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Experiments were carried out to assess the protectant ability of cow dung ash (CDA) to maize grains against Sitophilus zeamais Motsch. under laboratory conditions of 28-32oC and 60-75% relative humidity (R.H.). The CDA at different doses of 0.625, 1.25, 2.50, 5.00, 10.00% (w/w) were used and permethrin powder at 0.625% used as positive control, negative control were also set up in different Petri dishes to which no permethrin or ashes were added. Five pairs of weevils were introduced into each of the Petri dishes and covered with muslin cloth. The experiment was arranged in a completely randomized design (CRD) and replicated three times. Effect of the treatments on adult mortality was determined. Adult emergence and weight losses in seeds treated with CDA at different doses were also assessed. Findings of the study revealed that the adult mortality of S. zeamais among different CDA doses differed significantly (p < 0.05) and ranged from 13.33 to 100.00% at 96 hours after treatment (HAT). Results of the study also showed that LD50 of CDA against S. zeamais at 24 hours after treatment (HAT) was 4.57 % (w/w). There were no F1 adult emergences of S. zeamais in all the treatments. Weight losses were found to differ significantly (P

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.

Simple Summary: Sitophilus zeamais is a worldwide pest that destroys many grain products, causing a loss of cereal quality and quantity resulting from its metabolites and behavior. Glutathione S-transferases (GSTs), as a group of odorant-degrading enzymes (ODEs), play an important role in degrading xenobiotic odorant molecules in insect olfactory sensing systems. However, there have been few reports about the function of the GST genes of S. zeamais in the odorant-degrading process. In this study, we characterized 13 full-length genes encoding GST sequences from S. zeamais and analyzed the expression pattern in different tissues of SzeaGSTd1. In addition, we investigated the ability of recombinant SzeaGSTd1 to degrade the volatile molecules of the host, and the data indicated that the content of capryl alcohol significantly decreased in the system. In summary, we believe SzeaGSTd1 plays a key role in the olfactory sensing system of S. zeamais. Odorant-degrading enzymes (ODEs) play an important role in rapidly degrading and inactivating odorant molecules that have completed information transmission, as well as in maintaining the stability and sensitivity of insect olfactory sensing systems. Glutathione S-transferases (GSTs), as a group of ODEs, supposedly bear the ability to catalyze the conjugation of glutathione (GSH) and xenobiotic odorant molecules in the degrading process. However, there are few reports regarding the role of the GST genes of Sitophilus zeamais in the degrading process. Thus, we characterized 13 full-length genes encoding GST sequences from S. zeamais, of which only SzeaGSTd1 contained a high abundance in the antennae. Ligand-binding assays implied that SzeaGSTd1 was able to catalyze the conjugation of GSH with 2, 4-dinitrochlorobenzene (CDNB). We investigated whether recombinant SzeaGSTd1 bears the ability to degrade the volatile molecules of the host; among the host volatiles, and found capryl alcohol to be a suitable substrate for SzeaGSTd1. These results strongly suggest that SzeaGSTd1 probably plays a role in auxiliary host location by degrading the host volatiles of capryl alcohol and exhibits a potential biological function in the olfactory sensing system of S. zeamais. Knowledge of the potential functions of SzeaGSTd1 will provide new ideas for biological control strategies for S. zeamais. [ABSTRACT FROM AUTHOR]

Using bioactivity-guided isolation of bioactive compounds; deacetylviguiestenin, 4-O-caffeoyl-2-methyloxirane-2-carboxylic acid and sandaracopimaradiene-1α,9α-diol were obtained from Tithonia diversifolia (Hemsl.) A. Gray leaves and identified using spectroscopic methods. Their feeding deterrence activity against Sitophilus zeamais (Motsch.) including those of methanol crude extract, fractions, and the essential oil was determined. Results showed that the essential oil of T. diversifolia could not show significant anti-feedant activity at a dose of ˂0.29 μL/mg of flour disks. The solvent crude extract, some fractions and the isolated compounds, however, demonstrated feeding deterrence against S. zeamais. The feeding deterrence index of sandaracopimaradiene-1α,9α-diol was 81.19 ± 5.94% at 0.1% w/w (1 mg/g food) compared to 97.45 ± 0.43% for neemazal extract (10% azadirachtin) (positive control) at 10%w/w (100 mg/g food). The EC50 of deacetylviguiestin, 4-O-caffeoyl-2-methyloxirane-2-carboxylic acid and azadirachtin (commercial antifeedant) against S. zeamais were 22140.23 ± 9103.29, 3654.28 ± 2715.09 and 14.59 ± 5.59 ppm respectively. Although these compounds showed less activity against S. zeamais compared to azadirachtin, their anti-feedant activity was significant and are valuable alternatives. [ABSTRACT FROM AUTHOR]

The relationship between T. castaneum and S. zeamais was studied through reciprocal selectivity experiment, single rearing and mixture rearing at 30 ℃, 75% RH. The results showed that the mutual selection behavior between the two species was not obvious in the same ecological environment. The number of T. castaneum adults in the population decreased first, then increased slowly with increasing treatment time,the maximum number of adults in the population reaching 11.5 times of the initial number after 56 d rearing alone in wheat. while the number of S. zeamais adults in the population increased obviously with increasing treatment time, and reaching 53.9 times of the initial number after 56 d rearing alone in wheat. Compared with rearing alone, the number of adults in the population of both T. castaneum and S. zeamais significantly increased under mixture rearing in wheat, the maximum adults in the population reaching 20.3 and 93.4 times of the initial number respectively after 56 d. Therefore, both T. castaneum and S. zeamais are important pest insects during wheat storage, and the S. zeamais infestation can promote the growth of T. castaneum population.

Plantas com efeito inseticida apresentam-se entre as alternativas como ferramenta de controle dos insetos-praga de grãos armazenados. No presente estudo, objetivou-se caracterizar a eficiência dos pós de origem vegetal sobre Sitophilus zeamais em grãos armazenados. Foram avaliados 14 pós vegetais (Arnica montana Baccharis trimera Less., Coriandrum sativum L., Coffea arabica, Cymbopogon martini, Helianthus annuus, Lippia gracillis, Mentha pulegium L., Moringa oleífera, Nicotiana tabacum, Piper aduncum, Piper hispidinervum, Sesamum indicum e Vitis labrusca) obtido de material vegetal triturado, e comparado com um tratamento controle. O experimento foi realizado em delineamento inteiramente casualizado, com seis repetições cada tratamento. Nos testes, 0,5 g dos pós inertes foram misturados aos grãos (50 g) de milho híbrido AS 1551 dentro de frascos plásticos, sendo infestados com 10 S. zeamais adultos emergidos. Após 20 dias da infestação avaliou-se a oviposição e iniciou-se a contagem de adultos emergidos. Ao fim do período de infestação, foi avaliado o peso seco dos insetos, o peso de grãos consumidos e o período de desenvolvimento (ovo-adulto). A maioria dos pós vegetais apresentou atuação efetiva sobre os insetos emergidos. Constatou-se nos pós testados redução na oviposição, exceto Vitis labrusca e Sesamum indicum cujo número de ovos foi superior ao controle, também apresentaram menor efeito sobre o desenvolvimento das larvas do caruncho. O baixo peso de adultos provenientes de grãos de milho tratados com pó de Nicotiana tabacum sugere a ocorrência de deterrência na alimentação das larvas de S. zeamais.

