Steel Bins Research Articles

Mechanical stirring of bulk-stored maize in steel bins to suppress maize weevils and other beetle populations

This study investigates the effectiveness of periodic stirring as a non-chemical approach to suppress maize weevils, Sitophilus zeamais, and other beetle populations in large-scale grain storage bins. The research was conducted in a farm steel bin with a diameter of 9.8 m holding 127 Mg of maize, and a control bin of diameter 7.3 m holding 102 Mg of maize. Both bins were loaded with maize at 13% moisture and infested at a commercial tolerance rate of 2 weevils/kg of maize. Probe traps monitored beetle populations except for S. zeamais before stirring was initiated. Maize samples were collected at depths of 0, 0.9, 1.8 and 2.7 m with a vacuum-probe sampler prior to stirring and at 10, 20, 30 and 40 days of continuous stirring machine operation. Stirring achieved 100% control of live S. zeamais while the control bin experienced an increase in its S. zeamais population after 40 days. The stirring process also led to a significant reduction in dominant beetle populations such as hairy fungus beetles, Typhaea stercorea, and foreign grain beetles, Ahasuerus advena. Although the quality of maize in both bins changed at different depths and storage times, the treatment bin had higher bulk density (732.7 ± 3.98 kg/m3 to 768.9 ± 2.41 kg/m3), lower insect damage (0.02 ± 0.02% to 0.9 ± 0.28%), and higher allowable storage time (>249 days). Moisture content and molded kernels increased in the control bin, reaching 26.4 ± 1.29% and 3.2 ± 0.53%, respectively. The average percentage of broken corn and foreign material (BCFM) in the sweepings on the floor of the emptied treatment bin was 6.5 times higher than that in the control bin. Calculated packing factor values below 1.5 from the sweepings indicated that BCFM concentrations did not affect airflow. Stirring maize provides an alternative to the use of chemicals to control stored maize insect pests at a production scale.

Effects of weather on temperatures of the grain bin components and headspace of a 10-m diameter corrugated steel bin.

The mean global temperatures are increasing as a result of climate change. To understand how the change in ambient weather influences the temperature of the stored grain, the temperature fluctuation patterns of the floor, roof, sidewalls, and headspace were monitored from mid-August 2019 to the end of October 2021 in Winnipeg, Canada. The bin was filled with 300 t of wheat at an initial average moisture content of 12.5 ± 0.1% (wet basis). The thermocouples were installed at 17, 9, and 12 locations on the floor, roof (outside), and sidewalls (outside) of the bin, respectively. Sixteen temperature and relative humidity sensors were installed at different locations with varying distances from the surface of the grain in the headspace. The ambient weather (air temperature (°C), relative humidity (%), barometric pressure (kPa), average solar radiation (W/m2), precipitation (mm), wind speed (m/s), and wind direction (degrees with reference to the north)) were also measured near the bin during the study period. The temperatures of the roof, sidewalls, and headspace were influenced by the ambient temperature and solar radiation. In Year II (November 2020 – October 2021), the floor, roof, sidewalls, and headspace temperatures were higher by 2.1 ± 0.1°C, 3.9 ± 0.1°C, 3.5 ± 0.2°C, and 1.9 ± 0.1°C than that in Year I (November 2019 - October 2020), respectively. The ambient temperature increased by 1.8°C in year II, compared to year I. These results can be used in the prediction of temperatures in grain bins caused by weather changes.

Study on 300 t of wheat stored in corrugated steel bin for two years in Canada. Part II – Movement and distribution of Cryptolestes ferrugineus (Stephens) and Tribolium castaneum (Herbst)

