Stored-product Insect Pests Research Articles

(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.

Insecticidal Effects of Two Plant Extracts of (Bidens pilosa and Rumex dentatus) and Neem Oil Against Certain Stored Grains Insects.

The insecticidal activities of methanolic extracts of two weedy plants leaves Bidens pilosa L. and Rumex dentatus L. at three different concentrations 3, 5 and 7% were tested against three stored grain pests, Rice weevil Sitophilus oryzae L. Saw-toothed grain beetle Oryzaephilus surinamensis L., and Bean weevil Acanthoscelides obtectus Say, compared to Neem oil as a commercial product at the same concentrations for exposure periods 24, 48, 72 and 96 hrs of treatment under laboratory conditions. Results revealed that different concentrations and exposure periods of the two extracts and Neem oil had significant lethal effects against these tested grain pests. In general, R. dentatus extract was found to be the most toxic against the tested grain pests and caused the highest mortality (100.00%) for the three pests S. oryzae, O. surinamensis and A. obtectus when applied at its highest concentration (7%) for an exposure time of 96 hrs (the highest time), followed by Neem oil 90.0±10.0, 70.00±13.3 and 90.00±2.8%, then B. pilosa extract 75.83±5.8, 79.33±5.46 and 87.50±7.2%, respectively at the same concentration and exposure time, indicating that the obtained mortality percentages were concentration and exposure time-dependent. Finally, these results demonstrate that, R. dentatus extract can be used as a promising pesticide against the three stored products insect pests investigated under this study, and strongly recommended to be used as stored grain protectants in the future.

A rapid assay for the detection of resistance to phosphine in the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

Resistance to the fumigant phosphine in stored product insect pests is a global problem. Diagnosis of resistance relies on a bioassay developed by the FAO that involves a mortality assessment after 20-h fumigation of a pest population at a discriminating concentration of gas, followed by a 14-day post fumigation assessment. This bioassay is impractical for monitoring and early detection of phosphine resistance in routine pest management. We utilized the procedure of a commercial resistance detection test kit for rapid detection in field populations of lesser grain borer, Rhyzopertha dominica (F.). We established a knockdown effect of either susceptible or resistant insects by exposing them to a high concentration of phosphine. We assessed the relationship between adult knockdown times and the FAO method for 18 beetle populations utilizing knockdown criteria for a single beetle in a chamber, or for 50% or 100% knockdown times for groups of beetles, exposed to 3000 ppm of phosphine. We also determined the most effective concentrations that would elicit the quickest knockdown while estimating the recovery times from exposure. Results suggest that a KT100 test was better than the KT50 and the KTsingle tests. Based on the responses of susceptible populations, we established that a KT100 of approximately 18 min can be used as a viable knockdown time to distinguish a susceptible from a resistant populations. Higher concentrations of phosphine significantly elicited a quicker recovery in strongly resistant populations compared to susceptible populations. These findings have potential for developing a robust commercial kit for practical phosphine resistance detection in populations of R. dominica by commercial fumigators, and could be incorporated in a resistance management program.

Effects of developmental stage, cold acclimation and diet on the cold tolerance of three species of Cryptolestes (Coleoptera: Laemophloeidae)

Flat grain beetles (Coleoptera: Laemophloeidae) are common stored-product insect pests in Canada, infesting cereals in grain bins, equipment and end products in flour mills. We studied the cold tolerance of the three most common flat grain beetles: Cryptolestes ferrugineus, Cryptolestes turcicus and Cryptolestes pusillus, by measuring the survival at −10 °C and supercooling point (SCP) for different life stages (egg, young larva, old larva, pupa and adult) reared on flour mixed with brewer’s yeast. Probit analysis was used to estimate the lethal time for 50 and 95% mortality. This was done with non-acclimated individuals (only held at 30 °C) or cold-acclimated individuals (held at 18, 10 and 5 °C, for 1 week/temperature). In general, adults were the most cold-hardy stage for each of the species. Acclimated insects were anywhere from no increase in cold tolerance to 14-fold more cold-tolerant than the corresponding non-acclimated stage and species. Cryptolestes ferrugineus was most cold-tolerant species (58 d at −10 °C to reach 95% mortality for acclimated adult), C. turcicus was the next most cold-tolerant, (39 d) and C. pusillus was the least cold-tolerant (11 d). The cold tolerance of adults reared on three diets was measured both for acclimated and non-acclimated insects. The adults reared on grain diet (whole wheat kernels, cracked wheat kernels and wheat germ (90:5:5 mass ratio) were the most cold-tolerant, adults reared on white-wheat flour and brewer’s yeast diet (95:5 mass ratio) had the next highest cold tolerance followed by the adults reared on 100% white-wheat flour. Supercooling point (SCP) of insects ranged from −20.6 to −26.7 °C. In general, acclimated insects had slightly lower SCP than non-acclimated insects.

