Contact Toxicity and Repellent Effects of Essential Oils from Toddalia asiatica against Two Stored-Product Insects.

Insect infestations continually endanger stored goods, underscoring the significance of discovering eco-friendly insecticides for pest management. Essential oils (EOs) from different parts of Toddalia asiatica (leaf, fruit and branch) were extracted by hydrodistillation and analyzed by GC-MS. Carvene, p-cymene and muurolene are the principal compounds of T. asiatica leaf (TAL), T. asiatica fruit (TAF) and T. asiatica branch (TAB) EO respectively. Our work aimed to assess the contact toxicity and repellent effects of EOs on two storage pests, Tribolium castaneum and Lasioderma serricorne. All tested EOs exhibited obvious contact toxicity, especially, TAL EO against T. castaneum (33.48 µg/adult) and TAF EO against L. serricorne (16.42 µg/adult). Repellency tests revealed that TAL and TAF EOs, at a concentration of 78.63 nL/cm2, achieved nearing 100% efficiency against T. castaneum. These results suggest that EOs of T. asiatica could be used as effective botanical insecticides for managing stored-product insects.

Assessment of Contact Toxicity and Repellent Effects of Essential Oils from Piper Plants Piper yunnanense and Piper boehmeriifolium against Three Stored-Product Insects.

Storage is a crucial part during grain production for the massive spoilage caused by stored product insects. Essential oils (EOs) of plant origin have been highly recommended to combating insects which are biodegradable and safe mode of action. Hence, to make the fullest use of natural resources, essential oils of different parts from Piper yunnanense (the whole part, PYW; fruits, PYF; leaves, PYL) and Piper boehmeriifolium (leaves, PBL) were extracted by steam distillation method in the present study. Gas chromatography-mass spectrometry (GC-MS) characterization revealed bicyclogermacrene (PYW), γ-muurolene (PYF), δ-cadinene (PYL) and methyl 4,7,10,13,16,19-docosahexaenoate (PBL) as the principal compound of each essential oil. Sesquiterpene hydrocarbons were also recognized as the richest class accounting for 56.3 %-94.9 % of the total oil. Three storage pests, Tribolium castaneum, Lasioderma serricorne and Liposceis bostrychophila, were exposed to different concentrations of EOs to determine their insecticidal effects. All tested samples performed modest contact toxicity in contrast to a bioactive ingredient pyrethrin, among which the most substantial effects were observed in PYF EOs against T. castaneum (35.84 µg/adult), PBL EOs against L. serricorne (15.76 µg/adult) and PYW EOs against L. bostrychophila (57.70 µg/cm2 ). In terms of repellency tests, essential oils of PYF at 78.63 nL/cm2 demonstrated to have a remarkable repellence against T. castaneum at 2h and 4h post-exposure. The investigations indicate diverse variations in the chemical profiles and insecticidal efficacies of P. yunnanense and P. boehmeriifolium EOs, providing more experimental evidence for the use of the Piper plants.

Competition between Prostephanus truncatus and Sitophilus oryzae on maize: the species that gets there first matters.

Laboratory tests were carried out in order to examine the population growth of Prostephanus truncatus (Horn) (Coleoptera: Bostrychidae) and Sitophilus oryzae (L.) (Coleoptera: Curculionidae) on maize. These two species were placed either simultaneously or one species was allowed to colonize the kernels 7 days earlier than the other, at two temperatures, 26 and 30 °C for 65 days. Apart from progeny production, grain quality parameters, such as insect-damaged kernels (IDK) and undamaged kernels (NDK), the weight of frass and kernel weight were measured. Our data confirms that temperature plays a key role in the competition of these two species; P. truncatus seems to perform better at the higher temperature (30 °C), regardless of the presence of an additional species. Moreover, the results of the present study demonstrates that P. truncatus outcompetes S. oryzae. Sitophilus oryzae produced fewer progeny than P. truncatus in all combinations. Given the outcome of a competition, we hypothesize that most of the kernel damage was due to feeding by P. truncatus. Based on these data, we surmise that P. truncatus has a competitive advantage as an invasive species in new areas with stored maize, even in the presence of S. oryzae.

