyme in association with oxidative imbalance created on the insect's antioxidant enzyme systems.

Effiiency of the Essential Oil of Porophyllum linaria (Asteraceae) a Mexican Endemic Plant Against Sitophilus zeamais (Coleoptera: Curculionidae).

The insecticidal and repellent effect of essential oil isolated from fresh leaves of Porophyllum linaria on maize weevil was evaluated, as well as the effect on the grain germination after treated. In total, 28 constituents were identified by gas chromatography coupled with mass spectrometry accounting for 99.86% of whole essential oil. The main majority compounds were ß-myrcene (41.94%), D-limonene (20.29%), and estragole (20.03%). Contact toxicity significantly increased with dose and time after treatment. With the 800 ppm (highest concentration), the mortality (%) obtained for the tenth and fifteenth day was 43 and 82%, respectively, whereas with 50 ppm (lowest concentration) 30% mortality was obtained at the end of the experiment (fifteenth day). At 15 d (end of the experiment), the LC50 y LC90 were obtained with values of 329.01 ± 44.35 y 1058.86 ± 117.76 ppm, respectively. For a concentration of 800 ppm, a selection index of zero was obtained, indicating the preference of the pest to the untreated maize (control). The maize grains germination test showed a significant reduction both in the length of hypocotyl and radicle of maize grain. So, in the highest dose, the hypocotyl and radicle length was 1.40 ± 0.34 and 9.14 ± 0.55 cm, respectively, whereas the control group registered 3.28 ± 0.39 and 13.02 ± 0.97 cm, respectively. This finding is promising since as it could result in the identification of botanical substances capable of suppressing maize weevil, Sitophilus zeamais development.

A novel biofumigant from Tithonia diversifolia (Hemsl.) A. Gray for control of stored grain insect pests.

For the well-being of human health as well as ecological concerns and the development of insect resistance to conventional chemical insecticides, efforts have increased worldwide, to find eco-friendly, effective and safer insect control agents which are of natural origin. A bioactive biofumigant molecule named dihydro-p-coumaric acid was isolated and characterized from the leaves of Tithonia diversifolia Hemsl. A. Gray following laboratory bioassays against the rice weevil, Sitophilus oryzae L (Coleoptera: Curculionidae); the lesser grain borer, Rhyzopertha dominica F (Coleoptera: Bostrichidae) and the rust-red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae). The isolated compound acted as a fumigant, toxic to adults of stored grain insect pests with LC50 values of 17.86, and 11.49 µg/L (S. oryzae), 19.80 and 10.29 µg/L (R. dominica) and 24.41 and 17.80 µg/L air (T. casatneum) respectively. Further, in vivo data reveal that the percentage of inhibition of acetyl cholinesterase (AChE) was dose-dependent and in vitro results showed potent AChE inhibitor. The isolated compound acts as an efficient biofumigant against the stored grain insect pests and has no adverse effect on seed germination. From this study, we assume that the isolated biofumigant molecule has the ability for used in IPM programs for stored-grain pests because of its biofumigant activity.

Effects of Insect Density, Movement Period, and Temperature on Three-Dimensional Movement and Distribution of Adult Cryptolestes ferrugineus (Coleoptera: Laemophloeidae).

Knowledge on three-dimensional (3D) movement and distribution of Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) in grain bulks assists in the prediction of their distribution inside a bin. The following experiments were conducted to determine the 3D dispersal patterns of adult C. ferrugineus in wheat with 14.5% moisture content: 1) at various insect densities (0.35, 1.77 and 3.53 A/kg (adults/kg) at 20°C and in 24 h movement period; 2) in different movement periods (6, 24, and 72 h) at 20°C and 0.35 A/kg insect density; and 3) at different temperatures (20, 30 and 35°C) at 0.35 A/kg density in 24 h movement period. To create the densities of 0.35, 1.77, and 3.53 A/kg, 100, 500, and 1,000 adults were introduced in about 285 kg wheat, respectively. The 285 kg of wheat was kept in 343 mesh cubes, which in turn were packed in a wooden box. The introduced adults were counted at the end of the movement periods. Adult C. ferrugineus tended to move downward from the point of introduction, and then diffused throughout the grain bulk. The effects of insect densities, movement periods, and temperatures on the dispersion pattern of insects were similar in 1D columns, 2D chambers, and 3D grain bulk.

