Malathion for the control of Oryzaephilus surinamensis in stored oats

Malathion was applied at an overall dosage of 8 or 12 ppm to layers of stored oats transferred with an auger to small bins of 12·3 metric tons capacity. The oats were heating (35–40°C) and were heavily infested (231 insects/kg) with Oryzaephilus surinamensis (L.). Malathion controlled the infestation at 12 ppm but not at 8 ppm. A bin of 10·8 metric tons of uninfested cool (22–25°C) oats treated at 8 ppm remained uninfested for 10 weeks when stored near infested bins.     

Wheat disinfestation using microwave energy

A pilot-scale industrial microwave system operating at 2.45 GHz was used to determine the mortality of three common species of stored-grain insects, namely Tribolium castaneum, Cryptolestes ferrugineus, and Sitophilus granarius. Wheat samples (50 g each) at 14%, 16%, and 18% moisture content (wet basis) were infested with 5, 10, or 15 insects. The infested samples were then exposed to microwave energy at four different power levels 250, 300, 400, and 500 W for two exposure times of 28 and 56 s. Complete kill of adults of all three species and of post-embryonic stages of T. castaneum was achieved at 500 W with an exposure time of 28 s. There was a significant difference in the mortality of T. castaneum and C. ferrugineus adults at 14% and 16% moisture content (m.c.) wheat but there was no significant difference in the mortality at 16% and 18% m.c. Mortality of insects increased with either power or exposure time or both. Germination of wheat kernels was lower after treatment with microwave energy. Milling and baking tests were done for the samples at which 100% mortality was obtained. There was no significant difference in the quality of grain protein, flour protein, flour yield, flour ash, and loaf volume of wheat treated with microwave energy.     

Detection of internal wheat seed infestation by Rhyzopertha dominica using X-ray imaging

Standardization for grain grades has been established in most countries to maintain the quality of a crop until it reaches consumers. Different methods have been investigated for their potential to detect insect infestations in grain destined for domestic and export markets. The potential of detecting infestations caused by Rhyzopertha dominica in wheat kernels using a real-time soft X-ray method was determined in this study. Artificially infested wheat kernels were incubated at 30°C and 70% relative humidity and X-rayed sequentially for larval, pupal, and adult stages of R. dominica. Algorithms were used to extract histogram features, textural features, and histogram and shape moments from the X-ray images of wheat kernels. A backpropagation neural network (BPNN) and statistical classifiers were used to identify uninfested and infested kernels using the 57 extracted features. The BPNN correctly identified all uninfested and infested kernels and more than 99% of kernels infested by R. dominica larvae. The classification accuracies determined by the BPNN were higher using all 57 features than when using the histogram and textural features separately. The BPNN performed better than the parametric and non-parametric classifiers in the identification of uninfested and infested kernels by different stages of R. dominica.     

Effect of microwave heating on quality and mycoflora of sorghum grain

Sorghum (cv. Maldandi M35-1) was modified to 12, 14 and 16% moisture content (m.c.) and heat-treated with microwave energy at 3 levels, for 30 sec (=4.5, 9 and 18 kJ), and 60 sec (=9, 18 and 36 kJ). The effect of microwave heating on rise and subsequent fall in grain temperature, reduction in m.c. and quality characteristics including germination, seedling dry matter, free fatty acids (FFA) and contaminant fungi was determined. The temperature attained and the moisture loss in the sorghum grain was affected by grain m.c. and the time of exposure. At the lowest and highest microwave treatment level grain temperatures reached 30–40°C and 90–101°C, respectively. However, a 60-sec treatment at the highest energy level was lethal for the grain, particularly at 14 and 16% m.c. The FFA values were unaffected by microwave treatment. Statistical analyses showed that the microwave power level and time individually, and power level × time interactions were significant for most quality characteristics. The fungi present most abundantly on the sorghum grain were Eurotium spp., Aspergillus candidus, A. niger and Penicillium spp. Increasing m.c. and microwave heating resulted in elimination of most fungi after a 30-sec exposure time. With a 60-sec exposure period, practically all fungi were eliminated from the grain.     