Synergism of deltamethrin with a mixture of short chain fatty acids for toxicity against pyrethroid-resistant and susceptible strains of Tribolium castaneum (Coleoptera: Tenebrionidae).

Deltamethrin is one of the most effective pyrethroid compounds used in stored product protection to control a wide range of pests. However, the development of resistance to deltamethrin in many pest species has been reported and useful research to overcome this problem is required. The present study investigated the possible synergistic effect of a commercial formulation of a mixture of the short chain fatty acids, octanoic, nonanoic and decanoic acid, in a formulation called "C8910" on the lethal activity of deltamethrin against susceptible (Lab-S) and relatively pyrethroid-resistant (Pyr-R) strains of T. castaneum. The possible mechanisms of synergism were studied by investigating the inhibitory effect of C8910 on the activity of detoxification enzymes including cytochrome P450s, esterases, and glutathione S-transferases (GST). In addition, the possible role of C8910 in enhancement of cuticular penetration of deltamethrin through insect cuticle was studied using GC analysis. The results showed that C8910 enhanced the toxicity of deltamethrin at mixing ratios of 1:5 and 1:10 against the Lab-S strain after 24 and 48 h of exposure, and synergistic factors (SF) ranged between 5.69 and 13.59. C8910 also showed greater synergism on the deltamethrin toxicity against the resistant strain than the susceptible one after 24 and 48 h of treatment at 1:5 and 1:10 ratios with SF values ranging from 22.82 and 47.16. C8910 showed strong inhibition of cytochrome P450 of rat microsomal fraction with IC50 value of 6.24 mM. Meanwhile, C8910 inhibited the activity of general esterases in Lab-S and Pyr-R strains with IC50 values of 26.22 and 51.73 mM, respectively. However, weak inhibition of GST activity was observed with inhibition of 52.0 and 22.6% at concentration of 100 mM of C8910 for Lab-S and Pyr-R, respectively. In addition, the results showed no significant difference between the unpenetrated amounts of deltamethrin when insects were treated with deltamethrin alone or with deltamethrin+C8910 (1:20) through the insect cuticle. Results suggested that the synergism between C8910 and deltamethrin could be related to the ability of C8910 to inhibit the detoxification enzymes such as cytochrome P450 and esterases. Therefore, C8910 could be a promising synergist to enhance deltamethrin toxicity and to be a possible natural alternative for conventional synergists such as piperonyl butoxide.

Phenolic constitutents, antioxidant and repellent activities of coriander (Coriandrum sativum L.) fruits using different solvent extracts.

The organic solvent extracts (hexane, chloroform, acetone, methanol and water) of coriander fruits were reported for their antioxidant and repellent activities. The methanol and acetone extracts revealed the highest antiradical activity as compared to the other solvent extracts. HPLC analysis revealed that phenolic acids were the major compounds in chloroform and acetone extracts, whereas flavonoids in methanol and water extracts. The methanol extract of coriander fruits exhibited the highest repellent effect against coleopteran insects. Additionally, the hexane extract of coriander fruits also exhibited potent repellent and toxic activities against rice weevil. It appeared that coriander fruit extract obtained with the apolar solvent had more repellent potential against Sitophilus oryzae as compared to Tribolium castaneum. For Lasioderma serricorne, the methanol extract of coriander fruits reduced in a very significant way the adults followed by the chloroform and hexane extracts.

Intergenerational Transmission of Resistance of Callosobruchus maculatus to Essential Oil Treatment.