Carlina acaulis essential oil nanoemulsion as a new grain protectant against different developmental stages of three stored-product beetles.

BACKGROUND: Plant essential oils (EOs) represent eco-friendly alternatives to conventional insecticides for managing pest populations. Carlina acaulis root EO showed a wide insecticidal spectrum, being highly effective against insect pests and vectors, coupled with low mammal toxicity. To boost the chemico-physical properties of this EO and its main active ingredient, carlina oxide, C. acaulis EO was encapsulated in a nanoemulsion [NE, 6% EO (w/w)], and its insecticidal properties evaluated against larvae and adults of Tribolium castaneum, Tribolium confusum and Tenebrio molitor. Two NE concentrations (500 and 1000 ppm) were applied on stored wheat. Mortality was determined after 4, 8 and 16 h and 1, 2, 3, 4, 5, 6 and 7 days. RESULTS: The NE was toxic to larvae of T. castaneum and T. confusum, killing 93.9% and 98.9% at 1000 ppm after 7 days of exposure, respectively. Tenebrio molitor larvae were tolerant: only 18.9% were dead after 7 days of exposure on stored wheat treated with 1000 ppm NE. However, the NE exhibited high adulticidal activity leading to 85.2% mortality at 1000 ppm, 7 days post-exposure. The mortalities of T. confusum and T. castaneum adults were low (21.4% and 23.3% respectively) at 1000 ppm, 7 days post-exposure. CONCLUSIONS: A NE based on C. acaulis EO could be regarded as an efficacious green adulticide or larvicide, depending on the target insect species and its life stage, advancing and specifying the pest management strategies of the tested species in an eco-friendly way. © 2022 Society of Chemical Industry.

Three-dimensional Movement and Distribution of Cryptolestes ferrugineus (Coleoptera: Laemophloeidae) Adults in Stored Wheat Under Constant Temperatures and Moisture Contents.

Understanding the movement and distribution of insects inside a grain bin is crucial to develop an effective stored grain management protocol. The three-dimensional movement and distribution of adult Cryptolestes ferrugineus (Stephens) at 20 and 30°C were determined in a 0.7 × 0.7 × 0.7 m3 (internal dimensions) wooden box filled with wheat of uniform moisture contents (12.5 ± 0.1%, 14.5 ± 0.1%, and 16.5 ± 0.1% wet basis). The wheat at a constant moisture content was filled into 343 mesh cubes (0.1 × 0.1 × 0.1 m3) and placed inside the wooden box. The center mesh cube in the box had one hundred adult insects introduced at the beginning of the movement. After 24 h, the 343 mesh cubes were removed from the wooden box in less than 45 min. Finally, the contents of each mesh cube were sieved, and the insects counted. Each experiment was replicated three times. A maximum of 17% of insects stayed at the introduced cube (center of the wooden box). About 50-88% of the introduced adults moved downward from the introduction location at the studied temperatures and moisture contents. This 24 h study showed that C. ferrugineus movements in three dimensions follow a diffusion pattern in the horizontal direction and move downward due to the 'drift' effect and geotaxis in the vertical direction.

Control and Real-Time Data Acquisition of an Experimental Platform for Stored Grain Aeration Study.

Aeration is one of the most important methods to keep stored grain safe and maintain its quality. Experimental platforms are used for stored grain aeration study in a laboratory-scale. The purpose of this paper was to provide the real-time data acquisition and control system design of a new experimental platform with multifunction for stored grain study. Requirements of the aeration experiments were analyzed, and multi running modes were designed. The aeration inlet air conditions were designed to be adjustable and multi variables need to be controlled simultaneously, which was a key problem to be solved for the platform. An ON/OFF-PID based multivariable cooperative control method was proposed, and two control loops were formed where inlet air temperature and humidity were considered separately while could be controlled simultaneously with a logic judgement strategy. Real-time data needed to be monitored was acquired with different sensors and displayed intuitively. Experiments were carried out to test the static and dynamic characteristics of the control method and three inlet air flow rates of 0.03, 0.08 and 0.13 m·s-1were used. Performance of the data acquisition system was also tested. The results showed that, the inlet air conditions control error was within ±1 °C and 10% for temperature and relative humidity, respectively. The real-time data acquisition of multi parameters during aeration process was realized. The experimental platform can be used for studies of different aeration objectives.