The mortality of Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) and Sitophilus oryzae (L.) (Coleoptera: Curculionidae) at moderate temperatures

A method using conductive heating is described for quickly obtaining and maintaining moderate temperatures in grain while minimising grain moisture loss. A model is developed to analyse insect mortality at a range of conditions on log-time logit and log-time probit scales. Values of LT 50, LT 99, and LT 99.9 are presented for adult and immature stages of Sitophilus oryzae in wheat from 42 to 48°C at 12% m.c. and for immature stages of Rhyzopertha dominica in wheat from 45 to 53°C at 9, 12 and 14% m.c. Data show that the heat tolerance of all life cycle stages for both species are different, with a degree of progressive change relative to each other as temperature changes. For R. dominica, the thermal tolerance of life cycle stages also changes relatively with changes in grain moisture content. In general, all stages survive longer at a given temperature as grain moisture increases and the effect of moisture on survival increases as temperature decreases. Values for LT 99.9 for the most heat tolerant stage of R. dominica at 9% m.c. range from 78.22 to 2.49 h between 45 and 53°C. At 12% m.c. they range from 96.81 to 3.36 h, and at 14% m.c. from 114 to 4.14 h. In general, at 12% m.c. the heat tolerance of S. oryzae is about 5°C less than R. dominica with LT 99.9 ranging from 37.36 to 3.71 h between 42 and 48°C. At this level of mortality, immature stage three is generally the most heat tolerant stage of R. dominica, whereas it is stage two for S. oryzae. The results are discussed in relation to practical applications of heat disinfestation and in terms of a general model of mortality. The results are also considered in the context of other available information on the heat treatment of both species.     

History of an insect infestation in durum wheat during transport and storage in an inland terminal elevator in Canada

A bulk of 242 tonnes of infested durum wheat from a primary elevator was sampled when it was loaded into four boxcars in August 1974, when it was unloaded at the inland terminal elevator and when it was turned in the terminal elevator. During a storage period of 1 year, the wheat was cleaned once and turned 4 times. Grain temperature was recorded each time samples were taken. Three methods of collecting 1-kg samples were used; dip sampling during transfer of the grain at both elevators, vacuum probe sampling in the terminal elevator bin and drop sampling from the bottom of the terminal elevator bin. Samples were placed in Berlese-Tullgren funnels for 6 hr to remove insects. Adults and larvae of Cryptolestes ferrugineus (Stephens) and of Tribolium castaneum (Herbst) were found, with larvae of the former species being most prevalent. In insect traps placed in the loaded boxcars, an adult C. ferrugineus was caught in one, T. castaneum adults in three, and adult Lathridius minutus (L.) in all of the boxcars; no insects were found in traps placed in the grain in the terminal elevator bin in September and October. Cleaning the grain during storage was ineffective as a means of disinfestation. The number of insects in the samples decreased as the duration of storage increased and as grain temperature decreased. Only four insects were found after November, three of which were C. ferrugineus larvae (one third and two fourth instar) and one was a Trogoderma larva. The last insect found was a fourth instar larva of C. ferrugineus in February 1975. It had a starved desiccated appearance. Even after 1 year of storage, grain temperature did not exceed the 19°C recorded at the time the grain was placed in the elevator.     

Predicting insect density from probe trap catch in farm-stored wheat

Insect populations infesting wheat stored in four bins on two Kansas farms were monitored from early July 1996 through to the middle of January 1997. Estimates of adult insect density based upon the numbers of adult insects caught using probe traps differed from those based upon the number of insects found in grain samples. These differences were a result of differences in numbers of insects found and percentages of traps or grain samples with insects. Traps detected insects 15 to 37 d earlier than grain samples. The depth of traps below the grain surface tended to influence both the total number and species composition of the insects that were caught. Traps inserted with the top just below the grain surface collected an average of 1.9 times more Cryptolestes ferrugineus (Stephens), 1.2 times more Rhyzopertha dominica (F.), 4.1 times more Ahasverus advena (Waltl) and 77.4 times more Typhaea stercorea (L.) than traps inserted with the top 7.6 cm below the grain surface. However, trap depth did not have a significant effect on the number of R. dominica caught and on only 12 to 21% of sampling dates did trap depth have a significant effect on the number of insects of other species that were caught. Grain temperatures in three of the bins averaged 30°C during the first 70 d of storage and then decreased by 0.2°C/d. Grain in the other bin was initially more than 10°C warmer and grain temperature decreased by 0.2°C/d over the full storage period. The numbers of insects captured in traps decreased as grain temperature decreased even though grain samples indicated that insect populations were still growing. Thus, trap catches did not estimate insect population density consistently throughout the storage period. A method was developed in the current paper to adjust for the effect of seasonal changes in temperature on trap catch.     