Due to the rise of numerous legal restrictions as well as the increasing emergence of resistant populations, the number of available pesticides is decreasing significantly. One of the potential alternatives often described in the literature are essential oils (EOs). However, there is a lack of research addressing the potential emergence of resistance to this group of substances. In this paper, we investigated the multi-generational effects of sublethal concentrations of rosemary oil (Rosmarinus officinalis) on physiological and biochemical parameters of the cowpea weevil (Callosobruchus maculatus) such as egg laying, hatchability, oxygen consumption and acetylcholinesterase activity. Imago, which as larvae were exposed to EO at concentrations equivalent to LC25, showed significantly lower mortality. The results obtained indicate the potential development of resistance in insects exposed to EO in concentrations corresponding to LC25. In addition, in the case of the group treated with an EO concentration corresponding to LC3.12, a stimulation effect of the above-mentioned parameters was observed, which may indicate the occurrence of a hormesis effect. The obtained results may be an important reference for the development of future guidelines and EO-based insecticides.

Study on Gas Chromatographic Fingerprint of Essential Oil from Stellera chamaejasme Flowers and Its Repellent Activities against Three Stored Product Insects.

The objective of this study was to establish the chromatographic fingerprints of the essential oil (EO) from Stellera chamaejasme flowers collected from various natural sites by gas chromatography (GC) combined with chemometric methods. The EO was obtained by hydrodistillation, and its chemical composition was analyzed by gas chromatography-mass spectrometry (GC-MS). Most components were identified as ketones and the relatively high-content components were fitone (38.973%), n-hentriacontane (5.807%), myristic acid (4.944%) and phytol (3.988%). In addition, the repellent activities of the EO from S. chamaejasme flowers and its four main chemical compounds were evaluated against three stored product pests (Tribolium castaneum, Lasioderma serricorne, Liposcelis bostrychophila) for the first time. In this work, the EO and the four chemical compounds showed a repellent effect against three storage pests after 2 and 4 h exposure. The experimental method and repellent activity of S. chamaejasme flower EO could provide a basis for the development of botanical pesticide and the utilization of the rich plant resources of S. chamaejasme in the future.

Toxicity and repellency of essential oil from Evodia lenticellata Huang fruits and its major monoterpenes against three stored-product insects.

In this work, the essential oil (EO) was extracted from the fruits of Evodia lenticellata, and the fumigant toxicity, contact toxicity and repellency against three stored-product insect species were evaluated for the obtained EO and several of its chemical components. The target insects were the adults of Tribolium castaneum (Coleoptera: Tenebrionidae), Lasioderma serricorne (Coleoptera: Anobiidae) and Liposcelis bostrychophila (Psocoptera: Liposcelididae). The EO was obtained with hydrodistillation and its chemical components were analyzed with the gas chromatography-mass spectrometry (GC-MS). Twenty-seven compounds, accounting for 83.1% of the total amount of the oil, were identified from the EO sample. The main compounds included linalool (12.0%), ß-pinene (11.5%), 3-carene (9.6%), caryophyllene oxide (8.7%) and ß-caryophyllene (7.9%). Among them, the amounts of monoterpenes and sesquiterpenes were as high as 52.7% and 22.7% to the total amount of EO respectively. The results of bioactivity test showed that the EO and its testing compounds had interspecific toxicity and repellent activity. So that, it might be expected that the EO extracted from the fruits of E. lenticellata could be developed to a new type of eco-friendly natural insecticide or repellent for the control of stored-product insects.

Potential of pyrethroid-synergised pyrethrum on stored product insects and implications for use as prophylactic sprays.