Phenotypic and molecular analyses in rice weevil, Sitophilus oryzae (Linneaus) (Coleoptera: Curculionidae): identification of a super kdr mutation, T929I, conferring resistance to deltamethrin.

BACKGROUND: The rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) is a cosmopolitan pest of stored cereal grains and other commodities globally. Infestations caused by S. oryzae makes grains unsuitable for consumption, processing, and export. Deltamethrin, a synthetic pyrethroid insecticide, is widely used in major grain storages in India as a prophylactic treatment to control this pest. However, recurrent use of this insecticide had led to genetic resistance in S. oryzae, questioning its ongoing use at the current recommended concentration. RESULTS: Dose response analysis of resistant (Delta-R) and susceptible (Lab-S) strains of S. oryzae collected from grain storages across southern India, revealed that Delta-R was 134-fold more resistant than the Lab-S at median lethal concentration (LC50 ). A concentration of 180 ppm over 48 h effectively discriminated 16 resistant field populations from Lab-S with per cent resistance ranging from 8.72% to 75.86%. Exposing all the resistant populations to 1000 ppm over 48 h identified 12 populations with strongly resistant individuals and confirmed the existence of two distinct resistance phenotypes, 'weak' and 'strong' in S. oryzae. Furthermore, sequence analysis of the voltage-gated sodium channel (vgsc) gene in Delta-R identified a single target site mutation, T929I conferring resistance in S. oryzae. CAPS (Cleaved Amplified Polymorphic Sequence) marker analysis of this allele confirmed that frequency of resistance is high (up to 0.96) supporting the results of phenotypic analysis. CONCLUSION: Both phenotype and molecular marker analyses clearly demonstrated that deltamethrin at 180 and 1000 ppm can be used to discriminate weakly and strongly resistant populations in S. oryzae, respectively. Resistance diagnostics based on the mutation, T929I, supports our phenotypic data and indicates that resistance to deltamethrin in S. oryzae is prevalent in southern parts of India, stressing the need to identify a synergist or suitable alternatives. © 2021 Society of Chemical Industry.

Persistence and efficacy of enhanced diatomaceous earth, imidacloprid, and Beauveria bassiana against three coleopteran and one psocid stored-grain insects.

The residual efficacy of the enhanced diatomaceous earth (DE) formulation DEBBM alone and in combination with Beauveria bassiana (Hypocreales: Cordycipitaceae) or with the neonicotinoid insecticide imidacloprid against Tribolium castaneum (Coleoptera: Tenebrionidae), Rhyzopertha dominica (Coleoptera: Bostrychidae), Cryptolestes ferrugineus (Coleoptera: Laemophloeidae), and Liposcelis paeta (Psocoptera: Liposcelididae) was investigated in the laboratory. The combination treatments were more effective compared to the single treatments against all examined species. The combinations of DEBBM and imidacloprid and imidacloprid with the highest dose rate of B. bassiana provided the highest mortality values against all tested species for 90 days of storage period. The combination of DEBBM plus B. bassiana resulted to the highest mortalities and to the lowest offspring production of all combinations tested after 180 days of storage. Mortality of adults for each test insect species was decreased over the storage period of 6 months, and the progeny production was increased with the extended storage period. Among the tested insect species, L. paeta was the most susceptible to all three grain protectants followed by C. ferrugineus, R. domina, and T. castaneum. The findings of the current study suggest that the use of DEBBM, imidacloprid, and B. bassiana as grain protectants may provide elevated control of major stored-grain insect species during a prolonged period of storage.

Unique genetic variants in dihydrolipoamide dehydrogenase (dld) gene confer strong resistance to phosphine in the rusty grain beetle, Cryptolestes ferrugineus (Stephens).

