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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]

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]

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]

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]

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 present work was undertaken in three successive years in three different regions of Nigeria to study the impact of age on the postharvest biological performance of maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) adults infesting maize grain. Eight different age groups of S. zeamais adults which ranged from 1 to 56 d were used. The study assessed important parameters and was carried out using standard methods at mean temperature and relative humidity of 28.2°C and 87.5%, respectively. Results indicated that age affected bionomics of S. zeamais adult infesting maize grain in storage. The minimum age threshold for prolific oviposition in the females was 8 d. Weevils in the age groups 8–14 and 15–21 d showed highest fecundity. There was no effect of age on progeny emergence and development time for weevils younger than 36 d. Consequent upon infestation, only S. zeamais adults of ≤35 d old caused great damage and loss to grains in storage. The susceptibility of infesting weevil to cypermethrin was not greatly influenced by weevil age except at an elderly age of ≥43 d. Observations signal that weevil adults are physiologically fittest at ≤14 d old but indicate that adults of ≤35 d old pose the highest food security threat. The S. zeamais ecotype studied showed resistance to the pyrethroid insecticide at 24 h evaluation period and that also has implications for food security. [ABSTRACT FROM AUTHOR]

Sitophilus oryzae (Coleoptera: Curculionidae) and Sitophilus zeamais (Coleoptera: Curculionidae) are major insect pests of farm-stored grains in China. Moreover, their respective distribution and prevalence are not yet assessed for grain storage facilities in China. The two species are often difficult to identify by morphology because they are immature or their presence is only evident from fragments. Species-specific primers were, therefore, designed based on the cytochrome c oxidase subunit I (COI) of 34 populations found throughout China and three foreign populations. Following the validation of this molecular-based approach for species identification, the distribution of the two species in China was determined from 68 different grain storage facilities. The results indicate that S. zeamais is prevalent throughout the country whereas S. oryzae is mainly present in the south and the center of China. It is believed that this distribution pattern is in function of ecological adaptation, mostly determined by temperature and the grain species. This is the first report of its kind, demonstrating the distribution of S. zeamais and S. oryzae in grain storage facilities throughout China and analyzed by species-specific primers of COI. [ABSTRACT FROM AUTHOR]

The maize weevil Sitophilus zeamais Motschulsky is one of the most serious stored-product pests worldwide. It causes significant damage and major post-harvest losses in global production as a result of adults and larvae feeding on stored grains and contaminating food products. The fine structural morphology of mouthparts, including the distribution of sensilla in adult S. zeamais, was observed using a scanning electron microscope. The mandibulate mouthparts are situated at the tip of the long rostrum. The sclerotized mandibles are irregular, serving as pincers. The maxillae are bilaterally flattened and lay almost perpendicular to the segmented venter, situated in longitudinal clefts with a four-segmented palp on each side of the labium. The cardo, stipes, palpifer, lacinia, and galea are described in detail. The tongue-like labium is considerably specialized with a pair of threesegmented palps. Four types of sensilla basiconica occur in the distal cavity of the maxillary palp and digitiform sensilla are located on the distal maxillary segment. Two types of sensilla basiconica with a 4 + 3 arrangement are present in the distal cavity of the labial palp, whereas a kind of sensilla basiconica is present at the base of the labial palp. The evolution of the mouthpart morphology and the putative functional significance of their sensilla are discussed, providing insight into the feeding mechanism. [ABSTRACT FROM AUTHOR]

On-farm trial with a total of 32 farmers in eight villages of Naivasha and Nakuru areas of Kenya was conducted between December 2013 and September 2014 to evaluate hermetic grain storage technologies under farmers' management conditions. The storage technologies evaluated were metal silo and SuperGrain IV-R bag alongside the standard woven polypropylene bag with or without Actellic super dust. Moisture content, insect population, grain discoloration, and weight loss were analyzed 90, 180, and 270 d after storage. Grain moisture content remained stable over the storage period. Both metal silo and SuperGrain IV-R bag suppressed insect population, prevented grain loss and cross-infestation of insects from the surrounding environment. On the contrary, polypropylene bags allowed rapid build up of insect population and re-infestation from the surrounding environment. Grain weight losses were 1.5% in the metal silo and 1.8% in the SuperGrain IV-R bags compared to 32% in the polypropylene bags without Actellic Super dust, 270 d after storage. The present study, therefore, demonstrates that storing grains either in metal silo or SuperGrain IV-R bags would benefit farmers in reducing grain losses and improving quality. The study was of great interest to the farmers, grain storage scientists, and food security experts. [ABSTRACT FROM AUTHOR]