The study was conducted to evaluate the synergistic effects of 2% pyrethrum extract with synthetic pyrethroids on the mortality of stored product insects. Contact toxicity was performed at variable concentrations observing mortality at 12, 24 and 48 h durations. The results of the present study indicated that, pyrethrum + deltamethrin combination (25:1 ratio) was effective on the adults of Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst). On the other hand, pyrethrum + cypermethrin combination proved effective against Sitophilus oryzae (L.). The efficacy of the tested combination showed reasonable increase in mortality response in treated insects over increasing exposures. At 48 h, 450 ppm pyrethrum + deltamethrin combination induced 25, 90 and 97% mortalities in S. oryzae, T. castaneum and R. dominica adults; while, pyrethrum-cypermethrin combination recorded 75, 45 and 75% mortalities respectively. On the other hand, it was observed that, among the pyrethrum alone treatments i.e. at 300, 450 and 600 ppm concentrations, maximum mortality (62.5%) was observed in S. oryzae exposed to 600 ppm pyrethrum for 48 h. The effective LC50 concentrations for pyrethrum (600 ppm) + deltamethrin combination was estimated to be as 0.1987 and 0.7039 µl/cm2 for R. dominica and T. castaneum adults respectively. Contrastingly, for treatments with S. oryzae, a LC50 value of 0.8673 µl/cm2 was recorded for pyrethrum (600 ppm) + cypermethrin mixture. This investigation strengthens the fact that pyrethrum along with pyrethroids is effective against storage insect pests which can be promisingly a safer insecticidal combination.

Biological activity of two new pyrrole derivatives against stored-product species: influence of temperature and relative humidity.

Members of the pyrrole group are likely to have interesting properties that merit additional investigation as insecticides at the post-harvest stages of agricultural commodities. In the present work, the insecticidal effect of two new pyrrole derivatives, ethyl 3-(benzylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-carboxylate (3i) and isopropyl 3-(benzylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-carboxylate (3k) were studied as stored-wheat protectants against two major stored-product insect species, the confused flour beetle, Tribolium confusum Jaquelin du Val adults and larvae and the Mediterranean flour moth, Ephestia kuehniella Zeller larvae at different doses (0.1, 1 and 10 ppm), exposure intervals (7, 14 and 21 days), temperatures (20, 25 and 30°C) and relative humidity (55 and 75%) levels. For T. confusum adults, in the case of the pyrrole derivative 3i, mortality was low and it did not exceed 32.2% in wheat treated with 10 ppm 3i at 30°C and 55% relative humidity. Progeny production was very low (<1 individual/vial) in all combinations of 55% relative humidity, including control. In the case of the pyrrole derivative 3k, mortality reached 67.8% at 30°C and 55% relative humidity in wheat treated with 10 ppm after 21 days of exposure. Progeny production was low in all tested combinations (≤0.7 individuals/vial) of 55% relative humidity, including control. For T. confusum larvae, in the case of the pyrrole derivative 3i, at the highest dose, mortality was 82.2% at 25°C and 55% relative humidity whereas in the case of 3k it reached 77.8% at the same combination. In contrast, mortality at 75% relative humidity remained very low and did not exceed 13.3%. For E. kuehniella larvae, the highest mortalities, 44.4 and 63.3%, were observed in 10 ppm at 25°C and 55% relative humidity for both pyrrole derivatives. The compounds tested here have a certain insecticidal effect, but this effect is moderated by the exposure, the target species, the temperature and the relative humidity.

Chemical Composition and Bioactivities of the Essential Oil from Etlingera yunnanensis against Two Stored Product Insects.

The chemical composition of the essential oil of Etlingera yunnanensis rhizomes and its contact and repellent activities against Tribolium castaneum (Herbst) and Liposcelis bostrychophila (Badonnel) were investigated. The essential oil obtained from E. yunnanensis rhizomes with hydrodistillation was performed by gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. The main components of the essential oil were identified to be estragole (65.2%), ß-caryophyllene (6.4%), 1,8-cineole (6.4%), limonene (5.2%), and α-pinene (2.4%). It was found that the essential oil of E. yunnanensis rhizomes possessed contact toxicity against T. castaneum and L. bostrychophila (LD50 = 23.33 µg/adult and LD50 = 47.38 µg/cm², respectively). Estragole, 1,8-cineole, and limonene exhibited stronger contact toxicity (LD50 values of 20.41, 18.86, and 13.40 µg/adult, respectively) than ß-caryophyllene (LD50 = 41.72 µg/adult) against T. castaneum adults. Estragole possessed stronger contact toxicity (LD50 = 30.22 µg/cm²) than ß-caryophyllene, 1,8-cineole, and limonene (LD50 values of 74.11, 321.20, and 239.62 µg/adult, respectively) against L. bostrychophila adults. Repellency of the crude oil was also evaluated. The essential oil and constituents possessed strong repellent activity against T. castaneum adults. The four individual constituents showed weaker repellent activity than the essential oil against L. bostrychophila adults. The results indicated that the essential oil of E. yunnanensis rhizomes and the individual constituents had the potential to be developed as a natural insecticide and repellent for the control of T. castaneum and L. bostrychophila.