Thermal imaging to detect infestation by Cryptolestes ferrugineus inside wheat kernels

Canada's zero tolerance for live insects in grain received from farmers, and shipped to domestic and export buyers, has necessitated the development of an accurate insect detection method. An infrared thermal imaging system was developed to detect infestation by six developmental stages (four larval instars, pupae and adults) of Cryptolestes ferrugineus under the seed coat on the germ of the wheat kernels. The artificially infested wheat kernels were removed from the incubation room (30 °C), refrigerated (5 °C) for 60 s, maintained at ambient conditions for 20 s, and imaged using a thermal camera to identify each developmental stage (n=283). The means of the highest 5% and 10% of all temperature values on the surface of the grain were significantly higher (=0.05) for grains having young larvae inside and lower for grains having pupae inside. Temperature distribution on the surface of the infested kernels with different stages of C. ferrugineus was highly correlated with the respiration rate of each developmental stage (r=0.83–0.91). The overall classification accuracy for a quadratic function was 83.5% and 77.7% for infested and sound kernels, respectively, and for a linear function, it was 77.6% and 83.0% for infested and sound kernels, respectively, in pairwise discriminations. Thermal imaging has the potential to identify whether the grain is infested or not, but is less effective in identifying which developmental stage is present.     

Fungal colonists of maize grain conditioned at constant temperatures and humidities

Fungal colonization of shelled maize (Pioneer 3320) harvested from a field near Furman, South Carolina, in 1992 was determined after 348 and 751 days of continuous storage at each of seven temperatures (10, 15, 20, 25, 30, 35, or 40°C) and four constant relative humidities, giving equilibrium grain moisture contents ranging from 9.4% to 17.5% m.c. in 28 grain conditioning environments. Twenty fungal species infected surface sterilized seeds and were recorded from these conditioned grain treatments, including species commonly found in preharvest maize [e.g. Acremonium zeae, Aspergillus flavus, Fusarium moniliforme (syn. F. verticillioides), Penicillium pinophilum (syn. P. funiculosum), etc.]. Eupenicillium cinnamopurpureum and Monascus ruber were recorded only from conditioned grain treatments. Eurotium chevalieri colonized 50–96% of the kernels from grain conditioning treatments with the highest moisture content for each incubation temperature. Grain samples with>33% E. chevalieri infection had a decreased occurrence of F. moniliforme and A. zeae, and no kernels from these samples germinated. No fungi colonized more than 50% of the kernels conditioned at 30–40°C and 9.4–14.2% m.c. The results of this study indicate that individual patterns of fungal colonization during grain conditioning were a function of the survival rates for preharvest fungal colonists and their potential replacement by E. chevalieri.     

Evaluation of different temperature management strategies for suppression of Sitophilus zeamais (Motschulsky) in stored maize

Three years of experimental trials (2001–2003) were conducted in 12.7 t capacity pilot-scale bins to determine the survival, reproduction and suppression ofSitophilus zeamais Motschulsky under three temperature management strategies, no aeration (NA, control), ambient aeration (AA, 23.9 °C), and chilled aeration (CA, 18.3 °C) from May to November in Indiana, USA. One-way ANOVA indicated that the number of progeny for small adult populations of caged insects (0.14–0.28 insects per gram maize) embedded 0.6 m deep in the stored grain mass varied among temperature strategies for some, but not all of the storage periods. Progeny numbers in the CA strategy were significantly lower (P<0.05) than those for the NA and AA strategies for periods with longer hours of grain temperature 15.0 °C. There were no differences in progeny numbers between the NA and AA strategies for most of the storage periods. This may have been due to higher mortality, lower oviposition and fecundity from overcrowding of S. zeamais under the NA strategy caused by factors in the caged insect microclimate (e.g., rapid food depletion, heating, moisture, molding, and high CO₂ levels). Our results suggest that maintaining stored maize at temperatures 15.0 °C for longer periods suppressed S. zeamais progeny more effectively than at 18.3 °C. In addition, leaving the stored grain bulk unaerated early in the spring so it remained cool at 15.0 °C due to winter aeration resulted in early suppression of S. zeamais progeny.     