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.

It has been planned to minimize the yield and quality impairment of the seed corn, which is strategically important in the world, by pests under storage conditions with a biological product produced with a biotechnological approach. In this context, the present study aimed to control the maize weevil Sitophilus zeamais, known as a warehouse pest, using a nanoformulation. In the study, the chitinase enzyme from Lactobacillus coryniformis was purified first using ammonium sulfate precipitation and then by using the HiTrap Capto DEAE column, and the molecular mass of the purified enzyme was determined to be ~ 33 kDa, and the optimum pH and the values as pH 6.0 and 65–75 °C, respectively. Five different doses of nanoformulation (2, 4, 6, 8 and 10 mg/L) were applied to corn grains by the spraying method with three repetitions so that the insect can ingest the formulation through feeding. The effects of the applications on the death rate and mean time of death of Sitophilus zeamais were determined. According to these findings, it was concluded that the best practice was nanoformulation with 6 mg/L, considering both the mortality rate (100%) and the average death time (2.4 days). Chitinase from L. coryniformis is a promising candidate for corn lice control and management. [ABSTRACT FROM AUTHOR]

The performance of six grain storage technologies for the control of insect pests in maize was evaluated over a 36-week (9-month) storage period. The six technologies used were: two ZeroFly® hermetic bag brands (laminated and non-laminated); Purdue Improved Crop Storage (PICS) bag; non-hermetic ZeroFly® bag; woven polypropylene (PP) bag containing maize grain treated with Actellic Gold® Dust (pirimiphos-methyl 1.6% + thiamethoxam 0.3%) and woven PP bag containing untreated grain. Each bag was filled with 50 kg maize grain and four replicates of each were set up. With the exception of the non-hermetic ZeroFly® bag, 50 live adults of the larger grain borer Prostephanus truncatus and of the maize weevil Sitophilus zeamais, were introduced into all the bags. Insects were not introduced into the non-hermetic ZeroFly® bag to assess its effectiveness in repelling infestation from outside. Parameters recorded were gas composition (oxygen and carbon dioxide) levels inside the bags; weight of flour generated by insect feeding activities; grain moisture level; live adult insect counts; grain damage and weight loss; grain germination rate and aflatoxin level. At termination, the plastic liners of the hermetic bags were examined for perforations. Results show that oxygen depletion and carbon dioxide evolution were faster in ZeroFly® hermetic compared to PICS bags. Throughout the 36-week storage trial, grain damage remained below 4% and weight loss below 3% in all the treatments except in the untreated PP bags in which it increased to 81.1 and 25.5%, respectively. The hermetic PICS, ZeroFly® and Actellic Gold dust-treated PP bags maintained grain germination at 60%, which was lower than the initial 90%, while in untreated control, it reduced to 4.7%. The mean aflatoxin levels fluctuated between 0.39 and 3.56 parts per billion (ppb) during 24 weeks of storage in all the technologies tested, which is below the acceptable maximum level of 10 ppb in maize. Based on the evaluation results, it can be concluded that hermetic PICS and ZeroFly® bags and woven PP bag with Actellic Gold dust-treated grain effectively protected stored maize grain from insect attack and weight losses. Appropriate strategies and mechanisms for the effective and efficient adoption of hermetic storage bag technology at scale would contribute towards global food security. [ABSTRACT FROM AUTHOR]

The loss of stored grains due to the activity of insects is one of the main problems in maize production. The maize weevil, Sitophilus zeamais , is one of the major pests found in storage systems. We developed and evaluated the insecticidal efficiency against S. zeamais of three different bioactive fabric bags (cotton, polypropylene, and fibranne) loaded with latex paint-based formulation and pulegone, alpha-methly-trans-cinnamaldehyde, and a mixture of both compounds (at 24 and 48 h of exposure). Additionally, we determined the phytotoxicity of these formulations on maize grains and the release from the bags of the formulation with pulegone, that is, the amount of pulegone that is emitted from the bags. We found that at 24 h of exposure pulegone (1%) fibranne and cotton bags (26.71% and 15.81% respectively) were more effective against weevils than pulegone (1%) polypropylene (5.34%). The bags painted with the pulegone formulation at higher concentrations (at 2% and 3%) were effective, regardless of the fabric type used (cotton, polypropylene, or fibranne fabrics). The formulations with pulegone were not phytotoxic. Moreover, cotton bags showed the highest release of pulegone. These results are of interest because cotton bags painted with formulations based on pulegone-paint could serve as a potential tool for controlling the maize weevil in a grain storage system, such as in small storage in sacks or silo-bags. • Pulegone (1%) formulation impregnated fibranne and cotton bags were more effective. • Formulations with pulegone were not phytotoxic. • Cotton bags showed highest release of pulegone. [ABSTRACT FROM AUTHOR]

Purpose: The control of stored-grain insect pests is predominantly done through the use of synthetic insecticides. However, the extensive and constant (mis)use of these chemicals has brought complications that include faster evolution of resistant forms of pests, hence a global call for alternative control measures to reduce chemical applications. The aim of this research was to evaluate the repellent and toxic effects of E. citriodora leaf powder on adult P. truncatus and Sitophilus zeamais. Research Method: A completely randomized design was adopted in all the experiments. A choice test arena was set up to evaluate repellent effects of E. citriodora leaf powder on P. truncatus and S. zeamais. The toxic effect of E. citriodora was also evaluated, with untreated grain and conventional insecticides used as negative and positive controls, respectively. Findings: Results showed that E. citriodora leaf powder had repellent properties of up to 68.9% against both P. truncatus and S. zeamais populations. Nonetheless, low adult P. truncatus mortalities were recorded when the protective effects of the E. citriodora leaf powder (at the rate of 10% w/w) were tested against the beetle. Additionally, the efficacy of the synthetic insecticides was relatively higher when applied singly than when in combination with E. citriodora leaf powder. Research limitations: Time was the major limiting factor to consider other parts of E. citriodora plant (e.g. roots) on their usefulness in stored-product insect pest management. Originality/Value: Small plantations of E. citriodora may be established to offer a temporary grain protection against primary insect pests.