Residual Efficacy of Two Diatomaceous Earths from Greece for the Control of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) on Wheat and Maize.

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

Exploring the Efficacy of Four Apiaceae Essential Oils against Nine Stored-Product Pests in Wheat Protection.

The Apiaceae family, known for aromatic plants producing bioactive essential oils (EOs), holds significance across sectors, including agrochemicals. This study evaluated the insecticidal potential of four Apiaceae EOs from Crithmum maritimum L., Trachyspermum ammi (L.) Sprague ex Turrill, Smyrnium olusatrum L., and Elwendia persica (Boiss.) Pimenov and Kljuykov against various significant storage pests (Sitophilus oryzae (L.), Trogoderma granarium Everts, Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), T. confusum Jacquelin du Val, Oryzaephilus surinamensis (L.), Alphitobius diaperinus (Panzer), Acarus siro L., and Tenebrio molitor L.) on wheat. Insect mortality rates were monitored at intervals of 1, 2, 3, 4, 5, 6, and 7 days. Smyrnium olusatrum EO exhibited the highest efficacy, followed by T. ammi, C. maritimum, and E. persica EOs, although efficacy varied by species, developmental stage, and concentration. Notably, complete mortality occurred for several pests at 1000 ppm of S. olusatrum and T. ammi EOs. Gas chromatography-mass spectrometry (GC-MS) analysis revealed key compounds in these EOs, including myrcene, germacrone, and curzerene in S. olusatrum EO, and thymol, γ-terpinene, and p-cymene in T. ammi EO. These findings emphasize their potential as botanical insecticides. Smyrnium olusatrum and T. ammi EOs emerge as promising eco-friendly pest management options due to their efficacy, highlighted compound composition, and availability of biomass from both wild and cultivated sources.

The Fumigation Toxicity of Three Benzoate Compounds against Phosphine-Susceptible and Phosphine-Resistant Strains of Rhyzopertha dominica and Sitophilus oryzae.

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

Effects of sulfur dioxide fumigation on mortality of confused flour beetle (Coleoptera: Tenebrionidae) and rice weevil (Coleoptera: Curculionidae).

Sulfur dioxide (SO2) fumigation was studied in laboratory to determine its potential as an alternative treatment for postharvest control of stored product insects, confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae), and rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae). Three-hour fumigations with 0.1%-2.0% SO2 were conducted against eggs, immature stages, and adults of the 2 insects at 20 °C. Effective control of both insects was achieved. However, there were considerable variations between the 2 insects and among different life stages. Confused flour beetle was more susceptible to SO2 fumigation than rice weevil. Complete control of adults and all life stages of confused flour beetle was achieved in 3-h fumigations with 0.5% and 2.0% SO2, respectively. For rice weevil, 3-h fumigation with 1.5% SO2 resulted in 96.5% adult mortality and the fumigation with 2.0% SO2 resulted in 99.27% mortality of adults and 87.5% mortality of immature stages. Three-hour fumigations with 1% SO2 resulted in <5% egg survival to adults. The study demonstrated high efficacy of SO2 fumigation against the insects and suggested that SO2 fumigation has good potential for postharvest pest control on stored products.

Natural Warriors against Stored-Grain Pests: The Joint Action of Beauveria bassiana and Steinernema carpocapsae.

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

Combinations of Beauveria bassiana and spinetoram for the management of four important stored-product pests: laboratory and field trials.