Movement and distribution of Cryptolestes ferrugineus and Tribolium castaneum inside a 10 m diameter corrugated steel bin containing 300 t of wheat (initial moisture content of 12.5 ± 0.1%), were monitored by using Insectors® (electronic traps) installed at 65 locations, from September 6, 2019, to October 31, 2021, in Winnipeg, Canada. The data from only 38 locations were available throughout the experimental period due to the failure of some Insectors®. During the first and second week of September 2019, C. ferrugineus adults (combined insect density of 0.25 A/kg) were introduced on the centre grain surface in two equal batches. During the second week of September 2020, the same number of T. castaneum adults (insect density of 0.25 A/kg) were introduced at the same location in two batches. The temperature inside the bin was higher than 7.8 °C, at least at one location throughout 26 months. At the end of the study, both C. ferrugineus and T. castaneum survived inside the bin. Cryptolestes ferrugineus activity was not recorded near the sidewalls at 0.1 m depth from the grain surface, from February to April 2020, when the temperature dropped below 2.5 °C. Cryptolestes ferrugineus activity was recorded when the temperature increased above 4.5 °C. Tribolium castaneum activity was not recorded near the sidewalls at 0.1 m depth when the temperature dropped below 22 °C (mid-October 2020) and the activity was recorded when the temperature increased above 22 °C (mid-July 2021). Although adult T. castaneum were mainly captured at top grain layer (about 1 m depth from the grain surface), they could be captured at any place in the bin. The insect activity near the sidewalls reduced drastically because of the temperature drop. The insect counts and insect activity increased with increase in temperature. Therefore, highest insect counts were recorded inside and around the hot spot for both insects.

Study on 300 t of wheat stored in corrugated steel bin for two years in Canada. Part I – Temperature and moisture profiles of the grain

Grain temperatures, moisture contents, and germination inside an un-aerated, 10 m diameter corrugated steel bin filled with 300 t of wheat with an initial moisture content of 12.5 ± 0.1% (w.b.), were monitored from September 2019 in Winnipeg, Canada. The hourly temperatures were recorded until October 2021, while moisture content and germination were monitored every month until August 2021. During the 26-month period, the temperatures inside the bin were above 7.8 °C, at least at one of the measured locations. The temperatures and the moisture contents of the grain varied with changes in ambient weather conditions. The grain moisture changes and temperature fluctuations near the surface of the bulk and temperature fluctuation near the walls were higher than those inside the grain bulk. The temperature gradient-induced convective currents and the hotspot development triggered the moisture migration inside the bin. The presence of high moisture grains (as a result of snow leakage) inside the grain induced a hotspot development, which in turn influenced the grain temperature and moisture content. Germinability of the grain near the walls dropped later than those near the surface and inside the grain bulk, in the presence of insect infestation. The drop in ambient temperature could either cease the hotspot or lower the grain temperature.

Segregation of dockage and foreign materials in wheat during loading into a 10-m diameter corrugated steel bin

Segregation of dockage and foreign materials (DFM) is an unavoidable phenomenon in bulk grain and causes many problems. In this study, distributions of DFM, and shrunken and broken kernels (SBK) were determined during loading of wheat in a 10-m diameter flat-bottom cylindrical bin. Wheat was loaded through a vertical funnel (spout) into the bin from five drop heights (1.6, 2.5, 3.4, 4.3 and 5.2 m). Samples were collected using a sampling tube (29 cm diameter and 50 cm deep) inserted vertically at five locations (0.00, 1.25, 2.50, 3.75 and 5.00 m of horizontal distances from the center) along three radii of the bin for each drop height. The impurities from each collected sample were divided into five categories with different sizes (other grains, other particles, SBK, fine particles, and dust and fragments) by sieving analyses. Impurities larger and smaller than wheat kernels were categorized as large and small impurities, respectively. Drop height significantly influenced the radial distribution of fine particles, dust and fragments, but not the distribution of other grains and other particles. Fine particles and dust and fragments mainly accumulated in the center, while SBK accumulated mostly near the wall of the bin. Both true density and apparent test weight (bulk density) of unclean wheat and test weight of clean wheat significantly changed along the radius of bin. Apparent test weight of unclean wheat was minimum in the center and close to the wall of bin. Drop height did not influence true density and apparent test weight of clean and unclean wheat. Thousand kernel weight, dimensions, and sphericity of wheat kernels were similar at different radial locations of bin for all drop heights. This study can be used as a reference for further studies on grain handling and associated effects on grain grading system and design of aeration, drying, and insect control. .