Characteristics of carbon dioxide sorption by stored wheat

The sorption of carbon dioxide gas (CO₂) by wheat was determined in glass flasks at four temperatures (0, 10, 20 and 30 °C) and four moisture contents (m.c.) (12, 14, 16 and 18% wet basis). The gaseous concentrations were analyzed by gas chromatography and the vacuum developed from the sorption of CO₂ by wheat was measured with a mercury manometer. The calculated amount of CO₂ sorted at equilibrium was a non-linear function of both temperature and moisture content. Sorption of CO₂ by wheat decreased with increasing temperature from 0 to 30 °C at 14% m.c., and the initial rate of sorption increased with increasing m.c. from 12 to 18% at a temperature of 20 °C. Sorption was modelled using non-linear regression at two conditions (0–30 °C at 14% moisture content and 12–18% moisture content at 20 °C). The maximum mass of CO₂ sorbed in 60 h was 0.510 g/kg of wheat at 18% m.c. and 0 °C and the lowest was 0.224 g/kg at 18% m.c. and 30 °C. A linear relationship existed between the initial CO₂ concentration and the concentration after 60 h when 250 g of wheat of 14% m.c. at 20 °C was exposed in 500 ml flasks.     

The effects of a previous field infestation upon Ephestia cautella (Walker) and Lasioderma serricorne (F.) infesting carobs

In laboratory trials, larvae of Ephestia cautella (Walker) successfully developed upon sections of the pods of the carob tree (Ceratonia siliqua L.) which had previously been infested in the field by Ectomyelois ceratoniae (Zeller), but failed almost completely to develop upon sections of the pods which had not been infested in the field. Significantly more eggs were laid by Ephestia cautella adults on previously infested carob than on previously uninfested carob, and when newly-hatched Ephestia cautella larvae were given a choice between previously infested carob and previously uninfested carob, significantly more of them selected the previously infested carob.Larvae of Lasioderma serricorne (F.) developed successfully on both previously infested carob and previously uninfested carob, and neither adult nor larval Lasioderma serricorne could be shown to discriminate between previously infested and undamaged carob.     

End-use quality characteristics of hermetically stored paddy

Four paddy varieties (Bg 352, Bg 300, Bg 358 and Bg 360) were stored in hermetic IRRI bags and common woven polyethylene bags (polybags) at room temperature either uninfested or infested with rice weevils (Sitophilus oryzae (L.)). After 9 months of storage, samples were tested for insect mortality, gas contents, moisture content (m.c.), thousand grain mass (TGM), porosity, hardness, whiteness, total milled rice yield (TMR), head rice yield (HRY), gelatinization temperature, amylose (AC), crude protein (CP), crude fat, free fatty acid (FFA), thiamine and niacin contents and sensory characteristics. These properties after storage were compared with their initial condition. The oxygen content dropped from 21% to 7% and 13.8% for infested and uninfested IRRI bag samples, respectively. The results showed that m.c., of the IRRI bag samples increased significantly (P < 0.05) by 5% when compared to the initial sample but it increased by 15% in polybag stored samples. After 9 months, dry matter loss (DM) was 65% higher in polybag than IRRI bag samples. Highest DM loss was observed in Bg 300 and the lowest DM loss was observed in Bg 358 and Bg 360. Paddy samples stored in IRRI bags showed reduced whiteness compared to polybag stored samples. Storage in IRRI bags significantly increased (P < 0.05) TMR, HRY, AC and sensory values compared to polybag samples. However, paddy samples stored in polybags significantly increased (P < 0.05) their CP and FFA contents while decreasing sensory values, thiamine and niacin contents. The FFA value of polybag samples was 2.5 times higher than IRRI bag samples. Hermetic storage of dry paddy improved overall paddy quality but different end-use quality parameters were observed in the two paddy grain types of short round (Bg 352 and Bg 300) or intermediate bold (Bg 358 and Bg 360).     

Integrated pest management in stored grain: Combining surface insecticide treatments with aeration