Alternative methods of control against different parasites affecting livestock and agriculture are currently being sought. The essential oil of Peumus boldus Molina has anthelmintic and insecticidal activity against the nematode Haemonchus contortus and stored cereal insect pests. The present study aimed to assess the in vitro activity of P. boldus essential oil against H. contortus (L3) unsheathed and Sitophilus zeamais, Tribolium castaneum, and Plodia interpunctella. The essential oil was obtained from leaves of P. boldus and its principal compounds identified by phytochemical analysis. Essential oil was tested at concentrations of 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75 and 2.0 mg mL-1 on unsheathed L3 H. contortus larvae and in concentrations of 0, 35, 70, 100, 125, 150, 175 and 200 μL L-1 air on adult insects. The main constituents detected in the essential oil were 1,8-cineole, terpineol, terpinene-4-ol, γ-terpinene, p-cimene, methyl eugenol, safrole, (E)-germacrene D, β-tujene, and ascaridol. The nematode H. contortus and insects were exposed to the essential oil for 72 h. In a bioassay with H. contortus larvae, treatment with 2.0 mg mL-1 showed the highest toxicity with 99.2% mortality. Regarding insecticidal activity, S. zeamais was the most susceptible species with a mortality of 90% at 200 μL L-1 air. The present study suggests that the essential oil of P. boldus has potential anthelmintic and insecticidal activity. [ABSTRACT FROM AUTHOR]

The maize weevil (Sitophilus zeamais) is one of the main insect responsible of significant losses in stored products, and to keep nutritional value of them to find effective and safe solutions are very important. The Hypericum genus might be a potential source of new bio-insecticides due to the chemical composition of essential oils. In this study, components of essential oils of three Hypericum species were investigated for first time by Gas Chromatography-Mass Spectrometry (GC-MS) and, fumigant and contact toxicities as well as the repellent activity of essential oils of them were evaluated against S. zeamais adults. While the main components in H. mexicanum oil were determined as n-nonane (53.08%) and α-pinene (25.28%), the major constituents were determined as α-pinene (45.52%) and β-caryophyllene (13.59%) in the essential oil of H. myricariifolium. Chemical composition of essential oil of H. juniperinum were found to be n-nonane (12.0%), α-pinene (8.25%), geranyl acetate (7.93%), and β-caryophyllene (13.60%). The results revealed that H. mexicanum and H. myricariifolium oils have fumigant toxicity (LC50 < 500 µL/L air) and a potential action as repellents (RP > 70% at 6.2--22.7 μL/L air) for the control of the pest. [ABSTRACT FROM AUTHOR]

BACKGROUND: Allyl isothiocyanate (AITC) is a volatile organic compound with a potent insecticidal activity to the stored‐grain pest Sitophilus zeamais Motschulsky, which severely damages grain storage and container transport worldwide. Our previous study showed that mitochondrial complex IV was the primary target of AITC in adult Sitophilus zeamais. To further verify the targets of AITC, we employed RNA interference (RNAi) by using double‐stranded RNA (dsRNA) to knockdown three core subunits of cytochrome c oxidase (COX)‐I, ‐II and ‐III in 18‐day‐old larvae prior to their exposure to AITC to detect susceptibility changes. RESULTS: The susceptibility of dsRNACOX‐I and ‐II injection treatments to AITC significantly increased at 72 h while the mortality reached up to 85.56% and 67.78%, respectively, and dsRNACOX‐I and dsRNACOX‐II injection showed the same subcellular structural characteristics showing vacuolization and vague mitochondrial cristae and decrease of COX activity during AITC fumigation treatment, suggesting the potential of COX‐I and COX‐II as the targets of AITC. High mortality reached up to 75.55%, 71.88% and 82.22%, respectively, and the phenotype of larvae turning from milky white to dark brown in the thorax and death eventually was confirmed after dsRNACOX‐I, ‐II and ‐III injection. CONCLUSION: COX‐I and ‐II were elucidated as the potential targets of AITC and dsRNACOX‐I, ‐II and ‐III have the potential to be developed into nucleic acid pesticides for their robust lethal effects and are worth pursuing for improving AITC fumigation activity in Sitophilus zeamais control. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Sitophilus zeamais and Prostephanus truncatus can cause weight loss of about 20 to 90% of untreated stored maize seeds. This study assesses four plants (Lantana camara, Moringa oleifera, Citrus sinensis and Hyptis suaveolens) extracts as seed maize protectants against the two insects in Ghana. The study was laid out in a CRD with three replications. Dried powders (5 and 10% w/w) and aqueous extracts (0.05 and 0.1 g/mL) of the botanicals were evaluated for their insecticidal activity with untreated control and Actellic included as checks. Oviposition and survivorship of insects decreased in grains treated with plant extracts. The phytochemical analysis revealed that compounds such as alkaloids, saponins, tannins and phenolic, steroids, flavonoids, anthraquinones, phlobatannins, cardiac glycosides and terpenoids were recorded in all four plant extracts. These compounds may have caused lower progeny emergence, inhibitory effect, repellent action and antifeedant effect to S. zeamais and P. truncatus in grains treated with the botanicals. Maize seeds treated with botanicals after 10 weeks in cribs recorded a reduction in the percentage of seeds damaged and weight loss caused by the two insects compared to the untreated seeds. The study proposes that the botanicals tested, especially H. suaveolens have the potential to enhance quality seed production thereby boosting growth in the seed industry. The botanicals are recommended for use by seed producers and farmers to control P. truncatus and S. zeamais in stored maize seeds.

Considering the edibility of insects’ species associated with storage ecosystem, chemical control methods can be easily replaced by environmental and economically sustainable alternatives. Use of biogenerated atmospheres is an inexpensive method that tolerates insect presence. In Portugal, during one year, hermetic bags were used to store paddy under 65-75-85% relative humidity (RH) and 14-17-24ºC temperatures. Brown rice infested with Sitophilus zeamais adults was placed inside the hermetic bags. Biogenerated atmosphere was naturally produced inside the hermetic bag, at 85% RH, with low O2 and high CO2 contents, showing that S. zeamais can survive but has no progeny at 14º-17ºC, or attained 100% mortality before producing progeny at 24ºC. The most abundant fungi isolated were Alternaria alternata and Epicoccum nigrum. The results showed the importance of the RH on changes in atmospheric gas content of paddy, due to biological agents’ activity. Analysing the edibility of insects species associated with stored grain, preliminary studies were carried out to evaluate the nutritional value of immatures stages of Tribolium castaneum. Larvae of T. castaneum had a content of 21.4% protein, 9.1% lipids, 8.8% fiber, and a relevant content of eight essential amino acids and also manganese and copper. The edibility of insects must be consider given their high nutritional value, low emissions of Green House Gases (GHGs), low requirements for land, and by reducing and mitigating the need for chemical control.

The objective of this study was to investigate the characteristics of adult Sitophilus zeamais and Tribolium castaneum, and the 21.1% dry base (d.b.) MC of rough rice by ATR-FTIR spectra, and determine the theoretical optimum infrared (IR) heating temperature of the tested samples. In laboratory experiments, a ceramic IR drying device was used to heat infested rough rice to research the mortality of Sitophilus zeamais and Tribolium castaneum, the drying characteristics of rough rice, and milling quality. The theoretical calculation optimum temperature of IR heating was 300 ˚C according to the results of FTIR spectra. In addition, the effects of the different IR radiation intensities and heated rough rice temperatures on mortality of insects, moisture removal, and milling quality were determined in this text. A high insect mortality, heating rate and corresponding high moisture removal were achieved by using IR heating. After heating, tempering process significantly increased insect mortality when the heated tempered rice temperature was less than 55 ˚C, and improve moisture removal and milling quality of rough rice during nature air cooling. When the rice heated under the IR radiation intensity of 2780 W/m2 for 110 s, the rice temperature reached 60.2˚ ± 0.5˚C, 100% mortality of S. zeamais and T. castaneum, and 3.97 percentage points of moisture removal during the heating period after tempering and natural cooling. In addition, the high rice milling quality can be achieved after tempering treatment. Therefore, it can be concluded that the optimum conditions of simultaneous disinfestation and drying were 60 ˚C rice temperature under the IR radiation intensity of 2780 W/m2, followed by tempering and natural cooling.