Comparative study of finite element analysis of steel silos with rectangular and I stiffeners

Silos are used by a wide range of industries to store bulk solids in quantities ranging from a few tones to hundreds or thousands of tones. They can be constructed of steel or reinforced concrete. Steel bins range from heavily stiffened flat plate structures to efficient unstiffened shell structures. They can be closed or open. They are subjected to many different static and dynamic loading conditions, mainly due to the unique characteristics of stored materials. Wind and earthquake load often undermine the stability of the silos. A steel silo with and without stiffeners is adopted and static structural analysis and dynamic analysis is done. The analysis is done by idealizing geometry, material and boundary conditions.
 Keywords: steel, reinforced concrete, silos.

Evaluation of plastic and steel bins for protection of stored maize against Insect Infestation in Ghana

Maize is a staple food in Ghana where there is ever increasing demand for its use to also support poultry and livestock production. However, post-harvest loss of maize is high in Ghana. This study evaluated the effectiveness of plastic and steel bins as bulk storage structures to reduce maize post-harvest loss in Ejura, Ghana during the period from February 2016 to January 2017. Maize pre-disinfested with a solar biomass hybrid dryer was stored in the following treatments: i. a white 7-ton plastic bin filled with untreated maize, ii. agreen 7-ton plastic bin filled with untreated maize, iii.a 6-ton Kikapu steel bin filled with untreated maize, iv. six 50-kg polypropylene (PP) bags filled with maize treated with Betallic Super (80 g pirimiphos-methyl and 15 g permethrin per liter as an emulsifiable concentrate (EC)), and v. six 50-kg PP bags filled with untreated maize ascontrol. Moisture content, insect pests, insect damaged kernels (IDK), grain weight loss, aflatoxin and fumonisin levels data were collected monthly. Sitophilus zeamais, Tribolium castaneum, Cathartus quadricollis, and Cryptolestes ferrugineus were the dominant insect species collected from maize samples. At the end of 12 months of storage, % IDK in the control was >17% while IDK values in the other treatments were <3%. Mean grain weight losses of <1% were recorded in the bin treatments. Mycotoxin levels in the control were above the allowable threshold of 15 ppb. Our data suggest that use of plastic and steel bins has potential to reduce post-harvest loss of maize during storage.

Impact of a polyethylene liner on the storage of winter canola seed in unaerated steel bins

Winter canola has potential as a rotational crop for small cereal grains throughout the southern United States. However, canola is typically harvested just before wheat and is not yet considered a primary crop in the south. This combined with already tight storage capacity has led producers and facility managers to look for ways to press older, low-quality storage bins into service. One idea has been the use of grain bag material as a liner for older bins that lack functional aeration systems. This project compared the storage quality of canola in lined and unlined steel grain bins without aeration. There was not a significant difference in storage quality between the lined and unlined bins. Canola seed at 5.4% moisture content was stored without loss in grade for eleven months. Lining the entire bin with grain bag material does not appear to be justified, however, there may be merit in lining the bottom of older grain storage bins to prevent moisture intrusion.

Influence of Storage Bin Design and Feed Characteristics on Flowability of Pig Diets Containing Maize Distillers Dried Grains with Solubles