Three aerated, commercial stores of 5000–10,000 t of wheat in England were discovered to have surface infestations of Sitophilus granarius in mid-winter when the grain temperature was 4–9°C. The infestations were monitored using pitfall and probe traps and catches dropped to zero after the application of etrimfos or pirimiphos-methyl 2% dust into the top 0.3 m at 50g/m². The effects of surface treatments in cooled bins were also examined in a farm scale experiment. Six, 20 t bins of wheat, were each aerated at 10 m³/h/t with an 0.02 kW fan and infested with 1/kg each of S. granarius and Oryzaephilus surinamensis and 0.5/kg of Cryptolestes ferrugineus as well as the mites Glycyphagus destructor and Acarus siro. The surface of three bins were treated with 45 g/m² of 2% pirimiphos-methyl dust. Insect numbers, as determined by pitfall traps and probe traps at the surface, 1 and 2 m, fell in all bins during the winter as temperatures fell to 5°C. As the bins warmed up in the spring, numbers of O. surinamenis rose again in the untreated bins. In the second year, S. granarius reached peak numbers in the untreated bins in mid-winter. The much lower numbers of insects trapped in the treated bins were a result of the surface treatment and the few found may have been attributable to migration from the untreated bins. A. siro and G. destructor, together exceeded 1500/kg at the surface of untreated bins, but were less than 10/kg in treated bins. In the second year, few of either species were found and the predatory mite, Cheyletus eruditus, reached 200/kg in all bins, before declining. The experiment showed some of the shortcomings of an integrated pest management system for stored grain, based on cooling, storage at 15% m.c. and monitoring of pest numbers. These were surface populations of mites in the first winter, spring surface re-occurrence of O. surinamensis and surface populations of S. granurius in the second winter. These were overcome by adding surface admixture to the other elements of the IPM system. The IPM programme cost less than half of the cost of admixing the bulk with the cheapest insecticide and used 10% of the insecticide.     

Response of storage molds to different initial moisture contents of maize (corn) stored at 25 °C, and effect on respiration rate and nutrient composition

Maize was stored for 2 months in chambers maintained at 25 °C to simulate conditions observed in the central part of the “Corn Belt” of the United States when the grain warms because of high summertime temperatures after a period of winter storage. Maize was brought to three moisture contents (m.c.) within the range typically observed in farm and commercial storage, and was inoculated to simulate the amount of storage mold contamination typical of this situation. Certain of the experimental units were packed in insulation so that heat could accumulate within the grain masses to simulate hot spots. The wettest grain heated rapidly and became semi-anaerobic. The hot grain then dried rapidly, with the amount of moisture loss influenced by the ratio of water vapor pressures inside and outside the grain. The hot grain cooled and became more aerobic over time. New infections by storage molds, disappearance of viable field molds, development of kernel damage, and changes in atmospheric gases within the grain masses were correlated with the grain moisture or temperature and the rate at which the moisture and temperature changed. The rate of increase in new kernel damage was as high as 3.3% per week. Both the rate of respiration and the estimated ratio of starch to fat consumed were associated with the mean grain m.c. during the trial, and the estimated ratio of starch to fat consumed was in the range of 2.2/1–2.6/1 in the grain containing 16.6–18.2% m.c. That both fat and starch were consumed calls into question loss estimates based on starch metabolism alone. The fat content of the grain decreased more than 10% in some experimental units, but increased less than 5% in others. The protein content generally increased as other grain constituents were consumed.     

Mortality of Sitophilus oryzae (L.) and S. granarius (L.) in atmospheres produced by an exothermic inert atmosphere generator

The exposure to atmospheres with low O₂ required to kill 50 and 95% of the developing Sitophilus oryzae (L.) and S. granarius (L.) indicated that the earlier and later stages were more susceptible and the middle stages were less susceptible. At 27°C, the duration of exposure required to produce 95% mortality during the 4th instar through early pupal development was about 10 days for S. oryzae and 6 days for S. granarius. The toxicity of the atmosphere produced by an exothermic inert atmosphere generator to each stage of S. oryzae was higher at 27°C than at 21°C. Larvae and pupae of S. granarius were more susceptible to the atmosphere than corresponding stages of S. oryzae. The type of grain in which the S. oryzae were developing did not significantly alter the mortality due to the generated atmosphere.     

Two-dimensional diffusion of Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) populations in stored wheat under constant environmental conditions

Insect movement inside a stored-grain bulk increases the chance for the pests to find biologically suitable locations for their development and multiplication. The movement of rusty grain beetle, Cryptolestes ferrugineus, adults was determined in a 0.1×1×1 m wooden box filled with wheat. There were 12 combinations of temperature (20, 25, 30, or 35 °C), number of adults (125, 250, or 500), moisture content (12.5, 14.5, or 16.5%), and time periods (3, 6, 12, 24 or 72 h) over which movement could occur. The diffusivities in each set of environmental conditions were calculated using a developed procedure (program) and experimental data. The diffusivity at 14.5% m.c. and 20 °C in the 24 h movement period was 2.5±0.3×10⁻⁴ m²/h. The diffusivity increased with increasing temperature, decreasing moisture contents, decreasing movement periods, and increasing insect numbers. Adult numbers in each section of the wooden box were predicted using an analytical model and calculated diffusivities. There were no significant differences between measured and predicted adult numbers. This research suggests that distribution and dispersal of the C. ferrugineus adults in stored wheat follow a diffusion pattern under constant environmental conditions.     