Four common Portuguese rice varieties-Thaibonnet, Gladio, Albatros, and Eurosis-were tested for their relative susceptibility to Sitophilus zeamais Motschulsky, a common pest of stored rice in Portugal and in tropical countries. Physical (moisture content, hardness, length, and width) and chemical (by attenuated total reflection-Fourier transform infrared spectroscopy) properties of rice kernels were measured. Insect bioassays measured median developmental time, Dobie's index of susceptibility, percentage of damaged grains and weight loss, and progeny developed. This was done for paddy, brown rice, and polished rice for each variety. There were small, but significant, differences in insect resistance among the varieties. However, it was different for paddy and polished rice. In paddy, these differences were correlated with hull damage, and Eurosis was the most susceptible variety. In polished rice, resistance was correlated with hardness, and Thaibonnet was the most susceptible variety. In general, paddy rice was more resistant to insect attack, followed by polished rice and then brown rice. Paddy kernels selected with undamaged hull were completely resistant to attack. Implications for IPM and breeding for resistant varieties are discussed. [ABSTRACT FROM AUTHOR]

The maize weevil, Sitophilus zeamais Motschulsky, is a major pest of rice and other postharvest grain stocks in tropical countries. Heating and cooling treatments have been adopted to control this pest. Because heat shock protein (hsp) genes respond to temperature stress, we examined the association of hsp genes with development and thermal stress in S. zeamais. The temperature response of the insect to heat and cold treatments was assessed at four developmental stages: egg, larva, pupa, and adult. LT50 values at high temperatures were similar among the four developmental stages, while adults were the most tolerant to low temperatures, and eggs, larvae, and pupae exhibited similar LT50 values. Expression levels of three hsps--Szhsp70, Szhsc70, and Szhsp90--fluctuated substantially throughout the four stages at a rearing temperature of 28°C. Heat shock and cold shock increased the expression of all three hsps, and the highest upregulation was observed at 40°C, although the intensity of upregulation varied among the three genes: strongly in Szhsp70, moderately in Szhsp90, and slightly in Szhsc70. Basal expression of the three hsps at 28°C and gene responses to heat and cold shock also varied significantly at the tissue level. [ABSTRACT FROM AUTHOR]

The article focuses on a study conducted in order to evaluate the insecticidal activities of the essential oil of Illicium difengpi (I. difengpi) stem bark and its constituent components against grain storage insects including the Sitophilus zeamais and red flour beetle Tribolium castaneum. It discusses the identification of 37 components of the essential oil of I. difengpi. The study revealed the importance of the essential oil obtained from I. difengpi stem bark in controlling insect pests.

Rice weevils, Sitophilus oryzae (L.), and maize weevils, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), are important pests of stored grain. We have observed that rice weevil adults have a greater propensity than maize weevils to climb upward after physical disturbance of stored grain. Our objective was to quantify this climbing behavior in both species under a variety of environmental conditions to assess whether out anecdotal observations were correct. We confirmed that, after a disturbance, significantly more rice weevils climb than maize weevils when reared on fresh wheat, Triticum aestivum L., and corn, Zea mays L., and at relatively low and high population density. This greater climbing tendency is apparently exclusively due to S. oryzae males, which climb significantly more often than females. This work not only elucidates the divergent evolutionary histories of these sibling species but also may provide useful information for the monitoring and control of these stored grain pests. [ABSTRACT FROM AUTHOR]

