Effectiveness of carbon dioxide in compressed gas or solid formulation for the control of insects and mites in stored wheat and barley

Le bioxyde de carbone peut être utilisé comme un fumigant efficace des grains entreposés dans des mini-silos relativement étanches. Du CO2 a été ajouté à du blé (Triticum aestivum) sous forme de gaz comprimé, ainsi qu'à de l'orge (Hordeum vulgare) sous forme solide (glace sèche) dans des amas de grains de 322 kg. Le blé a été entreposé à une température passant de 18 à 10°C au cours d'une période de 12 semaines. Les mini-réservoirs de blé ont été laissés ouverts, scellés sans ajout de C02 ou avec ajout de C02, à des concentrations de 25, 34 ou 46%. L'orge a été entreposé à une température passant de 25 à 20°C au cours d'une période de 8 semaines. Les mini-silos d'orge ont été laissés ouverts, scellés sans ajout de C02 ou avec ajout de C02, à des concentrations de 23, 29 ou 34%. Les teneurs en humidité du blé et de l'orge ont été de 14,5- 16,3% et de 14,5-16,1%, respectivement. Les teneurs en O2 du blé ont reflété le déplacement de l'air par le C02; cependant les niveaux plus faibles de C02 dans l'orge ont reflété une combinaison du déplacement de l'air par le C02 et de l'utilisation d'O2 pour la respiration des grains et des microorganismes aux températures plus élevées. Les insectes Cryptolestes ferrugineuset Tribolium castaneum ont été réprimés en 2 semaines à 34% de C02 et 15% d'02 à une température passant de 18 à 10°C, ou à 29% de C02 et 3% d'02 à une température passant de 25 à 20°C. Les acariens Tarsonemus granarius, Lepidoglyphus destructor et Aeroglyphus robustus ont été réprimés en moins de 2 semaines à ces concentrations de C02. La germination des grains et la microflore n'ont pas été affectées par tous ces environnements gazeux.Carbon dioxide can be used as an effective stored-grain fumigant in relatively air-tight bins. Carbon dioxide was added to wheat (Triticum aestivum) as a compressed gas and to barley (Hordeum vulgare) as a solid (dry ice) in 322-kg grain bulks. Wheat was stored at temperature decreasing from 18 to 10°C over a 12-wk period. Bins were left open, sealed without C02 added, or with C02 supplemented at 25,34, and 46% levels. Barley was stored at temperature decreasing from 25 to 20°C over an 8-wk period. Bins were left open, sealed without C02 added, or with C02 treatments of 23, 29, and 34%. The wheat and barley moisture content were 14.5-16.3% and 14.5-16.1%, respectively. Oxygen levels in the wheat reflected air displacement with C02, but lower O2 levels in the barley reflected a combination of air displacement by C02 and consumption of O2 by respiring grain and microorganisms at the warmer temperatures. The insects Cryptolestes ferrugineus and Tribolium castaneum were controlled in 2 wk at 34% C02 and 15% O2 at temperature decreasing from 18 to 10°C, or 29% C02 and 3% O2 at temperature decreasing from 25 to 20°C. The mites Tarsonemus granarius, Lepidoglyphus destructor, and Aeroglyphus robustus were killed in less than 2 wk at these C02 levels. Seed germination and microflora were unaffected by all gaseous environments

Impact of pirimiphos-methyl and cold temperatures on arthropod populations in stored wheat

