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Stored maize is frequently attacked by different pests, such as insects and microorganisms. The aim of the present study was to evaluate the bioactivities of sulcatone (6-methyl-5-hepten-2-one) against the maize weevil Sitophilus zeamais and the phytopathogenic fungi Fusarium verticillioides, Aspergillus flavus, and A. parasiticus. Sulcatone showed a strong repellent effect with a maximum value of −92.1 ± 3.2% at 40 µM in two-choice olfactometer bioassays and an LC95 value of 17.2 µL/L air (95% 16.5–18.1) in a fumigant toxicity experiment. The antifungal effect of sulcatone was evaluated through the fumigant method, reporting MIC values of 3.5, 3.8, and 3.9 mM for F. verticillioides, A. parasiticus, and A. flavus, respectively. Additionally, a silo-bag experiment containing all pests was conducted to evaluate the potential use of sulcatone in a real storage system. Sulcatone caused 71.69 ± 1.57% weevil mortality in silo-bags and proved to be effective as a fungicidal and antimycotoxigenic agent since both ergosterol and fumonisin B1 content were significantly reduced by 60% in silo-bags containing sulcatone. This study demonstrated that sulcatone has the potential to be used for the control of both insects and fungi of stored maize, without affecting the germination of grains. [ABSTRACT FROM AUTHOR]

Simple Summary: The house cricket, Acheta domesticus, is one of the species recently authorised for production and commercialisation as novel food by European legislation. Powder from this insect can be used to enrich bread, extruded snacks, and pasta. The aim of this work was to analyse the behavioural response of one of the main pests of alimentary pasta, the maize weevil (Sitophilus zeamais), to different types of semolina pasta enriched or not enriched with increasing proportions of house cricket powder. In five-choice behavioural bioassays, the number of maize weevil adults attracted to 100% durum wheat pasta was significantly higher than those attracted to the other pasta types enriched with house cricket powder. In two-choice behavioural bioassays, all types of pasta had a positive and significant attraction. In similar experiments, cricket powder alone was not attractive, indicating a neutral effect towards insects. These observations suggest that the lower attractiveness of pasta enriched with cricket powder is mainly due to a masking effect of host food odours. The behavioural response of adult maize weevil, Sitophilus zeamais, to different types of semolina pasta enriched or not enriched with increasing proportions (5%, 10%, and 15%) of house cricket (Acheta domesticus) powder was investigated in olfactometer arena bioassays by using trap devices. In the five-choice behavioural bioassays, the number of S. zeamais adults attracted to 100% durum wheat semolina pasta was significantly higher than those attracted to the other pasta types enriched with A. domesticus powder. In the two-choice behavioural bioassays, the Response Index for each pasta type was positive and significant. However, although not significant, there was a progressive reduction in the Response Index as the cricket powder content increased. In similar experiments, there were no significant differences between cricket powder alone and the control in the number of attracted S. zeamais, indicating a neutral effect towards insects. These observations suggest that the lower attractiveness of pasta enriched with house cricket powder is mainly due to the masking of host food odours. Solid-phase microextraction coupled to gas chromatography–mass spectroscopy identified a total of 18 compounds in the head-space samples of the different types of pasta, highlighting differences in volatile composition. Some volatile compounds were only present in the pasta produced with cricket powder. In particular, 1-octen-3-ol and phenol were present in the samples containing 5%, 10%, or 15% cricket powder; pentanal, benzaldehyde, and dimethyl disulphide were present in samples containing 10% or 15% cricket powder; and 2,5-dimethyl-pyrazine was present in the sample containing 15% cricket powder. Further investigation with individual compounds and mixtures is needed to define the chemical basis of the differences in the insect olfactory preference observed in this study. [ABSTRACT FROM AUTHOR]

Maize is the mainstay of food and animal feed globally. Maize weevil, Sitophilus zeamais, accounts for a significant global loss of stored maize annually. Twenty-one maize genotypes were evaluated for their reaction to attack by maize weevil during storage and the influence of nutritional contents on their response to the weevil attack. Fifty grams of whole grains of each genotype were infested in three replications with 20 unsexed weevils in a 250 ml test tube and kept under ambient conditions for 36 days. The nutritional attributes of the maize genotypes were determined. Genotype TZB-SR-A had the thickest (7.32 mm) grains, while TZEE-WSTR had the thinnest grains (3.46 mm). Crude protein ranged from 8.43 to 12.78% for NG/SA/07/029 and TZB-SR-B, respectively. Beta-carotene ranged from 38.91 to 51.22% for Igbogbo Local and EVDT-Y2000-STR, respectively. Genotypes TZM-212, TZM-1296, TZB-SR-B, and TZM-1311 showed no appreciable loss in grain weight, while EVDT-Y2000-STR, which had the highest beta-carotene content, showed the highest weight loss of 2 g. These indicate sufficient differences among the maize genotypes for improvement for weevil resistance. Furthermore, the findings of the present study suggest a potential role of beta-carotene in influencing the feeding preference of S. zeamais on maize grains. Genotypes TB87/97/15, TZB-SR-A, TZB-SR-B, TZM-1311, and TZM-144 should be targeted for future improvement of the trait. [ABSTRACT FROM AUTHOR]

Abstract The objective of this work was to compare methods of sampling insect pests in wheat (Triticum aestivum) grains stored in bulk. The data were collected in three agricultural seasons (2012, 2016, and 2020), 90 days after phosphine fumigation, in 10 replicates. Three treatments were evaluated: pitfall traps, manual probe, and pneumatic probe. During the entire evaluation period, the manual probe showed an inferior performance in sampling live insect pests. The pneumatic probe is more efficient for the collection of maize weevils (Sitophilus zeamais), and the pitfall trap, for capturing the rusty grain beetle (Cryptolestes ferrugineus).

Abstract The thrust of the study was to determine the chemical composition of the essential oils extracted from Thymus pallescens de Noé and Cymbogon citratus Stapf. as well as to evaluate their efficacy in controlling Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst) in either single or combined populations. Carvacrol (56.04%) and geraniol (20.86%) were identified as the major constituents of T. pallescens and C. citratus respectively. The tested essential oils showed pronounced insecticidal activity against the pest species in relation with the applied doses. T. pallescens EO had the highest efficacy and S. zeamais was found to be more susceptible to both individual and combined treatments. With reference to the contact and fumigation assessments, T. pallescens EO effectuated corrected mortality rates ranging from 42.5–100% to 25–100% in S. zeamais with corresponding lethal concentration (LC50) values of 17.7 µl/ml and 15µL/L air respectively. Whereas, the T. pallescens EO exhibited corrected mortality rates of 42.5–100% and 20–100% with corresponding LC50 values of 18.1 µl/ml and 15.5 µL/L air against T. castaneum in contact and fumigation assessments, respectively. The corrected mortality rates increased for both insect species when using combination treatments, with significant increases in the LC50 values, ranging from 8.59 to 49.9% for both pest species. Analysis of energy biomarkers in the treated insects indicate significantly increased protein and carbohydrate contents and decreased lipids levels. The study therefore demonstrated the bio-insecticidal toxicity of the EOs from T. pallescens and C. citratus against two important maize post-harvest pests, concurrently revealing significant positive and negative insecticidal activity gradients in relation to single or combined populations.