Persistence and ingestion characteristics of phytochemical volatiles as bio-fumigants in Sitophilus oryzae adults

Fumigant toxicity of phytochemical volatiles has been widely reported against stored product insect pests. Such volatiles are considered as natural fumigants and bio-fumigants in post-harvest food protection research. In the present study, persistence and ingestion of diallyl disulfide, citral, eucalyptol, eugenol and menthol were investigated in Sitophilus oryzae adults in comparison with fumigant toxicity and microstructural impact in elytra. The fumigant toxicity bioassay was performed with increasing concentrations of phytochemical volatiles at 25, 125, 250 and 500 μL/L air against S. oryzae adults in 50 mL glass vials. The phytochemical residues were examined from the treated adults by Gas Chromatography coupled with Flame Ionization Detector (GC-FID) and their pathological impacts on the elytral surface was observed under Scanning Electron Microscopy (SEM). After 72 h of fumigation, diallyl disulfide and eucalyptol were identified as potential fumigants with 5.24 and 8.30 μL/L air LC50 values, respectively. GC-FID analyses showed that diallyl disulfide and eucalyptol molecules persistence (1.29 and 2.60 ppb persistence with 0.94 and 0.90 r2 values respectively at 72 h exposure) on the body surface of weevil was positively correlated with the fumigation exposure and toxicity. Whereas, phytochemical molecules ingestion into the body of weevils was not directly linked with the insect mortalities. The SEM observations indicated that diallyl disulfide and eucalyptol molecules caused severe microstructural impacts on the elytra of weevils compared to other molecules. As a result, the present study suggested that phytochemical fumigants are persisted on the body surface and caused insecticidal toxicities in S. oryzae adults. In addition, it was predicted that persisted molecules might be entered into the body of weevils via cuticular penetration.

Protection of organic cereals from insect and rodent pests in a warehouse by combined use of traps and sticky tapes

Several options of protection of organic cereals (winter and spring wheat, rye and maize) from insect and rodent pests, using a combination of traps (with or without pheromone/ attractant) and sticky tapes and no chemicals, were tested in a warehouse over the summerspring season of 2019/2020. Temperature in the warehouse was 14-29?C and humidity around 50%. The average grain moisture of winter and spring wheat and rye was 10-11%, while it was 12-14% in maize grain, and the average grain temperature of all cereals was 13-27?C. Regarding stored-product insect pests, five coleopteran, two moth and one Psocoptera species were detected, and the coleopterans predominated (98.5%) along with secondary pest insects (94.0%). Regarding rodents, only specimens of Mus musculus were found throughout the test period, their maximum monthly frequency being 72 (in January 2020). A combination of traps (with or without pheromones) and sticky tape barriers was found to provide an effective tool for trapping insects. Also, snap traps and trapping boxes for killing rodents, when used simultaneously with sticky tape barriers, were found to provide good protection of cereals from house mice. The pest control effect was also confirmed by collecting samples of organic cereal grain, which showed no significant presence of stored-product insects or grain damage (0.94% and 0.96% in spring wheat and rye, respectively) at the end of the test period. The results showed a great potential of combined application of traps and sticky tapes for protecting organic cereals in horizontal bulk storages, but the use of chemicals approved for organic food production would be required under extended storage periods.