ECO₂FUME® fumigation of maize bag stacks under gas proof sheets was conducted to establish the optimal dosages (application rate) and exposure times (fumigation period) against mixed-age cultures of Sitophilus zeamais and Tribolium castaneum. The Complete Randomized Design (CRD) experimental design was employed, with 3 replications and 4 treatments. The experiments were divided into three groups: 1) treatment with a 25 g/m3 ECO₂FUME® application rate (350 ppm phosphine) for 3, 4, and 5 days and a control treatment; 2) treatment with an ECO₂FUME® application rate of 50 g/m3 (700 ppm phosphine) for 2, 3, and 4 days and a control treatment; and 3) treatment with a 70 g/m3 ECO₂FUME® application rate (1,000 ppm phosphine) for 1, 2, and 3 days and a control treatment. The three target phosphine concentrations of 350 ppm, 700 ppm and 1,000 ppm were maintained during the whole fumigation period. Results of the studies showed that no insect was alive at all dosages and exposure times. The studies also indicated that fumigation with ECO₂FUME® could reduce the fumigation period by increasing the phosphine concentration. The effective fumigation protocols on maize against mixed-age cultures of S. zeamais and T. castaneum were ECO₂FUME® application rates of 25 g/m3 for 3 days, 50 g/m3 for 2 days and 70 g/m3 for 1 day. The target phosphine concentration must be maintained throughout the fumigation period to achieve 100% mortality of all stages of insects.

Filter cake and Triplex are powdered by-products of aluminum sulfate and soap factories, respectively. There is limited data about the use of these powders as grain protectants. This study was aimed at determining contact toxicity of both powders against Sitophilus zeamais, a common pest of stored grains. Lethal concentration of both powders to S. zeamais was determined by exposing 10 adults for 12 h in 9 cm diameter concrete arenas inside Petri dishes dusted with filter cake (0 - 8 g/m²) or Triplex (0 - 9 g/m²). Lethal time was determined by exposing adults to 3 g/m² filter cake and 9 g/m² Triplex for 1 to 24 h. Each treatment was replicated 3 times. At the intended exposure time, adults were transferred to 150-ml round plastic containers with 30 g of wheat and held at 28 degree Celsius and 65% r.h. for 14 d to determine mortality. Adult progeny production was determined after 42 d. A 50% mortality of adults was obtained at 0.61 g/m² of filter cake and 1.61 g/m2 of Triplex concentrations with a 12 h exposure. The corresponding effective concentrations for 50% reduction of progeny production were 0.18 g/m² of filter cake and 2.66 g/m2 of Triplex. Lethal times for 50% mortality of adults after exposure to 3 g/m² of filter cake and 9 g/m2 of Triplex were 4.42 and 4.29 h, respectively. The corresponding effective times for 50% reduction of progeny production after exposure to 3 g/m² of filter cake and 9 g/m² of Triplex were 1.74 and 2.34 h respectively. The overall result indicated that filter cake was highly toxic to S. zeamais than Triplex. Therefore, filter cake is a potential powder to be included in the integrated pest management practice in small holder farmers’ storage structures after tested under real field conditions.

Plants are a source of substances for protection of stored products. The Cuban flora has not yet been fully studied as a source of pesticides for postharvest protection, partly due to its great diversity. The toxicity of four Cuban plant derivatives against Lasioderma serricorne (F.) and Sitophilus zeamais Motschulsky was investigated. The anti-insect activity of the powders and the essential oil from plants belonging to Asteraceae, Fabaceae and Piperaceae was tested. Mortality and emergence of adult insects and the repellent effect of products were evaluated. Two products derived from Piper aduncum subsp. ossanum, caused high mortality (81,6 and 100%), reduced emergence (27,9 and 0,4%) and exhibited strong repellent activity on L. serricorne. Against S. zeamais, treatments with the highest mortality values were stems of Lonchocarpus punctatus (72,4%), seeds and stems of Canavalia ensiformis (64,9 and 69,9%), and leaves of Tithonia diversifolia (67,2%). The progeny production of S. zeamais was inhibited by powders of L. punctatus stems (31,8%), C. ensiformis seeds (40,5%), leaves (43,7%) and stems (30,6%), and T. diversifolia leaves (38,7%). The stems of C. ensiformis, leaves of T. diversifolia and L. punctatus had the highest repellent effect. These products have potential for small-scale treatments of grains for protection against both insects, and P. aduncum subsp. ossanum-based products to control L. serricorne infestation in tobacco. Identification of local candidates to develop effective and safe pesticides offers new alternatives to the Cuban agriculture in the control of storage pests.

Combinations of botanicals could enhance biological activity against insects. This in turn, will reduce amount of botanical used in storage protection. In this issue, the bioassay was carried out on Sitophilus zeamais to assess the effectiveness of binary combinations of Hymenocardia acida wood ash and Plectranthus glandulosus leaf powder regarding adult toxicity, progeny inhibition, and reduction of damage and germination ability. Plectranthus glandulosus leaf powder, H. acida wood ash and their binary combinations significantly induced mortality of S. zeamais adult (P? 0.0001). The higher mortality rate was achieved by the highest content (40 g/kg) of H. acida wood ash (94.66%) and 25PG75HA (94.59%) within 14 days of exposure. The combinations of P. glandulosus leaf powder with H. acida at different proportions produced different interactions. The combination made up by 75% of P. glandulosus leaf powder with 25% of H. acida wood ash produced synergistic effect whereas that made up by 50% of each of two powders had antagonistic effect in weevil mortality. The three combinations of H. acida and P. glandulosus significantly reduced the progeny production. In term of inhibition of F1, the combination 25PG75HA revealed more effective than the two other. The grain damage and population increase were significantly reduced. In general, the non-infested maize grain had a good germination rate than the infested ones. The treatments did not have negative effect on seed germination. From These results, the two powders and their binary combinations could be used to reduce grain infestation by insect while taking in account the proportions of insecticidal powders implied in the combination.