Weevil infestations cause post-harvest losses and have become important constraints to storage entomology and food security in Nigeria. The present study is aimed at assessing the efficacy of Azadirachta indica-treated storage materials against Sitophilus zeamais and Sitophilus oryzae. Storage materials such as bagco bags, calico bags, and plastic containers were treated with different concentrations (0.5, 1.0, and 1.5mg/ml) of A. indica oil. Untreated storage materials served as the control. These treatments were replicated three times following a completely randomized design in the laboratory and monitored for 100 days. The results showed a significant decrease (p<0.05) in weight loss of infested maize and rice grains with different concentrations of the extract and with the different storage materials compared to the control. The highest weight loss among the treatment concentrations across all the storage materials treated with Azadirachta indica was recorded for rice grains stored in calico bags at 0.5mg/ml with mean value of 10.61±0.37 and7.12±1.41 for maize grains, while the least value of 1.14±0.09 was recorded for rice grains stored in plastic containers at 1.5mg/ml and 0.75±0.21 was recorded for maize grains stored in plastic containers at 1.5mg/ml. there was a significant increase (p<0.05) in mortality of S. zeamais and S. oryzae with increased concentrations of the extracts compared to the control. There was no significant increase in mortality of S. zeamais and S. oryzae compared with the storage materials. The highest mortality for S. oryzae 8.00±0.58 was seen in rice grains stored in plastic containers at 0.5mg/ml concentration and least mortality 4.00±0.58 was seen in those stored in bagco bag at 1.0mg/ml concentration. For S. zeamais, there was no significant increase on the mortality of S. oryzae between 0.5mg/ml and 1.0mg/ml concentrations in A. indica treated bagco bags and between 1.0mg/ml and 1.5mg/ml concentrations in A. indica treated plastic containers. S. oryzae in maize grains stored in plastic containers at 1.0mg/ml had the highest mortality 9.00±1.53 and the least mortality (3.00±0.00) was recorded for S. zeamais in maize grains stored in calico bag at 0.5mg/ml of A. indica treated materials. Results of the storage materials (Bagco bag, Calico bag, and Plastic container) treated with Azadirachta indica leaves extract showed significant decrease (p<0.05) in adult emergence of S. zeamais and S. oryzae in the different concentrations of extracts compared to the control. There was no significant decrease among the A. indica treated storage materials for S. zeamais and S. oryzae emergence. The highest S.oryzae emergence in A. indica treated bags was recorded for S. oryzae stored in Bagco bag at 1.0mg/ml with mean value of 177.67±9.21 and the least value of 107.33±3.76 was recorded for S. oryzae infesting rice grains stored in plastic containers at 1.5mg/ml. There was a significant decrease (p<0.05) in the number of holes bored by S. zeamais and S. oryzae in maize and rice grains treated with Azadirachta indica leaf extract compared to control across various concentrations and storage materials. The highest number of holes bored by S oryzae 390.00±28.22 in infested rice grains was recorded in Calico bag at 0.5mg/ml concentration and the least was recorded in plastic containers at 1.5mg/ml concentration (134.67±11.26). Similar trends were observed with Weevil perforative index and percentage damage. The study concludes that bagco bags treated with A. indica at 1.5mg/ml are more effective for protection of maize and rice grains in storage. [ABSTRACT FROM AUTHOR]

The thrust of the study was to determine the chemical composition of the essential oils extracted from Thymus pallescens de Noé and Cymbogon citratus Stapf. as well as to evaluate their efficacy in controlling Sitophilus zeamais Motschulsky and Tribolium castaneum (Herbst) in either single or combined populations. Carvacrol (56.04%) and geraniol (20.86%) were identified as the major constituents of T. pallescens and C. citratus respectively. The tested essential oils showed pronounced insecticidal activity against the pest species in relation with the applied doses. T. pallescens EO had the highest efficacy and S. zeamais was found to be more susceptible to both individual and combined treatments. With reference to the contact and fumigation assessments, T. pallescens EO effectuated corrected mortality rates ranging from 42.5–100% to 25–100% in S. zeamais with corresponding lethal concentration (LC50) values of 17.7 µl/ml and 15µL/L air respectively. Whereas, the T. pallescens EO exhibited corrected mortality rates of 42.5–100% and 20–100% with corresponding LC50 values of 18.1 µl/ml and 15.5 µL/L air against T. castaneum in contact and fumigation assessments, respectively. The corrected mortality rates increased for both insect species when using combination treatments, with significant increases in the LC50 values, ranging from 8.59 to 49.9% for both pest species. Analysis of energy biomarkers in the treated insects indicate significantly increased protein and carbohydrate contents and decreased lipids levels. The study therefore demonstrated the bio-insecticidal toxicity of the EOs from T. pallescens and C. citratus against two important maize post-harvest pests, concurrently revealing significant positive and negative insecticidal activity gradients in relation to single or combined populations. [ABSTRACT FROM AUTHOR]

The maize weevil, Sitophilus zeamais Motschulsky, is a hidden pest that presents serious risk to grain quality during postharvest storage. Lipid-derived volatile detection is considered a key reference for early prediction of S. zeamais infestation. However, the exact compositions of fatty acids and volatile organic compounds (VOCs) in S. zeamais -infested wheat are yet to be determined. In this study, we aimed to explore the effect of S. zeamais infestation on lipid metabolism in wheat infested with S. zeamais eggs (4 days), larvae (20 days), pupae (35 days), and adults (45 days). Compared to those in the control group, the activities of lipid oxidation enzymes, such as lipase, lipoxygenase, and alcohol dehydrogenase, increased by 82.73%, 105.12%, and 487.86%, respectively, during the storage period of 1 life cycle of S. zeamais. Additionally, the fatty acid composition of S. zeamais -infested wheat was significantly altered (palmitic acid [1.10-fold], oleic acid [1.07-fold], and linoleic acid [0.95-fold]). Furthermore, 91 VOCs were identified in all wheat samples; then, multivariate statistical analyses categorized these samples into 4 groups: uninfested, longer storage, lightly infested, and heavily infested. Moreover, 31, 26, and 45 potential VOCs were identified to distinguish uninfested wheat from those in the other 3 groups. These results demonstrated that S. zeamais infestation induces an elevation in lipid-related enzymatic activities, which potentially leads to a decrease in lipid content alongside the production of specific VOCs (undecan-4-olide, heptaldehyde, and 2-nonenal). These findings provide novel insights for rapidly identifying grains infested by hidden pests and effectively managing these pests during grain storage. [ABSTRACT FROM AUTHOR]

Simple Summary: The two closely related maize and rice weevils exhibit differential host preferences among stored maize, wheat, and paddy grains. The maize weevil adults prefer to select maize, followed by paddy and wheat, while rice weevil adults mainly migrate towards wheat. The 2-ethylhexanol, piperitone, and (+)-Δ-cadiene are the major components in volatiles from both maize and wheat, but the abundance of these chemicals is much lower in maize than in wheat. The volatile limonene was only detected in paddy. The 2-ethylhexanol, piperitone, and (+)-Δ-cadiene were all attractive to both weevils, whereas limonene was attractive only to rice weevils. The different volatile profiles among the grains and the sensitivity of the two pest species towards these volatiles may explain the behavioral differences between maize and rice weevils in selecting host grains. The variance in sensitivity of maize and rice weevils towards host volatile chemicals with abundance differences is likely a determinant driving the two insect species to migrate towards different host grains. The Sitophilus zeamais (maize weevil) and Sitophilus oryzae (rice weevil) are two insect pests that have caused huge economic losses to stored grains worldwide. It is urgent to develop an environmentally friendly strategy for the control of these destructive pests. Here, the olfactory-mediated selection preference of the two weevil species to three stored grains was analyzed, which should help establish a pull–push system in managing them. Bioassays showed that maize weevil adults prefer to select maize, followed by paddy and wheat, while rice weevil adults mainly migrate towards wheat. Volatile analyses revealed that 2-ethylhexanol, piperitone, and (+)-Δ-cadiene are the major components in volatiles from both maize and wheat, but the abundance of these chemicals is much lower in maize than that in wheat. The volatile limonene was only detected in paddy. Y-tube bioassays suggest that 2-ethylhexanol, piperitone, and (+)-Δ-cadiene were all attractive to both weevils, whereas limonene was attractive only to rice weevils. Overall, maize weevil appeared more sensitive to the tested volatiles based on having much lower effective concentrations of these volatiles needed to attract them. The differences in volatile profiles among the grains and the sensitivity of the two species towards these volatiles may explain the behavioral differences between maize and rice weevils in selecting host grains. The differences in sensitivity of maize and rice weevils towards host volatile components with abundance differences are likely determinants driving the two insect species to migrate towards different host grains. [ABSTRACT FROM AUTHOR]