BIOLOGICAL STUDIES ON THE CIGARETTE BEETLE, Lasioderma serricorne (F.) ON DIFFERENT BOTANICAL FOODS

The cigarette beetle, Lasioderma serricorne (F.) is a serious economic insect pest of many stored products, spices and dried fruits. This work was carried out in the Laboratory of Plant Protection Department, Faculty of Agriculture, Zagazig University, Egypt, to study the effect of eight different botanical foods as insect diets (standard insect rearing diet, wheat germ, oat grains, cumin seeds, corn flakes, chamomile flowers, roselle flowers and fenugreek seeds) on some biological aspects of this insect, population growth after one and three months as well as percentage of weight loss. Also, the effect of the heavy insect infestation on certain chemical constituents of the tested foods as food moisture content, total carbohydrates, total proteins, ash, total fats and total fibers was determined and compared to control after three months of storage. The standard insect rearing diet and wheat germ were the best foods since the insect larval period was very short (14.45 and 15.36 days, respectively), while fenugreek was less preferred food as larval diet (30.55 days). Pupal period ranged from 7.18 to 11.81 days on wheat germ and corn flakes, respectively. The shortest complete developmental period was 30.67 days on wheat germ and the longest one was 53.21 days on fenugreek seeds. Values of the susceptibility index ranged from 3.03 to 8.08% for fenugreek seeds and wheat germ, respectively. The standard insect rearing diet and wheat germ were the best food kinds since they produced the highest mean progeny number after one and three months of storage (204.33, 151.67 and 3151.30, 4313.30 adults, respectively). Mean weight loss percentage ranged from 0.52 to 5.20% on corn flakes and oat grains after one month from insect infestation, respectively. However, it reached its maximum value (31.13%) on the standard insect rearing diet and minimum value on cumin seeds (1.23%) after three months. The highest relative weight loss per each adult insect was 23.75% on chamomile flowers and the lowest one valued 2.66% on corn flakes after one month of storage. After three months the value increased on corn flakes, standard insect rearing diet, roselle flowers and cumin seeds, while decreased on the other tested food kinds. A positive correlation was found between the heavy insect infestation on some foods and the chemical constituents as moisture content, total carbohydrate, total proteins, total fats, ash and total fibers. In contrast a negative one was recorded on the other foods. Positive correlation coefficients with all tested chemical constituents on sound and infested foods were detected by highly significant for total carbohydrates and total proteins as well as significant for total fats. The heavy insect infestation increased both the progeny number and the incurred weight loss and affected the chemical constituents of the different tested food kinds compared to control. All tested food kinds were infested by the cigarette beetle L. serricorne and no immune food was found free from the insect infestation with preferable some tested food kinds to the insect. Moreover, the heavy insect infestation after three months affected the chemical constituents of the tested food kinds.

Evaluation of Spinosad Applied to Grain Commodities for the Control of Stored Product Insect Pests

Evaluation of Spinosad Applied to Grain Commodities for the Control of Stored Product Insect Pests

Acute toxicity and repellent activity of essential oil from Atalantia guillauminii Swingle fruits and its main monoterpenes against two stored product insects

ABSTRACT The objective of this work was to analyze the essential oil from Atalantia guillauminii fruits in China and evaluate their chemical compositions, insecticidal and repellent activities against Tribolium castaneum and Lasioderma serricorne adults. The essential oil was obtained by hydro-distillation and its yield was 0.12% (V/W). All together 25 chemical compositions were identified by GC-FID and GC-MS, and the main chemical compositions were D-limonene (41.8%), β-pinene (10.9%) and selina-3,7(11)-diene (6.8%). The bioactivity of the obtained essential oil and its two main compositions (D-limonene and β-pinene) was investigated by fumigation, contact and repellent activity bioassay. The essential oil and its two main compositions all showed significant fumigant toxicity, contact toxicity and repellent activity against two target insects. These results suggest that the essential oil and its two main compositions have potential to be developed as natural insecticides and repellents for the control of stored product insect pests.