Infestation of pouch-packaged spaghetti by Sitophilus oryzae (L.) (Coleoptera: Cur- culionidae) was observed in Japan in May 2006. It was suggested that 30% of all shipped pasta products sustain damage to the packages heat-sealed before reaching retail stores. Hence, we investigated the mechanisms by which S. oryzae and Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) adults invade pasta packaged in polypropylene pouches. In the damaged packages, both species entered through the breaks in the seal and laid their eggs on the pasta However, in the intact packages, the adults of both species bit around air vent holes in the film, but they did not make the holes big enough for entry into the pouch. We also compared each species' developmental periods from oviposition to emergence in pasta and brown rice (Oryza spp.). The average developmental period of both species at 25°C was shorter in rice than in pasta The number of individuals emerging from brown rice was significantly higher than that from pasta Finally, we suggested a measure to prevent infestation by insect pests in pouch-packaged pasta products. [ABSTRACT FROM AUTHOR]

Identifying and using native insect resistance genes is the core of integrated pest management. In this study, 10 experimental corn, Zea mays L., hybrids and 10 inbred lines were screened for resistance to major ear-feeding insects in the southeastern Coastal Plain region of the United States during 2004 and 2005. Ear-feeding insect damage was assessed at harvest by visual damage rating for the corn earworm, Helicoverpa zea (Boddie), and by the percentage of kernels damaged by the maize weevil, Sitophilus zeamais Motschulsky, and stink bugs [combination of Euschistus seruus (Say) and southern green stink bug, Nezara viridula (L.)]. Among the eight inbred lines and two control populations examined, C3S1B73-5b was resistant to corn earworm, maize weevil, and stink bugs. In contrast, C3S1B73-4 was resistant to corn earworm and stink bugs, but not to maize weevil. In a similar manner, the corn hybrid S1W*CML343 was resistant to all three ear-feeding insects, whereas hybrid C3S1B73-3*Tx205 was resistant to corn earworm and maize weevil in both growing seasons, but susceptible to stink bugs in 2005. The silk-feeding bioassay showed that corn earworm developed better on corn silk than did fall armyworm. Among all phenotypic traits examined (i.e., corn ear size, husk extension, and husk tightness), only corn ear size was negatively correlated to corn earworm damage in the inbred lines examined, whereas only husk extension (i.e., coverage) was negatively correlated to both corn earworm and maize weevil damage on the experimental hybrids examined. Such information could be used to establish a baseline for developing agronomically elite corn germplasm that confers multiple ear-feeding insect resistance. [ABSTRACT FROM AUTHOR]

To characterize in more detail the cathepsin L-like cysteine proteinases from Sitophilus zeamais (SCPs) cloned in our previous study [Matsumoto et al. (1997) J. Biochem. 121, 464–476], we established a system for their functional expression and purification using a glutathione S-transferase (GST) fusion gene vector from Escherichia coli. The proenzyme forms of two representative SCPs, proSCPcl and proSCPg3, were expressed as GST-fusion proteins and purified on a glutathione Sepharose column. GST-proSCPcl undergoes auto-proteolytic cleavage into the mature form efficiently at acidic pH, and exhibits significant proteolytic activity toward various substrates including hemoglobin and Z- Phe-Arg-MCA. The enzymatic characteristics of the activated form of SCPc1 are similar to those of mammalian cathepsin L, but its pH optimum for the hydrolysis of hemoglobin is significantly lower. The other proSCP, GST-proSCPg3, which has a shorter COOH-terminal domain than SCPc1, undergoes almost no autolytic processing and shows only very slight proteolytic activity, although the other enzymatic characteristics of GST-proSCPg3 are similar to those of GST-proSCPcl. [ABSTRACT FROM AUTHOR]

The fruit of the osage orange tree, Maclura pomifera (Raf) Schneid (Moraceae), has long been thought to be repellent to insects. A preliminary study reported here confirmed repellency of fruit extracts to the maize weevil, Sitophilus zeamais Motschulsky. Two isofiavones, osajin and pomiferin, were isolated from the mature fruit of M. potnifera in high purity (?95%). Testing of purified osajin and pomiferin failed to show repellency. Repellency is likely caused by factors other than isoflavones in the fruit. [ABSTRACT FROM AUTHOR]