In this study, essential oil was obtained by hydrodistillation from the leaves of Ocimum basilicum and it was analyzed by GC-MS. Eucalyptol (11.19 %), trans-iso eugenol (13.12 %), hexadecanoic acid methyl ester (19.26 %) and 9-octadecenoic acid (z)-methyl ester (25.12 %) had been the leading four main components of the plant leaves of the essential oil. The unmodified and modified kaolin was characterized and analyzed by XRD, FT-IR, TGA and SEM/EDX and thus the principal mineral of the nanoclay was proved to be kaolinite. The hydrodistiled essential oil in the absence of the clay support was evaluated within 24 h of exposure time and the outcome revealed that it was insecticidally active against the maize weevil, S. zeamais adults. Moreover, the exposure time effect, the formulation efficiency, the effect of remnant and stability of the prepared formulations were investigated and the results indicated an enhancement of bioinsecticides for a long period with upgraded persistence against the S. zeamais. Finally, the results recommend that O. basilicum essential oil - modified kaolinite formulations should be used as best options to chemical insecticides in pest control of stored products like stored maize grain insects, S. Zeamais.

Maize is a staple grain cereal that is consumed worldwide for the supply of daily energy requirements. However, its infestation by the weevil, Sitophilus zeamais often results in both qualitative and quantitative losses, which must be managed effectively. The health hazards that are associated with the application of synthetic insecticides for the management of pest infestations of stored products have necessitated the continual sourcing of safer and affordable alternatives. Hence, a laboratory experiment was conducted to assess the effects of morphological, biophysical and some intrinsic factors in fifteen improved maize varieties on their susceptibility or otherwise resistance to infestation by the maize weevil, S. zeamais. Firstly, the morphological and biophysical characteristics of the maize varieties were determined. Copulating pairs of adult S. zeamais were placed in containers that contained undamaged maize grains for seven days to allow for oviposition, after which the adults were removed. Thereafter, the number of eggs laid and adults that emerged were counted. The susceptibility index of each maize variety was calculated from the data obtained from oviposition and adult emergence. Also, the proximate, elemental, and antinutrient compositions of the maize varieties were determined. There was no significant difference (p > 0.05) in the size and hardness of seeds among the varieties with the size range of 0.78–0.95 cm3 while the hardness ranged from 17.43 N in SAMMAZ-15 F to 19.08 N in SAMMAZ-35. The maize varieties differed significantly with respect to proximate, elemental, and antinutrient compositions. The susceptibility of the seeds to infestations by S. zeamais differed significantly among the varieties and across the generations, with the potential for loss of resistant property during later generations. The data from the susceptibility index revealed that TZL COMP4, TZEE W POP and SAMMAZ-29 were the most resistant to infestations by S. zeamais. Although, several factors could have been responsible for the susceptibility or resistance of maize seed varieties to infestations by S. zeamais, however oviposition hardness and moisture were the most important factors in the present study. [ABSTRACT FROM AUTHOR]

The invasive larger grain borer (Prostephanus truncatus) and the maize weevil (Sitophilus zeamais) co-occur in many regions of the world. While competition between these 2 species has been studied extensively, there is little information on spatial dispersion patterns in bulk storage of grain. To evaluate potential overlap in realized niche, we evaluated the short-term spatial dispersion behavior of P. truncatus and S. zeamais in monolayers of maize alone or together for 1 day compared to 7 days. We evaluated competition under three different densities, namely 10–20, 75–150, and 150–300 insects/kg for P. truncatus and S. zeamais. The monolayers were equally divided into 24 zones to track location the abundance of insects and damage to maize. We found that both species generally aggregated together and were correlated to the same location as heterospecifics. After 1 day, most of the insects for both species were near the top of the monolayer, but by 7 days, most individuals were at the bottom of the monolayers. In monolayers, when alone, P. truncatus created a clear path of destruction to the bottom of the monolayer, but when S. zeamais was present, damage was lessened and shifted upwards in the grain column. In an olfactometer assay, P. truncatus preferred maize odors, while S. zeamais exhibited no preference among maize, conspecifics, and heterospecifics. In evaluating relative emissions, each of these treatments emitted unique odors but with significant overlap. These data may improve targeting of chemical control tactics by identifying the position of these insects in the grain mass. [ABSTRACT FROM AUTHOR]

Stored maize is frequently attacked by different pests, such as insects and microorganisms. The aim of the present study was to evaluate the bioactivities of sulcatone (6-methyl-5-hepten-2-one) against the maize weevil Sitophilus zeamais and the phytopathogenic fungi Fusarium verticillioides, Aspergillus flavus, and A. parasiticus. Sulcatone showed a strong repellent effect with a maximum value of −92.1 ± 3.2% at 40 µM in two-choice olfactometer bioassays and an LC95 value of 17.2 µL/L air (95% 16.5–18.1) in a fumigant toxicity experiment. The antifungal effect of sulcatone was evaluated through the fumigant method, reporting MIC values of 3.5, 3.8, and 3.9 mM for F. verticillioides, A. parasiticus, and A. flavus, respectively. Additionally, a silo-bag experiment containing all pests was conducted to evaluate the potential use of sulcatone in a real storage system. Sulcatone caused 71.69 ± 1.57% weevil mortality in silo-bags and proved to be effective as a fungicidal and antimycotoxigenic agent since both ergosterol and fumonisin B1 content were significantly reduced by 60% in silo-bags containing sulcatone. This study demonstrated that sulcatone has the potential to be used for the control of both insects and fungi of stored maize, without affecting the germination of grains.

The behavioural response of adult maize weevil, Sitophilus zeamais, to different types of semolina pasta enriched or not enriched with increasing proportions (5%, 10%, and 15%) of house cricket (Acheta domesticus) powder was investigated in olfactometer arena bioassays by using trap devices. In the five-choice behavioural bioassays, the number of S. zeamais adults attracted to 100% durum wheat semolina pasta was significantly higher than those attracted to the other pasta types enriched with A. domesticus powder. In the two-choice behavioural bioassays, the Response Index for each pasta type was positive and significant. However, although not significant, there was a progressive reduction in the Response Index as the cricket powder content increased. In similar experiments, there were no significant differences between cricket powder alone and the control in the number of attracted S. zeamais, indicating a neutral effect towards insects. These observations suggest that the lower attractiveness of pasta enriched with house cricket powder is mainly due to the masking of host food odours. Solid-phase microextraction coupled to gas chromatography–mass spectroscopy identified a total of 18 compounds in the head-space samples of the different types of pasta, highlighting differences in volatile composition. Some volatile compounds were only present in the pasta produced with cricket powder. In particular, 1-octen-3-ol and phenol were present in the samples containing 5%, 10%, or 15% cricket powder; pentanal, benzaldehyde, and dimethyl disulphide were present in samples containing 10% or 15% cricket powder; and 2,5-dimethyl-pyrazine was present in the sample containing 15% cricket powder. Further investigation with individual compounds and mixtures is needed to define the chemical basis of the differences in the insect olfactory preference observed in this study.