Morphology of antennae and mouthpart sensillae in Lasioderma serricorne (fabricius) (Coleoptera: Anobiidae)

The cigarette beetle, Lasioderma serricorne (Fabricius) (Coleoptera: Anobiidae), is an important stored-product insect pest. In the present study, the external morphologies and distribution of the sensilla on the antenna and mouthparts of L. serricorne were described following scanning electron microscopy with the aim of understanding the behavioral mechanisms of this insect pest. On the antennae, various sensilla types were identified: Böhm bristles, three basiconic sensillum subtypes, two chaetica sensillum subtypes, three styloconic sensillum subtypes, as well as trichodea, capitulum, and campaniform sensilla. Interestingly, campaniform sensilla and two subtypes of styloconic sensilla (St1 and St2) were reported for the first time on L. serricorne antennae. The mouthparts of L. serricorne carried six different sensory structures including chaetica, basiconic, styloconic, auricillic, and trichodea sensilla, as well as long macrotubercles. Two subtypes of chaetica sensilla were recorded on the labrum, mandibles, and maxillary and labial palpi. A basiconic sensillum subtype (BS3) was distributed on the galea and lacinia, while subtype BS2 was also found on the lacinia along with long fan-like macrotubercles, which are hypothesized to help clean the area of the preoral cavity directly below the base of the labrum. Auricillic sensilla were also found on the galea. The labial palpi showed three subtypes of basiconic sensilla (BS3, BS4, BS5), whereas the maxillary palpi bears BS4, and BS5. Styloconic sensilla were also found at the top of the maxillary and labial palpi. Blunt basiconic (BS6) and trichodea sensilla were found on a tongue-shaped structure (pharynx) situated entirely at the midline of the preoral cavity. These findings improve understanding of the sensory perception of an important insect pest and could help to develop suitable control methods.

The effectiveness of low temperature (5 °C) on Sitophilus oryzae (L.), Sitophilus zeamais (Motch.) and Sitophilus granarius (L.) in wheat grain: The impact of pre-acclimation

Laboratory trials were conducted in wheat grain to assess the effectiveness of low temperature (5 °C), applied at intervals of 5, 7, 9, 11, 20, 25, 30 and 35 days (d), as a control measure for stored product insect pests of the genus Sitophilus, and compared the results with the impacts of 7 d pre-acclimation at 15 °C and non-acclimation. Mortality was determined after 1, 2 and 7 d of recovery in the laboratory at 25 ± 1 °C and 60 ± 5% r. h., while progeny were assessed 7 weeks later. Acclimation had the strongest impact on S. oryzae after 5 d exposure to 5 °C and 7 d recovery, while the same effect on S. zeamais was shown after 20 and 25 d of exposure and 1 d recovery, and the same impact on S. granarius occurred after 30 and 20 d of exposure and 1 and 7 d recovery, respectively. Low temperature was found to be the most effective against S. oryzae, and the least effective against S. granarius. Mortality was high (≥96%) in both S. oryzae test groups after 11 d of exposure and 7 d recovery, S. zeamais mortality was high (>97%) after 35 and 30 d of exposure and 2 and 7 d of recovery, respectively, and S. granarius mortality was ≤87% in all test variants. Total reduction (100%) of non-acclimated S. oryzae, S. zeamais and S. granarius progeny required 8, 25 and 30 d of exposure to 5 °C, respectively, while acclimated weevils required 11, 30 and 30 d, respectively.

Sunflower seed hulls waste as a novel source of insecticidal product: Pyrolysis bio-oil bioactivity on insect pests of stored grains and products

The edible oil industry produces abundant sunflower seed hulls (SSH) as waste. Pyrolysis offers a sustainable method for producing high-value bioproducts from this lignocellulosic residue. This paper reports on the bioefficacy of SHH pyrolysis bio-oils from raw SSH (named SSH bio-oil) and acid pretreated hulls (named PTH bio-oil) as bioinsecticides against Sitophilus oryzae, Lasioderma serricorne and Tribolium castaneum. Raw SSH and pretreated hulls with 10% H3PO4 were subjected to fast pyrolysis in a vertical reactor at 450 °C. Results show that PTH bio-oil is a furfural enriched bio-liquid with storage stability and a yield of 33%. SSH bio-oil was unsuitable for evaluating biological activity since it produce high variability in mortality data. In contrast, PTH bio-oil produces high insecticidal activity in S. oryzae (LC50 = 0.51 mg cm−2) by contact toxicity bioassay, followed by L. serricorne and T. castaneum. In behavioral assays, PTH bio-oil shows a slight repellent effect and mobility reduction. Moreover, PTH bio-oil affects the nutritional physiology of S. oryzae and T. castaneum producing a modification of nutritional indices and antifeedant effects. Our study provides information on the potential of fast pyrolysis bio-oils from SSH waste to develop novel bioinsecticides as an alternative to the use of conventional synthetic pesticides.