The aim of this study was to determine the insecticidal efficacy of mixture of NeemAzal a commercial neem product and Plectranthus glandulosus leaf powder against Callosubruchus maculatus and Sitophilus zeamais. Mixed at various proportions (100 + 0, 75 + 25, 50 + 50, 25 + 75 and 0 +100%, these powders were tested on adult mortality, inhibition of offspring production and their persistence on C. maculatus and S. zeamais. All the mixed NeemAzal and P. glandulosus caused significant mortality to adult C. maculatus and S. zeamais. No significant difference was observed among the mixed powders that were subjected to the three mixture proportions regarding the mortality they caused to the weevils. The mixed 75% NeemAzal + 25% P .glandulosus of powder led to a higher mortality (100%) of both insect species, three (5 g/kg) days post exposure. The three days LC50 values decreased with ascending proportion of NeemAzal in the mixture from 3.21 g/kg (25% NeemAzal + 75% P. glandulosus) to 0.24 g/kg (75% NeemAzal + 25% P. glandulosus) in S. zeamais. In C. maculatus, the opposing effect was observed. The number of F1 progeny produced reduced significantly (P ≤ 0.01) in both insect species with the mixture proportion of botanicals. The mixtures reduced better the adult progeny production than the botanicals applied alone. The 75% P. glandulosus + 25% NeemAzal persisted well on grains up to 180 days for all dose levels. Powder from NeemAzal and P. glandulosus leaves stand as good candidates to protect maize and cowpea against the infestation of S. zeamais and C. maculatus respectively during storage. Mixing these products could not be advantageous since the binary mixture gave similar result as when they were applied alone.

Abstract Background Botanicals are generally assumed to be more biodegradable, leading to less environmental problems. Combination of botanicals could enhance biological activity against insect pests. Hence, the amount of botanical used for the control of stored grain pests may be minimised. In this study, the bioassay was carried out on Sitophilus zeamais to assess the effectiveness of binary combinations of Hymenocardia acida wood ash and Plectranthus glandulosus leaf powder. The quantities of mixed products were added to maize grains to constitute the contents of 5, 10, 20 and 40 g/kg. Then, the bioassays on toxicity within 1, 3, 7 and 14 days exposure, progeny production, population increase, grain damage and germination ability of protected grains were carried out. Results The major compounds (pinene, α-pinene, α-terpineol, thymol, β-myrcene and 3-carene) of P. glandulosus leaf powder were monoterpenes. The major non-monoterpenic constituent was an oxygenated sesquiterpene, β caryophyllene oxide. The chemical analysis of H. acida ash showed that calcium (5800 mg/kg) and phosphorus (2782 mg/kg) recorded higher content than the other minerals. Plectranthus glandulosus leaf powder, H. acida wood ash and their binary combinations significantly induced mortality of S. zeamais adult (P

Sitophilus zeamais and Prostephanus truncatus can cause weight loss of about 20 to 90% of untreated stored maize seeds. This study assesses four plants (Lantana camara, Moringa oleifera, Citrus sinensis and Hyptis suaveolens) extracts as seed maize protectants against the two insects in Ghana. The study was laid out in a CRD with three replications. Dried powders (5 and 10% w/w) and aqueous extracts (0.05 and 0.1 g/mL) of the botanicals were evaluated for their insecticidal activity with untreated control and Actellic included as checks. Oviposition and survivorship of insects decreased in grains treated with plant extracts. The phytochemical analysis revealed that compounds such as alkaloids, saponins, tannins and phenolic, steroids, flavonoids, anthraquinones, phlobatannins, cardiac glycosides and terpenoids were recorded in all four plant extracts. These compounds may have caused lower progeny emergence, inhibitory effect, repellent action and antifeedant effect to S. zeamais and P. truncatus in grains treated with the botanicals. Maize seeds treated with botanicals after 10 weeks in cribs recorded a reduction in the percentage of seeds damaged and weight loss caused by the two insects compared to the untreated seeds. The study proposes that the botanicals tested, especially H. suaveolens have the potential to enhance quality seed production thereby boosting growth in the seed industry. The botanicals are recommended for use by seed producers and farmers to control P. truncatus and S. zeamais in stored maize seeds. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Ciencias Agricolas is the property of University of Narino, Faculty of Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of the current study was to investigate the entomopathogenic capacity of the mold Fusarium verticillioides and the effect of its mycotoxins fumonisins, on the grain beetle Sitophilus zeamais. We evaluated the capacity of this fungus to infect live insects, the antifungal activity of constituents of the insect's epicuticle, and the effect of a fumonisin extract on the fitness of the insects. We found that F. verticillioides could not penetrate the cuticle of S. zeamais and that the fumonisin extract had no negative effects on the fitness of the insects. However, the progeny of the insects increased, and the fumonisin extract had repellent effects. This is the first report about the effects of fumonisins on the relationship between F. verticillioides and S. zeamais, which may provide useful information about interactions between pathogenic microorganisms and insects, especially on stored product pests. [ABSTRACT FROM AUTHOR]

The Maize weevil, Sitophilus zeamais Motchulsky (Coleoptera: Curculionidae), is one of important pests of storage maize in Turkey. Laboratory experiments were carried out to investigate the effect of two local diatomaceous earth (Aydın and Ankara) and Silicosec® (Biofa, Germany) against S. zeamais adults at 25 and 30°C and 50-65% relative humidity. Maize grains (cultivar Decalp 6664) were treated with three doses of DEs (1000, 1500 and 2000 ppm) and untreated seeds were regarded as control. The dead adult counts were made 2, 3, 5, 7, 14 and 21 days after DEs. The progeny of S. zeamais was determined separately for each treatment after 60 days from end of the experiment. The highest mortality (100%) of the maize weevil was observed with 2000 ppm Ankara DE on 14th day after application at 25 °C, which was followed by Aydın and SilicoSec® DEs (99.0 and 90.1%). The insecticidal activity of native DEs increased with increasing application dose, exposure time and temperature. The highest insecticidal activity at 30 °C was determined for Ankara and Aydın DEs with 2000 ppm on 14th day (100%), followed by SilicoSec® (97.9%). All doses of Ankara DE had the highest insecticidal activity than rest of the DEs examined. New adult emergence (F1 offspring) was recorded in all DEs treatments; however, emergence was very low than control treatment. It is concluded that the native DEs (Ankara and Aydın) are very effective and promising against S. zeamais adults and might be used for its successful control in storage maize. [ABSTRACT FROM AUTHOR]

Maize weevil, Sitophilus zeamais, whose management has largely been via traditional control practices, is a key pest of stored maize grains causing severe losses. This study explored the use of Nigerian Raw Diatomite (RD) in the management of the weevil. A 3-replicated split plot designed laboratory experiment was conducted for 6 months duration. The treatments were Raw Diatomite (RD) at the rate of 250, 500, 750 and 1000 mg/kg and a control (untreated) across four improved maize grain varieties. Data collected were on mortality, F1 progeny produced, grain weight damage, and loss. Data were analyzed with variance analysis and significantly different means were separated using Turkey Kramer HSD test at P<0.05. Results showed that the control had the least weevil mortality across the varieties throughout the periods of assessment. Highest weevil mortality was recorded with increase in dose rates of RD and progresses to 100% - largely at the 14th day post-treatment. Control recorded the highest weight loss and grain damage of 16.5% and 38.1%, respectively when compared to all the other treatment rates on the most tolerant variety (SAMMAZ 25). The study revealed that RD had a promising potential to substitute synthetic insecticides and can be incorporated into the integrated pest management strategy against maize weevil. We therefore suggest that further work be done to refine the Nigerian RD so as to standardize the most effective dosage application rate for management of insect pests of stored maize and other cereals. [ABSTRACT FROM AUTHOR]