The repellency of solvent extracts of Calpurnia aurea leaves was evaluated on the maize weevils and the red flour beetles. Nine-cm Whatman number 1 filter paper that is partitioned into treatment, neutral and non-treatment portions was used for the experiment. Each solvent extract treatment was applied at 2.5, 5 and 10% rates. Insects were released in the neutral portion, while the untreated part served as a control. A choice bioassay experimental method that is laid down in a completely randomized design within three replications was used. 5 and 10% rates of the polar solvent extracts of Calpurnia aurea leaves induced significantly (p

Insecticides of synthetic origin used indiscriminately to manage insect pest populations are known for genotoxicity, neurotoxicity and teratogenicity in non-target organisms as well as the development of resistance in target insects. These issues have focused insect pest management research towards the use of plant-based chemicals of a volatile nature. In this study, two plant-origin volatile compounds, carvacrol and menthone have been evaluated for their potential insecticidal properties against the maize weevil Sitophilus zeamais (Coleoptera: Curculionidae). These two natural volatile chemicals repelled adults and caused lethality in adults as well as larvae. These two volatile chemicals inhibited acetylcholine esterase enzyme activity in adults when fumigated with sub-lethal concentrations. Both volatile chemicals reduced oviposition potential, progeny production and feeding behavior as well as prolonged the developmental period of the insect. Therefore, it can be concluded that these two natural volatile chemicals can be used in the preparation of volatile chemical-based formulations in the management of maize weevil S. zeamais. DOI: http://dx.doi.org/10.5281/zenodo.10145014

Insecticides of synthetic origin used indiscriminately to manage insect pest populations are known for genotoxicity, neurotoxicity and teratogenicity in non-target organisms as well as the development of resistance in target insects. These issues have focused insect pest management research towards the use of plantbased chemicals of a volatile nature. In this study, two plant-origin volatile compounds, carvacrol and menthone have been evaluated for their potential insecticidal properties against the maize weevil Sitophilus zeamais (Coleoptera: Curculionidae). These two natural volatile chemicals repelled adults and caused lethality in adults as well as larvae. These two volatile chemicals inhibited acetylcholine esterase enzyme activity in adults when fumigated with sub-lethal concentrations. Both volatile chemicals reduced oviposition potential, progeny production and feeding behavior as well as prolonged the developmental period of the insect. Therefore, it can be concluded that these two natural volatile chemicals can be used in the preparation of volatile chemical-based formulations in the management of maize weevil S. zeamais. [ABSTRACT FROM AUTHOR]

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 β-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. [ABSTRACT FROM AUTHOR]

Sitophilus zeamais causes significant losses to maize produce worldwide. The use of biodegradable and environmentally friendly botanicals as an alternative to synthetic pesticides is increasingly becoming important. Therefore, we sought to determine the use of plant extract formulations to manage S. zeamais during storage. Crude Zanthroxylum usambarense and Warburgia ugandensis stembark extracts were used for contact toxicity and repellent bioassays against S. zeamais. The formulations that exhibited the highest repellence and mortality were tested for insecticidal activity during storage for six months. Phytochemical profiles of the extracts were determined using GC-MS, and molecular docking of active compounds against insect target proteins was done. Mortality analyses revealed LD50 values of 114.89 µg/mL and 197.19 µg/mL for Z. usambarense's hexane and methanol organic extracts, respectively. Warburgia ugandensis extracts had LD50 values of 69.25 µg/mL and 163.52 µg/mL, respectively. Extract formulations achieved weevil perforation index values of <50.00 in all treatments. The docking analysis showed the pesticidal potential of several compounds, and mortality could be attributed to Eugenol (19.28%), 1,8-cineole (5.78%) and Linalool (21.42%). The tested botanicals have demonstrated their ability to suppress S. zeamais development in stored maize and could be utilized to protect maize grains during storage. [ABSTRACT FROM AUTHOR]

Maize weevil is a major pest of stored maize grains in many regions of the world including Nigeria. A laboratory investigation was conducted to assess the potency of Ocimum gratissimum L. leaves for Sitophilus zeamais control. The O. gratissimum powder was used for ethanolic extract preparation by soaking 300 g of dry powdered plant material in 1.5 L of absolute ethanol for 24 hours at room temperature with continuous stirring for 10 minutes. The ethanolic extract tested for phytochemical constituents, including tannins, alkaloids, saponins, phenolic compounds, terpenoids, steroids, glycosides, and flavonoids, showed that they were all present except steroids. Exposure of adult S. zeamais to different concentrations of ethanolic extract generated significant cumulative mortality, and increased as the concentration increased; 35.5%, 64.4%, 95.5%, and 100% mortalities of S. zeamais were recorded at 30, 150, 250, and 750 mg/mL extract, respectively. The capacity of the extract to induce 100% mortality at 750 mg/mL concentration revealed its potential as an insecticidal agent. The powder caused low weight loss and seed damage of grains treated with the highest dosage. The ethanolic extract of O. gratissimum displayed a high level of insecticidal activity against maize weevil suggesting a high possibility of using it as toxicant, repellent, and feeding deterrent in integrated pest management strategies of S. zeamais. [ABSTRACT FROM AUTHOR]

According to the United Nations (UN), the global population may skyrocket to 9.8 billion people in 2050 and 11.2 billion in 2100, placing an overwhelming burden on food security as the world will have to meet this growing demand. Maize is the largest staple grain crop produced in developing countries. The maize weevil, Sitophilus zeamais, is one of the most destructive post-harvest pests of stored cereals and grains. The maize weevil contributes up to 40% of total food-grain losses during storage, mainly in developing countries. Current synthetic pesticides are ineffective, and, moreover, they raise serious environmental safety concerns as well as consumer health hazards. Drawing from past oversights and current environmental realities and projections, the global population has been switching to green living by developing sustainable strategies. In our context, these new greener strategies include the utilization of medicinal plants to control maize weevil infestation, which unlocks unlimited innovative possibilities, and, thus, improves the yield, quality, and safety of maize. Medicinal plants are less toxic, easily biodegradable, and capable of protecting grain from pests. This paper systematically outlines the literature on host plants as well as the feeding and associated diseases of the maize weevil. In light of this, we cement medicinal plants as excellent candidates in the pursuit of greener, sustainable, more potent, and cost-effective pesticides. [ABSTRACT FROM AUTHOR]

Sitophilus zeamais (maize weevil) is one of the most destructive pests that seriously affects the quantity and quality of wheat (Triticum aestivum L.). However, little is known about the constitutive defense mechanism of wheat kernels against maize weevils. In this study, we obtained a highly resistant variety RIL-116 and a highly susceptible variety after two years of screening. The morphological observations and germination rates of wheat kernels after feeding ad libitum showed that the degree of infection in RIL-116 was far less than that in RIL-72. The combined analysis of metabolome and transcriptome of RIL-116 and RIL-72 wheat kernels revealed differentially accumulated metabolites were mainly enriched in flavonoids biosynthesis-related pathway, followed by glyoxylate and dicarboxylate metabolism, and benzoxazinoid biosynthesis. Several flavonoids metabolites were significantly up-accumulated in resistant variety RIL-116. In addition, the expression of structural genes and transcription factors (TFs) related to flavonoids biosynthesis were up-regulated to varying degrees in RIL-116 than RIL-72. Taken together, these results indicated that the biosynthesis and accumulation of flavonoids contributes the most to wheat kernels defense against maize weevils. This study not only provides insights into the constitutive defense mechanism of wheat kernels against maize weevils, but may also play an important role in the breeding of resistant varieties. [ABSTRACT FROM AUTHOR]