Appliqué à une concentration moyenne de 6,4 mg m.a. kg-1 à 5 t de ble (Triticum aestivum) dans un grenier du sud du Manitoba, l'insecticide pyrimiphos-méthyl est resté actif pendant plus de 24 mo. La plupart des insectes et des acariens qui vivaient dans le grain traité n'ont pu survivre, à l'exception d'un psoque, Liposcelis sp., ainsi que les acariens Tarsonemus granarius et Aeroglyphus robustus, dont les populations ont été considérablement réduites par rapport à celles qui vivaient dans du blé non traité. À 1 m de profondeur, la concentration en résidus de l'insecticide a diminué de 52% en 12 mo, passant de 8,1 mg kg-1 à 4,0 mg kg-1 puis est restée stable jusqu'à la fin de la période de 24 mo. La teneur en humidité du grain à cette profondeur était constamment supérieure (plus de 14%) à celle mesurée en surface du blé, où les résidus sont demeurés à une concentration voisine de 4,5 mg kg-1 pendant les 24 mo. La température du blé fluctuait entre des maximums estivaux voisins de 23°C et des minimums hivernaux de près de -40°C à la surface du blé. Après 24 mo d'entreposage, du blé traité a été contaminé avec des adultes du Tribolium castaneum; le taux de mortalité observé a été d'environ 80%. Des populations de T. castaneum ou de Rhyzopertha dominica introduites dans 5 t de blé non traité ne se sont pas établies; de petites populations de Cryptolestes ferrugineus se sont établies, mais elles ont été éliminées par le froid. Les populations de Liposcelis sp. et des acariens A robustus, T. granarius, Blattisocius keegani et de Cheyletus eruditus étaient les plus élevées à la fin de l'été et en automne. La germination des grains et la microflore n'ont pas été directement affectées par le pyrimiphos-méthyl. La lente décomposition de cet insecticide dans le grain empêcherait des communautés d'arthropodes de se développer autant que dans un écosystème constitué de blé entreposé et non traité sur une période de 24 mo.The insecticide pirimiphos-methyl applied at a mean concentration of 6.4 mg a.i. kg 1 to 5t of wheat (Triticum aestivum) in a farm granary in southern Manitoba remained active over 24 mo. Most insects and mites in the treated grain could not survive except a psocid, Liposcelis sp., and the mites Tarsonemus granarius and Aeroglyphus robustus, and their populations were sharply reduced relative to those in a bulk of untreated wheat. Insecticide residues at a 1-m depth decreased ca. 52% in 12 mo from 8.1 mg kg-1 to 4.0 mg kg-1, then remained constant until 24 mo. Grain moisture content (MC) at this depth was consistently higher (over 14% MC) than at the top of the wheat bulk where residues remained near 4.5 mg kg-1 over 24 mo. Grain temperatures fluctuated from summer maxima near 23°C to winter minima near -40°C at the bulk surface. Bioassay of treated wheat with adult Tribolium castaneum after 24 mo of storage resulted in about 80% mortality. Populations of T castaneum or Rhyzopertha dominica introduced into 5 t of untreated wheat did not become established; small populations of Cryptolestes ferrugineus were established but were eliminated by winter cold. Populations of Liposcelis sp. and the mites A. robustus, T. granarius, Blattisocius keegani and Cheyletus eruditus were highest in late summer and autumn. Seed germination and microflora were not directly affected by pirimiphos-methyl. The slow rate of degradation of this insecticide in grain would prevent communities of arthropods from developing to the same extent as in an untreated stored-wheat ecosystem over 24 mo