Spatiotemporal evaluation of red flour beetle (Tribolium castaneum) dispersion under the effect of climate and topography in South Korea

Control of Tribolium castaneum, a stored product insect pest, requires analysis of the post-introduction dispersion pattern to determine the most effective time and place for preventive measures. However, the indoor habitat characteristics of T. castaneum limit the choice of tools that can be used for spatiotemporal evaluation of its dispersion. In this study, we evaluated potential T. castaneum distribution in South Korea in response to climate change and predicted its likely dispersion pattern from major grain-importing ports by considering seasonal wind status and location of agricultural facilities. Climatic suitability for T. castaneum was evaluated by recording the locations of indoor cultivation areas, and the dispersal range of T. castaneum from major grain-importing areas was estimated by considering flight direction and distance along with seasonal wind patterns. The results showed that climatic suitability for the insect would increase with climate change, and a high potential for dispersion could be expected during the summer. This study proposes data that can assist in decision making for T. castaneum control as well as a model-based methodology applicable for evaluating a stored product insect.

Effectiveness of long-lasting insecticide netting on Tribolium castaneum is modulated by multiple exposures, biotic, and abiotic factors.

Prevention is the first line of defense in mitigating losses of post-harvest crops. Long-lasting insecticide treated (LLIN) could be used in food facilities to expose insects to insecticide at different areas within a facility. Prior research has shown that single short exposures reduce movement and longer exposures increase mortality for stored-product insect pests, but we do not know how multiple short duration exposures and biotic and abiotic conditions affect insects exposed to LLIN. Here, we repeatedly exposed red flour beetles, Tribolium castaneum, to LLIN to assess the cumulative effects. We also examined the effects of beetle age and time of day during exposure, and temperature, humidity and food availability during recovery after a single exposure to LLIN. We found that four repeated 10-min exposures had similar knockdown effects as a single 30-min exposure. We also found that beetles were more affected when aged 1-6 days versus 14-20 days or were exposed at mid- or late in the day versus earlier in the day. Higher recovery levels were observed with food and at higher relative humidity. In addition, older beetles were more active than younger beetles during exposure, which could reduce time in contact with netting and partially explain why older beetles tended to be less affected. Some individuals can recover after exposure to LLIN, dependent on exposure duration and environmental factors, but our study shows that sublethal effects likely persist and future work should consider the physiology of T. castaneum before, during, and after exposure to LLIN. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Exposure of Tribolium castaneum (Herbst) females to pirimiphos-methyl alters the fitness of their progeny

Insecticidal treatment is a common practice for the control of stored-product insect pests. Most studies are focused on the direct effects of insecticides on target insects, while there are no data on the indirect effects on adults in terms of progeny fitness. This study deals with the effect of pirimiphos-methyl on adults of Tribolium castaneum (Coleoptera: Tenebrionidae), investigating their exposure time cost to progeny fitness. For this purpose, females of T. castaneum were exposed for 1, 3, 8, 16, 24, and 72h to pirimiphos-methyl and progeny birth or death rates were calculated. The fecundity, as well as the survival of progeny, was affected by the parental exposure to the insecticide. When females were exposed for 1 and 3h to pirimiphos-methyl, the net reproductive rate of the progeny was 4.1 and 4.3 females/female, respectively, which did not statistically differ with the progeny in control treatment (6.3 females/female). Further exposure time to pirimiphos-methyl affected significantly the progeny net reproductive rate, where the lowest value was observed at the 72-h exposure time (0.97 females/female). The intrinsic rate of increase, as well as the finite rate of increase, did not differ between the progeny of the control treatment (0.029 females/female/day and 1.029, respectively) and the progeny of exposed females at 1h (0.021 females/female/day and 1.021, respectively) or 3h (0.023 females/female/day and 1.023, respectively). By increasing the time of exposure to pirimiphos-methyl, a detrimental effect to progeny fitness was revealed based on the values of the intrinsic and finite rate of increase. The lowest values of these parameters were observed at the 72-h exposure time (0.001 females/female/day and 1.000, respectively). The same trend was observed in the values of the doubling time. In contrast, the mean generation time did not statistically differ between control and all insecticide treatments. The fact that the exposure of parental females of T. castaneum to pirimiphos-methyl negatively affects the demographic parameters of their offspring production should be seriously taken into account when management strategies are applied against this notorious stored-product insect species since it could reduce the repeatedly insecticidal applications in storage facilities.