Sitophilus zeamais Motschulsky and Tribolium castaneurn (Herbst) adults were equally susceptible to contact toxicity of either safrole orisosafrole. Safrole also possessed equal fumigant toxicity to adultsof both species. However, adults of S. zeamais were twice as tolerant as T castaneum to the fumigant toxicity of isosafrole. In both contact and fumigant tests, 12- and 14-d-old larvae of T castaneum showedsimilar susceptibility to each of the compounds, but 16-d-old larvaebecame more tolerant than the younger larvae. Isosafrole was generally more toxic than safrole to the insects tested. In flour disk bioassays, safrole showed very slight feeding deterrence against S. zeamais adults, and it had nb feeding deterrence against T castaneum adultsand larvae. In contrast, isosafrole was a more effective feeding deterrent than safrole, with feeding deterrence indices of 31% for S. zeamais adults at 5.4 mg/g of food, and 72 and 40% for T. castaneum adults and larvae, respectively, at 10.8 mg/ g of food. It reduced relative growth rate, relative consumption rate, and efficiency of conversion of ingested food of adults of both species, but only relative growth rate and relative consumption rate of T castaneum larvae. Isosafrole was a stronger feeding deterrent against S. zeamais than against T castaneum. Both of the compounds showed inhibitory effects on a-amylase activity from T castaneum larvae in vitro. Safrole also inhibited the larval a-amylase in vivo. However, isosafrole inhibited a-amylase activity at the lower concentration but activated it at the higherconcentration in vivo. [ABSTRACT FROM AUTHOR]

Toxicity and antifeedant activity of allyl disulfide, a volatile compound from garlic, Allium sativum L., to adults and larvae of Tribolium castaneum (Herbst) and adults of Sitophilus zeamais Motschulsky were investigated. Topical application was used for contact toxicity, filter paper impregnation for fumigant toxicity, and a flour disk bioassay for antifeedant activity. The filter paper impregnation bioassayalso was used to study the effects on egg hatch and the subsequent progeny emergence of T. castaneum. Adult T. castaneum were more susceptible to allyl disulfide than adult S. zeamais in both toxicity tests. Allyl disulfide was 3 times more potent to T. castaneum adults thanto S. zeamais in contact toxicity tests, with LD50s of 7.16 and 22.47 5g/mg insect, respectively. In the fumigant bioassay, allyl disulfide was approximately 5 times more effective to the adults of T. castaneum than to S. zeamais, with LC50 values of 0.030 and 0.146 5mg/cm2, respectively. The larvae of T. castaneum were more tolerant of allyl disulfide treatment than the adultsin both toxicity tests. Egg hatching and subsequent progeny emergence from treated eggs were reduced with increasing concentrations. Allyl disulfide was a more potent antifeedant to T. castaneum adults thaneither T. castaneum larvae or S. zeamais adults. A concentration of 7.43 mg/g of food deterred feeding by 85.7% among the T. castaneum adults, but feeding was deterred only by 31.5% at 12.77 mg/g of food and 21.2% at 29.15 mg/g of food for T. castaneum larvae and S. zeamais adults, respectively. [ABSTRACT FROM AUTHOR]

Floral extract of Mexican marigold, Tagetes minuta (L.), was toxic to adult male and female maize weevils, Sitophilus zeantais Motschulsky, under illuminated and dark conditions. The LD50 values ranged from 35 to 17 Mu g per weevil across sex and photoperiod, whereas LD99 values ranged from 319 to 816 Mu g per weevil. Fractionation tended to decrease toxicity. Generally, both sexes were similarly susceptible to a given treatment. Although the original extract and certain fractions probably contained photoactive thiophenes, which are toxic to certain larval Lepidoptera, there was no obvious effect of illumination on toxicity for this beetle species. Air exposure for 24 h, in the presence or absence of light, greatly reduced thetoxicity of the unfractionated extract. Chromatographic profiles indicated that fractionation procedures had a significant effect on sample composition and on the amount of nonvolatile material. Air exposure for 24 h had a much more dramatic effect, with concomitant 365-nm UVA or incandescent light causing even greater degradation. Degradation under illumination is the end result of the process that causes photoactivation in susceptible species. Apparently, S. zeamais was not adversely affected by the amount of photoactivation that occurred as the extracts or fractions were degrading under our test conditions. These results are discussed in terms of maximizing the control potential of labile material in subsistence agriculture, particularly when purification is required to remove undesired compounds. [ABSTRACT FROM AUTHOR]