The instintive behaviour exhibited by insects in the selecting food is always a matter of interests to entomologists, and it is one of the fundamental principles underlining the application of entomology to agriculture, horticulture and forestry. Food seclection is an important characteristic of insects that help them survive in periods with insufficient foods. Three grain types of food, maize grain, long-grain rice and soybean grain, were used in this sudy for detecting food selection behaviours of maize weevil, Sitophilus zeamais. Grains were kept in box traps put in the different stores in Son La during 90 days. The result showed that maize weevil, Sitophilus zeamais, prefered traps with maize grains (71.4%) considerably more than ones with long-grain rice (14.3%) and soybean grain (14.3%). Meanwhile, the cornsap beetle, Carpophilus dimidiatus, was mostly observed in maize grain (98.5%) and to a lesser degree, in soybean grain (1.5%); and the dried-fruit beetle, Carpophilus hemipterus, was abundantly observed in maize grain (93.1%) and less in soybean grain (6.9%). The red flour, Tribolium castaneum, also tended to select all the three food grain, i.e. maize grain: 53.5%, long-rice grain: 35.2%, and soybean grain: 11.3%. Comparing beetle individuals captured on three types of food grains showed that the maize weevil, Sitophilus zeamais, is the most abundant species. The percentage this store beetle among all beetles observed in maize, soybean grains and long-rice grains were 57.0%, 84.9% and 27.6%, respectively. Interestingly, Ahasverus advena, foreign grain beetle, occurred abundantly on long-rice gain (61.7%), i.e. this grain is a suitable food for the development of this beetle. [ABSTRACT FROM AUTHOR]

Our understanding and prevention of postharvest losses are critical if we are to feed a growing global population. Insect infestation-related losses of stored commodities are typically considered only in terms of quantitative, physical weight loss. Insect infestation affects the nutritional value and some nutritional components are impacted more severely than others. We infested maize and cowpea grain with commonly occurring stored product insect pests, and mapped infestation levels against nutritional composition over a 4-to-6 month storage period to analyse how insect infestation relates to different macro- and micro-nutrient contents. Insect infestation decreased the carbohydrate content of the stored grains, causing a relative increase in the proportion of protein and fibre in the remaining grain, and moisture content also increased. Sitophilus zeamais preferentially fed in the floury endosperm of maize, resulting in more carbohydrate loss relative to protein loss. Conversely, Prostephanus truncatus consumed the germ and endosperm, disproportionately reducing the fat, protein, iron and zinc grain contents. Nutrients are distributed more homogenously within cowpea than in maize grains, but Callosobruchus maculatus infestation increased the relative protein, fat, iron and zinc to carbohydrate ratios. This indicates how the nutrient content of insect-infested stored grain depends upon the grain type, the infesting insect, and the infestation level. Insect infestation therefore has consequences for human nutrition beyond those of grain weight loss. Using data collected on the changing nutritional composition of grain over time, with and without insect infestation, we modelled the associations between infestation and nutritional quality to predict estimated nutritional losses that could be associated with consumption of insect-infested stored maize and cowpea. [ABSTRACT FROM AUTHOR]

Plants with insecticidal effect are among the alternatives as a tool to control the insect-pest of stored grains. The objective of this study was to characterize the efficiency of plant-based powders on Sitophilus zeamais insects in stored grains. Using fourteen plant species (Arnica montana Baccharis trimera, Coriandrum sativum, Coffea arabica, Cymbopogon martini, Helianthus annuus, Lippia gracillis, Mentha pulegium, Moringa oleífera, Nicotiana tabacum, Piper aduncum, Piper hispidinervum, Sesamum indicum and Vitis labrusca) obtained from tritured vegetable material, and compared with a control treatment. The experiment carried out in a completely randomized design, with six replicates each treatment. In the tests, 0.5 g of the inert powders mixed into the grains (50 g) of hybrid corn AS 1551 into plastic vials and infested with 10 emerged adult of S. zeamais. After 20 days of infestation, oviposition evaluated and counts of emerged adults. At the end of the infestation period, evaluated the dry weight of the insects, the weight of grains consumed and the period of development (egg-adult). Most of the vegetal powders presented effective action on the emerged insects. By the use of the powders, it verified reduction in the ooposition, except for Vitis labrusca and Sesamum indicum whose egg numbers were higher than control, also had less effect on the development of caruncho larvae. The low weight of adults from corn kernels treated with Nicotiana tabacum powder is related reduction in feeding of S. zeamais larvae. [ABSTRACT FROM AUTHOR]

Aromatic plant essential oils (EOs) represent a promising alternative to synthetic compounds for humans, food and crop protection from insect pests. However, although many studies have demonstrated the toxic and repellent effect of EOs against harmful insects, some studies indicate that EOs can act, on the contrary, as attractants for harmful insects. In the practical use of EOs as active ingredients in insecticidal/repellent formulations, these contrasting effects may generate unexpected responses from insects. In this work, we tested the hypothesis that EOs may act in a hormesis biphasic concentration-response effect characterized by a low-concentration stimulation (attraction) and a high-concentration inhibition (repulsion) of the insect chemotaxis. For this purpose, the EOs obtained from twelve aromatic plant species belonging to eight botanical families were chemically characterized and tested for their toxicity (by fumigation) and attractiveness or repellence (by two-choice olfactometer bioassays) against the stored cereals pest Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). EO compositions were variable both qualitatively and quantitatively: while phenylpropanoids were the most represented chemical class in the EOs of Cinnamomum verum , Myristica fragrans , Ocimum basilicum , Piper aduncum , and Syzygium aromaticum , monoterpene hydrocarbons dominated the Citrus aurantium and Citrus reticulata EOs compositions, and they represented over 60% of the Schinus molle EO; the Clinopodium nubigenum and C linopodium tomentosum EOs, as well as the Elettaria cardamomum EO, were mainly rich in oxygenated monoterpenes, while Piper nigrum was the only species among those studied whose EO composition was mainly represented by sesquiterpene hydrocarbons. Toxicity tests showed a wide range of activity among the tested EOs, with LC 50 values ranging from 2.19 to 218.32 µL L−1 for C. nubigenum and C. verum EOs, respectively. Behavioral tests showed that C. aurantium , C. nubigenum , C. tomentosum , and O. basilicum EOs exerted an overall repellent effect, which was significant at concentrations ranging from 1.19 to 23.87 µL EO L−1 air. Conversely, C. verum and S. aromaticum EOs were predominantly attractive, with a significant attractiveness in the range of concentrations from 2.39 to 11.94 and at 23.87 µL EO L−1 air, respectively. However, half of the tested EOs (C. reticulata, E. cardamomum , M. fragrans , P. aduncum , P. nigrum , and S. molle) showed both negative and positive chemotaxis depending on the EO concentration. Overall, the results indicated that EOs can exert attractive and repellent activity depending on their chemical composition and concentration. Since EOs contain volatile substances whose concentration varies over time after the application, the implication of these results will be discussed in relation to their possible use as insect repellents for active packaging or as attractive lures for trapping. [Display omitted] • All tested essential oils (EOs) were toxic against Sitophilus zeamais. • 6 of 12 EOs showed both repellent and attractive activities against S. zeamais. • Chemotaxis response by insects to EOs was hormetic-like concentration-dependent. • No relationship between EOs toxicity and attraction/repellence was found. [ABSTRACT FROM AUTHOR]