Food security is contingent upon increasing crop yields but also upon reducing crop losses to post-harvest pests and diseases. Weevils are particularly important agents of post-harvest losses in grain crops. A long-term evaluation of a biocontrol agent, Beauveria bassiana Strain MS-8, at a single dose of 2 × 109 conidia kg−1 of grain was formulated in kaolin as a carrier at levels of 1, 2, 3, and 4 g kg−1 of grain and screened against the maize weevil, Sitophilus zeamais. After six months, the application of B. bassiana Strain MS-8 at all levels of kaolin significantly reduced the maize weevil populations compared to the untreated control (UTC). The best control of maize weevil was observed in the first 4 months after application. Strain MS-8 applied in a kaolin level of 1 g kg−1 performed the best, resulting in the lowest number of live weevils (36 insects/500 g of maize grain), the lowest level of grain damage (14.0%), and the least weight loss (7.0%). In the UTC the number of live insects was 340 insects/500 g of maize grain, the level of grain damage was 68.0%, and weight loss was 51.0%. [ABSTRACT FROM AUTHOR]

The Sitophilus zeamais (maize weevil) and Sitophilus oryzae (rice weevil) are two insect pests that have caused huge economic losses to stored grains worldwide. It is urgent to develop an environmentally friendly strategy for the control of these destructive pests. Here, the olfactory-mediated selection preference of the two weevil species to three stored grains was analyzed, which should help establish a pull–push system in managing them. Bioassays showed that maize weevil adults prefer to select maize, followed by paddy and wheat, while rice weevil adults mainly migrate towards wheat. Volatile analyses revealed that 2-ethylhexanol, piperitone, and (+)-Δ-cadiene are the major components in volatiles from both maize and wheat, but the abundance of these chemicals is much lower in maize than that in wheat. The volatile limonene was only detected in paddy. Y-tube bioassays suggest that 2-ethylhexanol, piperitone, and (+)-Δ-cadiene were all attractive to both weevils, whereas limonene was attractive only to rice weevils. Overall, maize weevil appeared more sensitive to the tested volatiles based on having much lower effective concentrations of these volatiles needed to attract them. The differences in volatile profiles among the grains and the sensitivity of the two species towards these volatiles may explain the behavioral differences between maize and rice weevils in selecting host grains. The differences in sensitivity of maize and rice weevils towards host volatile components with abundance differences are likely determinants driving the two insect species to migrate towards different host grains.

Maize weevil is a major pest of stored maize grains in many regions of the world including Nigeria. A laboratory investigation was conducted to assess the potency of Ocimum gratissimum leaves for Sitophilus zeamais control. O. gratissimum powder was used for ethanolic extract preparation by soaking 300g of dry powdered plant material in 1.5 litres of ethanol for 24 hours at room temperature with continuous stirring for 10 minutes. The ethanolic extract tested for phytochemical constituents, including tannins, alkaloids, saponins, phenolic compounds terpenoids, steroids, glycoside, and flavonoids, were all present except steroids. Exposure of adult S zeamais to different concentrations of ethanolic extract generated significant cumulative mortality, and increased as the concentration increased; 35.5%, 64.4%, 95.5%, and 100% mortalities of S zeamais at 30,150, 250, and 750 mg/ml extract, respectively. The capacity of the extract to induce 100% mortality at 750mg/ml concentration revealed its potential as an insecticidal agent, evoked low weight loss, and seed damage against the weevils on grains treated with the highest dosage of the extract.The ethanolic extract of Ocimum gratissimum displayed high level of insecticidal activity against maize weevil suggesting high possibility of using it as toxicants, repellents, feeding deterrents, and food poisoning agents in integrated pest management strategies of Sitophilus zeamais.

Microbial enzymes produced using biological processes are of great importance due to their contribution to sustainable solutions for agricultural production. In our previous study, the chitinase enzyme from Lactobacillus coryniformis was purified, immobilized to zinc oxide (ZnO) nanoparticles, and its effectiveness as a bioinsecticide against the storage pest Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) was determined by forming a nanoformulation. In this study, the effectiveness of immobilized chitinase (nanoformulation), free chitinase, malathion, ZnO, and L. coryniformis on intestinal enzymes such as alkaline phosphatase (ALP), adenosine triphosphatase (ATPase), and lactate dehydrogenase (LDH) were tested to elucidate some of the mechanism of insect death. The effects of the applications on the activity of ALP, ATPase, and LDH enzymes were found to be statistically significant (p < 0.01). The lowest activity in the ALP enzyme was measured in Malathion and 8 mg/L applications. While the lowest activity in the ATPase enzyme was measured in the 8 mg/L application, the lowest activity in the LDH enzyme was observed in the malathion and 6 mg/L applications. Applications caused a decrease in enzyme activities (LDH, ALP, and ATPase). This situation affected the intestinal activities negatively, disrupted the feeding physiology of the insect, and caused its death. Obtained results showed that the formulation created may have an important role in the protection of corn from this pest. [ABSTRACT FROM AUTHOR]

Sitophilus zeamais (Motsch.) (Coleoptera: Curculionidae) has a global distribution and is one of the most important post-harvest pests of maize (Zea mays L.). Some Mexican maize races could be a novel source of resistance against S. zeamais to improve commercial maize, generating lines, varieties, and hybrids with resistance to the pest. These are original races from the center of origin of maize and have been exposed to selection pressure from S. zeamais and other pests for thousands of years, which probably resulted in some type of resistance. We studied the resistance of Mexican maize races to S. zeamais focusing on antixenosis, antibiosis, and tolerance. Antibiosis reduces the survival and reproduction of the insect or prolongs the time between generations, whereas antixenosis reduces the rate of initial and successive accumulation of the insect population. Obligate-antibiosis and free-choice bioassays were performed, and in those experiments, resistance traits and the consumption by S. zeamais were measured. The most resistant accession showed high adult mortality and fewer adults in the 1st generation, where the number of emerged adults is an ideal trait to evaluate the level of maize resistance to the pest. Net consumption (in grams) is the most economically important trait because it indicates the gross amount lost in a store, while yield losses (percentage of consumption) allow for studying tolerance. The type of endosperm did have an influence on the resistance/tolerance to S. zeamais. The flint varieties showed significantly higher mortality of adults before entering the seed, a lower quantity of emerged adults of the first generation in the obligate-antibiosis bioassay, and lower net consumption and percentage in both bioassays. In general, the varieties of the races Cristalino de Chihuahua, Apachito, and Azul showed high levels of resistance, with the Cristalino-079 (flint) and Azul (floury) accessions also being tolerant, and low levels of consumption by S. zeamais. Both could be used in breeding programs to reduce losses caused by S. zeamais. [ABSTRACT FROM AUTHOR]