Larvicidal Action of Cannabidiol Oil and Neem Oil against Three Stored Product Insect Pests: Effect on Survival Time and in Progeny.

Simple SummaryEach year, agricultural produce suffers significant loss and quality deterioration upon infestation by stored product insects. Synthetic insecticides represent a ready-to-go, effective pest control solution, albeit with several environmental and health risks. In this light and within the framework of integrated pest management research, the present study focuses on the potential insecticidal effect of two essential oils, neem oil and CBD, against 4th instar larvae of the harmful Tribolium confusum, Oryzaephilus surinamensis and Plodia interpunctella, on wheat, rice and corn seeds. CBD, especially, has been under-researched in this regard. Treatment efficacy was expressed as larval mortality in relation to dosage, time exposure intervals and product. In comparison with the control, the results showed clear dose-dependent pesticidal activity for both oils, expressed as significant larval mortality at high dose application, as high as 100% at the highest dose (90 mg/mL). Moreover, the overall survival time of the tested larvae was also considerably shorter than that of control larvae, while the treatments also produced considerably fewer offspring in the tested insects. Our results reinforce the prospect of incorporating botanical insecticides in Integrated Pest Management programs.Stored product pests can be detrimental to agricultural produce. As much as chemical pesticides are effective control agents, they involve several environmental and health risks. Within the framework of studies on alternative pest management methods, interest has focused on a plethora of plants whose extracts have demonstrated promising action as insecticides. Azadirachta indica and the derived neem oil have been extensively tested against many harmful insect species. In contrast, Cannabis sativa L. and its main compound, CBD, a highly concentrated cannabinoid, have not been investigated much. The present study examined the potential insecticidal activity of CBD and neem oils against 4th instar larvae of Tribolium confusum, Oryzaephilus surinamensis and Plodia interpunctella on wheat, rice and corn seeds. Treatment efficacy was expressed in terms of larval mortality. Mortality was observed in relation to dosage, time exposure intervals and product types. The results showed clear pesticidal activity for both oils, which at high doses induced significant mortality. The treatments produced significantly fewer offspring in the insect species tested than the control. The efficacy of treatment in progeny suppression was, as expected, dose dependent.

Design and efficacy evaluation of a modern automated controlled atmosphere system for pest management in stored dates

The use of high-pressure carbon dioxide and heating applications has been more popular against stored product insect pests recently. We designed and constructed a modern automated controlled atmosphere system based on carbon dioxide under different pressures and temperature regimes for the management of the red flour beetle (Tribolium castaneum) (RFB) and saw-toothed grain beetle (Oryzaephilus surinamensis) (SGB) infesting stored dates (cv. Sagai). The findings of this study showed that the minimum exposure time that killed 100% of all developmental stages of the two beetles was 30 min at a pressure of 300 kPa and a temperature of 45 °C. This combination was optimal in the consumption of electrical energy and carbon dioxide. Based on the lethal time that killed 50% (LT50) and 95% (LT95) of the test insect population, RFB showed more susceptibility to the treatment than SGB. The optimal combinations of carbon dioxide concentration, pressure, and temperature at minimum exposure time that killed 100% of the test insects have no significant detrimental effects on the essential characteristics related to date quality. The designed prototype of the controlled atmosphere system, based on the pressure of carbon dioxide and heat, proved to be effective against the two target insects in stored dates. The findings encourage further studies for testing and evaluating the system under field conditions at a larger scale.