Three different solvents namely; hexane, ethyl acetate and ethanol were used in partitioning the extracts obtained from Piper guineense seeds and solvent extracts were investigated for the presence or absence of secondary metabolites. Extracts were further evaluated on adult maize weevils, Sitophilus zeamais. Experiment was carried out under laboratory conditions at 27 ± 2 °C ambient temperatures and 65 ± 5% relative humidity and was arranged in a completely randomised design in four replicates. Parameters assessed, including contact toxicity, repellent effects as well as effect of solvent extracts on the germination of maize seeds. Results obtained showed that the solvent extracts contained all the secondary metabolites tested except flavonoids and steroids. As well, all the solvent extracts were lethal and possessed high repellent action against S. zeamais, with ethanol fraction being the most potent. There was no significant difference in the germination of seeds treated with the solvent extracts as well as the ethanol control. The results obtained from this study reveal P. guineese as a potential candidate for bio insecticide and could serve as an alternative to synthetic insecticides.

The complete mitochondrial genome (mitogenome) of Sitophilus zeamais was determined by an Illumina platform. This mitogenome was 18,531 bp in length, containing 13 protein coding genes, 2 rRNA genes, 22 tRNA genes that is typical among curculionoidea. Stop codon was incomplete for ND4 gene and ND5. The non-coding intergenic regions have increased in size to 1033 bp due to expansion of tandem repeat arrays. Phylogenetic analysis on mitogenome of S. zeamais would further contribute to resolve phylogenetic position and interrelationships of Sitophilus.

The complete mitochondrial genome of the maize weevil Sitophilus zeamais (GenBank accession number: MN905575) from Guizhou Province consists of a circular DNA molecule of 18,421 bp (with 75.69% A + T content), which is longer by 316 bp than that of the mitogenome of S. zeamais from Nigeria. The mitogenome comprises 13 protein-coding, 22 tRNA, and two rDNA genes. The protein-coding genes have typical ATN (Met) initiation codons and are terminated by typical TAN stop codons.

Agricultural produce is commonly stored in warehouses after the harvest period, before being utilized and fulfilling the crop stock. However, crop threats are not only present during cultivation and harvest, but crops can also be infected during storage, which leads to agricultural loss. This research aimed to observe the resistance level of corn varieties of Bisma, Bisi 18, Bisi 19, Pioneer 21, Pioneer 29, and Pertiwi 3 to the Sitophilus zeamaispest of stored product insects. This resistance was based on the mechanism of non-preference (antixenosis) resistance, measured with the Free Choice Test Method (FCTM), and antibiosis resistance mechanism, measured with the No Choice Test Method (NCTM). The results showed that based on the susceptibility index (Dobie, 1974), corn varieties of Pertiwi 3 were categorized as resistant to S. zeamais pests, while the varieties of Bisi 19, Bisma, Bisi 18, Pioneer 21 and Pioneer 29 were moderately resistant.

Chemical control of the maize weevil (Sitophilus zeamais) has been ineffective and presents serious collateral damage. Among plant-derived insecticides, essential oils (EOs) are suitable candidates to control this stored products pest. In this work, the insecticidal activities of 45 natural EOs against S. zeamais adults were screened, and the most promising ones (24 EOs) were characterized by GC–MS. The repellent and toxic effects (contact and fumigant) of these 24 EOs were determined, and by a cluster analysis they were classified into two groups considering its fumigant activity and contact toxicity. For the EOs with the highest fumigant potential (14 oils) and their main active constituents (17 compounds), lethal concentrations were determined. The most active EOs were those obtained from L. stoechas and L. alba, with LC50 values of 303.4 and 254.1 µL/L air and characterized by a high content of monoterpenes. Regarding the major compounds, the oxygenated monoterpenes R-(+)-pulegone (LC50 = 0.580 mg/L air), S-(-)-pulegone (LC50 = 0.971 mg/L air) and R-(-)-carvone (LC50 = 1.423 mg/L air) were the most active, as few variations in their concentrations significantly increased insect mortality.

Terpinen-4-ol showed highly insecticidal activity to stored-grain pest Sitophilus zeamais , and cytochrome P450s were strongly induced in response to terpinen-4-ol fumigation. Understanding of the function of P450 enzyme system in the susceptibility to terpinen-4-ol in S. zeamais will benefit the potential application of terpinen-4-ol in controlling stored-grain pests. In the present study, the synergist piperonyl butoxide increased the toxicity of terpinen-4-ol to S. zeamais , with a synergism ratio of 3.5-fold. Two isoforms of NADPH-cytochrome P450 reductase (SzCPR) were identified, with the difference at the N-terminal. SzCPR contained an N-terminal membrane anchor, FMN, FAD, and NADP binding domains. Expression levels of SzCPR were upregulated by tea tree oil (TTO) and its main constituent terpinen-4-ol under different concentrations and time periods. RNAi was generated for S. zeamais by feeding adults dsRNA and the knockdown of SzCPR increased the susceptibility of S. zeamais to terpinen-4-ol, with higher mortality of adults than control under terpinen-4-ol fumigation. Further RNAi analysis showed that P450 gene CYP6MS1 mediated the susceptibility of S. zeamais to terpinen-4-ol. These results revealed that cytochrome P450 enzyme system, especially CYP6MS1 participated in the susceptibility of S. zeamais to terpinen-4-ol. The findings provided a foundation to clarify the metabolic mechanisms of terpinen-4-ol in stored-grain pests. Unlabelled Image • PBO increased the toxicity of terpinen-4-ol to S. zeamais , with a synergism ratio of 3.5-fold. • SzCPR was upregulated in response to TTO and its main constituent terpinen-4-ol fumigation. • RNAi through dsRNA feeding was successfully applied in S. zeamais adults. • Knockdown of SzCPR increased the susceptibility of S. zeamais to terpinen-4-ol. • Knockdown of CYP6MS1 increased the susceptibility of S. zeamais to terpinen-4-ol. [ABSTRACT FROM AUTHOR]