The rusty grain beetle, Cryptolestes ferrugineus, a major pest of stored commodities, has developed very high levels (>1000×) of resistance to the fumigant phosphine. Resistance in this species is remarkably stronger than reported in any other stored product pests demanding the need to understand the molecular basis of this trait. Previous genetic studies in other grain insect pests identified specific variants in two major genes, rph1 and rph2 in conferring the strong resistance trait. However, in C. ferrugineus, although the gene, rph1 was identified as cytochrome-b5-fatty acid desaturase, the rph2 gene has not been reported so far. We tested the candidate gene for rph2, dihydrolipoamide dehydrogenase (dld) using the recently published transcriptome of C. ferrugineus and identified three variants, L73N and A355G + D360H, a haplotype, conferring resistance in this species. Our sequence analysis in resistant strain and phosphine selected resistant survivors indicates that these variants occur either alone as a homozygote or a mixture of heterozygotes (i.e complex heterozygotes) both conferring strong resistance. We also found that one of the three variants, possibly L73N expressing "dominant" trait at low frequency in resistant insects. Comparison of dld sequences between Australian and Chinese resistant strain of this species confirmed that the identified variants are highly conserved. Our fitness analysis indicated that resistant insects may not incur significant biological costs in the absence of phosphine selection for 19 generations. Thus, we propose that the observed high levels of resistance in C. ferrugineus could be primarily due to the characteristics of three unique variants, L73N and A355G + D360H within dld.

Spatial Distribution and Flight Patterns of Two Grain Storage Insect Pests, Rhyzopertha dominica (Bostrichidae) and Tribolium castaneum (Tenebrionidae): Implications for Pest Management.

The lesser grain borer, Rhyzopertha dominica, and the rust red flour beetle, Tribolium castaneum, are two major beetle pests commonly found infesting stored products worldwide. Both species can cause severe economic damage and their management is complicated by their potential to develop resistance to several of the limited chemical options available. However, pest management strategies can be improved by understanding the ecology of the pest insect. To determine the spatiotemporal activity of R. dominica and T. castaneum, we conducted a trapping study over two years in a temperate region of south-eastern Australia, with traps located near grain storages and fields. We captured higher numbers of R. dominica than T. castaneum, and both species were more prevalent in traps located close to grain storages. Similar and consistent seasonal patterns were displayed by both species with activity ceasing during the winter (June-August) months. We found linear correlations between maximum daily temperatures and trap catches, and minimum threshold temperatures for flight activity were 14.5 °C and 15.6 °C for R. dominica and T. castaneum, respectively. The results are discussed in relation to the ecology of these pests along with their implications for pest management.

Evaluating the combination of Metarhizium anisopliae and an enhanced form of diatomaceous earth (Grain-Guard) for the environmentally friendly control of stored grain pests.

Stored grain pests cause great damage to various grain products, and protection against these pests is currently based on synthetic insecticides and fumigants. As a result, these chemicals cause problems, including grain contamination with chemical residues and the development of resistance by insect pests to these chemicals. Therefore, to combat this issue, in the present study, an enhanced form of diatomaceous earth (DE), Grain-Guard, and Metarhizium anisopliae (Metschnikoff) Sorokin (Ascomycota: Sordariomycetes) were evaluated alone and in combination against adults of Liposcelis paeta (Pearman) (Psocoptera: Liposcelididae), Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae). M. anisopliae was used at a rate of 1.7 × 104 conidia kg-1 grain alone as well as with two doses of DE (25 and 50 ppm) on wheat under different exposure time courses (4, 7, and 14 days). It is worth mentioning that the combination of M. anisopliae and DE was highly effective against the adults of L. paeta, C. ferrugineus, R. dominica, and T. castaneum after 14 days of exposure. When DE and M. anisopliae were applied alone, DE showed more effectiveness than fungal conidia. Progeny emergence was decreased when modified DE was applied at a high dose rate with the fungus and suppressed at a low dose. The cadavers of all species in the trials showed a maximum percentage of mycosis, and sporulation (conidia/ml) also showed the same result when the fungus was tested alone, while low mycosis and sporulation were achieved under the application of a mixture with a high dose of modified DE. Our findings indicate the best possible combination of DE (at low dose rates) along with a fungus that might contribute to lowering health and environmental risks.