. Maize dried distillers grains with solubles (DDGS) is a valuable ingredient in the swine industry but when incorporated into diets at high levels (40%) poor flowability of the feed often results. Researchers have investigated the physical properties of DDGS and use of anti-caking agents to determine their influence on flowability but few studies have evaluated effects of feed storage structures on flowability. Thus, two experiments were designed to evaluate the effects of feed bin design and passive agitator use on flowability of a commercial swine finishing diet containing 40% DDGS. Six bins of three different designs were used, which included: a galvanized steel, seamless bin with a 60° cone (Steel60; Dealers Livestock, Glenwood, Minn.); a galvanized, corrugated steel bin with a 67° cone (Steel67; PigTek, Milford, Ind.); and a white, polyethylene bin with a 60° cone (Poly60; Prairie Pride, Winnipeg, MB). In Experiment 1, rate of feed flow from each bin was assessed on days 3, 7, and 21 post-feed delivery. Feed flow from Poly60 (736.8 kg/min) was faster than Steel60 (602.9 kg/min), with Steel67 having intermediate flow (663.3 kg/min). In Experiment 2, passive feed flow agitators (Sure Flo Agitator, Farmer Boy Ag Supply, Myerstown, Pa.) were installed in one bin of each design. Feed flow was evaluated on days 2, 3, 6, 7, 20, and 21 post-feed delivery. Feed flow from Poly60 (900.7 kg/min) was greater than flow from either Steel60 (826.7 kg/min) or Steel67 (843.8 kg/min). The passive agitator increased flow in Poly60 (970.0 vs. 831.4 kg/min), tended to improve feed flow in Steel67 (880.2 vs. 807.4 kg/min), but had no effect in Steel60 (826.8 vs. 826.7 kg/min). Results indicate feed bin design can influence flowability of feed containing 40% DDGS. Of the bins tested, the passive agitator appeared to improve feed flow in some, but not all bin designs.

Effectiveness of Sulfuryl Fluoride Fumigation for the Control of Phosphine-Resistant Grain Insects Infesting Stored Wheat.

A field experiment was conducted in eight 13.6-MT steel bins containing 6.8 MT each of wheat to assess efficacy of sulfuryl fluoride or SF fumigant to control phosphine-resistant and susceptible Rhyzopertha dominica (F.) and Tribolium castaneum (Herbst). Approximately 400 adults of each type of beetle were added to each bin. Additionally, muslin bags containing immature stages and adults, with their respective diets, were also placed in bins. Four bins were fumigated with SF and others were untreated control bins. The SF dosages in treated bins ranged from 1,196–1,467 mg-h/liter. Mortality of adults in each bag was assessed 5 d postfumigation; diet minus adults was incubated in a jar, and number of adults counted after 8 wk. No significant change occurred in number of insect-damaged kernels in SF-treated bins. In trier samples from SF-treated bins, R. dominica numbers declined from 24 prefumigation to 0 at 3- and 6-wk postfumigation; T. castaneum numbers were unchanged. In WBII traps from SF-treated bins, numbers R. dominica and T. castaneum declined from 25 and 33, respectively, prefumigation to 0 or near 0 at 3- and 6-wk postfumigation. Mortalities of resistant and susceptible adult R. dominica, and adult and large larvae of T. castaneum in SF-treated bags was 100%. For all four types of beetles, adult numbers in jars associated with SF-treated bins were 0 or near 0. Results show SF is effective against all life stages of phosphine-resistant R. dominica and T. castaneum, and can be used for phosphine resistance management.

Stored Grain Pack Factors for Wheat: Comparison of Three Methods to Field Measurements

Storing grain in bulk storage units results in grain packing from overbearing pressure, which increases grain bulk density and storage unit capacity. This study compared pack factors of hard red winter (HRW) wheat in vertical storage bins using different methods: the existing packing model (WPACKING), the USDA Risk Management Agency (RMA) method, and the USDA Farm Service Agency Warehouse Licensing and Examination Division (FSA-W) method. Grain bins containing HRW wheat were measured in Kansas, Oklahoma, and Texas. Packing was measured in corrugated steel bins and reinforced concrete bins with diameters ranging from 4.6 to 31.9 m (15.0 to 104.6 ft) and equivalent level grain heights ranging from 4.1 to 41.6 m (13.4 to 136.6 ft). The predicted masses of compacted stored wheat based on WPACKING, RMA, and FSA-W were compared to the reported mass from scale tickets. Pack factors predicted by WPACKING ranged from 0.929 to 1.073 for steel bins and from 0.986 to 1.077 for concrete bins. Pack factors predicted by the RMA method ranged from 0.991 to 1.157 for steel bins and from 0.993 to 1.099 for concrete bins. Pack factors predicted by the FSA-W method ranged from 0.985 to 1.126 for steel bins and from 1.012 to 1.101 for concrete bins. The average absolute and median differences between the WPACKING-predicted mass and reported mass were 1.64% and -1.26%, respectively, for corrugated steel bins and 3.75% and 2.16%, respectively, for concrete bins. In most cases, WPACKING underpredicted the mass in corrugated steel bins and overpredicted the mass in concrete bins. Comparison of the RMA-predicted mass and reported mass showed an average absolute difference of 4.41% with a median difference of 1.91% for HRW wheat in steel bins and an average absolute difference of 3.25% with a median difference of 1.03% for concrete bins. For the FSA-W-predicted mass versus reported mass, the average absolute and median differences were 3.40% and 3.86%, respectively, for steel bins and 4.34% and 3.50%, respectively, for concrete bins. Most of the mass values were overpredicted by both the RMA and FSA-W methods. Some of the large differences observed for concrete bins can be attributed to the unique geometry of these bins and the difficulty in describing these bin shapes mathematically. Overall, compared to the reported mass, WPACKING predicted the mass of grain in the bins with less error than the current RMA and FSA-W methods. Some of the differences may be because the RMA and FSA-W methods do not include the effects of grain moisture content, bin wall type, and grain height on pack factors.