BACKGROUND: The ozonation of grains in a closed system at low pressure is a strategy with the potential for treating packaged products. Research is necessary to characterize the reaction kinetics of ozone in this type of injection system so that it is possible to design chambers and determine the ozone concentrations suitable for commercial-scale applications. The objective of this study was therefore to characterize the low-pressure ozone injection system in relation to the physical properties of the grains and determine possible changes in their quality. Samples (5 kg each) of common beans, cowpea beans, corn, popcorn kernels, paddy rice, and polished rice were exposed to ozone in a 70 L hypobaric chamber. Initially, the internal pressure of the chamber was reduced to 500 hPa. Then, ozone was injected at a concentration of 32.10 g m-3 at a volumetric flow rate of 1 L min-1 until reaching a pressure of 1000 hPa. To relate the decomposition of ozone to the grains that were being evaluated, different physical properties were determined, and quality analysis was conducted. RESULTS: Ozone gas half-life outside and inside the package depended on the grain type. Ozone decomposition was quickest in polished rice and slowest in common beans. The half-life of the different grains ranged from 17.8 to 52.9 and 16.4 to 52.9 min, outside and inside the package, respectively. Considering the physical properties, specific surface (Ss), surface area (SA), and sphericity (φ) exhibited a significant correlation with the decomposition rate constant (k) of ozone. However, the variables volume (V), permeability (K), porosity (ε), and specific mass (ρ) showed no correlation with k. CONCLUSION: The physical properties of grain influenced the reaction kinetics of ozone gas during the low-pressure injection process. Ozone gas injection at low pressures did not alter the quality attributes of the grains under study. [ABSTRACT FROM AUTHOR]

Studies were carried out to determine the efficacy of three spices (Allium sativum L., Capsicum frutescens L., and Zingiber officinale Rosc.) against Sitophilus zeamais reared on maize grains. Application rates of 0.5, 1.0 and 1.5 g of each of A. sativum, C. frutescens and Z. officinale and 0.12 g of Permethrin were applied to 20 g of maize grains infested with S. zeamais under controlled conditions of 30 ± 2°C and 65 ± 5% R.H. In all the treatments, 100% mortality of adult S. zeamais reared on maize was obtained. The effect of the spices on adult mortality was significantly different (p

The insecticidal activity of Foeniculum vulgare (Apiaceae) and Myristica fragrans (Ranunculaceae) volatile oils was determined against maize weevil, Sitophilus zeamais (Coleoptera: Curculionidae). Repellent, toxic, oviposition and growth inhibitory, and feeding deterrent actions were evaluated for the two extracted oils from the individual plant parts. In the toxicity assay, both F. vulgare and M. fragrans oils were toxic to adults and larvae, but adults were comparatively less susceptible than larvae. When fumigated with sublethal concentrations, these two volatile oils reduced acetylcholine esterase activity in adults. Both volatile oils significantly reduced oviposition, progeny production, and feeding but increased the developmental period. Therefore, it can be concluded that these two oils can be used to develop volatile oil-based formulations for S. zeamais management in stored grains. [ABSTRACT FROM AUTHOR]

The repellency of solvent extracts of Calpurnia aurea leaves was evaluated on the maize weevils and the red flour beetles. Nine-cm Whatman number 1 filter paper that is partitioned into treatment, neutral and non-treatment portions was used for the experiment. Each solvent extract treatment was applied at 2.5, 5 and 10% rates. Insects were released in the neutral portion, while the untreated part served as a control. A choice bioassay experimental method that is laid down in a completely randomized design within three replications was used. 5 and 10% rates of the polar solvent extracts of Calpurnia aurea leaves induced significantly (p < 0.05) higher percentage weevils and beetles repellency (≥50.00%) at 2 days after treatment than non-polar and partial polar solvent extract treatments and the untreated check. 10% dosage of Calpurnia aurea leaves' polar solvent extract treatments caused 100% weevils and beetles repellency three days after treatment. Consequently, the polar solvent extracts of the tested plant were potent and could be used at 5 and10%rates for the maize weevils and the red flour beetles' management under farmers' maize storage conditions. Nevertheless, their impact on cost-effectiveness, natural enemies and human beings needs additional study. [ABSTRACT FROM AUTHOR]

Boring pests such as Sitophilus zeamais (S. zeamais) are major threats in grain storage. However, how these pests affect the proteins of stored grains remains largely unknown. Here we aimed to investigate the effect of S. zeamais infestation on wheat protein during postharvest storage. In this study, wheat grain infested by S. zeamais was sampled at egg (4 d), larval (20 d), pupal (35 d), and adult stages (45 d), respectively. The protein's physicochemical and structural properties and the edible quality of whole wheat noodle were analyzed. The results showed that S. zeamais infestation significantly decreased the quality of wheat protein by altering its constitution and structure properties. Especially, compared with the control, the content of wet and dry gluten, gluten index, sodium dodecyl sulfate sedimentation volume, sulfhydryl groups, and disulfide bonds in insect-infested wheat decreased by 19.40, 5.42, 18.40, 8.12, 29.13, and 14.30%, respectively, during the storage period of one life cycle of S. zeamais. Additionally, the proportions of wheat protein fractions (albumin [1.16-fold], globulin [0.96-fold], gliadin [1.16-fold], and glutenin [0.95-fold]) and secondary structures (α-helix [0.91-fold], β-fold [0.96-fold], β-turn [1.06-fold], and random coil [1.05-fold]) of protein changed significantly, and the gluten network structure was broken in S. zeamais-infested wheat. Furthermore, the color of whole wheat noodle became darker, cooking loss rate increased, and textural properties (hardness, adhesiveness, springiness, cohesiveness, chewiness, and resilience) decreased as well. The results in the present study provided new insights for analyzing the quality deterioration mechanism and further quality improvement of boring pests-infested wheat grain. [ABSTRACT FROM AUTHOR]

Sitophilus zeamais is a primary pest of maize. Our aim was to perform a qualitative review and meta-analyses with 56 scientific articles published from 1 January 2000 to 1 October 2022 dealing with direct (topical application) and indirect (impregnation of essential oils, EOs, onto filter paper or maize grains) contact toxicity of EOs against S. zeamais. Three independent meta-analyses of single means of LD50 (direct contact) and LC50 (indirect contact) were conducted using a random effect model. Essential oils more frequently evaluated were those belonging to Asteraceae, Apiaceae, Lamiaceae, Myrtaceae, Piperaceae, and Rutaceae. The LC50 global mean values were 33.19 µg/insect (CI95 29.81–36.95) for topical application; 0.40 µL/cm2 (CI95 0.25–0.65) for filter paper indirect contact; and 0.50 µL/g maize (CI95 0.27–0.90) for maize grains indirect contact. The species Carum carvi, Salvia umbratica, Ilicium difengpi, Periploca sepium, Cephalotaxus sinensis, Murraya exotica, Rhododendron anthopogonoides, Ruta graveolens, Eucalyptus viminalis, Ocotea odorifera, Eucalyptus globulus, Eucalyptus dunnii, Anethum graveolens, Ilicium verum, Cryptocarya alba, Azadirachta indica, Chenopodium ambrosioides, Cupressus semperivens, Schinus molle, Piper hispidinervum, Mentha longifolia, and Croton pulegiodorus showed LC50 or LD50 values lower than the global means, indicating good insecticidal properties. Our results showed that EOs have great potential to be used as bioinsecticides against S. zeamais. [ABSTRACT FROM AUTHOR]