Analysis of the Essential Oils of Eucalyptus camaldulensis Dehnh. and E. viminalis Labill. as a Contribution to Fortify Their Insecticidal Application

The use of synthetic chemicals, with harmful effects on the environment and human health, is the principal strategy in the management of stored-product insect pests such as Oryzaephilus surinamensis and Sitophilus oryzae. Various studies in recent years have highlighted the possibility of using plant essential oils as available and low-risk factors in insect pest management. Therefore, in the present study, the possibility of controlling O. surinamensis and S. oryzae was investigated using Eucalyptus camaldulensis and Eucalyptus viminalis leaf essential oils. The essential oils were obtained by hydrodistillation of the leaves of the 2 Eucalyptus species, and the chemical compositions were determined by gas chromatographic-mass spectral analysis. The essential oil of E. camaldulensis was dominated by p-cymene (24.8%), cryptone (18.9%), and spathulenol (12.4%), while the major components in E. viminalis essential oil were 1,8-cineole (51.6%) and α-pinene (15.8%). The essential oils displayed promising fumigant toxicity against insect pests, which was positively dependent on utilized concentrations and exposure times. Oryzaephilus surinamensis, with low median lethal concentrations, was more susceptible than S. oryzae to the essential oils after 24, 48, and 72 hours. Also, E. viminalis essential oil, with a high level of insecticidal monoterpenes such as 1,8-cineole and α-pinene, was more toxic to insect pests than E. camaldulensis oil. According to the results of the current study, E. camaldulensis and E. viminalis essential oils, rich in insecticidal terpenes, can be alternative candidates to synthetic chemicals in the management of O. surinamensis and S. oryzae.

Alpha-Amylase Enzymes of Tribolium castaneum (Herbst) and Callosobruchus maculatus (F.) And Their Response to A-Amylase Inhibitor from Rice أنزبم الألفا أمیلیز فى حشرتى خنفساء الدقیق الحمراء Tribolium castaneum (Herbst) وخنفساء اللوبیا Callosobruchus maculatus (F.) واستجابتهم لمثبط ألفا أمیلیز من الأرز

Insect α-amylase has recently become a target of insect control strategies using plant-derived α-amylase inhibitors especially for the control of stored product insect pests. The first step to establish such strategy is to characterize the α-amylase enzymes in the target pest. In the current study, α-amylase was biochemically characterized in the larval and adult stages of Tribolium castaneum and Callosobruchus maculatus. T. castaneum was found to have higher α-amylase activity with lower temperature stability compared to that of C. maculatus. The optimum pH for α-amylase activity was 5-6. Zymogram pattern revealed the presence of two α-amylase isoforms with high molecule weight in T. castaneum. C. maculatus has two α-amylase isoforms in the adult stage and three isoforms in the larval stage. Rice α-amylase inhibitors was purified and found to have strong inhibitory effect against α-amylase of both insects and also negatively affected their life parameters.

Bioefficacy of Ethanolic Leaves Extract of Azadirachta indica Against Stored Product Insect Pest, Tribolium castaneum (Herbst.)

Tribolium castaneum is a species of beetle in the family tenebrionidae, the darkling beetle. Conventional insecticides used for controling stored product pests are expensive and arguably associated with various severe adverse side effects hence the need to develop botanical pesticides that are effective as alternative. Though Azadrachta indica has been used for the control of so many insects, review of the literature show no scientifically investigated report of its effectiveness against T. castaneum. This study was therefore designed to evaluate bioinsecticidal activity of ethanolic leaves extract of Azadirachta indica against stored Tribolium castaneum. Different concentrations (60, 70, 80, 90, and 100%) of ethanolic leaves extract of A. indica was applied on the filter paper and were allowed to dry for a reasonable time period. Control was maintained by treating the filter paper with water only. For examining the percent mortality, 15 adults was taken in the Petri dishes embedded with Whitman’s filter paper, covered with lid and tightened with scotch tape on both sides. The A. indica extracts at different concentrations tested showed insecticidal activity against T. castaneum. Further, phytochemical screening results showed that the A. indica extract have phytochemicals associated with insecticidal activity. The study has established that the ethanoloc extract A. indica is effective in managing stored product pest.