Negative pressure consolidation of silt inside bucket foundation

A series of model experiments of bucket foundations concerning suction installation and negative pressure consolidation in saturated silt were carried out in a cube steel bin at Tianjin University. The experimental results show that the silt inside the bucket has been strengthened by negative pressure, and the strengthening effect decreases with the increase of the distance from the bucket. A three-dimensional numerical model of the experiments was built by means of finite element software ABAQUS with fluid-solid coupling method. The results show that the bearing capacity of the silt inside the bucket foundation increases significantly at the former stage of negative pressure consolidation, while the increasing trend slows down over time. The rotation centers of the bucket foundation and the inner soil region tend to be closer to each other based on the consolidation. The bearing capacity of the bucket foundation is improved effectively with the increase of soil strength. The effects of negative pressure consolidation on the bearing capacity of bucket foundation were also illustrated by an actual offshore wind power project case.

Pack Factor Measurements for Corn in Grain Storage Bins

Shelled yellow corn is commonly stored in concrete or corrugated steel bins. Granular materials compact under their own weight, primarily due to particle rearrangement, leading to an increase in bulk density and a change in volume when stored. Reliable grain pack factors are needed to estimate storage capacities and to accurately monitor grain inventories. A science-based model (WPACKING) of pack factors is available that uses the differential form of Janssen’s equation and takes into account the variation in density caused by pressure variation with height and moisture content of the grain and accounts for the effects of grain type, test weight, bin geometry, and bin material. However, this model needs to be compared to field data over a wide range of conditions to ensure robust prediction accuracy. The objective of this research was to determine the field pack factors and bin capacities for on-farm and commercial bins used to store corn in the U.S. and compare them to predictions of the WPACKING program. Bin inventory measurements were conducted in concrete bins with depths up to 31.4 m (114.8 ft) and corrugated steel bins with diameters up to 32.8 m (156 ft). These values were also compared to the techniques used by the USDA Risk Management Agency (RMA) and the USDA Farm Service Agency, Warehouse Branch (FSA-W). The differences between predicted and reported mass were -4.54% (maximum underprediction) to +4.53% (maximum overprediction) for WPACKING, -2.69% to 4.97% for the RMA method, and -3.33% to + 5.67% for the FSA-W method. The absolute average difference was lowest for the WPACKING model (0.90%) compared to the RMA and FSA-W methods (1.61% and 1.86%, respectively). WPACKING had less than half as many prediction differences above 1% (13 out of 51 bins) as did the RMA and FSA-W methods, which had 29 out of 51 and 33 out of 51, respectively. The RMA and FSA-W methods do not take into account the variations in pack factor due to bin type and moisture content of the stored grain.

Assessment of fan control strategies for in-bin natural air-drying of wheat in Western Canada.