The current study examines the efficacy of the semi-synthetic insecticide spinetoram and entomopathogenic fungi Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae) as wheat protectants against the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), the granary weevil, Sitophilus granarius (L.) (Coleoptera: Curculionidae), and the khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), under laboratory and field trials. One dose of B. bassiana, i.e., 1 × 107 conidia/kg wheat, two doses of spinetoram, i.e., spine1: 0.05 ppm (mg/kg wheat), spine2: 0.1 ppm, and their combinations (Bb + spine1, Bb + spine2) were evaluated at 20, 25, and 30 °C. All treatments provided significantly higher mortality at 30 °C compared with the other two temperatures. Maximum mortality levels were observed in the treatments where B. bassiana was combined with the higher dose of spinetoram (0.1 ppm). All treatments reduced progeny production in comparison with the control groups. Maximum progeny reduction was observed at 30 °C, on wheat treated with the Bb + spine2 combination. The combination Bb + spine2 also provided elevated mortality rates in both laboratory and field persistence trials, but at 180 days caused moderate mortality to all tested insect species. Concerning progeny, at laboratory persistence trials, the combination Bb + spine2 exhibited the lowest offspring emergence to all tested species compared to the other treatments and control. Overall, our study showed that R. dominica was the most susceptible species followed by S. granarius, T. castaneum, and T. granarium. Our findings revealed that the combination of B. bassiana and spinetoram may be a useful tool for efficient and advanced integrated pest management strategies for long storage periods under multiple temperatures.

Insecticidal Effect of Diatomaceous Earth Formulations for the Control of a Wide Range of Stored-Product Beetle Species.

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

Evaluation of the susceptibility of Alphitobius diaperinus meal to infestations by major stored-product beetle species.

The projections for the production of insects as food and feed show an enormous increase for insect production in the near future, which will subsequently lead to the increase of the stored quantities of insect meals and related products. However, information on the susceptibility of insect meals to infestations by stored-product insects is rather limited. To this end, the objective of the present study was to evaluate the potential of major storage insect species to grow and reproduce on insect meals that are based on larvae of the lesser mealworm, Alphitobius diaperinus. The progeny production of thirteen stored-product insects on A. diaperinus meal, as well as their instantaneous rate of increase, as a measure of population growth, was recorded for each species. Based on the results, six out of the thirteen examined insect species (A. diaperinus, Tenebrio molitor, Trogoderma granarium, Lasioderma serricorne, Tribolium confusum, and Tribolium castaneum) were able to infest pure A. diaperinus meal, as they grew well and developed progeny on the insect meal substrate. Tribolium confusum, T. castaneum, and especially T. granarium gave the highest progeny production numbers in the A. diaperinus meal with the latter giving an instantaneous rate of increase of 0.067. Expecting the upcoming increase in the production of insect-based products globally, further research in this field is needed for improved production and storage facilities, detection and estimation methods, and technologies to minimize insect infestations without causing negative effects to farmed insects.

Quick knockdown results in high mortality: is this theory correct? A case study with phosphine and the red flour beetle.

BACKGROUND: The fumigant phosphine is used all over the world for disinfestation of stored grains and commodities. Adults of 23 different populations of Tribolium castaneum from 10 different countries were evaluated for phosphine resistance using a modification of the Detia Degesch Phosphine Tolerance Test Kit (DDPTTK). Adults were exposed to 3000 ppm and recorded for 5-270 min for their mobility. RESULTS: Among the tested populations, high levels of phosphine resistance were recorded in populations from Brazil, Serbia, and Spain. No survivals were recorded after 7 days post exposure for eight of 23 in a tested population. CONCLUSIONS: Our work revealed four scenarios: 1, quick knockdown-low (or no) recovery; 2, Slow knockdown-high recovery; 3, Quick knockdown-high recovery; and 4, Slow knockdown-low recovery. Our data indicate that post exposure period is critical for the evaluation and characterization of phosphine resistance. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.