BACKGROUND: Frequent application of chemical fumigants has contributed to the development of resistance in stored‐product pests. Essential oils provide a novel and environmentally friendly alternative to conventional chemical pesticides. In this work, the fumigant activity of Taxodium 'zhongshansha' essential oil (TZEO) and main active components against Sitophilus zeamais were evaluated. In addition, the molecular mechanisms mediating the fumigant activity of limonene were assessed. RESULTS: TZEO showed strong fumigant activity against Sitophilus zeamais, with a 50% lethal concentration (LC50) of 22.90 μL L−1 air in 24 h. The main components of TZEO were identified using gas chromatography–mass spectrometry, the main active ingredient (limonene) showed an LC50 of 9.93 μL L−1 air in 24 h which had a serious dose‐time‐effect. The LC50 value of the positive control (aluminum phosphide) was 1.91 μL L−1. In total, 3982 up‐regulated and 3067 down‐regulated genes were sequenced in limonene‐fumigated Sitophilus zeamais, the genes related to metabolic detoxification were significantly enriched. The mortality rate of 7 day‐old Sitophilus zeamais adult mediated with knockdown of SzCYP6MS5 and SzCYP6MS6 raised up to 65.67% and 67.65% after fumigation with limonene in 24 h, respectively. The results showed that SzCYP6MS5 and SzCYP6MS6 are closely involved to the detoxification of limonene. CONCLUSION: In this study, candidate genes affected by limonene treatment in Sitophilus zeamais were identified. These findings provided insights into the systemic metabolic response of Sitophilus zeamais to limonene and established a basis for the development of limonene as a botanical pesticide for the control of stored‐product pests. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

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Maize ( Zea mays ) is a major global food crop and a source of industrial raw materials. Effective postharvest storage is important for national food security programs, international trade, and global agriculture economics. The maize weevil ( Sitophilus zeamais ) is a primary postharvest insect pest that infests maize during storage and leads to significant losses. Using multivariate discriminant analysis of volatile profiles collected from intact and infested maize, we identified two volatile apocarotenoids, 6-methyl-5-hepten-2-one and 6-methyl-5-hepten-2-ol, as indicators of maize weevil infestation in stored maize. Emission of these biomarker compounds rapidly signaled maize weevil infestation and showed a significant correlation with oviposition damage to the stored kernels. The pattern of elevated biomarker emission after weevil exposure was consistent across all seven maize lines examined. These volatile biomarkers can be used for early detection and removal of infested maize and can aid in the control of this pest.

In order to evaluate the insecticidal activity of a formulation of the mixture made of ammoides verticillata essential oil with diatomaceous earth on Sitophilus zeamais, the Sitophilus were exposed to diatomaceous earth at 1 mg/cm on filter paper in petri dishes, and to different concentrations of the essential oil (00 µl, 01 µl, 02 µl, 04 µl and 8 µl). We checked their mortality rate after 24 h and 48 h. After having positive results for diatomaceous earth as well as the essential oil, we tested the effectiveness of our formulation (1 mg of diatomaceous earth/8 µl essential oil/cm2) in petri dishes, and in boxes which contain 20 corn seeds and 20 individuals of Sitophilus (1 mg of diatomaceous earth/8 µl essential oil/cm3). The repellent activity of the essential oil gives us a repellency rate of 52.5% to 75.5% according to the doses. The insecticidal activity of the essential oil on Sitophilus showed significant results as a function of dose and time. We obtained an LC50 of 1.99 mg/cm3. After 24 h of exposure of Sitophilus to diatomaceous earth, we noticed that the average mortality is 40%, and 80% after 48 h. While the average mortality of Sitophilus after 24 h of exposure to the formulation is 80%, and 90% after 48 h. For the population treated with the mixture in the boxes, we noticed an average mortality of 100% and no seeds attacked by insects. [ABSTRACT FROM AUTHOR]

In Nigeria, maize serves as a staple food and a good source of carbohydrates, protein, vitamin B and minerals, hence, the need to protect it against Sitophilus zeamais. This study was conducted to determine the phytochemical properties and insecticidal potentials of Allium sativum bulb and bulb coat powders against Sitophilus zeamais. Allium sativum bulb and bulb coat were collected, dried, and pulverized into fine powder. A 0, 2.0, 3.0, 4.0, and 5.0g of the plant powder were used. Each treatment had 16 newly emerged maize weevils. The weevils were mixed with 250g un-infested maize grains in 500ml bottles and kept at room temperature. Mortality was observed for 7 days at 24 hours intervals post treatment. The experiment was laid out in a Completely Randomized Design and treatments were replicated three times. Data obtained were analyzed using a one-way ANOVA and means were separated using Duncan multiple Range test. The results revealed that both parts showed significant percentage mortality (P ≤ 0.05). The results showed that as the dosage of the bulb powder increased from 2 - 5g, percentage mortality increased from 16-32.8%. For bulb coat powder, percentage mortality increased from 16.5-32.1%. The control showed mortality of 3.0 and 2.8% for the bulb and bulb coat powders, which were significantly different (P < 0.05) from the mortality in treated maize. The most effective dosage for both powders is 5g. Based on the results obtained, Garlic bulb and garlic bulb coat could be used in the management of Sitophilus zeamais infestation.

Background: Sitophilus zeamais is a major pest of stored grains in Ghana and its control can be achieved through an Integrated Pest Management approach, which includes the judicious use of effective and selective insecticides. However, persistent use of synthetic protectants can cause insecticide resistance, militating against control. It is therefore important to monitor the effectiveness of these products to justify their continuous use and to detect the emergence of resistance. This study evaluated the efficacy of two commonly used commercial insecticide products namely Agricombi® (30% fenitrothion + 10% fenvalerate) and Betallic Super® (80 g pirimiphos-methyl + 15 g permethrin) on adult S. zeamais populations from three districts in the Central region of Ghana. Results: The median knockdown times (KT50s) of the products at their recommended label concentrations (RLCs) were 15.13–53.42 min for Agricombi® and 17.17–63.70 min for Betallic Super® while mortalities after 24 h of insecticide exposure were 52.00–80.00% and 21.33–58.67%, respectively. Concentration-response effect of the composite insecticide products showed median lethal concentrations (LC50s) of 8149–12827 mg/L for Agricombi® and 2638–4411 mg/L for Betallic Super®. Comparisons of the RLCs of the products and their respective LC50s and LC95s indicate decreased susceptibility in the weevil populations. Conclusions: The insecticides were ineffective against the S. zeamais populations at their recommended label concentrations. The decreased susceptibilities pose challenges for effective management of the pest and hence the need for alternative effective management methods or products with different active ingredients in these communities.

Inappropriate use of synthetic insecticides in pest management programs contribute in ozone depletion, neurotoxicity, carcinogenicity, teratogenicity, mutagenesis and resistance. These negative outcomes have diverted attention towards the use of plant products in insect’s population management. In this study, dill (Anethum graveolens) and star anise (Ilicium verum) essential oils were isolated by hydrodistillation method using clevenger apparatus, and evaluated for repellent, toxic and oviposition inhibitory potential against maize weevil Sitophilus zeamais (Coleoptera: Curculionidae) by fumigation and contact methods. In toxicity assay by fumigation method, median lethal concentrations (LC50) recorded were 0.316 and 0.243 μlcm-3 air; 0.362 and 0.284 μlcm-3; and 0.497 and 0.418 μlcm-3 of A. graveolens and I. verum oils and pure limonene after 24 and 48h exposure to S. zeamais adults, respectively. In contact toxicity assay, LC50 were 0.219 and 0.159 μlcm-2 area; 0.269 and 0.226 μlcm-2; and 0.567 and 0.386 μlcm-2 of A. graveolens and I. verum oils and pure limonene after 24 and 48 h exposure to S. zeamais adults, respectively. Both A. graveolens and I. verum oils and limonene reduced progeny production and acetylcholinesterase activity in S. zeamais adults when fumigated with sub-lethal concentrations. The outcomes of this study will help in preparation of essential oil based formulations for stored grain insect pest management.