Grains (common term referring to cereal grains, oilseeds, pulses) are usually harvested at high moisture content and then dried to straight grade (dry) or safe storage moisture levels. Grain drying in freestanding, corrugated galvanized steel or welded steel bins using natural air is the most cost effective drying method with optimum grain quality. Adverse weather conditions and inappropriate fan control strategies may result in poor drying, higher drying cost (electricity and fuel), and grain spoilage. Several traditional fan control (continuous ON, only Day ON, only Night ON) and automated fan control (Natural Air Drying (NAD) and Self-Adapting Variable Heat (SAVH)) strategies were investigated using IntegrisPro model software (OPIsystems Inc.©) for their drying potential for wheat using 30 years of historical weather data (1983-2012) from 14 locations in Western Canada (Alberta, Manitoba, and Saskatchewan provinces) which cover nearly 75% of Canada’s farming area. Effects of initial wheat moistures (20, 18, and 16%), start dates (August 20th, September 1st, September 15th, and October 1st), locations, airflow rates (0.52, 0.78, and, 1.04 m3min-1t-1) and supplemental heat on drying performance were studied. High moisture wheat (18-20%) can only be dried effectively with sufficient airflow rate (0.78, and, 1.04 m3min-1t-1) and early drying start date (September 15th or earlier). Without automated control, Continuous ON fan control was a better control strategy. The SAVH control strategy gave the optimized results in terms of fan run hours, target moisture, moisture spread, and shrink (over-drying). The Night ON fan control strategy gave the poorest drying results.

Damage to industrial structures due to the 27 February 2010 Chile earthquake

This paper provides a summary of the damage to industrial facilities in the Mw 8.8 Chile earthquake of 27 February 2010. The types of damage observed include failure of elevated tanks, collapse and cracking of concrete silos, buckling of steel silos, collapse of conveyor systems, failure of steel bins, and failure of anchor rods. Damage to industrial buildings included buckling of bracing members, failure of brace connections, shear failures of reinforced concrete columns, and shear failures of heavily loaded steel girders. Aspects of the current Chilean design code for industrial structures are reviewed and discussed. Recommendations are proposed for the development of Canadian seismic design provisions for industrial structures.

Spatial Associations of Insects and Mites in Stored Wheat

The spatial association pattern of insect and mite populations in a steel bin containing stored wheat, Triticum durum Desf., in central Greece, was studied using the Spatial Analysis by Distance IndicEs (SADIE). The monitoring was carried out for 7 mo by using grain trier samples and probe traps. The most abundant insect species were Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae). For mites, the most abundant species were the phytophagous Lepidoglyphus destructor (Schrank) (Acari: Glycyphagidae) and the predator Blattisocius tarsalis (Berlese) (Mesostigmata: Ascidae). Both for P. interpunctella and C. ferrugineus, trap catches were associated with numbers of individuals in the trier samples, but the overall association index calculated among trap and sample counts was significant only in the 33% of trap-sample pairs of values. Generally, P. interpunctella had the main patch areas in the central part of the bin, with few exceptions, during the entire monitoring period. Similar trends also were noted in the case of C. ferrugineus, which was clearly aggregated in the center of the grain mass. Spatial association maps indicated a stable positive association in the central part of the bin, but in most of the other sampling zones the association was negative. However, distribution of L. destructor, based on trier samples, indicated increased presence in peripheral zones of the grain sampling area. Moreover, B. tarsalis presented the most dispersed distribution among all four species. For each species, the association between two consecutive samplings was significant in the majority of cases, indicating a stable spatial pattern. Finally, B. tarsalis was spatially associated to a higher degree with the insects found rather than with L. desctructor. Moreover, there was no association of insect and mite presence with grain temperature and moisture content. The results of the current study suggest that the coexistence of insects and mites in bulked grain follows a complex pattern, with significant interactions, especially in the case of mite predators, which are spatially associated with insect species.