Toxicity of phosphine to the diapausing stages of Ephestia elutella, Plodia interpunctella and other lepidoptera

Diapausing larvae of the stored product moths Ephestia elutella (Hübner) and Plodia interpunctella (Hübner) were tolerant of phosphine only in short exposures, the tolerance of E. elutella being at least twice that of P. interpunctella. The tolerance of a freshly collected wild stock of each species was, at some temperatures, about two or three times that in a laboratory reared stock. The wild stock of E. elutella required concentration-time (CT) products of 36 mg hr/l in 4-day exposures at 10° and 15°C, and 18 mg hr/l in 2-day exposures at 20°C and above for 100% kill. The tolerance of E. elutella larvae in diapause was not dependent on the manner in which diapause was induced, maintained or subsequently terminated. Longer exposures to phosphine were more effective than shorter ones of similar CT product because an initial period of about a day in each exposure was required for insects in diapause to be killed. At 25°C, a concentration of 0.03 mg/l was below the threshold level for mortality of some larvae, long exposures at such very low concentrations proving ineffective.

Diapausing pupae of an outdoor species, Pieris brassicae (L.), and eggs of the univoltine race of Bombyx mori (L.) were highly tolerant of phosphine at 10°C.     

Effect of low pressures on the survival of three cocoa pests at 30°C

This study forms part of an effort to eliminate the need for methyl bromide fumigation to control insects in stored commodities, through development of a novel “vacuum-hermetic” technology. The effects of low pressures and exposure times on the mortality of insects in stored cocoa beans were studied at a temperature of 30°C in order to simulate cocoa bean storage conditions in tropical climates. Insects were exposed within test chambers containing the cocoa beans at a moisture content in equilibrium with 55% r.h. and at a constant temperature of 30°C. Three species of insects were used, all being major pests of cocoa beans in producer countries: Ephestia cautella (Walker), Plodia interpunctella (Hübner) and Tribolium castaneum (Herbst). At 50±5 mmHg, the egg stage was the most resistant in all three species, times needed to obtain 99% mortality being 45, 49 and 22 h, respectively. Results show that low-pressure treatment can provide an additional and more effective option to the 5 days fumigation with phosphine used today in the replacement of methyl bromide. The use of low pressures allows the control of insect pests at shorter exposure times without the need for toxic chemicals with their environmental impact.     

The effect of moisture level on high-moisture maize (Zea mays L.) under hermetic storage conditions—in vitro studies

Under humid and warm conditions harvested grains are susceptible to molding and rapid deterioration. Therefore, they should be dried to safe moisture levels that inhibit the activity of microorganisms. Drying to these moisture levels is not economical for farmers in developing countries. Preservation of grains at intermediate moisture levels under hermetic storage conditions could be feasible and economical in warm and moist climates.

The purpose of the current study was to examine the effect of various moisture contents (m.c.) on the quality of maize grains in self-regulated modified atmospheres during hermetic storage.

Maize at 14, 16, 18, 20 and 22% m.c. was initially conditioned for 28 days in tightly wrapped plastic bags and then stored in sealed containers at 30 °C for up to 75 days. Carbon dioxide produced within the containers replaced the oxygen. As the m.c. increased the time for O₂ depletion shortened, from 600 h at 14% m.c. to 12 h at 22%. The maize at 20 and 22% m.c. exhibited the highest dry matter (DM) losses, the lowest germination rates and the highest yeast and bacteria counts. The major fermentation product in the hermetically sealed maize was ethanol (0–5 g kg⁻¹ DM), along with lower concentrations of acetic acid (0–1 g kg⁻¹ DM).

The results obtained from the in vitro experiments indicate that maize at the tested moisture levels can be stored satisfactorily under sealed conditions in which self-regulated atmospheres provide protection against microflora damage. Further large-scale trials will be needed to evaluate the economic feasibility of storing high-moisture maize.