According to the United Nations (UN), the global population may skyrocket to 9.8 billion people in 2050 and 11.2 billion in 2100, placing an overwhelming burden on food security as the world will have to meet this growing demand. Maize is the largest staple grain crop produced in developing countries. The maize weevil, Sitophilus zeamais, is one of the most destructive post-harvest pests of stored cereals and grains. The maize weevil contributes up to 40% of total food-grain losses during storage, mainly in developing countries. Current synthetic pesticides are ineffective, and, moreover, they raise serious environmental safety concerns as well as consumer health hazards. Drawing from past oversights and current environmental realities and projections, the global population has been switching to green living by developing sustainable strategies. In our context, these new greener strategies include the utilization of medicinal plants to control maize weevil infestation, which unlocks unlimited innovative possibilities, and, thus, improves the yield, quality, and safety of maize. Medicinal plants are less toxic, easily biodegradable, and capable of protecting grain from pests. This paper systematically outlines the literature on host plants as well as the feeding and associated diseases of the maize weevil. In light of this, we cement medicinal plants as excellent candidates in the pursuit of greener, sustainable, more potent, and cost-effective pesticides.

Food security is contingent upon increasing crop yields but also upon reducing crop losses to post-harvest pests and diseases. Weevils are particularly important agents of post-harvest losses in grain crops. A long-term evaluation of a biocontrol agent, Beauveria bassiana Strain MS-8, at a single dose of 2 × 109 conidia kg−1 of grain was formulated in kaolin as a carrier at levels of 1, 2, 3, and 4 g kg−1 of grain and screened against the maize weevil, Sitophilus zeamais. After six months, the application of B. bassiana Strain MS-8 at all levels of kaolin significantly reduced the maize weevil populations compared to the untreated control (UTC). The best control of maize weevil was observed in the first 4 months after application. Strain MS-8 applied in a kaolin level of 1 g kg−1 performed the best, resulting in the lowest number of live weevils (36 insects/500 g of maize grain), the lowest level of grain damage (14.0%), and the least weight loss (7.0%). In the UTC the number of live insects was 340 insects/500 g of maize grain, the level of grain damage was 68.0%, and weight loss was 51.0%.

Synthetic pesticides are used indiscriminately in insect pest management, which damages the ozone layer and causes resistance in target organisms as well as neurotoxicity, carcinogenicity, teratogenicity and mutagenesis in non-target organisms. Due to these negative consequences, research is now focused on using plant-based techniques to control insect pests. The maize weevil, Sitophilus zeamais (Coleoptera: Curculionidae), was tested in the laboratory to determine the insecticidal effects of two pure essential oil constituents, namely ɑ-pinene and ß-caryophyllene. These two terpenes were tested against S. zeamais for their toxic, ovipositional, developmental, and feeding inhibitory effects. When S. zeamais adults were fumigated for 24 and 48hrs, the median lethal concentrations (LC50) of ɑ-pinene and ß-caryophyllene were 0.412 and 0.305 µlcm-³ and 0.486 and 0.315 µlcm-³ air respectively. When S. zeamais adults were exposed for 24 and 48hrs in a contact toxicity assay, the LC50 values for a-pinene and ß-caryophyllene were 0.388 and 0.256 µlcm-² and 0.308 and 0.216 µlcm-² area respectively. Adults exposed to sub-lethal concentrations of both terpenes experienced decreased acetylcholine esterase (AChE) enzyme activity. In S. zeamais, a-pinene and ß-caryophyllene decreased oviposition, progeny output and eating. According to this study, a-pinene and ß-caryophyllene can be used to make environmentally acceptable formulations and as a substitute for synthetic insecticides. [ABSTRACT FROM AUTHOR]

Maize weevil (Sitophilus zeamais) is a very destructive pest of stored maize, accounting for about 15 - 25 % of loss, and sometimes 100% in severe infestation. Synthetic pesticide is often the first step of control, which is often costly, scarce, detrimental to the environment and human health. As a result, more environmentally friend options like the use of botanicals are encouraged, in line with the United Nation Sustainable Development Goals. The purpose of this study was to assess how fast to kill and how hazardous are four medicinal plant powders on maize weevil. The study was conducted in June-July, 2020 in the Food Science laboratory of Catholic University of Cameroon, Bamenda. Plant powders of pawpaw Carica papaya seeds, cypress Cupressus macrocarpa leaves, piper Piper nigrum seeds and a control (no-input) were assessed. Mortality was observed every 48 hr for 192 hr (8 days). The data was subjected to survival analysis using SPSS ver. 23. The proportion of Event (mortality) and Censored (no mortality) at varied amongst treatment with Event in piper significantly higher ((X² = 26.2, df = 7, P < 0.001) than Censored, and the reverse was the case for the other treatments. Only the piper treatment had 50% lethal time (LT50) of 144 hr. The Kaplan-Meier survival probability curve of piper had many sharp drops unlike the flat curves for control and pawpaw. Hazard ratios were 0.553, 2.47and 0.819 for pawpaw, piper and cypress, respectively. We proposed the possibility of exploring the angle formed between the line linking both ends of the survival curve and the horizontal line linking the end of the survival curve and the y-axis to assess the degree of hazardousness. The findings of this study revealed that piper powder killed the maize weevil very fast and was also the most hazardous treatment. We strongly recommend the integration of piper seed powder in the management of stored maize in order to prolong the shelve life, and maintain the quality and quantity of stored maize. [ABSTRACT FROM AUTHOR]

Our aim was to perform a qualitative review and a meta-analysis with 57 scientific articles (108 assays) published from 1 January 2000 to 31 June 2021 dealing with fumigant toxicity of essential oils (EOs) against Sitophilus zeamais. The studies were obtained from four electronic databases: Web of Science, SCOPUS, PubMed, and Google Scholar. The survey comprised 107 plant species belonging to 26 different families. Lethal concentration values (LC50) of EOs were included in a random-effect model, and two subgroups were defined: "until 24 h" and "more than 24 h". The EOs more frequently evaluated were those belonging to Lamiaceae (20.18%), Asteraceae (17.43%), Apiaceae (9.17%), and Rutaceae (6.42%). The global mean value was 21.37 (CI95 16.84–27.12), while the summary mean values of the subgroups were 41.45 (CI95 31.10–55.26) for "until 24 h" and 8.45 (CI95 5.72–12.48) for "more than 24 h". Most species belonging to Apiaceae, Lamiaceae, Asteraceae, and Schisandraceae reported the highest insecticidal effects with mean values that ranged from 1.31 to 27.39 for "until 24 h" and from 0.57 to 5.31 for "more than 24 h". Additionally, the toxicity of the most effective EOs was discussed by addressing their chemical composition and their major pure compounds chemical features. [ABSTRACT FROM AUTHOR]

Maize is one of the major staple foods in Sub-Saharan Africa and there is serious loss in maize storage due to insect damage. This study compared the bioactivity of Bamboo Leaf Ash (BLA) and Bularafa Diatomaceous Earth (BDE) against Maize Weevil (Sitophilus zeamais Motschulsky) under laboratory conditions. Insecto®, a commercialized DE was also tested as standard check. Adults of the insects were exposed on maize admixed with the BLA at dose rate of 5,000, 10,000 and 20,000ppm; BDE and insecto® at a dose rate of 1,000ppm, at 28.20C and 82.2% relative humidity. Mortality increased with increasing exposure duration and all treatments showed mortality of more than 80% after 14days post-treatment compared to negative control with 0%. The treatments suppressed F1 progeny. Treated grains have weight loss less than 4%, kennel damage less than 14% and grain germination showed no significant change. The decreasing efficacy of the dusts against this insect is Insecto®> BLA > BDE. BLA and BDE have potential for the management of insect pests of stored grain in Nigeria. [ABSTRACT FROM AUTHOR]