Movement of grain to control stored-product insects and mites

Des grains entreposés furent brassés à l'aide d'une vis sans fin ou d'un transporteur pneumatique pour déterminer les effets d'un tel procédé dans la lutte contre les insectes et les acariens. Au cours d'un essai pilote, on a utilisé neuf cellules métalliques soudées contenant chacune 322 kg de blé (Triticum aestivum). Dans trois cellules, on a déplacé le grain au moyen d'une vis sans fin : on a constaté un taux de mortalité de 89 % des insectes adultes pour les triboliums rouges de la farine (Tribolium castaneum) et de 94% des insectes adultes pour le cucujide roux (Cryptolestes ferrugineus). Le taux de mortalité des larves, mesuré en plaçant des échantillons de céréales dans les entonnoirs Berlese, était de 100%. Le déplacement pneumatique des céréales dans trois cellules a résulté en un taux de mortalité de 100% (espèces d'insectes et stades de maturité confondus), que l'on a mesuré à l'aide d'une sonde à grain et de pièges à insectes. Sur le terrain, on a procédé à des essais dans des cellules en bois contenant du blé et du maïs (Zea mays) infestés. Le contenu des cellules a été chargé dans un camion par un transporteur pneumatique, puis transvidé à la main dans les cellules métalliques soudées. On a effectué un test parallèle sur du blé et du maïs en utilisant une vis à tarière pour déplacer les céréales. Dans le cas du blé, le déplacement pneumatique a tué 100 % des acariens (Aeroglyphus robustus), des T. castaneum adultes et larves et des C. ferrugineus adultes. Le taux de mortalité des larves de C. ferrugineus et des psocoptères était respectivement de 79 % et de 83 %. Le déplacement du blé à la vis sans fin a tué 98 % des acariens, et respectivement 84 et 70 % des adultes et des larves chez T. castaneum, et 14 et 0 % chez C. ferrugineus. Le déplacement pneumatique du maïs a détruit 97 % des T. castaneum adultes, 73% des C. ferrugineus adultes et 100% des Cartodere constricta. Le déplacement du maïs à la vis sans fin a donné une mortalité des insectes inférieure à celle obtenue avec le déplacement pneumatique. Le déplacement pneumatique des céréales, en particulier du blé, est un moyen physique efficace de lutter contre les espèces communes d'insectes infestant les produits entreposés.The movement of stored grain by auger or pneumatic conveyor was evaluated for control of stored-product insects and mites. In a pilot scale test using nine welded steel bins each holding 322 kg of wheat (Triticum aestivum), movement of grain using an auger in three bins caused 89% mortality of red flour beetle, Tribolium castaneum adults and 94% mortality of rusty grain beetle, Cryptolestes ferrugineus adults. Larval mortality of both species, based on grain samples placed in Berlese funnels, was 100%. Pneumatic conveyance of grain in three bins caused 100% mortality of all stages of both insects based on grain samples and grain-probe insect traps. In field tests, infested wooden bins of wheat and corn (Zea mays) were moved by pneumatic conveyor to a truck and then hand-poured into welded steel bins. A parallel test on wheat and corn was done using a screw auger to move the grain. Pneumatic wheat movement killed 100% of mites (Aeroglyphus robustus), T. castaneum adults and larvae, and C. ferrugineus adults. Mortality of C. ferrugineus larvae and psocids was 79% and 83%, respectively. Augering wheat killed 98% of mites, 84% T. castaneum adults, 70% T. castaneum larvae, 14% C. ferrugineus adults, and 0% C. ferrugineus larvae. Pneumatic movement of corn killed 97% T. castaneum adults, 72% C. ferrugineus adults and 100% of the fungus beetle Cartodere constricta. Augering corn had less effects than pneumatic movement on insect mortality. Pneumatic conveyance of grain, especially wheat, offers an effective physical control for common stored-product insects

Toxic action of phosphine on the adults of copra mite Tyrophagus putrescentiae [Astigmata : Acaridae]

Nous avons mesuré chez des cirons des champignons ( Tyrophagus putrescentiae) adultes l'absorption de phosphine et étudié in vivo et in vitro les effets inhibiteurs de ce gaz sur la cytochrome C-oxydase et la catalase. Nous avons constaté que la phosphine a réduit l'activité des deux enzymes, les valeurs d'inhibition relative des enzymes pouvant être décrites comme suit : catalase in vivo > catalase in vitro, cytochrome C-oxydase in vivo in vitro catalase, in vivo cytochrome C oxidase < in vitro cytochrome C oxidase, and the inhibition effects of in vitro enzymes were proportional to the exposure period of phosphine applied to the cytosolic extracts. Although the uptake of phosphine by adults increased with an increase of phosphine concentration and exposure period, the rate of uptake was relatively slower than at low concentration and short exposure period. The absorption mechanism of phosphine between insects and mites appears to be different

Detection of sprouted wheat kernels using soft X-ray image analysis

Sprouted wheat kernels adversely affect bread and pasta making quality, thus lowering the grade and value to millers, bakers and grain dealers. In this study, the potential of using soft X-ray system in detecting the sprouted wheat kernels was evaluated. Sprouted kernels were produced by germinating seeds. Both the sprouted and healthy samples were X-rayed using a soft X-ray system. White specks were observed in all the sprouted kernel X-ray images. Algorithms were written to extract 55 image features including gray level modeling and histogram from the scanned images. Identification of sprouted and healthy kernels was determined using statistical and neural network classifiers. A four-layer back propagation neural network model correctly classified 90% and 95% of the sprouted and healthy kernels, respectively. Statistical classifier correctly identified 87% and 92% of the sprouted and healthy kernels, respectively