Efficacy of Ozone Fumigation Against the Major Grain Pests in Stored Wheat

Field experiments were conducted in steel bins containing 13,600 kg of hard red winter wheat, Triiticum aestivum L. One bin was treated with ozone and the second bin served as a control. Stored grain insects were placed in bins for 1-, 2-, 3-, and 4-d exposure periods in sampling tubes to test ozone concentrations of 0, 25, 50, and 70 parts per million by volume (ppmv). Ozone treatments on eggs and larvae of Plodia interpunctella (Hübner) were not effective, but pupae were more susceptible. Sitophilus oryzae (L.) adults were the most susceptible species with 100% mortality reached after 2 d in all ozone treatments. However, some progeny were produced at all concentrations and exposure periods. Tribolium castaneum (Herbst) adults had 100% mortality only after 4 d at 50 or 70 ppmv. No T. castaneum progeny were produced after 2-4 d at 70 ppmv. For Rhyzopertha dominica (F.), Cryptolestes ferrugineus (Stephens), and Oryzaephilus surinamensis (L.), 100% mortality was never achieved and progeny were produced at all ozone concentrations. Laboratory experiments, testing the effectiveness of ozone in controlling psocids, were conducted in two polyvinyl chloride cylinders each containing 55 kg of hard red winter wheat. Ozone treatment at a concentration of 70 ppmv was highly effective against adult female Liposcelis bostrychophila Badonnel and Liposcelis paeta Pearman after only 1 d of exposure. However, it was not effective against eggs of both species at all exposure periods. Ozonation has potential for the control of some stored grain insect pests on wheat.

Seasonal Changes in Storage Conditions of Rough Rice in Steel Bins of a Dry-Store

Seasonal Changes in Storage Conditions of Rough Rice in Steel Bins of a Dry-Store

Sampling Plans for the Psocids &lt;I&gt;Liposcelis entomophila&lt;/I&gt; and &lt;I&gt;Liposcelis decolor&lt;/I&gt; (Psocoptera: Liposcelididae) in Steel Bins Containing Wheat

Psocids are an emerging problem in grain storage, handling, and processing facilities in the United States. We used data from two steel bins each containing 32.6 metric tonnes of wheat, Triticum aestivum L., to develop sampling plans for Liposcelis entomophila (Enderlein), Liposcelis decolor (Pearman) (both Psocoptera: Liposcelididae), and a mixture of the two species. Taylor's coefficients a (a sampling factor) and b (an index of aggregation) for these pests were calculated and incorporated into sampling protocols to improve accuracy. The optimal binomial sample sizes for estimating populations of these psocids at densities of < 25 psocids per refuge were large; therefore, we recommend the use of numerical sampling within this range of densities. Numerical sampling of L. entomophila and L. decolor at densities of < 25 psocids per refuge should not be too laborious given the low psocid numbers involved; we recommend using 10 refuges per bin. For presence-absence sampling of L. entomophila or L. decolor, 20 refuges per bin should be used at densities of 25-100 psocids per refuge. The sampling plans we have developed based on the use of cardboard refuges are convenient for use in steel bins containing wheat because they are inexpensive, provide a rapid assessment of psocid population incidence, and are easy to implement. These sampling plans can be used to monitor populations of and the efficacy of management strategies used against L. entomophila and L. decolor.

Temporospatial Distribution of the Psocids &lt;I&gt;Liposcelis entomophila&lt;/I&gt; and &lt;I&gt;L. decolor&lt;/I&gt; (Psocoptera: Liposcelididae) in Steel Bins Containing Wheat

We studied the temporospatial distribution of psocids in steel bins containing 32.6 tonnes of wheat in 2005 and 2006 in Manhattan, KS. Psocids were sampled in the top 0.9 m of wheat using a 1.2-m open-ended trier; samples were taken from the bin center and in the four cardinal directions at 0.15 and 0.76 m from the bin wall. In addition, a 2.4-m partitioned grain trier with 16 compartments was used to sample psocids from a 2-m-diameter circle in the center of the bins and to a depth of 1.96 m. Only two species of psocids were identified in the study: Liposcelis entomophila in 2005 and L. decolor in 2006. Densities of psocids were low immediately after bins were filled in July 2005, peaked in October, dropped to almost zero in December as temperatures decreased, and remained at low levels until the study was ended in March. In 2006, densities of psocids increased gradually from August to mid-October and declined until the study was ended in early November. During the fall, psocids were more abundant at the center of the bin and at lower depths. In October to November of both years, the temperatures and moisture contents of grain in the center also were higher than that in other locations. This is the first report of temporospatial distribution of psocids in steel bins of wheat.