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Sitophilus zeamais causes severe damage to stored maize grains in Nigeria. Synthetic insecticides commonly used for its management could result in environmental pollution and development of resistant-insect strains. Information is scanty on the management of S. zeamais with resistant varieties. This study was conducted to screen four maize varieties against S. zeamais and to identify the sources of resistance against the insect pest. Grain samples (100 g) from four open-pollinated maize varieties: DMR ESR-Y, SUWAN ESR-Y, TZE COMP 3-W and TZPB SR-W (susceptible) were evaluated for resistance to S. zeamais, in the laboratory. The number of F1 progeny, Grain Weight Loss and Dobie Index (0-3: resistant, 4-7: moderately resistant, 8-10: susceptible, ≥11: highly susceptible) were measured. Biophysical factors of resistance: Grain Thickness (mm) and Grain Weight (g) and biochemical factors: Nitrogen Free Extract, Crude Protein, Phenolic Acid and Trypsin Inhibitor were assessed. The number of F1 progeny (38.5±1.44), Grain Weight Loss (2.4±0.30 g) and Dobie Index (4.6) were lowest on DMR ESR-Y maize variety and highest on TZPB SR-W (72.8±3.8, 8.14±0.5g and 11.6, respectively). The Grain Thickness ranged from 4.34±0.52 mm (TZPB SR-W) to 4.94±0.42 mm (SUWAN ESRY). SUWAN ESR-Y had the highest Grain Weight (0.28±0.2 g), while DMR ESR-Y had the least (0.21±0.2 g). DMR ESR-Y had the highest Phenolic Acid (0.4±0.1%), Trypsin Inhibitor (9.3±0.1%) and Crude Protein (14.9±0.3%), while the least were found on TZE COMP-3 (0.3±0.0%), TZPB SR-W (6.7±0.1%) and TZE COMP 3-W (11.8±1.2%), respectively. The Nitrogen Free Extract ranged from 70.4±1.2 (DMR ESR-Y) to 74.9±0.9% (TZPB SR-W). The use of maize variety such as DMR ESR-Y may reduce Sitophilus zeamais infestation and damage to maize grains. Mechanisms of maize resistance to S. zeamais infestation could be useful in successful breeding programs against post-harvest grain damage. [ABSTRACT FROM AUTHOR]

Filter cake and Triplex are powdered by-products of aluminum sulfate and soap factories in Ethiopia, respectively. This study was aimed at determining contact toxicity of filter cake and Triplex powders against maize weevil, Sitophilus zeamais Motschulsky. Lethal concentrations for 99% mortality (LC99) against S. zeamais were determined by exposing adults for 12 h to filter cake (0.5–8 g/m2) and Triplex (1–9 g/m2) in concrete arenas. Lethal times for 99% mortality (LT99) were determined by exposing adults over time (1–24 h) in concrete arenas to 3 g/m2 of filter cake and 9 g/m2 of Triplex. Exposed adults were transferred to containers with 30 g of organic wheat and held at 28°C and 65% RH for 14 d to determine mortality. LC99 values for S. zeamais adults were 7.54 and 23.46 g/m2 when exposed to filter cake and Triplex, respectively. The corresponding LT99 values were 21.92 and 39.62 h when exposed to filter cake and Triplex, respectively. Effective concentrations and times for the 99% reduction of progeny production were determined from percentage reduction in adult progeny relative to production in control treatments after 42 d. EC99 values for progeny reduction were 2.48 and 18.59 g/m2 for filter cake and Triplex treatments, respectively. The corresponding ET99 values for progeny reduction were 17.49 and 22.31 h for filter cake and Triplex, respectively. Sitophilus zeamais exposed to filter cake produced lower percentage insect-damaged kernels and weight loss than Triplex. Filter cake was more efficacious against S. zeamais than Triplex. [ABSTRACT FROM AUTHOR]

The maize weevil, Sitophilus zeamais (Motschulsky), is a serious pest affecting a wide range of cereal crops, such as maize, rice, beans and other stored dried grains. As a S. zeamais female can keep laying eggs for a long time throughout its life after chewing its way into the grains, most development stages of the maize weevil, such as eggs, larvae and pupae, can always be found in stored maize grains. Our experiment with S. zeamais on long grain rice showed that 10 days after eclosion and mating, maize weevil females started laying eggs for a period of 150 days. On average, a S. zeamais female laid 38.67 eggs, of which, up to 62.81% were laid in the first 7-8 weeks (with the remaining 37.19% in the latter half of the 150 day period), and 55.07% were laid within day 55-95. The egg laying pattern of S. zeamais was modeled using cubic polynomials, which described the maximum percentages of eggs laid at day 15, 35, 75, 95 and 105. [ABSTRACT FROM AUTHOR]

Biopesticide has become more important in stored product pest management, since the use of synthetic insecticides causes adverse effects to human health and the environment. The aim of this research was to determine the chemical composition and toxicity of essential oil from Indian borage, Plectranthus amboinicu (Lour.), leaves against adults of maize weevil, Sitophilus zeamais Motschulsky. The essential oil was investigated by Gas Chromatograph-Mass Spectrometer (GC-MS) technique. The efficacy of this essential oil against S. zeamais using impregnated filter paper and vapor-phase tests. Experiments were performed under Completely Randomized Design (CRD) with 4 replications. Contact toxicity towards maize was investigated at 6 concentrations of essential oil 0 5,000 10,000 15,000 20,000 and 25,000 ppm and fumigant activity was performed using bioassay at 6 concentrations including 0 50 100 150 200 and 250 μL/L air. Data were recorded as number of deaths maize weevil from 24 to 168 h. The principal compounds in the oil were carvacrol (40.49%), caryophyllene (16.76%), Ç-terpinene (11.61%), o-Cymene (8.50%), humulene (5.88%), caryophyllene oxide (2.75), p-mentha-1,4(8)-diene (2.17%), and terpinen-4-ol (1.19%). The essential oil of P. amboinicu leaves showed strong contact toxicity at 120 h and fumigant toxicity at 72 h against adults of S. zeamais with 100% adult mortality of 25,000 ppm and 250 μL/L air, respectively. The results indicated that the essential oil of P. amboinicu leaves showed potent for management of S. zeamais population. [ABSTRACT FROM AUTHOR]

Plant defensins are divided into 18 groups and are multifunctional proteins. The Zea mays defensin 1 (ZmDEF1) gene encodes the defensin 1 protein, which can inhibit alpha-amylase in the insect gut. In this study, the ZmDEF1 gene was transferred into two maize cultivars, LC1 and LVN99, to improve weevil resistance in maize. The recombinant ZmDEF1 protein was assessed for its ability to inhibit alpha-amylase in the gut of the larvae of the maize weevil (Sitophilus zeamais Motsch.). ZmDEF1 was cloned into a pBetaPhaso-dest vector, which harbours phaseolin, a seed-specific promoter, and the Agrobacterium tumefaciens strain C58 harbouring the pBetaPhaso-ZmDEF1 vector was used to transfer the ZmDEF1 gene into two maize cultivars using immature embryos. Transformed calluses were selected on selection media containing kanamycin. The stable integration of the ZmDEF1 transgene into the transgenic maize plant genome was confirmed using Southern blotting. The recombinant ZmDEF1 protein of approximately 10 kDa was expressed in three transgenic maize lines from the LC1 cultivar (C1, C3, and C5) and two transgenic maize lines from the LVN99 cultivar (L1 and L3). The ZmDEF1 transgenic efficiency based on the results of PCR, as well as Southern and Western blotting, was 1.32% and 0.82%, respectively, which depends on the genotypes of LC1 and LVN99. The recombinant ZmDEF1 protein inhibited the alpha-amylase activity of the maize weevil larvae, and its ability to inhibit alpha-amylase is 54.52–63.09% greater than the ZmDEF1 protein extracted from non-transgenic plants. [ABSTRACT FROM AUTHOR]