Characterization of the surface morphology of durum wheat starch granules using atomic force microscopy

Knowledge of the structure and properties of microscopic surfaces of durum wheat starch granules is essential for understanding the functional and physico-chemical properties. The nanoscale surface undulations on the starch granules inside durum wheat macroscopically influence the milling properties. The objective of this study was to visualize the surface morphology and the size of starch grains of vitreous and nonvitreous durum wheat kernels using atomic force microscopy. The distribution of starch granules in the vitreous and nonvitreous durum wheat starch samples were examined and compared. The results of our study confirm the 'blocklet' model of the ultrastructure of the starch granule surface. Image contrast enhancement using UV/ozone treatment of microtomed starch samples improved the imaging of growth rings on the starch samples. The observation of growth rings in the nonvitreous starch granule surfaces indicates that amylopectin is more common than amylose in nonvitreous starch when compared with vitreous starch

Detection of Fungal Infection in Canola using Near-Infrared Hyperspectral Imaging

Near-infrared (NIR) hyperspectral imaging was used to detect the presence of fungal infection in stored canola. Artificially fungal infected (Aspergillus glaucus group) canola was subjected to single kernel imaging every two weeks after incubation using an NIR imaging system in the wavelength range of 1000 to 1600 nm at 60 evenly distributed wavelengths. Three wavelengths 1100, 1230 and 1300 nm were identified as significant wavelengths and used in the analysis. Statistical discriminant classifiers (Linear and Quadratic) were used to classify healthy, two–, four–, six–, eight–, and ten–week fungal incubated samples. The linear and quadratic statistical classifiers gave maximum accuracy of 99% for healthy samples and 100% for fungal infected samples at later stages of infection levels and 90 to 95% for the first four weeks of A. glaucus infected samples

Investigation of 3D geometry of bulk wheat and pea pores using X-ray computed tomography images

Quantitative characterization of pore topology inside grain bulks is necessary to predict the air traverse time and the cooling or fumigation pattern for the design of storage management strategies. Quantification of 3D microarchitecture of the inter-granular airspace in the grain bulks can also contribute to the development of predictive models of insect movement and for designing acoustic systems for insect infestation detection. In this study, inter-connected 3D array of void spaces was characterized by geometrical quantities such as specific surface area, pore throat size and nodal pore volume. These features were obtained from a 13.1 cm × 13.1 cm × 5 cm volume of wheat and pea bulks. The grain bulks were imaged using a high resolution X-ray computed tomography system at 200 μm resolution. The spatial distributions were computed based on 3D medial axis analysis of the void space in the images using 3DMA-Rock software and a high performance Polaris computer. The other features calculated were medial axis tortuosity, throat surface area and porosity from the 3D images. Characterization of pore throat network provides reliable observation for facilitating realistic prediction of permeability and the nature of air and gas distribution inside grain bulks

Detection techniques for stored-product insects in grain

Cereal grains are the major source of food for humans and most domesticated animals. In many developing countries, overall post-harvest losses of cereals and legumes of about 10-15% are fairly common. Consumption of cereals and legumes by pests such as insects during storage and microbial spoilage or contamination may make these totally inedible. On farms, manual samples, traps, and probes have been used to determine the presence of insects. Manual inspection, sieving, cracking-floatation and Berlese funnels are being used at present to detect insects in grain handling facilities. These methods are not efficient and are time consuming. Acoustic detection, carbon dioxide measurement, uric acid measurement, near-infrared spectroscopy, and soft X-ray method have the potential for use at the industry level to detect insects in grain samples as their usefulness has been demonstrated in the research laboratories. Researchers have developed image analysis programs to automatically scan X-ray images to detect insect infestations. The use of near-infrared (NIR) spectroscopy has been investigated to detect hidden insects in wheat kernels. X-ray and NIR spectroscopy methods are cost prohibitive and current NIR instrumentation requires complex operating procedures and calibrations. The advantages and limitations of these insect detection methods are evaluated and the advantages of one technique over the other are described in this paper