Effect of synthetic amorphous silica powder on the cuticle of Tribolium castaneum and Sitophilus oryzae using hyperspectral imaging technique.

BACKGROUND: Synthetic amorphous silica (SAS) is safe for human consumption. SAS damages insect cuticles. Qualitative measurement of cuticle properties of insects affected by SAS is essential to understand the mode of action and develop new pesticides. A hyperspectral reflectance imaging approach was used to directly indicate the impact of SAS on the insect cuticle. RESULTS: There were significant differences in the LT95 values of hydrophobic and hydrophilic SAS against Tribolium castaneum and Sitophilus oryzae (P < 0.01). T. castaneum was more susceptible to hydrophobic SAS while no difference was found for S. oryzae exposed to both SAS types. In a hyperspectral study, the ventral reflectance of control groups was higher than that of SAS-treated groups in both visible and short-wave near-infrared wavelength ranges. The SAS-treated groups showed much higher dorsal reflectance. The differences in absorption characteristics of cuticular fat and protein may contribute to the varied performance. The effects of both SASs on insect cuticles was significant, as the 100% recognition rate of the back propagation neural network models suggested. Consistent with the assumption that the efficacy was different between the two SAS types, the lowest rates of the model for two treatment groups were 62.2 and 73.3% in the target and output class. CONCLUSION: The efficacy varied considerably between the two insect species and the two SASs. Hyperspectral image analyzing coupled with back propagation artificial neural network accurately recorded how SAS impacts the insect cuticle via the effective wavelengths. These findings showed that SAS is a promising candidate for new pesticide products. © 2019 Society of Chemical Industry.

Influences of Stored Product Insect Movements on Integrated Pest Management Decisions.

Insect movement inside and outside grain bulks and processed products influences pest management decisions. Movement allows insects to find essential food resources, shelters (refuges), warmer and/or humid locations, mating and egg-laying sites, even when they are rare in fields, buildings, mills, warehouses, and inside grain masses. This review discussed the advantages and disadvantages of stored product insect movements, and the influence of insect mobility on some integrated pest management practices. Insect movement (1) results in clumped insect spatial distributions and thus makes large sample sizes necessary for monitoring; (2) makes trapping more efficient, but is influenced by many factors; (3) allows control methods to be effective, but requires pest management programs to be area-wide; (4) makes eradication of quarantine pests difficult and commodities are quickly re-infested; and (5) results in a diverse genetic pool and speeds the development of resistance to pesticides. Any element of an IPM approach should use the knowledge of insect movement. Reasons for the difficult interpretation of cryptic movement behaviours of insects were provided and future research areas were suggested.

Sensory Quality of Essential Oils and Their Synergistic Effect with Diatomaceous Earth, for the Control of Stored Grain Insects.

Essential oils (EOs) have gained increasing interest as a low-toxic, eco-friendly alternative to synthetic repellents and insecticides against insect pests. However, they have scarce practical application in the protection of stored grain because of their limited efficacy and their interference with the organoleptic properties of the grain. In this study, we evaluated the olfactory profile of the EOs of Foeniculum vulgare, Pistacia lentiscus, and Ocimum basilicum, and their toxicity against the main stored grain pest Sitophilus granarius. Trained assessors identified O. basilicum and F. vulgare, as more suitable than the P. lentiscus EO for the wheat treatment. In laboratory tests, the most toxic EO was the P. lentiscus (LC50 = 36.36 µL∙kg-1) while, the least toxic, was the F. vulgare one (LC50 = 77.59 µL∙kg-1). The EOs were also tested combined with diatomaceous earths (DEs) showing synergistic effects (co-toxicity coefficient values ranging from 1.36 to 3.35 for O. basilicum and F. vulgare EOs, respectively). Overall, O. basilicum resulted as the best EO for the wheat treatment, considering its insect toxicity and olfactory profile. In real storage conditions, the wheat co-treated with O. basilicum EO and DEs showed a significantly lower mean infestation (1.5 insect kg-1) than the non-treated wheat (7.0 insect kg-1).